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!

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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

Correcting the Too-short Celestron Hand Control Cable

One of the perennial, if minor, "what were they thinking" topics in astronomy hardware is the short coiled cable used to connect Celestron hand controls to their mounts. The cable, stiffly coiled like an old phone handset line, is simply too short.

This wasn't so bad on my old CG5 ASGT where the mount head isn't all that large, but on my CGEM it couldn't be ignored. It was possible to have the handset pulled right out of its tripod leg cradle as the scope turned in RA. That's not something you want to see when you're imaging, since it means the coiled cord was torquing the mount and then letting the handset become a free-swinging weight in whatever breeze there might be.

One solution I tried for a while was a coiled extension cable. The added cable was so heavy and droopy that it was awkward to handle and tended to get snagged on the mount. Then I came across a video that shows how to replace the stock cable with one that's more user-friendly.

All you need is

• A piece of flat 6-conductor telephone cable, preferably one with at least one end having an RJ12 connector attached--if not, you'll have to do that yourself. These can be found many places; on Amazon they're typically around $5 to $6.
• A soldering gun and solder (A good, fast-heating gun is much preferable to the old pencil type)
• A wire cutter
• A craft knife for stripping very thin wires
• Heat-shrink wire tubing (I found this on eBay)

Extremely helpful to have is a soldering jig to hold the ends of the wires together as you solder them.

The most important consideration is getting the wire connections correct. In my case the wire colors and order in the cable exactly matched that used by Celestron, so it was easy to get things right. If you get the connections wrong its quite possible you'll ruin your handset.

The filter from the old cable will be reused on your new cable. Aside from that, you can discard the old cable. Or toss it into your pile of stuff you probably should trash but are keeping "just in case" it might be useful someday.

The job takes an hour or so, when you're done you'll have the kind of cable Celestron should have provided in the first place!

Two images from last weekend: M17, M20/21; Processing workflow.

I'm REALLY pleased with how this image of M17 came out:

Messier 17 (Omega or Swan Nebula), click for full size

The previous night's image was not quite as successful--M20 and 21. More about why in the next blog entry.

M20 (Triffid) and M21

Both images are full-frame. For all the gory details of acquisition, look at my gallery on AstroBin. By way of a quick summary, both are LRGB images made with an SBIG ST8300M CCD, TeleVue 102 apo and autoguided CGEM mount under mag 6+ skies. Dark and bias frames only, no flats.

Imaging is SO much faster doing LRGB in the dark than it is to use narrowband filters under light-polluted skies. 

I realize that the colors in the M17 image may look a little muted to you, but I kind of like them this way. What's particularly pleasing about the image from my standpoint is three-fold: The stars are nice and round right out to the edge of the field, meaning that my field flattener is doing its job perfectly; The merging of the LRGB channels seems to be spot-on. And finally, guiding with the Orion mini-guider works great at the 700mm focal length of the TV102 to correct mount errors. I'll eventually try out the mini on my C925.

My processing workflow continues to evolve. These two images were made by ping-ponging back and forth between Images Plus and Photoshop:

• Calibrate, align and stack using IP
• Stretch using PS
• Noise cleanup and star size reduction in IP
• LRGB combine in PS using Annie's Actions
• Color balance in IP
• Masked sharpening in PS

Yes, I know that's a mess, and some will say that all can be done in IP or PS or Maxim or whatever. Good for you if you can function with only one software package, but at this point I can't. I'm using IP 4.5, so probably some of the changes that have gone into later versions would make it a better processing tool. 

DIY Concrete Pier for a medium-sized SCT

What do you need for imaging with a Celestron 9 1/4" SCT operating at f/10 (FL 2350mm)? A mount with very little flex. In my case this works out to a Celestron CGEM mount. For a couple of years* now I've been working toward building a small observatory. I want to put the mount on a pier, and miracle of miracles I have actually gotten this part of the observatory done! Not without a lot of dithering about what sort of pier to install.

If you go to Cloudy Nights you'll see many people giving their ideas of what constitutes an adequate pier for imaging at a modestly long focal length. The largest telescope I anticipated using was a 9" SCT, so I felt much of the advice, though sound, was meant for larger loads. On the other hand, I decided that some suggestions were a little on the light side.

Some ideas I considered and rejected were for a pier made from 4x4" wood beams (possible polar realignment needed as the humidity changes), steel pipe piers (expensive), 10 or 12" concrete piers (overkill), 4-6" concrete piers (too much flex).

That left me with an 8" concrete pier as the ideal compromise. Cheap in cost, and easy to put together--even for me.

Materials:

1. Digging things, such as a hole auger and shovel
2. A little small gravel to line the hole bottom
3. Concrete forms
4. Duct tape
5. 2x4" lumber for holding the form level
6. Bagged Concrete (Quikrete, for example) 
7. Rebar
8. Pier to mount adapter
9. "J" bolts with hardware to match adapter
10. Mixing tub such an old wheelbarrow
11. Garden hoe for mixing concrete
12. Bucket to measure water
13. Water

Now, some lessons learned as applies to each of the above:

(1)
The frost line here is 42" down, so the hole must be at least that deep plus a few inches. Fortunately I had an old post hole manual auger that made digging a snap. It looks like this one, which can still be found for sale various places:

Manual Auger

Mine is actually an antique hand-me-down with a decayed wooden hand bar and several layers of rust on the metal parts, but it sliced into my mix of clay and gravel almost like the proverbial warm knife in butter. The only trouble I had was at 42" depth, where it ran into a larger rock (which now sits on a counter in front of me). The hole was deepened to 45" by using a long-handled shovel.

(2)

You just need enough gravel to put a few inches in the bottom of the hole for drainage. Pack it down with a 2x4".

(3)-(5)

Forms are usually available in 4 foot lengths (mine came from Home Depot). Because the total length of my pier was longer than this, I joined two forms by making a 1 foot long external sleeve and putting it all together with duct tape. The length is critical because the adapter will ride atop the form, which will be filled with cement to just below the top of the form. You need to plan things out so that the distance between the adapter bottom and the top of the cement is about 1.5" or so.

The form should fit nicely into the hole with a little wiggle room around it; level it and shore it up with 2x4"s:

Concrete form in place

Then I filled in the gap around the tube with the extracted dirt.  You can use the rebar to get that dirt packed in, and run some water into it to flush it down. (Don't add water unless you're ready to pour concrete; a wet form can lose its integrity in 24 hours).

(6)

You will need to know how much concrete to have on hand, calculated from the volume of the pier and the bag weight you're willing to handle. I was able to handle 60 pound bags, but smaller bags will spare you a possible blown back. I would suggest rounding up the amount you need by one bag, just in case. 

(7)-(13)

This is the fun part. You want everything ready before beginning, so cut the rebar to the right length (an inch or two shorter than the pier. I used one piece of rebar, centered in the pier, but some will say use three. Whatever your choice, make sure the rebar won't interfere with the J bolts.

You have, of course, already determined North, so that you know the way to orient the adapter!

Put together the pier adapter and J bolts so that the assembly is ready to put into the concrete. I used three 1/2" diameter 8" long J bolts (Home Depot) and the Starizona CGEM adapter. In my case the Adapter's diameter was smaller than that of the form tube, so I used shims to hold it in position and maintain reasonable level:

Pier Adapter in place with shims (after has been cement poured)

Now get your bags of quick-mix concrete, mixing tub, mixing tool, and water supply ready at hand. 

Note: Even if you're not using Quick-set concrete  you shouldn't let much time pass between one batch and the next. You won't take any breaks until you've embedded the adapter in the pier top. 

Dump a bag of concrete into the tub, add the manufacturer's suggested amount of water, and mix thoroughly. The common mistake (I've read) is to make the mix too wet, so try not to be tempted into adding more water. In my case I tried to avoid this error so diligently that I made the mix a little dry, but it seems to have worked out. Shovel the concrete into the form, minding the level.

After adding a second bag of concrete push the rebar into the poured concrete so that it's a the right height. You may need to hammer it to the right depth.  

Continue adding more batches of concrete, making sure your rebar remains centered in the form. You may also want to use a long rod from time to time to remove any trapped air pockets that form. When I made my pier I noticed that these pockets tended to form against the inside of the form.

The last batch of concrete should be large enough to complete the pier. Depending on the size of the shim(s), you will fill the form to about an 1.5" from the top. If needed mix in more concrete mix and water. You may want to make the last batch of concrete a little wet so that the J bolts will embed more completely. Shovel this into the form to the level you want and then push the adapter assembly into it. Make sure you have the adapter oriented to north correctly! Level the adapter and you're done!

Clean up your tools and the work site, then take a break. After 24 hours you can rip the form away. At this point inspect the J bolts to make sure they're solid--no wiggling allowed. If they're not, you have a problem. Post a comment if you do and I'll reply how I fixed this when it happened to me. 

Avoid the temptation to put a load on the adapter for at least several days (two weeks would be even better). If the weather is hot and sunny, moisten  the outside of the concrete from time to time and wrap it in plastic.

After a month you can apply a concrete sealer and paint the pier with an outdoor house paint. I went with white, but if fluorescent green is your thing, go for it.

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*Why a couple of years on the observatory? The winter of 2011-2012 was so mild here that I found I hardly needed an observatory. And I was so busy during the summer and fall of 2012 that my talent of procrastination bloomed fully. Maybe next summer I'll get to it?

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UPDATE, SPRING 2016: Still no observatory. There still seems little need for one; I'm doing more imaging at dark sites as the light pollution, neighbors' absurd "security" lights, and tree blockage all continue to increase. The wood planks on the platform have warped, but the pier continues to serve me well. Factoid: this blog entry is far and away the most viewed of all my posts (which isn't saying much).

Seagull Nebula and Gum 1

Imaging on four hour's sleep is a bad idea.

Take the other night, for example. My targets were the Seagull nebula and Gum 1 (the bird's head). My CGEM misbehaved (probably my fault), I forgot to switch to unbinned after focusing, my makeshift AT72ED mount adapter flexed in the wind. My target and guide star spent almost an hour behind a tree. I shot my dark and bias frames unbinned and had to reshoot them the next day. But it was clear and warm.



Seagull nebula

It's not that good, but it's an image. Details: AT72ED (420 mm FL), ST-8300M at -20C with H alpha narrowband filter. 8 x 10 minutes. 3x3 on-camera binned. ImagesPlus and Photoshop.

I have to get AT72 piggy backed on my guide scope, or do something about firming it up. And I need more sleep.

PEC at last, maybe.

Finally a clear night, maybe. And the end of my head cold, maybe. And an understanding of how to use PEC, maybe. Results to be posted here, maybe.

The results: PEC seemed to work fine, although I have no way at present to objectively confirm that. My setup (AT72ED and autoguiding ST80 side-by-side on the mount) was far out of balance, and I had to up the PHD signal length to 1000 ms. That allowed PHD to correct for the problem, but the results were less than desirable. My target was M44--high cirrus precluded looking at nebular targets--and it was more an exercise in LRGB imaging and processing. Here's the result:

Messier 44

This is a fairly unimpressive cluster, with quite a few blue stars. Normally I don't like diffraction spikes, but they might add some visual interest to the image. (L=20x3min, R=10x3min, G=5x3min, B=10x3min). I spent a lot of time trying to get the color right. I'll probably redo this using the color balance workflow suggested by Ron Wodaski.

Just to give you an idea of what the PEC was trying to deal with, here is the PE for my CGEM:

8-minute cycle of PE, average of 10 runs

That's about 18 arcseconds peak-to-peak.

I've now jury-rigged a couple of dovetails together to get my setup balance, so next time I'll see if I can get things tracking better. Next time promises to be some time off as the weather has moved into a period of instability. *sigh*

Clouds = Time to Plan

It's been cloudy, and that means time for making plans.  I now have my cables in order for doing upgrades to my mounts. It took a few tries, but I now have my CG5-ASGT updated. It can now do all-star polar alignments just like my CGEM. I really like this way of doing polar alignments. It's fast, reasonable accurate, and simple to do.

Next up is the CGEM. I'm going to look at its tracking. The last night it was producing "V"s, a back and forth motion in RA coupled with a motion in DEC (which may  be a drift caused by polar misalignment). I've got to make a "before" chart of mount periodic error, then run PHD and PECTOOL to see what they can do to correct this. It will probably take a couple of clear nights, so no imaging in the immediate future.

Cold Weather Performance

Tonight I'm shooting O-III frames of the NGC 2244 (the Rosette Nebula) to add to those already taken the other night. Tonight will probably be the coldest night we've had so far this winter, which is not really saying much.  The next couple of nights we will probably go below zero for the first time this winter.  It's hard to believe this is Minnesota! Oh, and there's just a trace of snow on the ground. Really strange.

How well does everything run at 9° F (-13° C, the current temperature on our screened porch)?

Happily:

• Gateway Laptop
• ST-8300M (which I'm running at -30° C just to match existing dark frames
• Extension cord from house (it's one of those low temperature cords, highly recommended. (Note added: at 5° F the cord began to stiffen a little, but it was still easy to coil for storage.)
• AT72ED, focuser remains smooth (Note added: at 5° F the focuser became rather resistant to change, as if the lubricant were solidifying or parts were tightening because of differential contraction.)

Less than perfectly, but passable:

• Me
• Cables (all are very stiff)

Not very well:

• SBIG filter wheel.  (reports an error when moving from filter to filter, but gets there okay. I've noticed that temperatures in the teens or lower cause this behavior. Maybe these are built for the weather in Santa Barbara?)
• CGEM mount. It looks like the mount is moving in fits and starts, elongating the stars in right ascension. I can't yet tell if this is periodic motion that can eventually be eradicated. It might well be something else, perhaps caused by the stiffening of lubricant? I tried to change the balance in RA, but that didn't help. Most of my images from the evening have very elongated stars. Maybe I can compensate by using the Ha image as luminosity and red, the OIII as blue and the SII as green?  Time to experiment!

It's perfectly clear tonight, with just the lightest breeze; by the end of imaging at midnight, the temperature had fallen to 5° F (-15° C). The poor CGEM simply couldn't track correctly in RA with the temperature in the single digits F. I'll have to look into this, as winter evenings around here are typically near that range.

Yet Another Accessory; Prelude to PEC

Like most go-to mounts, my CGEM can have its software upgraded. The CGEM also has the ability to compensate for periodic error in its tracking motion. Both of these require that the mount's hand control be connected to a computer. And there's the catch.

For some reason, Celestron refuses to create a cable that goes from hand control to a USB port on a computer. It continues to use a cable that requires the computer to have a serial port. Almost no laptops manufactured now have serial ports. Serial ports disappeared years ago, not long after parallel ports passed into oblivion. So why does Celestron continue to require them? Apparently so that they can overcharge for their branded serial to USB cable, which runs from $39 to $45, depending on the vendor. It's vaguely like what how many big-box stores charge for $60 HDMI cables that can easily be found elsewhere for $3.

In fairness, Celestron does include the hand control to serial port cable with the mount. So there's no need to purchase that half of the link.

Getting serial to USB is up to you. So far as I know any serial to USB cable will work; there's nothing magical about Celestron's model. So it's off to Amazon.com for a  cable that costs only about $11.