I'm just getting into DSO astrophotography (AP) and I'm trying to figure how you all go about purchasing a new scope. Based on my novice research, I've come up with the following list. The first category is the standard features that you look at based on how you want to use the scope. The second category is the features that set scopes apart from others, which in most cases might help decide about the quality of the scope you're looking for. I am personally looking for two types of scopes up front based on the standard features. One scope to capture larger DSO and another to capture smaller DSO.
What are some key features that you look for when buying a refractor telescope for AP? Are there others besides what I listed below? Finally, how do you rate these features? Meaning, what makes that feature great, good, ok, and bad?
- Focal Ratio (speed of the telescope; the lower the number the faster you can collect data, but you sacrifice magnification)
- Aperture (diameter of the objective lens; larger numbers provide better resolution, but less data can be collected)
- Focal Length (longer focal length the higher the magnification)
- Customer Service
Features that set scopes apart from others:
- Sharpness (are some scopes softer than others?)
- Glass Type (Ohara FPL-53, Hoya FCD100, fluorite, any others? Is there one better than others for AP?)
- Optical Design (triplet, doublet, petzval, apochromatic, achromatic. From my understanding, apochromatic triplets are the way to go for AP. Is that correct?)
- ED (Extra-low dispersion) and SD (special dispersion) (both used in the removal of chromatic aberration, but is there more to this?)
- Strehl Ratio (not exactly sure how to find this on the specifications or what it does, but I've seen it mentioned)
- Focuser (Are stock focusers ok? I've heard the term feather touch and the company Moonlite. What should we be looking for and can they be upgraded?)
- Brand (do some brands have an edge over others? If so, how does the community grade each brand?)
- Manufacturing (does it matter which country they are manufactured in? I've heard negative comments about China, but it appears a lot of them are made there under a company called Synta. How are manufacturers graded?)
- Premium line vs entry level (I've seen some that state premium, but it's difficult to tell what makes them premium other than a premium price tag)
- Build quality (how do the different brands compare?)
- Cooling time (I wasn't aware this was a thing)
As a landscape photographer, this is a lot more to think about than simply purchasing a wide angle and telephoto. I appreciate any advice you might have. Thanks!
Edited by thelosttrek, 14 November 2019 - 01:57 AM.