Imaging with a wedge requires a bit more effort during setup, but you can only do so much in Alt-az. Rather then just dropping the scope into the tripod, and locking it down, the wedge holds the scope at an angle facing Polaris. This is called polar aligning, and it is something that doesn’t have to be done with an Alt-az telescope. It is one of the reasons that Alt-az mounts are a good idea for beginners. Equatorially mounted telescopes have to be aligned on Polaris before you can do any observing or photography. Alt-az can be aligned on any star or stars. What Polar aligning does is allows the telescope to track the stars on only one axis. A poorly polar aligned scope or Alt-az will begin to show rotation in the corners of a long exposure image. While this may not bother a beginner, as you progress, field rotation as it’s called, becomes the enemy. What this means, is you spend more time setting up and making sure you’ve got perfect alignment before attempting to image. The wedge added 20-30 minutes to my setup routine. It also makes it tough to do a full daytime setup. I still have to wait to see a star before aligning my telescope.
Since I purchased my telescope, Celestron has offered a firmware update that allows me to polar align on any star, not only Polaris. This feature is called All-Star alignment and it is great! This means I can get a head start on my alignment, and can align on any of the bright stars, not just Polaris.
Imaging on a wedge improved my images to the point where I could get 1 minute exposures without trailing. That was all well and good, but I was only a single, but expensive upgrade away from having a full auto-guiding setup. I purchased a new refractor telescope as well as rings and a counterweight system. I also purchased an Orion Starshoot Autoguider. An auto-guider locks on a single star and guides the mount as it tracks the sky. It smooths out any bumps in the mount and allows you to image for very long periods of time. I’ve currently pushed it up to 10 minutes before it shows any trailing. This does require perfect polar alignment, but it also improves your images considerably. I’ve posted some of my most recent images with my newest fully guided setup.
Coming off a spending binge on astrophotography, I now have a serious imaging rig. While some may not quite look at a fork mounted telescope as a perfect imaging setup, it is stable, has good optics and outperforms many GEM style mounts. At this point, my photographs are only limited by the darkness of my skies, and the effort I’m willing to put into them. In future posts, I’ll go into some of my techniques and tips.