Stupid Imaging Trick #2

I'm impatient. When it comes to imaging, I want as much time with the shutter open that I can get. My setup, currently a cement pier, allows me to polar align my mount one night and leave it in place so long as good weather holds. Normally I polar align and also do a two-star alignment as well. When I'm done I return the mount to its "home" position and power it down.

The trick comes into play when I start up the next night. Instead of repeating the two-star alignment, I simply go to the alignment star nearest to my imaging target. For example, the last week that has meant Mizar, which a short distance from M101. Normally Mizar shows up somewhere in the finder scope's field of view. I then sync the mount to it with a little slewing. Then using go-to I move to M101, and it's right in the center of my CCD's field of view.

This doesn't produce a huge time saving, but syncing is faster than slewing to several stars. Every saved minute is a minute sooner you're able to pack up and go to bed!

Narrowband Imaging V: Image Processing

There's not much I can write here that hasn't been written better by others with vastly more experience than I have. Here are a few observations:

• Calibration, aligning and stacking of the collected light frames is important, but the processing that follows is where the art enters in. Most software packages dedicated to astrophotography will do the calibrations, alignment and stacking in an automated fashion. All you need to do is set a few preferences and wait.
• Whatever software you use for postprocessing, try to become familiar with its many features.
• Experimentation is good. Try to jot down the steps you take when in the final stages of postprocessing. This will help you replicate your methodology.
• Don't delete your original images.  As you learn more you may wish to reprocess them.
• These are your images.  You're the ultimate audience, and the only person you're trying to please.

When posting images for others to view:

• Don't post large full-scale images to forums. Reduce your images to a maximum dimension of about 800 pixels. Provide a link to a full-scale image housed on a web-based photo service if you want to people to see it. 
• When posting .jpg images, don't overdo the compression.  Overcompressing produces distracting artifacts, particularly around stars.
• Placing copyright text on an image is basically a waste of time. The only way to prevent people from using your images without your permission is to not post them. (This is a personal thing with me; I think copyright notices look pretentious.)

Speaking of matters of personal taste; here are some of mine:

• I don't like backgrounds that are absolutely black; a dark neutral gray is perfectly fine and more realistic.
• Stretching an image is easy to overdo and can cause hard edges on nebulae. I usually prefer a softer-looking image that is a bit understretched.
• If you want diffraction spikes on your stars, don't use software to create them. Get a telescope with a spider-supported secondary, or create a mask that holds fine threads across the optical path.  Better yet, learn to like images without spikes. 
• Don't overdo filtering. Unsharp masks and other sharpening algorithms can introduce artifacts that detract from image quality. Toggle between before and after to watch what an enhancement does to nebular texture. If it introduces features that are barely there in the "before" image weaken the enhancement.

Whining about the Weather

Ah, Minnesota in Winter. Some things that make observing during Winter special:

• Looking through an eyepiece only to have your eye begin to tear. That water sloshing around on your eye hardly helps you see clearly.  Usually it leads to frost on the eyepiece lens, and sometimes the joy of having a drop fall onto your eyepiece lens and freeze solid. Heaven help you if your eye bumps into an eyepiece that's at a temperature of -6° F.
• Snow amplifies sky brighness. Even dark-sky friendly lights can turn against you when their light bounces upward off the white stuff.
• Cold fingers. Which are marginally better than fingers coated with plastic-dissolving DEET needed to fend off mosquitoes.
• Cold feet. They say that the way to keep the extremeties warm is to keep the torso toasty. There's a limit to how many layers one can wear and still have use of one's arms and legs.
• Stiff mounts. The pasty goop that's used to lubricate most mounts can get very grippy in the cold, making drive motors labor duing slews. And they can get noisy too. I had a mount that whined when the temperature fell below zero. (Much like myself.)
• Feeble hand control displays. Some of these can become almost useless as the cold increases the display latency.
• Dead batteries.  Most batteries don't like being used in very cold temperatures, and give up the ghost far sooner than you might expect.
• Deep snow. Planting a tripod or work table in the deep snow can be difficult.
• The neighbors' backyard lit Christmas decorations. Not to wax humbuggy, but really, twinking lights seem much less festive when you're trying to hunt down something that's at the limits of your telescope and observing skills, your eyes are full of tears, your fingers are stiff with cold and the mount is screeching in your ears.  Just keep telling yourself, "Astronomy is a fun hobby."

So what to do, curl up next to the furnace until March?  Aside from earning the derision of the good folks up in Canada, sitting indoors will make you miss the splendor of the Winter sky. Get yourself some hand warmers for your hands and the hand controller. Get some really good winter wear. It's OK if you look like an escaped balloon from a Thanksgiving day parade so long as you're warm. Regrease your mount.

DO NOT use your .22 rifle to shoot out the neighbors' lights. That's both illegal and ineffective, as anyone who has ever watched How the Grinch Stole Christmas knows. (The cartoon version, of course.)

Best advice: Move someplace else. The worst thing about winter in Minnesota isn't the cold, it's the clouds. Take a look at this from the excellent web site ClimateStations.com:

This shows the percent of time the sky isn't clear enough for looking through anything better than "sucker holes," breaks in the clouds that optimists take as a sign that the sky is clearing.  During those long winter nights we generally spend more than half our time under cloud cover. What fun!

OK, enough whining.  The next clear night I'll be in the back yard humming something from the Grinch. Why just humming? Because my face will be frozen.