Sweetman Astrophotography

So here’s the story of my first astrophoto*. It gets the Marris asterisk because I entered this hobby from the world of visual astronomy, so of course I had tried holding my phone up to the telescope, and also taking zoomed in phone photos directly of the sky. This can yield surprisingly good results, but it’s never going to get you to a place that is actually good, or worthy of framing. For that there is no substitute for tracked, long-exposure images. That being said, my first photo was taken on a hacked together rig, and you absolutely should give strong consideration to starting with what you have. This hobby can be mind bogglingly expensive, but it also CAN be done on a budget…often it’s a trade off of time and effort vs. money.

So, how did this come together? I had a mount and optical tube(OTA) that I had purchased at a flea market for visual use. It’s the Celestron C8 and Advanced VX mount; a really great setup for visual astronomy, but for several reasons, not the best for photography. I’ll talk much more about the AVX mount in later posts, but for now it’s best to think of it as a great mount for visual astronomy, but merely a serviceable mount at the entry level of the serious astrophotography hobby. As for the OTA, a simple rule of thumb is that the longer the focal length of your OTA, the more important the quality of your tracking is to the final product. The focal length also directly relates to the field of view, long focal length = narrow field of view. You can think of it as looking through a straw, the longer the straw, the narrower the view gets. The C8 has a VERY long 2032mm focal length. Everything I read on the message boards suggested that for beginners something in the range of 300 to 600mm was more practical. I did pick up the recommendation that a field flattener/reducer would help somewhat, this is one of two new purchases that I made to get going. This brought the focal length down to approximately 1280mm.

So that’s the mount and OTA, the other critical element of photography is of course the camera. Again here I went with what I had at hand, a 14+ year old DSLR, the Canon Rebel T2i. Astrophotography is a very different hobby from terrestrial photography, so it’s counterintuitive at first, but megapixels and the traditional metrics aren’t so important in astrophotography. Much more important is things like sensor noise. The dedicated astronomy cameras go to great lengths to suppress or control noise during the capture and the reading of the image at noise levels that are far below anything that terrestrial photographers care about. The bottom line for me was that I would need to control for noise, but the senor on the quite old Canon was actually quite well sized for the OTA, I just need to connect it, and for that, a T-ring. I pulled an ancient laptop out of the closet, installed N.I.N.A, and for only about $200 out of pocket, I was in business.

Everyone’s entry point will be different, but almost everyone I’ve talked to has a similar origin story. They saw photos that inspired them, tried with what they had, and then found ways to improve. Up next is the remaining explanation of the Marris asterisk; while this is indeed my 1st photo, there were several failed attempts before I had a photo I was willing to call done.