Hardware & Software requirements.
This is a short list of what you need to have before you start imaging
- Telescope w/finder, eyepieces, reticle, batteries, small hand light, focusing aids, laptop/pc, camera and adapters for telescope, chair, leveller
- Software for astronomy(sky maps, etc) focusing, remote shooting, stacking and image processing
- Be dressed and prepared accordingly (especially in winter)
Choosing your site, date and time
Probably one of the most important decisions you will have to make is finding the right site at the right time for you to make the most of it.
- First you need to decide on a site with skies as dark as possible. Countryside is always point to look at if it's in your reach. Else you might want to investigate your backyard/garden for the darkest spot. You should keep an eye on the neighbour's lights/habit over time (some people keep their lights on latter at night which might interfere with your plans). Also light pollution from the city varies during the week or night and presumably more commercials, clubs, etc are on in high audience nights such as Saturdays until 2-3am.
- To decide the day and time you also need to consider the weather factor in your area. Is not only the aspect of being cloudy which you should look for but humidity, visibility, temperature(and possible variations) and wind.
- You need to check for the humidity factor. If humidity is high at the ground level visibility will be affected more or less but the worst will be fighting dew all night. To check humidity I found the best to simply brush your hand in the grass and see wet it gets. Check this before you set up your scope so in case of dew to prepare your dew shield/heater.
- High water vapours will give you a poor visibility and blurred images.
- Wind, will cause vibrations in your setup - so be careful when you pick your spot to check the wind direction and have some shielding if possible against wind.
- Sudden temperature variations could upset you focus as well as collimation. My advice is to have small thermometer placed on your telescope tube and check for temperature variations every half an hour or so.
- Make sure you are not near a road or a place where cars or even people wondering around will induce unwanted vibrations.
- Summer heat waves will give you a hard time - so better wait for a cooler night
- The best time at night to take a picture is usually after 4am - when the air cools down and some of the city lights are off.
Getting ready to start
Now, before you take your telescope outside make sure that:
- You have everything in proper order ready to use
- Make a list with all the steps you need to go through in setting up your scope. There are quite a few tasks and not once happen to me to forget something as silly as Harman mask on after focusing and wasting half of a beautiful night.
- Train your drives regularly and check your collimation
- Keep you telescope outside for 1-2 hours to allow the optics and the tube to adjust to environment temperature
1. align your telescope mount using a compass or Polaris so it will point as close as possible to north
2. level your tripod
3. mount your reticle/focuser on
4. level your fork arms
- check azimuth level with the scope upside down and bubble leveller (lx90 12)
- align 90 degrees azimuth and check parallel by rotation on a star
5. use your finder scope to set Polaris as per Dr. P Clay Sherrod's "Kochab's Clock".
6. align one star (lx90)
7. do iterative correction between Polaris and another star for or five rounds - until your goto will be in the centre of the reticle. Then goto a star and leave your scope to track for 5-10 minute and check for drift - if drift significant go to point 5.a
8. finally you can refine your alignment using drift method
1. Remove your reticle/eyepiece and mount your camera with care not to move the scope
2. Try to get as close as possible to the focus point using the viewfinder
3. For precise focusing a few methods are available
- Hartman mask
- Knife edge
- Micro focusers
- Focusing software: Dlsr Focus, Hocus Focus
4. On top of that you can use specialized software to aid you DSLR Focus Assist (for Canon DSLR cameras), HocusFocus
5. You need to make sure that there no serious variation in temperature or wind during your focusing procedure
Test your setup
Do a long exposure 4-6 minutes then check for star trailing and focus.
1. Start a short batch of shots, first 5 or 10, and then check them briefly for star trailing. Also check your telescope for dew.
2. If everything ok at point "1" start shooting long batches ie 30 shots per batch else you might want to redo some of the previous set up steps
3. Leave your telescope alone during the shooting - only check periodically (every 30 minutes) the sky, dew and your scope to make sure everything goes, as it should.
Storing & processing your shots
1. When you finished your astrophotography night - retrieve you images and store them on your computer into a folder by date-time/object.
2. Then go through all your shots and carefully examine every image and:
- if shot quality very bad - to much start trailing or light pollution or visibility - then remove
- else rename the other images by adding a suffix to show the quality ie img0001_q4
3. Check field rotation between first image and last. You can easily do this by overlapping these two images (ie in Photoshop) as layers with difference. Then align one central star in your image with reference to the other layer/image and check if the rest of your start are aligned as well - if not you might want to rotate your images to register perfectly
4. Stacking. Using specialized software as Registax align every star and stack
5. Final image processing.
Enjoy your results, reflect on your work and most importantly learn from your own mistake