Saturday, December 16, 2017

Andromeda Galaxy

Messier 31, the Andromeda Galaxy
Click here for full size.

Exposure: 18x90+8x45+8x20+8x10@ISO1600
Telescope: AT72EDII
FF/Reducer:  ATR8 (f/4.8)
Mount: Vixen Super Polaris
Camera: Canon EOS Rebel T3
Processing: Deep Sky Stacker, Photoshop CS6

As I've noted before, sometimes imaging sessions don't work out as planned. Technical problems, the limitations of the equipment, and sometimes just plain incompetence cause problems that create useless or sub-par data.

I had one of those cases a few nights ago.

My intended target was Messier 31, the Andromeda Galaxy. It was a little east of zenith when I started. As usual, my imaging time was short. That, and the fact that I cannot perform a reliable meridian flip with my rig (and I don't have software that can fix the image rotation), led me to decide to attempt to point the scope for imaging on the western half of the sky.

The scope barely cleared the side of the mount.

My first test image had some star trailing, but I assumed that it was the normal periodic error. Alignment seemed to have gone well, so I had no reason to suspect any problems.

The next several images had star trailing, too. Maybe it's the balance in this position, I thought. No problem, I tested the balance when it's pointed further west, so it will eventually settle itself out.

But the images never improved.

Time was running out. I decided that the best way to salvage the session was to shorten the exposure time. That yielded enough usable subs to produce the image above.

Still, I think it is my best image of the Andromeda Galaxy, yet. Did I mention that I'm really impressed with this little scope?

Saturday, December 9, 2017

First Light - AT72EDII

Wow! This little scope is a major step up from the ST80.

There is a lot that I want to cover in this post, so bear with me, please. If you're just here for the pictures, then skip down a bit.

The AT72EDII is an air-spaced doublet refractor with an FPL-53 element. The lenses are made by Ohara. The FPL-53 lens makes a huge difference in correcting chromatic aberration, rendering sharper images with much more realistic colors--closer in hue to those that I have gotten from the Epsilon-200. In comparison, I thought the colors I was getting from the ST80 were somewhat "cartoonish," even with the Baader Contrast Booster.

Here is the rig as it was on the night of first light. Using a little of my redneck engineering skills, I cobbled together a viewfinder mount out of plywood and plastic.

A new telescope calls for a new focusing mask, right?  Using the astrojargon Bahtinov Focusing Mask Generator, I printed the mask on card stock, then mounted it to a cap made of more card stock, peel-and-stick foam, and duct tape. It fits over the end of the dew shield.

Yes, I used duct tape.
So, after getting everything put together, the mount aligned, and the focusing mask in place, I pointed the scope at Deneb to set the focus. There wasn't a lot of interest to see during the focusing process, but when I took a 30 second exposure with the mask still on, I got this:

Diffraction spikes on Deneb. Aside from being reduced in size, this is an unprocessed image.
Note the lack of spurious color as compared to these images from the ST80:

I knew that I was in for a treat! So, I took off the mask and made a single, 30-second exposure of Deneb:

Unprocessed, resized image.
Yes, there is a bit of a halo around Deneb, at center, but it is far less prominent (and less purple) than similar images that I've taken with the ST80.

I wanted to image the Double Cluster in Perseus, first, but it wasn't in a good position for the mount when I started. So, I decided to grab a few images of Messier 45, the Pleiades, until the Double Cluster was a little higher in the sky.

Messier 45, the Pleiades
Click here for full size

Exposure: 10x180@ISO1600
Telescope: AT72EDII
FF/Reducer:  ATR8 (f/4.8)
Mount: Vixen Super Polaris
Camera: Canon EOS Rebel T3
Processing: Deep Sky Stacker, Photoshop CS6

This is a close-up (full-size) of a portion of the nebula:

Click here for full size

I admit that, at a quick glance, there isn't a lot of difference between this image and what I think is my best image of the Pleiades made with the ST80. A close look, though, will reveal that the new image has more detail and better color balance. In addition, it took A LOT of processing work to make the older image look like that--there were a lot of problems that had to be dealt with. Frankly, I wouldn't have posted a close-up of the older image. It just didn't look this good at full size!

The Double Cluster finally got high enough to image, but the Moon was only about an hour away from rising. Working quickly, I settled on a relatively short exposure time. Very little processing was required for this image:

NGC 869 (left) and NGC 884
Click here for full size

Exposure: 20x90@ISO1600
Telescope: AT72EDII
FF/Reducer:  ATR8 (f/4.8)
Mount: Vixen Super Polaris
Camera: Canon EOS Rebel T3
Processing: Deep Sky Stacker, Photoshop CS6

Cluster NGC 869 contains an asterism that I call Perseus Man. Some call it The Cowboy.

Now, for the negatives.

The scope is difficult to balance on the declination axis on the Vixen Super Polaris. Judging by the subs that I got, this is probably not a big issue. After all, the mount only has a right ascension motor, and I'm not autoguiding.

The only troubling issue has to do with the ATR8 field flattener/focal reducer. It was advertised as providing "images that are sharply focused out to the very corners of a large format DSLR chip." Although much better than the ST80 (with no flattener), the images still have distorted stars out toward the edges, as seen in this full-size clip from the Deneb image, above:

I'm not certain of the cause. I wonder if I didn't install the T-ring correctly. It's also possible that the flattener doesn't perform quite as advertised. I will do some investigation and testing.

Other than that, I am very pleased with the results. With the winter constellations coming up, there are a lot of targets to image. So what's next? Sword of Orion? Horsehead and Flame? Monkey Head? M35? Dare I try the Flaming Star or the Christmas Tree? I think a return to the X Bar Ranch is in order.

Wednesday, December 6, 2017

The New Scope is Here!

That was amazingly fast! Free ground shipping via FedEx from Astronomics in Oklahoma, and the scope was outside my door in Texas the next day!

Below are some preview pics:

The scope features a metal dust cap (not shown) and machined tube rings attached to a dovetail bar. Note the nifty dust cover over the dual-speed focuser control.

The image above shows the ATR8 focal reducer/field flattener installed. The compression ring on the focuser tube holds it in place very nicely. My Canon T-ring adapter (not shown) attaches to the back of the ATR8 via an included adapter.

The anti-reflective coatings on the lenses appear to be doing their job. There is very little reflection visible compared to the ST80.

Overall, it's a very solid-feeling scope. The focuser is very smooth, and I didn't detect any flexure.

I plan on making a Bahtinov mask for it tonight, and will probably try to figure out a way to attach a view finder tomorrow.

Now, if only the clouds will go away...

Sunday, December 3, 2017

I Made a Decision

In the previous post I expressed my frustration with not finding time and energy for astronomy. Work and household chores have taken it out of me, but I have decided that I am going to make a greater effort to keep on going. It won't be easy, and I don't expect to be out there observing and imaging like I was during the Golden Age of 2009/2010.

Still, there is new incentive...

...on the way... the mail...

...coming to my house.

Yes, I bought a new telescope! It's nothing fancy, but it is a full step up from my current primary imaging scope, the Orion ShortTube 80.

The new scope is an Astro-Tech AT72EDII. It has a 72mm aperture and 430mm focal length, which gives it a focal ratio of f/6 (slower than my ST80, which is f/5). The objective is an air-spaced doublet made with Ohara glass, with an FPL-53 lens to reduce false color (from chromatic aberration). It has a dual-speed rack-and-pinion focuser and a built-in camera angle adjuster.

I also ordered an Astro-Tech ATR8 focal reducer/field flattener. This reduces the focal ratio of the scope from f/6 to f/4.8. The field of view is also increased, which will be great for some of those large targets that I like to image.

Speaking of targets, I now have an excuse to re-image everything that I have imaged before! It's a case where everything old is new again. I am looking forward to this because now I can apply my new image processing skills to (hopefully) much-improved images.

The next big purchase will be a new mount. The Vixen Super Polaris is adequate for now. It produces good 3-minute subs consistently. Longer exposures tend to overexpose in my light polluted sky, so a CCD camera will be the next big item after the mount.

But these purchases are still a long way off. I have a great deal of difficulty buying things that don't have a practical purpose of some kind. It's not that I'm cheap, but there are tons of better things that the money can go toward. For example, I don't mind spending a good chunk of change on a good computer. But, on the other hand...I need a break. I need something fun to do. All work and no play is driving has driven me out of my mind. So, I'm going to make a better effort to do some fun stuff--and not just astronomy.

Anyway, the new scope will be here soon, and I've already lined up my first few targets!