M81/82/NGC 3077 under bright skies

Last week I was in another ALBN gap with nothing but large, very dim targets to image, and a nice bright gibbous moon to ruin any chance of actually doing that.

How about a nice bright Galaxy? Too windy, you say? Then use something short like an AT65. Which is what I did:

NGC 3077 (lower left), M81 and 82--you already know them

I don't think that my skills are up to battling the light. This had a terrible sky gradient that had to be removed. Shooting into sky over a city will do that, I suppose. There were also quite a few satellites that crossed the light frames, also. Do I sound like I'm making excuses?

What I learned is that I'd like to go back and image NGC 3077--it has an interesting core. Longer focal length and darker sky!

This next week is forecast to feature clouds every night. Not just clouds but dribbles of snow and rain, too! Doesn't the sky know I have things to image?

Next Time, adding a finder to an SBIG ST-8300M.

M 31 from the South Dakota Star Party

New dew controller in hand (see last entry) I was ready for the South Dakota Star Party. I had a short list of targets--The Iris Nebula, the Lagoon Nebula, the Heart Nebula. The one chosen would depend on the sky conditions. So much for plans.

Thursday night was partly cloudy with heavy dew and fog. I stayed home. Friday night started with high clouds, but went mostly clear as twilight ended. The view to the Lagoon was full of light from Sioux Falls, which was only about 15 miles away. I decided on the northern sky. I did a bore-sight polar align and tried to start with M 103. I switched over to M31 because I wanted to image something prettier. I got everything set up and running, but the first few frames were bad because the autoguider was losing the guide star in the remaining cirrus. There was a bright star at the edge of the autoguider's FOV, so I used that instead.

I set up the camera control to shoot five lights through each of the LRGB filters and then loop. That was at about 11:30. Amazingly, the system continued to run unattended for almost five hours! Focus held steady all that time, and tracking remained solid on all but one frame.

In the end I had to toss 25 frames because of clouds, one for tracking, and a couple because satellites passed right across M 31. Here's the result

Messiers 31, 32, and 110

Click for a larger version. Visit Astrobin for image details and a full-scale version.

I know the cores are overexposed, and maybe I need to do something about the blue fringing on some of the stars, and maybe I left it all a little dark. But I think I like it. Thank goodness I didn't cut the imaging short to chase after another object.

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. 

Another Year, Another M42

I've imaged good old M42 a couple of times in the past with my DSLR and ST80. This is a more ambitious try, using my ST8300 monochrome CCD and AT72ED:

M42 (click for full size)

What's ambitious is that it's my first serious attempt at an LRGB image where I've given some thought about how to properly combine luminance and color data. This could definitely use a longer integration time--it was only about 15 minutes per channel at f/6, made worse by fairly substantial light pollution.

Notice those spikes coming out of the brighter stars? They're from overhead power lines!

The next clear night I'll try taking some shorter exposures so that I can mask in the overexposed center of the nebula.

Coming shortly will be a report on the Orion 50mm mini-guider. I will be using it for autoguiding on scopes of different focal lengths. It cuts about five pounds off my mount's load by replacing my ST80, which weighs about 6.4 pounds when guiding. This is particularly significant because that 6.4 pounds rides piggyback on my telescopes and has a substantial moment arm.