Thursday, August 7, 2014

A Mobile Imaging Setup

This is the first summer of my retirement and I'm using it to go to a number of star parties. For the first time I've traveled to the Nebraska Star Party (just south of Valentine, NE), and coming up are the Iowa Star Party (near Coon Rapids, Iowa) and the Northern Nights Star Fest (northwest of Aitkin, MN). All three of these are intended to be imaging trips, and toward that end I've designed my imaging setup to be self-contained, compact, and reliable. I travel in a mid-sized sedan, so there's a natural limit to what I can carry.

The first thing to do is to leave the bells and whistles at home. Keep your gear simple and you'll be rewarded with less hassle when you set up or break down. Remember, if you forget something and no one can lend you a replacement you may be out of luck for the entire party.

What's the least you need? The essentials for imaging: an imaging telescope (including finder), an autoguiding scope (if you autoguide), a mount and tripod, a camera, an autoguider, cables for all these as needed, and batteries to power everything. If you anticipate a chance of dew, a dew prevention system is good to have on hand. Probably you'll need a laptop if you're using a CCD camera.

Oh, and let's not forget a table to put that laptop on. Like a good observing chair, a table is an important part of imaging. I use one much like this. Mine was purchased about 12 years ago from Target for a scant $20, and is one of the best astronomy accessories I've ever found. The roll-up aluminum table top is particularly nice as it's impervious to dew and frost and when you cook food, it doesn't care if you set a hot pan on it. Sadly, my table is reaching the end of its life and some plastic parts are starting to crack. I'm repairing it with J-B Weld as needed, but sooner or later it will need to be replaced.

Batteries will be the heaviest things you'll have to lug around. While it's certainly possible to use your vehicle battery as the sole power source, that's probably not practical for multi-night imaging. Remember that most car batteries are designed for starting your car, not supplying a several amps for many hours. Deep cycle batteries are better for this. You can pay a lot for these or get them at farm and ranch retail stores for far less, as I did.

I use three batteries, which is almost certainly overkill. Two are lead-acid deep cycle marine batteries with a combined capacity of about 140 Amp hours. These power the mount, laptop and camera. The third is a sealed lead battery with about 20 Amp hours that powers my dew strips and can power things like fans. (This battery has the advantage of being easy to recharge.) These batteries can power everything for at least 15 hours, which is a solid three night's worth of imaging on most trips. It's possible they can go longer, but I've never had that much good luck with consecutive clear nights!

[My CGEM mount draws about 1.5 A when tracking, the ST-8300m CCD about 2 A (that's a guess based on its 3 Amp requirement at peak cooling load), and the laptop about 1.8 A (also a guess based on the AC adapter and having a battery that's pretty much gone dead after all these years. That's a total of 4.3A. My two deep cycle batteries should be able to supply that for about 32 hours, or 16 hours if we only take the batteries down to 50%. So my 15 hour estimate above seems reasonable.]

Imaging Setup at the 2014 Nebraska Star Party
The above picture shows how this all looks, minus the "Y" stalked dual finder mount, CCD, and laptop which are all sitting in the shade at this point. The three batteries are sitting on the ground below the mount.

For this trip I took my little refractor, the AT65EDQ. That's the scope I'll take to ISP, but for NNSF the bulkier C9.25 is making the trip.

Regardless of the scope, all of this gear fits quite nicely in my car with room left over for everything I need to set up camp. Best of all, it seems to work quite well!

Friday, August 1, 2014

Two dark-sky images

Just back from the Nebraska Star Party and the smaller party in SW Minnesota.

First, from Minnesota, the Rho Ophiuchi nebula (IC 4604, the blue reflection nebula at top):

At bottom is the emission nebula IC 4603. This is about 1.5 hours of LRGB data. This will need to be reprocessed to get rid of a distracting satellite track. The image above has been reprocessed to get rid of the satellite tracks and improve the color balance.

The first image from NSP is the Iris (NGC 7023, vdB 139) at right in the image,

The small bright nebula at image left is Sh 2-136. About 3.7 hours of data went into this image. I'll probably reprocess this and adjust the color balance a little. It looks a tad too yellow-green to me.

Still awaiting processing are the Cat's Paw nebula, Sh 2-183, and NGC 1333 (vdB 17). For those I binned the color channels 2x2, and I need to shoot some dark frames to match.

More about NSP 2014 in a subsequent post.