When I started getting into astrophotography at the beginning of this year I didn’t know much about astronomy or photography. It’s taken half a year to learn and collect enough stuff (for now) to get the images I’ve been wanting to take. I’m much more interested in imaging Deep Space Objects (DSOs) which are very faint, often even in typical amateur telescopes. Astrophotography has many unique challenges to deal with, requiring that you can:
- Aim the telescope at something you likely can’t see
- Have the telescope accurately track the object as the Earth turns
- Take long exposures to collect enough photons from deep space objects (DSO)
- Minimize effect of light pollution and sky glow to prevent it from overpowering your image
- Prevent dew from fogging up your lenses
- Pull the ‘signal’ (your image) from the ‘noise’ (e.g. skyglow, bad pixels, dust motes, electronic noise, etc.)
- Process the stacked images to ‘develop’ the final image
There’s quite an array of hardware and software I use and luckily the majority of the software is open source. You can get a start with AP with a much smaller list of equipment, which I initially did, and of course, there’s many who have much more advanced equipment than what I have.
I think I have a pretty fair setup to take a lot of nice photos so I thought I’d put together a post describing all the stuff I’m currently using:
Hardware
- Mount: Orion Sirius EQ-G w/ Synscan Hand Controller
- Camera: Canon T1i (500D), with Baader modification
- Telescope: Explore Scientific ED-80 APO Triplet Refractor
- Field Flattener: Explore Scientific 2″ Field Flattener
- Autoguide Camera: Orion StarShoot Autoguider
- Autoguide Scope: Orion Mini 50mm Guide Scope
- Light Pollution Filter: 2″ IDAS LPS -D1
- Laptop: HP Pavilion G4
Imaging Software
- Telescope control: ASCOM
- Planetarium: Stellarium and StellariumScope
- Guiding and Dithering: PHD2
- Camera Control: Backyard EOS Premium
- Plate Solving: AstroTortilla
- Remote Laptop Control: TeamViewer
Image Processing Software
- Pre-processing: dcraw
- Stacking: Deep Sky Stacker
- Image Processing: StarTools
Miscellaneous
- T-ring for EOS camera – threads to Field Flattener to attach to telescope
- Dew controller and heater straps
- 12V battery and 3-socket power adapter
- 12V power adapter for mount
- 12V power adapter for camera
- 12V power adapter for laptop
- USB to Serial converter & HC cable – laptop to mount (hand controller)
- USB to mini USB – laptop to camera
- USB to autoguider – laptop to autoguide camera
- Compass and level – set up tripod, aligned to North
- Portable table and chair
Choosing, collecting and getting to understand how to setup and use each of these components took a while. Getting all the software to work together and with the mount has been even more challenging.
ASCOM is actually one of the most important pieces. Most of the imaging software listed above needs to send instructions to the mount and also get information back from it. ASCOM serves as middleware for all the software to talk with the mount. It connects to the mount and then creates a ‘virtual telescope’ on the laptop that all the software can connect to. ASCOM then becomes a hub between all the software and the mount.
Stellarium is a great planetarium application that lets anyone explore the night sky and is open source. If you have any interest in astronomy I’d highly recommend downloading it and playing with it. StellariumScope is a related application that allows Stellarium to connect to my mount. I can then click on an object in the night sky, then with a key press my telescope will automatically slew to it. It has a lot of other nice tools that come as part of the software as well.
Backyard EOS (BYE) is specifically designed to fully remote control Canon DSLR cameras for astrophotography. The nicest feature is the ability to schedule a whole series of images, with specific exposure settings. It then takes all the images automatically and even downloads them to the laptop. It also has a lot of other nice options that help with focusing, previewing your image and reviewing the histogram from the image.
AstroTortilla is perhaps my favorite software. Even with a good mount alignment and all the software used, once you slew to a target it’s not uncommon to discover your telescope is aimed a little (or sometimes a lot) off the center of what you want to image. AstroTortilla tells your camera software (BYE) to take an image of whatever the telescope is pointed at. It then plate solves the image, basically analyzing the stars in the image and figuring out the coordinates of the center of the picture. It can then even send slew instructions to the mount to realign the telescope exactly where you wanted it.
PHD2 is the software that my autoguider camera connects to. To get really sharp photos you want everything in your image (e.g. stars) to stay on the same camera pixel throughout the exposure. Even with careful setup, it’s common to get a little drifting and it becomes more pronounced with longer exposures. This software watches the pixels from a single star seen by the autoguider camera and if there’s any drift it sends commands to the mount to move it back to the original pixels. While keeping your image exactly on the same set of pixels throughout a single exposure is important, keeping it on the same set of pixels for every image can reinforce the noise in your images. This is where dithering, which is moving the image a relatively small, random number of pixels and in different directions, is equally important. BYE sends a message to PHD2 between exposures telling it to move the mount a little and then when it’s done PHD2 tells BYE to start taking the next image.
While all this seems pretty complicated, it’s really not that difficult once you get everything configured and setup properly. In fact, I’m finding that many of the software tools are making many things easier. For example, as I was starting my first imaging attempts I would have my diagonal and reticule eyepiece in my telescope so I could center the alignment stars during the initial mount setup. Once the alignment process was done I’d take off the diagonal and eyepiece and attach my camera in it’s place, then go through the whole focusing and setup routine for that. Now I can use the camera for alignment or even skip the alignment altogether and just let AstroTortilla help me get centered on what I want to image.
Now that I’ve got everything working and know how to use everything I should be able to put much more focus on capturing images!
October 2nd Update – My very first attempts at astrophotography was back in January when I could barely stand to be outside for more than a few minutes. With it starting to get a bit cooler at night I added TeamViewer to my PC (inside the house) and my laptop (outside). TeamViewer allows you to access and remote control one PC from another, among other things. Once I got everything setup and polar aligned I went back inside, connected to my laptop from inside the house and completely managed my whole imaging session from the comfort of my office. It’s hard to believe the level of automation is possible.