Even More Astrophotography

Everything what was described in previous tutorial should work on Windows as well. Fiji uses Java and works everywhere as advertised and GIMP installer for Windows certainly exists. How to install plugin registry on Windows I really do not know, Google is your friend.

We can go downloading and processing FITS files from many places beside mentioned LCOGT we can use Hubble data from http://hla.stsci.edu/hlaview.html or maybe data from Misti Mountain Observatory http://www.mistisoftware.com/astronomy/index_fits.htm to name few.

All that is nice, but real fun begins when we capture own data using our own camera.

Taking pictures without tracking

Any kind of camera, any kind of lens, capable of delivering sharp pictures will do. There is another inexpensive piece of equipment which is a must - tripod. I am using old Sony A290 DSLR with SAL75300 telephoto lens.
Now we go out place tripod and put camera on it. Select manual mode, adjust ISO to 800, maybe 1600 and exposure long as possible bat not too long to avoid star trailing. Shorter focal length will allow longer exposures. How long exposure can be? That depends on many things, your position on the globe, declination of target and so on. With 75mm focal length on DSLR what corresponds to 112.5mm on 35mm SLR I am happy with 4 to 5 seconds of exposure in Johannesburg, South Africa. If 50mm lens is available I would go for 6 to 8 seconds exposure. So, select exposure, go into drive mode select three or five shots burst, aim and fire.
If you are going to use some stacking software like Deep Sky Stacker you can take RAW and JPEG picture simultaneously. Deep Sky Stacker will not work on Linux and you will have to run Windows inside virtual machine to use it.
When you have few nice snapshots of for example Milky Way you can go back to computer and stack them using GIMP. We will describe stacking in the last part of article.

Manual tracking

Soon as you stack few snapshots appetite will start growing. Going for hundred snapshots is not way forward. Way forward is to increase exposure time. If you do not have $$$$ to spend on real telescope with computerised equatorial mount, you need to look for cost-effective solution. For example to build barn door tracker or you may just have cheap telescope with equatorial mount which is only good for taking Moon snapshots. Cheap telescopes are coming with poor quality equatorial mounts which are very shaky. Now worst thing which you may attempt is spending money to stabilise cheap mount. Attach weight to its tripod, few rounds of rope around legs to tighten it and that’s it. Doesn’t look nice but does job.

Placing camera on telescope could be done using proper piggyback mount or you can made one. I am using ordinary wire ties tightened between camera and quick release head. Don’t go too sloppy you may destroy camera in that way.
Placing eyepiece with higher magnification in and locating bright star close to edge of viewing field you are ready to go. My camera goes up to 30 seconds and after that BULB, for BULB I need remote, so 30 seconds is what I am aiming for. How long exposure can be? It depends of equatorial mount setup, with quick alignment you should be able to pool one minute. Tolerance for your tracking errors is again function of focal length, 300mm is likely just waste of time with maybe one  good frame out dozen.

Stacking frames in GIMP

I uploaded four re-sized frames of area around M 8 if you want to practice before you take own snapshots. Here are links:

https://docs.google.com/open?id=0B0cIChfVrJ7WbkJtZjg3LWlGbXM
https://docs.google.com/open?id=0B0cIChfVrJ7WSWF1LUZ5UnBVRTg
https://docs.google.com/open?id=0B0cIChfVrJ7WMzdnRXdmZmJOSDQ
https://docs.google.com/open?id=0B0cIChfVrJ7WNFplbk5kb2ozYUU

We open the first frame and possibly reduce noise, if required, as in previous tutorial.
If you are using my frames, which are re-sized, there is no need for noise reduction or hot pixels removal. Hot pixels removal will remove quite few stars on re-sized image.
Since those are longer exposure captures we will have hot pixels. To eliminate hot pixels we open Filters -> G’MIC -> Enhancement -> Hot pixels filtering and apply it with default values. Now we open as layer next frame, select it in layers and in Filters we Repeat “G’MIC”. Now we set mode from Normal to Screen, zoom to 100% or more and align layers. We repeat the same for remaining frames. At the end we Merge Visible Layers from context menu for layers (right click one) accepting default expand as necessary option. If picture is too bright what would be a case with supplied pictures, we will do contrast stretching. As we add frames we increase level of signal and histogram changes like this:

So, Colors -> Auto -> White Balance and after that Edit -> Fade Levels where we set mode to Multiply. This is what final result should look like:

That would be simple manual stacking of JPEG frames with satisfactory final result. We could also align color levels on this picture but that was not goal of this tutorial.