Back From the 2019 Nebraska Star Party

I was at the 2019 Nebraska Star Party for Sunday through Thursday nights and it could have gone better.

It's been a wet year in Nebraska and that means the usual mosquito herd is larger than normal. The first night, Sunday, there was only a modest breeze that faded around sunset; the herd emerged and immediately zeroed in on me. My bug spray was unable to hold them off and I was forced to retreat to a screened enclosure after obtaining only a polar alignment. No imaging.

Monday night had a partly cloudy hour, but Tuesday through Thursday Nights were all cloudy with episodes of rain. So for me NSP 2019 was a bust. At best I would have gotten one solid night had I been able to endure the biting.

I have a feeling that as the trend of increasing rainfall continues (thank you, global warming) this will be the case more and more often. That means it's time to adapt.

My thought is that if I can work from a screened enclosure I can manage even on those really buggy nights. This means I need an enclosure and a way to control my imaging rig from a distance of maybe 20 feet or so.

At present I control everything using a single USB cable from laptop to imaging rig. According to standards this limits me to about 16 feet between laptop and rig. Subtracting 6 feet for drops to and from the ground and I'm left with about 10 horizontal feet of separation, so I need to extend my USB. This can be done using powered USB repeaters, but that would mean added connections and power lines. the simpler way is to use an Ethernet extender like this:

This passes USB between two boxes via up to 60m of Cat5 or Cat6 Ethernet cable, with only the box on the rig requiring external power. Some serendipity: The required power is 12V DC and uses the same connector I'm already using with my USB hub on the rig. And the on-rig box acts as a powered four-port USB hub. The only drawback is that this is strictly USB 2, so if I add a USB 3 device I'm in trouble. This is available on Amazon for under US$60.

Focusing is not pleasant when you're being bitten, so a motorized focuser is needed. Unfortunately the only motorized focusers for an AT-65EDQ cost close to $1000 when all is said and done. This is a very nice little scope, but I'm not sure I want to spend that kind of money on it. A much less pricey option is a JMI Motofocus, but they have stopped making them for the AT65 and I could find no vendor who has one in stock.

Luckily some years ago I was given an Orion version of the Motofocus. It wasn't designed for the AT-65, but it was close. All I needed to do was add a small piece of aluminum sheet to it and buy a couple of longer bolts.  I made a nice long phone cord so that it can be used over a much greater distance than the coiled handset cord it came with.

The piece of aluminum (silver rectangle in the above image) is epoxied to the Orion-provided mounting bracket to extend it the required distance. The longer screws and small stacks of washers provide the needed offset to keep things square and allow the larger focus knob to rotate freely. Note that there is no clutch on this so while the motor is attached there is no manual focusing. If you need manual, just undo the two outermost screws on the bracket and replace the motor with the AT65's fine focus knob.

The last operation is one I can't really do much about: polar aligning. This will still require standing at the scope and adjusting azimuth and altitude by hand. Nothing is perfect :)


The final adaptation is a freestanding screened area that's large enough for setting up a small table and chair. I went with this one from Coleman:

This is available from multiple vendors for a wide range of prices. The footprint is a spacious 10'x10', so I'll even have room for a little lie-down while imaging. Despite this being floorless, it gets good comments about keeping the bugs out. We shall see. One thing, though--don't imagine that this is adequate as a sun or rain shelter. I purchased mine from Kohls.

So I'm now set for the mosquitoes. Unfortunately there's nothing I can do about clouds and rain, but that's always been the case.

DIY Sky Brightness Meter; Coleman Outdoor Compact Table; Lapdome; First light with Losmandy G11G

I've been tinkering with a microprocessor called an Elegoo Uno processor, and as a part of that I came across something called Phidgets. This is a collection of clever sensors and devices that can be controlled by laptops and mobile devices.

One of the sensors is a light detector. It's capable of measuring light down to 188 microlux, which just happens to match the value you would expect to measure for a nearly perfect dark sky site. That suggests it might be the basis for a night sky brightness measuring device. Fortunately it's built to report visual brightness and not full spectrum which can include a strong IR component.  The Phidget sensor is made up of two sensors; the second is IR and is used to correct the first.

The actual semiconductor sensors sits in a well with beveled sides within a plastic case. Rather than expose this to stray light I placed it in a PVC tube as shown in the picture and diagram below. This shield tube is probably too long, which means I'm blocking out some of the light cone entering the sensor compared to what it was normalized to receive.

Version 1: Long light shield

Version 1: Long Light shield

The length of the version 1 light shield was based on an incorrect calculation. Correcting the error gave a light shield length of 60mm, or about half of the Version 1 length. A few minutes of sawing gets us to Version 2, which is decidedly smaller in appearance:

Version 2 closed

Version 2 open

At this reduced length the shield is not much more than a way to keep the two caps together. In fact, it doesn't act as a shield at all; it's completely outside of the sensor's field of vision.

There are two black objects on top of Version 2. The smaller one is a combination temperature and humidity sensor; the larger is the hub used to communicate with my laptop via USB. The USB connection provides the power needed by the devices.

Thus far only Version 1 has been tested.The conditions were clear sky with a first quarter moon. (The sensor was pointed straight up and did not include the Moon in its field of view.) The reported light value was 2 millilux or about 2000 microlux. Is this a reasonable value?

It now gets a little complicated. First we need to correct for the oversized light shield. This introduces a factor of about 1.67 (a very uncertain value determined from indoor testing) so the measurement is now about 3330 microlux.

The site I was testing at was not Bortle 1, so the natural sky contributed some signal.  Assuming the site was at midpoint of Bortle 4, it was at about 520 microlux.

Next we have to add on the contribution of the first quarter moon, which takes a site from Bortle 1 to Bortle 5. A Bortle 5 sky at m = 19.7 has a value of about 1560 microlux, so the moon adds about 1370 microlux

In other words the sky starts at 520, to which we add 1370 from the moon for a total of about 1900 microlux.

Is 1900 close enough to 3340 to call it worth working on further? Yes, definitely, given the uncertainties in the numbers. If it had blown up or started a fire I'd say that it should be set aside, but this did neither.

I will continue to tinker with it, including rewriting the sample polling program to take time averages and log them. In addition to more local testing I'll also take this to this year's Nebraska Star Party, where the sky is Bortle 1 😃

__________________________

New Stuff:

1) My old field table finally fell apart after 15 years of service and has been replaced with a Coleman Outdoor Compact Table.

It seems sturdy enough and I like the solidity of the aluminum tabletop, but time will tell how well it holds up. So far the only negative I can say about it is the carrying bag; it's several times larger than it needs to be and allows the contents to flop around inside.

2) You know how when you try to make something you get the feeling that it's just not coming together and that you might be wasting your time? That sums up my attempt to make a portable light box for my laptop. I have thrown in the towel and puchased a LapDome. I haven't used this in the field yet, but it looks like it should be a great way to keep laptop light from interfering with visual observers without make the laptop difficult to use.

It seems really well made and should help with dew control, too. I kind of wish that it had side openings for cables in addition to the rear opening; my laptop has only side ports and none at the back.

One improvement I may make is to cut a board to fit the inside bottom to keep the laptop's air intakes happy.

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

Lastly, the same night I was tinkering with the light sensor and watching people try to get first light with the Cherry Grove Observatory Planewave 12.5" CDK I also got some time with my new mount. It worked great! The following image is little more than a simple trial: 14x60s luminance frames and 15 dark frames. First, the full frame, reduced in size. Click to see it at 31% of the original scale:

Obviously an AT-65EDQ doesn't give the best pixel scale for an object like M51.

Here is a crop to the target so you can see it a little better. Click the image to see it full scale.

Not bad for total exposure time of 14 minutes! (Camera = SBIG ST-8300M)

Luminance is nice, but I can't wait to try out the other three Astrodon filters.😀

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.

Happy New Year!

It's been a long time since the last post, mostly because I haven't had much to write about: Let's get right to the excuses:

• It was a terrible year for weather; it seemed as if every imaging opportunity was clouded out
• My transition to computerized imaging that started the winter of 2017-2018 kind of slowed me down
• There was the mini-fiasco of the very late arriving Planewave 12.5" scope for the imaging platform. It didn't arrive until after the Nebraska Star Party and didn't get onto the mount until late August. Basically the delay pushed the timeline back about 6 months
• Unlike a lot of years, this year winter arrived early (November 1) and stayed. There was no pleasant, gradually cooling autumn to image through

So, now that that's out of the way, we can get on to catching up. After such a dismal year what could a person do other than double down on what seems at times to be a frustrating hobby? That's right: I am upgrading things.

A) MOUNT

The old CGEM mount is out, replaced by a Losmandy G11G. In the pantheon of mounts, the CGEM is somewhere around "tier three." The best "lightweight" mounts are made by Astro-Physics (Mach 1GTO) and Software Bisque (MyT).  Both of these price in around six to eight thousand dollars when you add the usual bells and whistles. The G11G doesn't quite deliver the superb performance of these two "tier one" mounts, so I'll call it "tier 2," and it's about $4500 fully loaded. I went for the Gemini II version (that's the second 'G' in G-11G) even though it's not necessary for imaging--it's just nice to have in case I decide to return to visual astronomy.

The G-11G is a major upgrade from the CGEM. Let us count some of the ways:

1. It's solid. Push on the GGEM head and it wiggles a little, whereas the G11G doesn't budge. There is simply no play in it
2. I expect it will track far better than the CGEM. My CGEM had substantial periodic error that I could never really get rid of. The G11G will probably be an order of magnitude better
3. It can connect to my laptop by way of an Ethernet cable, not a funky USB-to-RS 232-to-hand control cable.
4. It's lighter than the CGEM. The head weighs over 10 pounds less and disassembles into two pieces to become even more portable. On the minus side, the field tripod is large and heavy compared to the CGEM's tripod.
5. Its carrying capacity is far greater than the CGEM's. There's no telescope I own or am ever likely to own that will push the G11G to anywhere near its capacity
6. There are more differences, but until I can actually begin using it (2018 crumby weather, see above) I'll not comment on them

B) FILTERS

I'm not going to say that my Baader filters are inadequate, but it's become clear that they do have internal reflection issues. And in the case of the narrowband filters their 7nm bandwidth is not as good at rejecting sky brightness as narrower filters.  So out they go to be replaced by Astrodons. I plan to purchase new LRGB filters. The H-alpha filter is a needed upgrade; but over the years I've hardly used my S-II narrowband filter, so that won't be replaced. I may not even replace the O-III filter. The size filters to get will depend on part (C)...

C) CAMERA

As I write this, my thought is to continue using my SBIG ST-8300. It will be interesting to see if it still functions after a few years of rest! If I stay with it the above filters would all be the 36mm round unmounted type.

This is kind of wide open-I have the option of upgrading my ST-8300 to an STF-8300 or maybe jumping to CMOS. Cooled CMOS monochrome is an intriguing technology, but I kind of feel it isn't quite mature enough yet. If I go that way or get a different CCD it's possible I'll be able to use 31mm filters and save a little money. I have some research to do!

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

I made a rare appearance at last night's monthly club meeting. I was there for two reasons-to take part in the pre-meeting meeting of the Cherry Grove Observatory committee, and to pick up some swag.  I did most of the graphics designs for the ALCON 2018 national meeting and had asked for payment in the form of some items my designs appeared on. One of the club officers was kind enough to bring some to the meeting for me.

I mention this because the planned guest speaker was unable to appear at the meeting and was replaced by a video presentation about climate and climate change. I admit at first I was skeptical of what the presenter's agenda was, but it turned out to be excellent.

The speaker, Dan Britt, is a physical geologist who has studied climate change on geological time scales. While he's rather circumspect about stating his conclusions, he clearly lays out the geological evidence that illustrates how anthropogenic carbon dioxide forcing is the driving force (by far) in contemporary climate change; surface temperature is increasing and the seas are rising in his view.

This is a presentation for a non-technical audience, so don't expect to be challenged by esoteric details of the science involved. But what he says is in perfect accord with my understanding of the science.

Highly recommended: https://www.youtube.com/watch?v=xgNxF2HlN3w

An Imaging Platform is Born

In the spring of 2017 an anonymous donor (hereafter called 'AD') came forward with an offer to fund what was needed to make the Minnesota Astronomical Society's dark sky site at Cherry Grove a high-end imaging site. Basically the AD was volunteering to fund the purchasing of a new imaging platform. The money would come with a few strings:

• The platform would make use of an existing underutilized mount in the observatory. This mount was a Mathis MI-500, a huge mount capable of carrying 180 pounds of imaging gear. The mount is already outfitted with an Astro-Physics GTOCP4 control box and handset.
• The platform must be easy for beginning imagers to use.
• Purchased telescopes must to be able to fit under the roof. The purchase of large refractors like those installed at the club's other two sites was discouraged along with truss-tube scopes.
• A person or people need to be found who will maintain the platform
• Adequate training must be provided for those wishing to use the platform

Existing Facility

Cherry Grove Observatory (CGO) is a large roll-off roof building located in Goodhue county, Minnesota, about 23 miles northwest of Rochester and 20 miles south of Cannon Falls. While it's not a truly dark site (light green zone), it's far darker than the other club observatories. Horizon glow from the metro area of Minneapolis/St. Paul 60 miles to the north can be seen, as is a growing glow of light in the southeast from Rochester.

Cherry Grove. Warming house at left, observatory on right

The Process

The task of choosing gear for the Imaging Platform was passed to the small committee that oversees CGO. None of the committee members are imagers, and they thought it best to form a task force of imagers to make recommendations for what to purchase. That's when I entered the story.

Recruiting task force members went reasonably well for something like this. Some people agreed to help, others said they weren't really qualified or had other obligations. Five volunteers were quickly selected and I was designated the chairperson, probably because I had advanced some ideas for what might be done in an earlier request for help from the CGO committee.

The early going was hindered by a lack of any idea for what the AD was willing to spend. We quickly settled on a two-tier recommendation for what might be possible at around $10K and $20K.

Guiding Thoughts

Beginners will be using it, many with DSLRs but a few with CCDs or newer cooled CMOS cameras. Astrographs for which no flatteners are needed are simple and convenient. Beginners wouldn't have to be concerned about having the correct spacing rings.

What will people want to image? Probably the objects that image well from dark sites: Diffuse and dark nebulae, but not solar system objects. That suggests a telescope with short focal length and fast optics.


Many objects are small. After diffuse nebulae likely targets will be planetary nebulae, globular clusters, and external galaxies. The way to image them is with a longer focal length scope. Since these tend to have higher surface brightness than many diffuse nebulae optical speed is less of an issue.

Beginners will bring a wide variety of learning skills. Some will be happy to learn how to use software to control the mount and camera while others may be reluctant to use more than the mount's hand control. We should try to accommodate as many people as is reasonable.

Given all of these factors we decided to go with a platform that would provide two imaging astrographs in tandem-one short focal length, the other much longer for those tiny planetaries and galaxies.

As we looked over the available scopes it became clear we the low cost option of about $10K was unrealistic. In fact given the cost of all the accessories, shipping and taxes the higher tier of $20K would be inadequate, too! After a talk with the AD it was decided to go with a budget of between $30K and $35K.

At that point we were ready with our recommendation: A Takahashi FSQ-130ED as the short, fast scope and a Planewave 12.5" CDK. Along with the Tak we decided to get the 0.6X focal reducer and 1.6X tele-extender to provide three focal lengths: 390mm, 650mm, and 1040mm.

Current Status

The club's Board signed off on the purchase and we placed our order with Oceanside Telescopes.

The Tak has arrived and is on the mount for testing. So far it's living up to the Tak reputation: Exceptional optics and build quality. It's a great scope!

Takahashi FSQ-130ED on the Mathis mount (to be remounted when the Planewave arrives)

The Planewave is scheduled to arrive in July.

We hope to have the platform fully functional by autumn -- if this year's run of cloudy nights will ever relent!  I'll post images taken using the platform as they are created.

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.