Iowa Star Party Imaging

I'm back from the Iowa Star Party! This is held each year at Whiterock Conservency; the observing field is located about five miles southeast of Coon Rapids, and 60 miles from the center of Des Moines.

2024 ISP had some differences from my previous attendances:

• This year's October party was much more pleasant than the steam baths provided by the usual summer dates. Every night had nice cool sleeping weather for us tenters
• The usual evening banquet wasn't prepared on-site and served in the picnic area; instead it was catered and held indoors at the very comfortable Bur Oak Visitor center. It was moved to lunchtime so that it wouldn't interfere with public night. The earlier time also allowed us to be at the field well before dark
• The field was in great shape, and the addition of a modern bathroom / shower facility was very welcome. I had the distinction of setting up farthest from the bathroom, so it was easy for me to get my daily steps in!
• Saturday night was clear, but the high winds during the day put a lot of dust in the air and really enhanced the brightness of local light domes, which have grown much more prominent in recent years. The low, very dark southern horizon may be thing of the past

But let's get to the imaging.

Friday night I was all set up, polar aligned, and ready. First target was Panel2 of my Veil Nebula mosaic, and the scope was doing its slew, center, and rotate thing. But it never finished because something was causing it to throw errors related to the mount control. 

The usual power cycling didn't clear it. What followed was several hours of swapping cables in and out and trying every other remedy I could imagine. Eventually I started to get the sense that the problem was my Pegasus Powerbox, so I recabled everything to remove it from the USB data flow (it remained acting as a 12V power hub, though). This worked, but it left me with no way to power and control my dew straps. Thank goodness it was as dry as it was, dew prevention was not needed that night or the next. 

To confirm where the fault was, I ran a USB cable to the Powerbox but did not connect anything to its output USB ports. The same errors returned suggesting that simply having the Powerbox as an active USB device was enough to cause the problem. 

I've read that the Powerbox can be harmed by connecting a 12V input line to its Adjustable Voltage port, and I know I've done that at least once recently. The poor Powerbox may have run afoul of Stupid User Error and had finally given out at ISP. Bummer. 

Anyway, I was up and running again and was able to collect light frames for my Veil mosaic.  I got everything I needed for Panel 2 Friday night, along with luminance for Panel 3 and a full set of flat frames. Saturday night I collected RGB for panel 3, along with some frames for the odd object seen in Panel 6 data.

Here is the Panel 2 LRGB result (click to see 1/4 scale version):

Panel 2 (NGC 6974, 6979, Pickering's Triangle, and the northern tip of NGC 6960)

Here is Panel 3: 

Panel 3 (NGC 6995, IC1340, and the Southern Knot) 

I've started to work on the full mosaic and noticed that my Panel 1 luminance frames were badly flatted and need to be reshot. If I can manage that this week, next time I'll have a first attempt at the full Mosaic!

Starting Imaging for 2023

[Note added 5/18/2023: The weather and smoke from Canadian fires led me to cancel this first attempt at state park imaging. I'll try again for the June new moon, if not sooner.] 

Here comes Spring! (I hope.) The May new moon is on the 19th, so I'm gearing up for this as a warm-up for using state parks this year in lieu of going to the Nebraska Star Party. The first "expedition" to a remote in-state site will have some fairly simple targets for refreshing my skills with NINA and all the hardware.

Before Midnight: 

• M44 (open cluster; big and bright, AL list member)
• M67 (open cluster; sort of a toned-down, more compact version of M44, AL List member)
• Collinder 463 (open cluster, AL List Member)

After Midnight:

• IC 4756 (open cluster)
• NGC 6633 (open cluster, same field of view as IC 4756, AL List member)
• NGC 6823 (bright nebula and open cluster, AL List member) 
• NGC 6882/6885 (open cluster and AL List member)
• NGC 6940 (open cluster)

I'm tempted to use my 200mm lens for IC 4756 and NGC 6633 to put them in the same field. It would make a pretty picture and look like this (per Stellarium) and might remind one of the well-known double cluster of NGCs 869 & 884.

This might make a pretty picture is reminiscent of the well-known double cluster of NGC 869 & 884. 

This long list assumes I'll have clear sky, which is doubtful in Minnesota in May. (Mid May sky is clear only about 1/3 of the time.)

One part of this exercise is finding a set of minimum exposures for imaging open clusters. The goal isn't super pretty pictures, but only passable images that capture the essence of the clusters. Yes, I'm still thinking about doing the AL Open Cluster list by imaging. I'd like to image them all using the same system and if possible the same exposures. I'm not sure if that's even possible, but it's worth a try.

The field of view of my FSQ and ASI is big enough for the largest clusters on the list, but the small clusters may get lost. Some are only 3 arcminutes across!

I'm going drop use of the L filter and use only short exposure RGB frames, perhaps 12x60s per channel for a start with dithering every 4th frame or so. I hope that keeps the brighter stars from saturating and still gives me enough sensitivity to harvest the dimmer stars.

The other thing I'd like to become proficient at is setting up NINA for multi-target sessions. Last year I fumbled around quite a bit with unnecessary slewing, centering, and autofocusing. 

And if by some miracle there's more than one clear night I'll finally test my ability to do solar power recharging in the field.

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The winter watch hobby is not shutting down entirely as the weather warms. I did attend a watch-enthusiast's show and swap meet, but it was a bit of a disappointment. About 4/5 of the tables were dedicated to modern (new) wristwatches and their collectors. That's not really my area of interest, so it was a short visit. I'll have to search somewhere else for inspiration.

A Wristwatch for Astronomy?

Let's take a short break from the Gandhi watch. It's currently being cranky--or at least its keyless works are. (Just so you know, the keyless works are the parts that enable the watch stem to wind the watch and adjust the time. They're nasty complicated and vary in design possibly more than any other part of old watches.) 

Today's question is: What do I really want out of a watch? And let me be specific, a watch that I would use, particularly during my summer hobby of astrophotography. 

I already have a quartz wristwatch and a cell phone. Both are great at giving me the time with wonderful accuracy. The phone is kind of clunky for that, though; the quartz watch is small and nice to look at during daylight but lacks the charm of a wrist-winding timepiece.

Mechanical watches of course have their own shortcomings. Accuracy isn't quartz-like; A modern hand-winder will probably have time errors of up to 10 seconds or so each day. I know, how horrible--in a week's time it may be off by a whole minute! You also won't get anything fancy like an electroluminescent display or Bluetooth compatibility, nor will it accept your calls or fetch email. 

What I want from a watch is readability at night and the ability to tell me when a certain time interval has passed. Accuracy is not terribly important because I want it to indicate approximately when an interval of only ten or twenty minutes has passed; an error of even a few seconds is acceptable. The timing error I mentioned above, 10 seconds per day, is equivalent to about 0.07 seconds per ten minutes. That's far better than I need!

I hit the wonderful age of 70 this summer (chocolate cake is preferred if you absolutely must get one) and my eyes are not what they used to be. I have some difficulty with visual acuity when using monochrome red light. So a big watch face with large numerals is a plus. And those numerals should have good contrast with the dial face. The same applies to the hour and minute hands. 

Chance and the cyclic nature of fads have combined to stage a rebirth of large watch movements with equally large faces. There are a wide variety of designer watch faces for these, so it's easy to find a face with large, luminous numbers. For the same reason wide luminous hands are readily available.

You may be wondering why I care so little about accuracy. Most astrophotography is highly automated now even for those of us who haul our gear to remote sites. Best Practice is to sit and watch over it, much like keeping your hands on the steering wheel of a Tesla in Autopilot mode because you just never know when it's going to do something bad. And if you image, you know something bad will happen because it always does. Granted, not driving off the road bad, but bad enough. So you want to be there when it happens, ready to jump in and start mashing keys and flinging the mouse cursor around in a mad attempt to get it all running again.

The reality is that this "Best Practice" stuff is not Fun. Actually, it's more like mind-numbing. There are other things to do that at least resemble fun, if fun can be had sitting around in the dark at 2 A.M. Allow me to suggest alternatives to Best Practice...

Usually there are other imagers around who you can talk to, even if it's only an excuse to eyeball their gear and incoming light frames of some obscure NGC object. You can tell them you also imaged NGC-whatever years ago and while their image will probably be "nice," it will look "better" after 40 or so hours of intense processing with whatever expensive software you use and they don't have.

Also, god forbid, there may be some visual people around looking at stuff with their eyes. You might grow nostalgic for your pre-imaging days when all galaxies were fuzzy little balls of lint barely brighter than the background sky. You might even be moved to ask for a peek at what they've got in the eyepiece. They will, of course, oblige, since it gives them the opportunity to comment on how they once considered imaging but decided it was too much work (true) and that wow, your laptop is kind of bright (not true, but that's visual people for you). At which point you are free to amble off and bother someone else.

It's also possible some of the non-imaging, non-observing public is wandering around. Because you're experienced you know how to say "Sorry, I'm Imaging" with a tone of voice both condescending and full of menace. By those three simple words you'll convey to them that they can't possibly understand what you're doing and that if they touch your very expensive imaging rig it's likely you'll have to hurt them badly. Remember that in the the dark they can't see what you look like, so try to sound like you're six foot eleven and can bench press their entire family. This almost always convinces them they are free to amble off and bother someone else. If they fail to take the hint you should simply direct them to the visual people who earlier slandered your laptop.

But you can't just wander away from your imaging gear for hours of Fun unless you want hours of worthless data. You need to make periodic glances back at all that technological stuff to see if it's still working. I usually do this every ten or so minutes, so that's what the watch tells me. I suppose I could have a timer that dings when ten minutes have passed, but that would be annoying and deprive me of the chance to flash my oversized, easy to read watch for all to see and admire.

OK now, let's look at this admirable watch. It's not the same exact one I made as part of the watchmaking class I attended, but it's close. The background color on the face of mine is a darker blue; like this one it has nice big luminous numbers and hands. (The face diameter is almost 40mm, compared to the 30mm of my quartz wrist watch.) Under red light the face appears black and the contrast is superb.

There's even a second hand should I ever need to time something with a little precision. 

Note that this is a wrist watch style case. If you prefer a pocket watch to one that sits on your wrist it's possible to wrap the movement in something called a Hunter case. This provides protection for the crystal if you want to keep other things in your pocket like coins, keys, hex wrenches, bottle openers, etc.

Hunter Case 

Open Face Case

Hunter cases usually have at least two hinged covers (front and back); notice that the stem is at the 3 o'clock position. The open face case has one hinged cover on the back to protect the movement and the stem is at 12 o'clock. (Bonus factoid: o'clock is short for "of the clock.")

Hunter cases are usually opened by slightly depressing a button on the end of the stem. And unlike how every old movie shows someone closing a hunter-style pocket watch with a loud snap that is not how it's done. You should press the little button again, close the case, and release the button. Snapping it shut causes the cover latch to wear quickly; too soon you've got a case that won't stay closed.

My preference is for the open face version--it's easy to use! Ease of use is important when it's 2 A.M. and you're feeling a little tired, believe me.The wrist watch form is easy, too, but those are designed for right-handed people. If you're a "righty" and doubt that, try doing what a "lefty" does. Wear your watch on your right arm and try to wind it (or adjust the time) using your left hand. See?

Jumping the APT ship for a ride with NINA

I hopped on the imaging automation wagon reluctantly because I'm very old school. My mounts had go-to that I seldom used; star hopping and a good finder were all I needed, right? Absolutely! I did the H400 pushing a non-electronic 10" Dob from star to star to H object, and it was fun. All I needed was a red light, star atlas, and dew strap for the finder.

Then I started imaging and kept right on hopping. That worked for awhile, but then it became evident (only because someone pointed it out to me) that I spent a lot of time hopping when I could have been collecting photons. Reluctantly I started to move into the 21st Century. A friend suggested a setup that included planetarium and acquisition software. 

The planetarium part was easy enough as I liked Stellarium's simplicity. For acquisition I already had ImagesPlus.  IP and photoshop handled my calibration and image processing needs. After completing the Astronomical League's Bright Nebula list I switched from CCD to DSLR and I changed to BackyardEOS for acquisition.

Then things happened.

I became involved with the creation of a club imaging platform. This brought me into contact with more modern imagers, and they gently suggested I modernize. For the platform I surveyed available acquisition software and put APT and SGP on the short list. APT looked horribly complex (partly due to the clunky interface) and the way SGP worked seemed counterintuitive to me. The decision was made by someone else after I left because of the pandemic, but for myself I decided on APT.

Next, a friend wanted me to learn PixInsight so that I could teach him. I knew PI was a fine package, and that eventually I'd want to wean myself from Photoshop, so PI became the third leg of my imaging tripod: Stellarium, APT, and PI.

Which was how it stood until yesterday when I revisited NINA. In 2019 I had considered NINA briefly but thought it was too new, too undocumented, and too undertutorialed (if that's a word). And since it was Open Source and free, I had concerns that it might wither and have a premature death. Now it's 2022 and none of those concerns are valid. So it is time to revisit NINA. And after a day inside seeing how well it plays with my equipment I'm ready to switch.

First and only somewhat important, NINA looks great. Better yet, the style of NINA complements its large set of features; it seems, at least to me, incredibly intuitive. I've already had a dry run with NINA and my complete imaging setup, and I'm ready to try it out when we have a clear night.

Revised Startup for APT/Stellarium/PHD2 et al.

I've updated all the software I use for image acquisition: APT, PHD2, Stellarium, and ASCOM. 

All the updating went without problems, so Yay!

However, my old way of starting all these in order of APT first, then Stellarium, and finally PHD2 seems to not work well any more. What seems to happen is that APT and Stellarium can't work through ASCOM correctly, and APT sometimes launches an instance of PHD2 out of impatience?

Some experimenting was needed, and the result is that the order of starting now goes like this:

1. Power the mount and allow time for it to boot. My Gemini 2 takes a couple of seconds, most others are probably faster
   
2. Power up everything else and insure it's all running and has made its USB connections.
   
3. Start Stellarium and let it connect to the mount (if all is good it should correctly show the direction in which scope is pointing)
4. Start PHD2 and connect it to the guide camera and mount
5. Start APT and connect it to the camera
6. Start the camera cooling via APT
7. Connect APT to the mount
8. At this point use PoleMaster to do a polar align using the ASCOM hand control, finishing with the scope in its park position (counterweight-down and approximately targeting the NCP)
9. Re-aim the scope far away from the NCP and train PHD2. You can delay this step until after you have pointed the scope at your target.
   
10. Sync the mount using APT's Point Craft (I use ASTAP for plate solving---it's amazingly fast and almost never fails to solve!
    
11. Use either Stellarium or APT's Go-To to acquire your imaging target. Do whatever composing you want.
    
12. Start PHD2 guiding or let APT handle things. 
13. Make sure your focus is perfect and start your exposure plan

Basically: power up, start the helper apps, start APT, start camera cooling, do polar align, sync the mount, acquire target, train PHD2, start imaging. If you're using autofocus, insert its setup where appropriate.

Worth noting is that the use of Stellarium (or any planetarium program) is entirely optional. APT provides extensive object lists and has similar Go-To and Sync features---everything you need to image.

FSQ106 First Light Image; Astronomical League Open Cluster Observing Program: A To-Do list for Astro Photography Tools (APT)

At last! My FSQ system was complete and I could take it out for a first light image. Nothing fancy, just a lot of stars. I also made it a point to process it only with PixInsight, replacing ImagesPlus for calibration and reducing my dependence on Photoshop. The image is here at AstroBin. Below is a preview, along with a 1:1 scale of M13 itself. Click each for larger views.

 

 

The image is based on a bit under three hours of LRGB. There's a lot of room for improvement in this image, I know, but it's wildly better than my previous efforts.

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I think one of my first long-term projects for the FSQ is going to be the AL Open Cluster Program list. The AL provides a PDF document listing the 125 objects in the program along with their coordinates which is helpful because quite a few of the clusters are from obscure catalogs like Berkeley, Trumpler, and Dolidze Dzimselejsvili.

I'm using Stellarium and APT to control the G-11 mount. Wouldn't it be nice if there was an observing list of the AL open clusters for one of those so that I could do simple a simple go-to for each object? Unfortunately Stellarium doesn't seem to support user-defined object lists but APT does. 

Some poking around failed to turn up a list. In APT it's fairly easy to create lists by loading objects into the ToDo list. Start by opening the Object Browser. If a cluster is in the Deep Sky list, find and select it, then click the "Add in ToDo" button. If an object isn't in the list, use the ToDo list's Add New button. When you're done creating a list, just export it. The data is put into an easy-to-read XML file.

This is just what I did! If you use APT and want a copy of the list, click this link:

https://app.box.com/s/l3ji97b1ysm3xxvpve2mgud34nv4x34c

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And now a footnote to my last post in which I was saying goodbye to the Nebraska Star Party for a while. I should mention the same applies to the Iowa Star Party. The last two times I've attended that the heat and humidity were incredible. Those were on the Labor Day weekends, and this year it's a week earlier--meaning the probability of excessive heat is even greater. Much as I hate to give up on ISP, I probably won't go back until they move it into late September or October. 

Yes, I know, I won't be missed by either event, and yes, I'm a weather wimp 😄

Getting to Know My Losmandy G11G

Yes, it's still winter, but eventually it will be time to resume imaging. I've got a new mount to use and I hope to return to imaging with my good old SBIG ST-8300M. The new wrinkle for this year is integrating all the software and hardware.

This morning I ran a little practice session to see if I had everything down for getting it all running together:

• StellariumScope for managing USB
• Stellarium for target acquisition
• PHD2 for autoguiding with a QHY5L-IIM
• PoleMaster for polar alignment
• ImagesPlus Camera Control for managing the SBIG
• ASCOM for controlling the mount

Amazingly the mount seemed to point in the right direction and all the software behaved itself. The QHY5L was happy with the powered USB hub, too. Who knows, maybe when I get out under the stars I'll even get AstroTortilla to work.

Tidbits learned along the way

• Some people say that the Ethernet cable you need to use for connecting a laptop and the Gemini2 controller can be an ordinary straight-through cable if you have a recent laptop. Well, maybe and maybe not. My Dell laptop is only a year old but it definitely needs a crossover cable.
• When running from laptop you can leave the Gemini hand control disconnected. This will save you a little power in the field.
• One 35Ah 12V battery can run an entire imaging system, or at least mine.  That includes laptop, SBIG ST-8300m with cooling running at about 60%, dew straps, guider and mount. No low voltage problems, at least with a freshly charged battery. I think the battery can probably keep it all running for an entire summer night before needing to be recharged.

Another item from the 2018 Nebraska Star Party

As an imager I'm supposed to despise green laser pointers, but we all know they can come in handy. A vendor was selling a nice one at NSP and I picked it up for occasional use.

The handle is made from white birch. This pointer is powered by 2 AAA batteries instead of tiny button batteries. If you want one for yourself, contact Brian Basiaga.

Yay for me!

This is blog post number 200! Next up is an entry about a nifty Photoshop plugin that can be used to enhance an image's dynamic range.

Remote Control Range

Here's my first report from the 2018 Nebraska Star Party. I realize it's now 2019, but better late than never, right?

In an earlier post I talked about exploring the ability to remote-control my imaging using a wireless router (the ASUS RT-N12) and Android tablet running TeamViewer. The theoretical range of this setup was 500m, and I posted a diagram showing a 250m radius around the anticipated imaging site:

This assumed I was going to set up on north end of the low hill north of the dinner shelter. I ended up imagining from a position further north (the blue dot in the diagram below):

The green dot is the location of the dinner shelter, from which one could see the setup point on the horizon. The signal there was strong enough to allow control of the imaging laptop. This is about 380m from the router. I did a little more exploring and found that at the yellow points there was good enough reception to be able to see the laptop display but not control it. The red dots indicate where the signal caused TeamViewer to give up.

I think it's fair to say if one can maintain a line-of-sight contact with the router the range of 500m is a fair estimate.

Modernizing my imaging setup

Yes, I'm finally going to move into the 21st Century by adding software mount control and plate solving! Along the way I'm consolidating all my cabling with both a 12V power hub and powered USB 3 hub.

I've resisted this move until now because it sounds really complicated and my imaging laptop wasn't up to running Astrotortilla. But the long winter gave me plenty of time and I've got a new laptop, too. And I have the motivation of doing something similar for the new imaging setup at the Minnesota Astronomical Society's Cherry Grove Observatory. (More about that in a coming post.)

What's New

• Power: My old wet lead-acid batteries have been replaced by smaller sealed AGM batteries, giving me a total of about 108Ah in the field (assuming an 80% discharge). This should be enough for four summer nights of imaging. The batteries can be connected in parallel.
• Software: BackyardEOS and PHD2 are now joined with StellariumScope, Stellarium, and Astrotortilla. ASCOM for everything, which permits me to do away with the cable from the guide camera to the mount! TeamViewer for remote monitoring and control.
• Cabling: A RIGRunner power hub and separate powered USB3 hub have been added. This means I only need to run one power cable to the mount, and one USB cable. All the cables now join securely using Anderson Powerpole connectors. A small DROK DC step down converter now acts as the power supply for my DSLR. This attaches to the power hub. 
• "Remote Control" via TeamViewer requires a wireless router for those times when the internet is available. I can control everything from my Android tablet.

ASCOM isn't nearly as difficult to implement as I had thought. Install the correct platform and drivers and you're good.

On the other hand, Astrotortilla has been a minor nightmare. The main problem has been the field of view that has to be specified. It really has to bracket* the FOV of your images. I have it solving now nice and fast, and working in conjunction with BYEOS and my mount.

*After running a lot of test cases I'm not so sure this is true. It seems like solving success mainly requires that the long axis of your image is slightly larger than the actual FOV. The short axis can be almost anything greater than zero and smaller than the long axis.

Remote Control of Imaging Laptop

It's still snowing here-15 inches last Saturday and Sunday, 2 to 4 more inches tomorrow. Naturally my thoughts have turned to Summer warmth. And where is the best summer warmth found? The Nebraska star party, of course!

Along with that warmth comes mosquitoes. They start coming out at dusk and can be pests the entire night. Your only options are hope for a good breeze, DEET up, or seek shelter. Breezes are not reliable, and DEET doesn't deter Nebraska mosquitoes from buzzing around your head. So option 3 is the most reliable, but how do you monitor your laptop while you're sitting in a vehicle or tent?

With TeamViewer you say! And you're correct, it's the remote access software of choice for many people in astrophotography. It's easy to use, powerful, and free for personal use. But it does come with one catch. As typically used it requires internet access. What do you do if you don't have that?

Conveniently, TeamViewer does permit a no-internet mode of operation. After you install it on your imaging laptop start the application and go to the menu's Extras / Options  dialog. Under "Network settings" change the Incoming LAN Connections to "accept exclusively," click OK and you're done!

(TeamViewer will now assume you're connecting to a LAN and will use the laptop's assigned IP address as "Your ID" on its main screen. Any other devices on the same router will now be able to connect with your laptop, even if the router isn't on the internet.)

Without the internet you need to set up some form of communication. I tried several methods to control my imaging laptop with my phone or tablet.

• Use the laptop as an access point, then have the controlling device connect to it. I couldn't get TeamViewer to work with this configuration.
• Use my tablet as an access point. Unfortunately my particular tablet couldn't do this.
• Use my phone as an access point. This worked, but turning on the capability required phone service to verify that it was allowed.  Since I don't have service at the Nebraska Star Party, this won't do for now. At other sites with service (like the Iowa Star Party) it may be the best option.
• Use a wireless router. This works perfectly. You don't need an expensive router for this, but there are a couple of considerations: the wi-fi bands used must be compatible with your devices; It should be reasonably waterproof on top to deal with dew, and you might want to look at the voltage requirement. I settled on the ASUS  RT-N12 ($20 from Amazon) that accepts 12V DC and can be powered directly from my batteries. The ASUS is found to consume a scant 2.3W which means it draws a tiny 0.2A.

The theoretical range of the ASUS is 500m, which would provide this coverage around my usual campsite (atop a very low rise) at NSP [CORRECTION: the red circle denotes a distance of 250m around the campsite, not 500m]:

ASUS Theoretical Range at NSP

Will it really be this good? I hope to do a little survey once I have it set up. if it allows me to see my laptop from Dob Row I'll be really pleased. If not, I'm quite confident it will easily reach my tent (maybe 3 to 5m away) and allow me to sit in mosquito-free comfort while imaging!

A Tale of Three Batteries

I recently complete my piggyback power and USB distributor that should allow me to image using only two cables running to the mount. (I'll have more about that after it's been field tested.) I'm standardizing power connections using Anderson Powerpole connectors, and the plan is to use all my batteries connected in parallel. This means adding Powerpole connectors to all of the battery boxes, which got me thinking about the batteries themselves.

The old batteries are 6 and 7 years old, and there was little doubt they were starting to show their age. Both are the wet lead-acid type, which is a little messy and a tad bit risky to haul around. They're also heavy, each being rather large (Form 27) and weighing about 55 pounds.  I could justify replacing them with nice new AGM sealed batteries if they proved to be in poor shape, which raised the question of how to test a battery's capacity.

Both batteries have reserve capacity (RC) values of 175 and were advertised as being deep-cycle. I can't attest to their deep-cycle ability, but they served me through several Iowa Star Parties and four Nebraska Star parties.

RC is the number of minutes a battery at 80°F can provide 25A before it is fully discharged (it's open circuit voltage falls to 10.5V). RC is not the same as amp hours, and certainly not the same as usable amp hours.

To see why, let's pretend we can convert RC to Ah directly:

Amp hour capacity = amps provided • elapsed hours =  25A • (RC  / 60) =  0.417 • RC

An RC of 175 gives a capacity of 72.9 Ah. Seem easy, doesn't it? The catch is that you almost never want to drain a battery that far-it will gradually decrease the battery's capacity. If you only discharge it about 80% you probably won't notice any loss of capacity until you're well past 200 discharges. 200 discharges is a lot of nights out imaging! So that 72.9Ah is really more like 58Ah. Sorry!

(Much of the literature about deep cycle batteries is written for solar power users who discharge their batteries nightly. In their case a maximum discharge of only 50% or less is needed if the batteries are to be economical.)

But wait, it gets more complicated! Astrophotography seldom requires anything like 25A. (For example, my setup for imaging with a DSLR requires only about 3 to 4A; it jumps to about 6A when using my CCD) Batteries are more efficient at providing power when the current is lower, meaning that the "real" Ah capacity in that case is higher. My batteries also have a stated alternate RC value of 200 based on 23A draw, which gives a full drain capacity of 23A • (200 / 60) =  76.7Ah. Two amps less and you get 3.8 more Ah. Great!

We're not done yet, though. What you're powering also will come into play. As the battery is drained its voltage falls, and as that happens voltage converters and inverters may have to work harder to provide regulated power. Some devices (Kendrick dew controllers, for example) may shut off. So draining a battery by 80% may not work for you.

Possibly the "best" way to determine how a battery will perform is to test it yourself. I recently found a nice way of doing this that employs a simple AC electric clock, AC lamp, and an inverter with a low voltage alarm. An inline DC power meter can be useful, too, but it's not necessary.

I used a 40W bulb to better match my typical current demand. (The calculation is easiest if we use amps = power / volts, so in this case 40W / 12V = 3.33A.) The inverter and clock draw power, too, so  My inline meter suggested that inverter, bulb and clock used about 43 watts and would draw about 3.6A initially. My inverter is programmed to sound an alarm when the loaded voltage drops to 11V; in reality it appeared to cut off at 11.2V

As a reality check I tested my relatively new and well cared for 35Ah AGM battery. I was unable to find an RC value for it that I could trust, so I took values from its spec sheet and (with the help of a spreadsheet) interpolated a capacity of 31.65Ah at a drain of 3.6A.

The battery powered the inverter for 399 minutes, and the meter reported 28.5Ah were provided, but a closer look at current and voltage measurements suggests this should be adjusted by a factor of about 0.93--so 28.5 becomes 26.5. given the uncertainties, I'll use that as the output of the battery. 26.5 is 83% of the estimated 31.65Ah capacity.

Even though all of these numbers are fairly approximate, I think it's safe to conclude that the relatively healthy 35Ah battery was able to provide something like 80% of its capacity before the voltage fell low enough to shut down the inverter. Given that, the test can be repeated with the other batteries; if they are  in perfect shape they could be expected to each deliver about 80% of their 73Ah, which is 58Ah. This is very likely an underestimate because we drain at a much lower amperage than 25A.

Battery One, which is seven years old and was once allowed to go dead, provided power for only 213 minutes. That means it provided only about 3.6A • 213 minutes • (1 hour / 60 minutes) = 13Ah. Awful!

Battery Two, which is six years old and was better maintained, provided power for much longer and ended up delivering 26.5Ah, which is still less than half of what a new battery its size could be expected to provide. It should be replaced, too.

The options are 50Ah batteries, $100 ($2/Ah), 30 pounds, or 75Ah, $140, ($1.90/Ah). I think I'll go with the 50Ah ones! Time to place an order!

Back To Imaging for a Bit; The Nebraska Star Party Nears

My wife got a new desktop computer after the 4th of July, and that translated into more than a week of transition from old computer to new. Because she didn't get a new monitor our ancient flat panel monitor was pressed into service so that she could run both computers at the same time. And because it was the monitor on my meteor-detecting computer, that activity was put on hold for the duration.

Luckily we just had a very nice run of third quarter moon clear nights. I was able to get out for two out of the three nights and tested the setup intended for the Nebraska Star Party. This year I'm not chasing any astronomical league program certificates so I'm keeping it simple: Big mount, DSLR, and short lenses.

From my second night out, here's an example:

It's the Lagoon and Trifid nebulae. This is a 200mm f/5.6 image based on only 10 4-minute light frames (ISO 800) and it gets reasonably deep.  This was taken at a light pollution yellow-green transition zone site; I'd like to try this again at NSP to see how much the difference in sky brightness affects the outcome.

Another target will be the Rho Ophiuci area and the dark lanes to its east. And, if there are enough clear hours, some of the dark nebulae that dot the area.  I may even try some super wide fields!

The weather at Valentine has been on the warm side, with some daily highs in the 100 to 105 degree range. The forecast for the first Sunday is much nicer at this point--A high of only 87, and a partly cloudy night with a pleasant low of 60. Monday's high is forecast to be only 88! It doesn't get much better than this.

The rest of this week is NSP preparation. No more imaging until then!

Virgo Cluster Mosaic Ib: A Less Aggressive Approach

Last time I settled on using a 200mm lens to make a mosaic of the entire--fifteen degree square--Virgo Cluster. This would require something on the order of 15 to 24 subimages.

A club member pointed out that the galaxies probably wouldn't look very good at that scale, and he was right. Here's a simulation of 200mm vs. 700mm.

700mm image

200mm simulation

The galaxies are starting to lose their distinction from stars, pretty much ruining the point of a galaxy cluster mosaic.

His solution is to image only the core of the cluster, an area of about 8° by 5°. That's roughly 1/5 of the entire cluster's expanse, but it does contain the densest concentration of galaxies of interest to visual observers.

I'm going to repeat the calculations from Part I for the AT65 telescope. N = 3.5 (round up to 4) and M = 3.25 (round up to 4). So this can be done with about 16 images using much better optics.

I had some time to put together the layout of the 16 frames:

Virgo Cluster mosaic layout. Blue box, suggested area to be imaged; green markers, centers of subframes; red marker, center of mosaic; red box, area of mosaic.

The final mosaic will have a pixel counts that are about three times the frame dimensions. Since I'll be using a Canon T2i, that will give a 162 megapixel mosaic!

Trying My New Battery; Color Balance Issues

The weather has been cooperating a little better this last week, and I've been able to try out my battery-based imaging setup. I haven't done much more than image an hour here, a couple of hours there, but the results are about as expected.

Here are two images from my inner red zone back yard,

M42:

As you can see I was unable to completely eradicate the sky brightness gradient.

The Rosette:

Both are taken without filters only because I don't have one. A decent filter would have improved these greatly.

Here are a couple from some distance north of the Twin Cities in a yellow zone,

75m of the M81/82 area:

I have this delusion that I'll be able to image the integrated flux nebula.

The southern portion of Auriga (including some dark lines from tree branches):

The first two images came out horribly red/magenta heavy, and it was a lot of work getting the color right. I passed that off as a consequence of the camera mod and light pollution. The second two appeared just as red on the display screen while working on getting the exposure right, but they came out fairly neutral because I chose the ImagesPlus RAW conversion that ignores the camera's white balance; I used "Bayer No White Balance" instead of "At Capture White Balanced Color."

Color balance isn't an issue when CCD imaging, particularly if your filters are balanced by the manufacturer to give equal white signals in each channel.

The question is now which is better, a custom white balance or using the "no white balance" processing option. There's only one way to find out, and that will require a sunny day, a few sheets of white printer paper, and a clear night. That's my next task.

Oh, and the battery worked perfectly. It's nice to have the power right there in such a light package. 35Ah, less than 23 pounds. My little battery case now has two power sockets, but the volt meter has yet to arrive.

The Lust for Power, Part 3: Generators

Last time I found two imaging configurations that called for the use of big, heavy, and expensive deep cycle batteries. The common alternative is to buy a generator; it will supply 110V AC, and then your AC adapters will feed your equipment.

Generators as the primary power source

Generators come in a variety of sizes. The factors to consider, roughly in order of their importance, include:

• Amperage rating (AC). While some generators have DC outputs, you'll probably be using the AC side.
• Running and peak wattage (W). Wattage is easily computed by taking the product of amps times volts. [Energy is watt-hours (Wh); A battery's available Wh is just the product of its Ah and voltage. For example, a 100Ah 12V battery has a capacity of 1200Wh, of which about 60% is available before recharging.] 
• Sound level. If you're at a remote site, chances are you'll have people camped nearby. Running a loud generator could get you booted out.
• AC regulation. Is the ouput voltage well regulated, and is it in the form of a relatively noise-free sine wave? This is difficult information to come by.
• Available low-energy modes. Does it reduce fuel consumption and sound level if the demand is small?
• Subjective things like ease of use, noise level, fuel consumption, reliability, etc. Generally the more you pay the more you get in terms of these.

What kind of power will we need? Configuration 1 (CCD, guided large telescope) required 6A. At 12V this is only about 72W. Peak amps is about twice that and demands 150W. Configuration 2 has an even smaller demand (130W peak).

The smallest generators have about 800W peak power and a price point around $300. The PortaSource IG800W ($313) has marginal amps; the Generac ix800 ($287) gets mediocre reviews and a lot of 1-star votes on Amazon.

Medium-capacity generators have around 1600 to 2000W running power and twice the amperage that I require. Prices range from $400 to $600, although some brands can demand about $1000. It's not clear that the added cost is worth it. These generally weigh 50 pounds or more.

In this class I think the Wen 56200i ($429) fits my needs best .

Generators with greater capacity are not needed for imaging, but can also serve as emergency generators. I'm not going to consider them. 

Generators to recharge batteries

It may make some sense to get a small generator and then use it to recharge a battery. because the recharge takes place during daytime noise is relatively unimportant. What matters is the amperage of the charger, since that will be "restocking" the Ah lost overnight. Because some chargers operate at lower amps than your imaging use, you may be able to get by with a generator that doesn't meet specs as the primary power supply.

The required charging time will be the number of hours you imaged  times the amps used while imaging divided by the charger's charging amps.

Example: Imaging at 6A for four hours and using a 1.1A charger. The recharge time is 4h x 6A / 1.1A, or almost 22h. The most you would probably recharge for would be 12h, so you could recover only 13Ah of the 24 you used the night before. Not practical.

Now imagine imaging at 2.9A for four hours and the 1.1A charger. Recharge time is now 4h x 2.9A / 1.1A, or  10.5h. That's actually doable.

I've used a relatively slow charger in this example. A 3.5A charger would cut these times by 2/3 , to 7 and 3.5 hours. A 50Ah battery and 800W generator could make a nice tandem.

Generators to Augment Batteries

Okay, why not power things from both a battery and small generator, thereby easing the power demands on both, then using daytime to top off the battery? Let's see some examples.

Let's consider Configuration 2, small telescope, CCD, guiding, dew prevention: 5.2A. the two big power consumers are the laptop and CCD. Let's let the generator power the laptop and mount (3A), the battery handle the CCD and dew prevention (2.2A). 3A is easily within reach of the small generators, and the nightly Ah drawn from the battery is 8.8Ah. Recharge time is 8 hours. Suppose it's fall and you can image for 6 hours; you'll pull 13.2 Ah out of the battery and need 12 hours to put it back. The generator will run a lot--18 hours a day.

The downside is that nighttime running of the generator brings noise back into consideration. And you'll be running the generator quite a bit--both during imaging and the daytime. It's an interesting approach to powering your gear, but I think either battery or generator is better than a hybrid solution.

The Lust for Power, Part 2

In Part 1 I looked at the power requirement of my gear with the purpose of seeing how I might replace my aging deep-cycle batteries. The required amps for several configurations can now be given. The Ah requirement for hour hours a night for four nights is given in parentheses.

1. C 9.25 on guided CGEM, CCD, dew prevention: 6.0A
2. AT65 on guided CGEM, CCD, dew prevention: 5.2A
3. AT65, guided GGEM, DSLR, dew prevention: 3.4A
4. Camera lens on DSLR, unguided CGEM, dew prevention:  0.9A

Don't worry if the numbers don't exactly map with the empirical values given in Part 1--I'm usually rounding up here. What are our power supply options for these configurations?

Commercial Portable power packs

Most of commercially produced power packs are based on 17Ah batteries. Examples are the Celestron PowerTank 17 ($122) and Orion Dynamo Pro ($145). When brand new, these may be capable of delivering 80% of that 17Ah. That's 13.6Ah. As time goes on you'll see that decrease depending on the number of times you cycle the battery and how well you maintain it. A battery pack like this is sufficient for 14 hours of Configuration 4 and marginal for one night of Configuration 3. It doesn't meet the 16-hour requirement for either case without one or more recharges.

Generally speaking power units like these are wildly overpriced--unless you put a high premium on bells and whistles like radios, spotlights, and DC outlets at other voltages. You're get much better economy if you buy a larger battery and charger. For example, a 35Ah sealed AGM battery and charger cost around $100.

Some power supplies (Duracell, Black and Decker, etc.) are more focused on cranking power and include inverters so you can run your gear as if you had a AC outlet at hand. An inverter sounds nice, but it will eat up a small portion of whatever power you need to supply; a battery build for starting cars is quite different from your need (prolonged low current for many hours).

Recommendation: Don't buy any power supply that includes car starting in its list of features--unless the low Ah rating it provides is all you need. Even in that case, you're better off to simply invest in a battery and charger.

Batteries

For lowest cost you can use flooded (also known as wet) lead-acid batteries. These have caps on top for adding water and venting gas during charging. While less expensive than other battery types they have several downsides. The acid can spill or leak out and damage equipment or even cause personal injury. For this reason wet batteries have to be kept upright at all times.

While charging hydrogen gas can accumulate and cause an explosion.

Fortunately there are sealed lead-acid batteries that are spill proof and can be used in any orientation. Those that employ Absorbed Glass Mat (AGM) technology and its variations also have better deep-cycle characteristics than flooded batteries. Other advantages of sealed batteries are that they can be shipped without worries about acid spills and the need for the user to initially add the acid, and that they're maintenance-free (aside from recharging).

(Important note: You can't use a flooded battery charger on an AGM battery unless that charger specifically has an AGM capability.)

The battery size you need will be determined by your gear and the type of battery. I think the only practical type of battery to consider is AGM; other technologies (mainly lithium ion) tend to be more expensive. If you take care of your battery (keep it charged, avoid thermal extremes and physical abuse) and use it infrequently (a dozen times a year, maybe?) it will provide years of 
reliable ability to deliver between 50 and 80 percent of its Ah rating. I'll apply the 60% rate in what follows in order to be conservative.

Configuration 1 (large scope and CCD): 6A x 6h is 96Ah. This is 70% of a 160Ah battery. A single battery with that capacity weighs over 100 pounds and costs $300 or more. This doesn't fit my definition of portable power.

Two 80AH batteries would be a somewhat better solution because although being higher in cost they're a bit more portable--each is about 50 pounds. I've imaged this way, but I don't enjoy lugging the batteries around, and consider it a marginal solution in this case.

Configuration 2 (small scope and CCD)

This needs a battery with about 140Ah capacity. This is also met by a single heavy, expensive battery. The same two-battery solution works here as in Configuration 1, so we're again stuck with the non-optimal use of very heavy batteries.

Configuration 3 (short lens or scope, guiding, dew and DSLR)

This needs a 90Ah battery. Two 50Ah batteries would provide more than enough power and cost about $180. Total weight would be around 70 pounds.

Configuration 4 (short lens and DSLR)

This is clearly a case where a battery is the best solution, requiring only a 24Ah battery. It can't be much easier.

The last two configurations clearly can use batteries to meet the requirements. But what about the first two? You can either lug big batteries around or find an alternative: A generator. That's for Part 3.

Imaging Planet X: Is It Possible?

The news is that there may be a ninth planet. It's being called "Planet X" for historical reasons, with the X designating "unknown" rather than the number 10. It gets a planet designation because even though this inferred object probably resembles a trans-Neptunian object it's thought to be be bigger than Earth.  (Please don't confuse it with the utterly fictional "Planet X" known to some as Nibiru.)

The ex-planet Pluto is easy to image as are many of the other dwarf planets; what about this new denizen?

Factors that dictate a planet's total brightness (as opposed to its surface brightness) are its distance from the Sun and from us, its average albedo, its size, and its phase. In the case of these distant objects phase is essentially always full and can be ignored; likewise the 2 AU annual change in the distance from Earth is neglected. To keep this simple I'll make a comparison between X and Pluto to estimate the former's relative brightness and magnitude.

Lets's start with some simplifying assumptions and say that X and Pluto have the same albedo and that X lacks a moon that contributes significantly to its brightness. (Charon represents about 1/5 of the Plutonian system brightness--if Pluto were to become invisible Charon would be easily imaged!)

So what are the speculated physical characteristics of X?

Size: Larger than Earth, smaller than Neptune. If it's simply a scaled up version of Pluto with 4500 times the mass, it should be about 16 times the size of Pluto. this puts it about 2.8 times the size of Earth and about 73% the size of Neptune. Close enough. This gives X a reflecting cross section about 256 times that of Pluto; we'll knock that down to 200 to account for its assumed lack of a bright moon.

Orbit: There's a lot of uncertainty here; the suggestion is that as X's orbit caries it between 200 to 1200 AU from the Sun. Unfortunately no one knows it's present distance, so we'll make estimates for both the extremes. At present Pluto's distance to the Sun is about 33 AU and it's magnitude 14.2. The distance factors are (33/200) to the fourth power and (33/1200) to the fourth power for perihelion and aphelion, respectively, using the assumption that X will resemble a point source such as a star.

Perihelion: 0.148 the brightness of Pluto, giving it a magnitude of about 16.3. This is easily within the range of amateur imaging.

Aphelion:  0.000114 the brightness of Pluto, with a magnitude of about 24.1. This is probably beyond amateurs. The deepest stars I've ever imaged are near magnitude 20; X would require a total exposure time about 40 times greater than that for a 20th magnitude star to image at its most distant point.

That perihelion magnitude is encouraging, but there are complications. Not much is known about X's orbit, so even if X is near perihelion we don't know were to look for it. Given that its orbit is probably fairly eccentric it will usually be found closer to aphelion, and therefore is usually very, very dim. And don't even think about waiting for the next perihelion, the orbital period is many times a human lifetime.

My recommendation is to leave X to the professional deep sky surveys. On the other hand, if you're feeling really lucky and have a whole lot of time, you could be the next Clyde Tombaugh.


------------------

It's been a miserably cloudy winter here. I've had only one night out to image, and that was to try to catch Barnard's Loop. Overhead power lines and a neighbor's lights really degraded the image.

Barnard's Loop (in hydrogen alpha)

 As you can see, above and left of center there are diagonal artifacts thanks to the power lines and at lower right, air traffic. Too much signal was lost trying to reject the obstructions. If the weather improves I might get another chance this winter.

I'm Still Learning How to Process Images

One of my friends is getting back into imaging after a few years doing other things during which he forgot a lot about processing. To help him get back up to speed I've been building a rather terse guide to processing.

I know, I know. It seems like every imager eventually ends up putting together a tutorial or guide. It's not like I'm a keeper of the Secrets of Imaging. I'm stretching credulity to call myself an intermediate skill level imager; it's a joke to use my name and APOD in the same sentence. You get the idea.

There's nothing like writing things down to demystify them and perhaps once and for all learn them. I started by outlining my usual slap-dash processing workflow, and now I'm improving it with some better processing methods and tools I've found roaming the web. This is a proverbial work in progress, so it will grow in time. So far I've only worked on one-shot color and RGB three-channel imaging, but I hope to add some LRGB information shortly.

To give you a look at what some simple processing can do for an image, compare this image of M51 processed in April with an improved version making use of a few of the things I've learned.

Left, as processed in April. Right, with a few improvements

Lots of excuses: The data here are poor, there were only dark and bias frames for calibration, the telescope was very badly collimated. The left image gives you an idea of where I was at only six months ago--it was the best I could do. The right image employs a synthetic flat created by applying median filtering, Gaussian blurring, and masks in Photoshop CS5. Also applied is a high-pass filter, but it doesn't add much because I had already mucked up the image with an Unsharp Mask. Lastly, flatting out that icky background has allowed me bring out the colors that had been hidden. That was done with curves in lab mode.

It's far from perfect--that strange magenta star to the left of the galaxy vexes me--but it's a light year or two better than it was.

---

What I lack in processing skills I counter with determination: I've finally bested the Astronomical League's Bright Nebula Observing Program (imaging option) and have been awarded certificate #9 (advanced). I ended up imaging 103 objects. Some of those images are going to get reprocessed in light of my improving skills.

Moonlight Imaging (broadband version)

Two months ago I wrote about how one could narrowband image under moonlight. Actually, you don't have to use narrowband filters to image with a full moon in the sky. But you do need to choose your targets with a thought to where the moon is. And it helps to have a haze-free sky that's otherwise fairly dark--yellow zone at least.

Here was the situation the night of the 26th: One night before the "supermoon" total lunar eclipse. The moon's magnitude was a brilliant -12.6 and at meridian crossing reached an altitude of about
42 degrees here in Minneapolis:

The Moon on the night of 9/26/15 at meridian crossing

This shows the part of the sky with an altitude of over 30 degrees. It's not going to be good imaging in Pegasus, but going further north things get better. Polaris is about 48 degrees from the moon, and if we can find something between that and the northern horizon it might be worth a shot.

So I chose objects that were on the northern side of the zenith well away from the moon and close enough to the celestial pole that they'd be available all night. And I imaged from a darker site than my backyard in the inner red zone. Here's how it turned out:

NGC 2276 (Arp 25) and NGC 2300 (Arp 114)

NGC 0040

Not too bad, really. I imaged at f/10 because these are small targets and partly in the hopes it would help contrast. The galaxies were imaged in the time before midnight and the planetary after followed by dark frames. As it ended up I was out there until after 4 A.M., but a clear night is not exactly a common event this year and I wanted to take full advantage of it.

Note that exposure times were kept short because of the moonlight. Unbinned luminance frames were only 180s and 2x2 binned RGB frames were a brief 90 seconds. As it was I got about two hour total exposure time for each image.

After three hours of sleep I went home the next day, to bed at 7 P.M. and slept right through the lunar eclipse. Imaging has a  price!

When To Go Off-List

It's possible to get caught up in an observing list and work on it to the exclusion of everything else. That's pretty much what I did while working on the Bright Nebula list, particularly when I got to the point of having a dozen or so items to go. Everything was dedicated to completing the list to the point that it dictated what gear would be used at star parties and how my time would be spent.

Perhaps a saner approach is to slow down and mix in non-list items for imaging along the way. That's what I did the other night, and it worked out well.

Lately I've been traveling to a friend's home north of the Twin Cities and we've been observing and imaging together. His sky (suburban-rural transition) is much darker than mine (inner red zone urban) and his gear is definitely better than mine and mounted in an observatory. I set up just as if I'm at a star party, polar align, and get to imaging. Then I'm free to help him while he works on reacquainting himself with the process of imaging--he's been inactive for several years--or hunts down deep sky objects with his 16" go-to Dob. It's the best of both worlds for me to have the benefit of his sky and telescope.

And just as at any star party, it's nice to have someone else around to talk to.

Plus at 4 A.M., I have a nice soft sofa to crash on instead of a tent!

Last Sunday was my latest trip to his place for imaging, and we succeeded in getting his imaging system working for the most part. His autoguiding wasn't working, but he's implemented a fix for next time based on what I use.

I had no specific plans for the evening other than imaging Arp galaxies for that Astronomical League list and maybe during the A.M. of switching to a planetary. My friend had his own list of favorites he was eager to observe using his big Dob and we looked at some of those. About the time I was wrapping up with my second Arp he mentioned NGC 891 and showed my his first light frame. In case you don't know 891, it's a large edge-on galaxy in Andromeda. It's cut in half by a dark dust lane dotted with bright knots and has a rather large and distinct nuclear bulge. In other words, it's pretty.

To some extent imaging is all about pretty, and after all the "bright nebula" imaging in monochrome I decided I wanted to make an image in color. My friend's suggestion of 891 is all I needed to drop my list plans for the rest of the evening and try to make something pretty. Here's the result:

NGC 891

(Details here at Astrobin.) Not a perfect image, but I'm happy with it, and glad I opted to give it a try instead of doing more list imaging!

The early imaging was mundane Luminance only. The target galaxies were so small that color was basically a waste of time. Here's what I mean:

NGC 7550 (Arp 99, Hickson 93)

NGC 7578 (Arp 170, Hickson 94; Note the plate solving error)

These two bring my Arp count up to 12 compared to my planetary at 13. I'll probably add a couple more monochrome Arps next time out to make the lists even in terms of percent completed and then go off-list again!