Video Astronomy - Getting Started
Updated: Jul 17, 2018
Getting started in video astronomy can seem daunting. Since it's not as well known as astrophotography, you can get advice which makes it sound out of reach. But the requirements for video astronomy are not as stringent as they are for astrophotography. So if you're asking advice from an astrophotographer, they may give you information based on what they do (which is expensive!). Here are the basics of what you need for video astronomy:
1. You need a telescope that can track the night sky by itself. Because the earth is turning, the sky appears to move, expecially when looking through a telescope. If your exposures are longer than one or two seconds, the stars will start to trail, becoming streaks instead of pinpoints of light. So any deep space object you're looking at will smear. Many telescopes have built in goto computers that can track the night sky. Even the less expensive ones like my Celestron 130SLT will work for video astronomy. It just has to be relatively stable once it's pointed at an object. They type of mount doesn't really matter for video astronomy (equatorial or Alt/AZ). It just has to be able to track on it's own.
2. Your telescope should be relatively "fast". You generally want a telescope that has a focal ration of around f/6 or faster (the lower the number, the faster the telescope). Most manufacturers print the f-ratio on the telescope or the box. But you can figure out a telescopes focal ratio by dividing it's focal length (in mm) by the size of the objective (in mm). For example, my Celestron 130SLT has a focal length of 650mm and the objective is 130mm wide (5"). So dividing 650/130 = 5 (f/5). My dobsonian telescope is 12" in diameter (305mm) and has a focal lenght of 1495.5mm. So it's focal ratio is 1495.5/305 = 4.9 (f/4.9). My 80mm refractor has a focal length of 472mm. So it's focal ratio is 472/80=5.9 (f/5.9).
3. You need a camera suitable for video astronomy, preferably one designed for it. They start around $200 but can be as expensive as $1000+. DSLR cameras will work but you may have difficulty getting it to focus with a newtonian style telescope. With a newtonian and a DSLR, you'll want what's called an "Astrograph" telescope. It's designed to work with DSLR cameras. DSLRs may also require a longer exposure (around 30 seconds) so you may need an equatorial mount.
4. You need a way to see the image. It can be with a computer or tablet or some cameras will allow you to send the image directly to a vga screen. #videoastronomy