As I get some questions, comments and even criticisms about a particular aspect of this article, I thought it was time to do an update to try and clarify some things, and also add images from my newest OTAs. So, some people tell me that images are not a good indication of the overall performance of a telescope in planetary viewing, especially when observing visually. I would say that this is not correct, but not entirely incorrect either. You will notice the article is called “shootout”, so it is primarily about shooting images, but my original intend indeed was to evaluate a scope’s overall performance, so I did make remarks about differences in visual observing. It is just that images are the only objective way to demonstrate planetary performance and they are so easy to take nowadays – any webcam will do – that most people will try them. So, what exactly is different in observing? What is it that photos can’t show? First of all, if you can see a specific detail in an image, there is a chance you can see it visually, but there is no way you can visually see more than an image made of hundreds of frames shows, hence think of the detail in an image sort of like the “ceiling” of what you can see when observing. However, how easy the detail is seen will also depend on things like contrast and color and this is where post-processing an image makes a big difference and “hides” difficulties you might have when observing. Specifically, while the amount of detail you can “pull out” of a picture is quite dependent on your aperture, the telescope design makes a big difference in what you can see in the eyepiece, as a smaller aperture with a smaller “ceiling” of detail that can show up in processed pictures, might have a much more contrasty and colorful image that will actually make some details very prominent and give an overall more pleasing picture. Since the biggest difference in visual vs photo comes from post-processing adjustment of contrast/color/sharpening etc I have added the stacked but not processed (just brightness-normalized) versions of the photos previously posted, which can give a better idea of what you will get visually out of each scope.
When choosing a new telescope you must decide what you want it for. If you want to see wide-field deep space objects, then many types of telescopes are considered inappropriate (Maks, SCTs, long tube refractors etc), since they would be too dim or simply not fit the objects in your field of view. If, on the other hand, you would like to see the planets, these same telescopes would be the best fit. However, could you still use a wide-field capable telescope for planetary viewing or photography? And in general how do various types of OTAs perform in the solar system. Since I have a nice little spectrum of OTAs, including refractors, catadioptrics and reflectors, I though I should try to answer these questions by doing a comparison test under similar conditions with Jupiter as the target.
4 of the test OTAs: 2 refractors, 2 catadioptrics.