Picking the Right Astrophotography Telescope
It can be very difficult to pick the right astrophotography telescope. Telescopes for astrophotography can range in price from a couple of hundred bucks to a few thousand bucks. When you are comparing astrophotography telescopes, you need to pay attention to the aperture, focal length and focal ratio of the telescope. How much money you spend on a telescope for astrophotography depends on your experience level and your budget. Of course, you want to purchase the best astrophotography telescope that you can afford so that you can obtain the highest quality astrophotography shots possible.
If you are not familiar with aperture, aperture controls how much light passes through the telescope. When you change the aperture setting on a telescope, you are changing the size of the opening in the telescope that is used to gather light. The key to astrophotography is obtaining the highest amount of photons in your shots as possible.
To obtain a high amount of photons, you will want to purchase a telescope that has a large aperture. Unfortunately, the more aperture a astrophotography telescope has, the more that telescope costs. Even if you are a beginner, you should try to purchase a telescope for astrophotography that has, at the minimum, an aperture of 66 mm. Those who are at an advanced astrophotography experience level should be looking for telescopes that have an aperture of 125 to 140 mm.
2. Focal Length
Next to aperture, focal length is the most important aspect of astrophotography telescopes. Basically, focal length controls the distance between the mirror and the light that is reflecting off of that mirror in the telescope. To obtain the best astrophotography shots, you want the most magnification possible. To get the most magnification possible, you need a long focal length. Like aperture, focal length is measured in millimeters. For beginners, you can get away with a focal length of around 300 mm. For intermediate and advanced astrophotography photographers, the telescope that you are looking at should have at least 700 mm of focal length.
3. Focal Ratio
Telescopes for astrophotography run off of an optical system. The speed of the optical system is based off of the focal ratio. The focal ratio defines the relationship between the aperture and the focal length of the telescope. If you purchase a telescope that has an aperture of 100 mm and a focal length of 900 mm, the focal ratio of that telescope will be f/9.
As a general rule, a telescope that has a low focal ratio is good for wide angle shots and a telescope that has a high focal ratio is good for capturing photos of bright objects in the sky, such as the sun and various planets. While it varies by telescope, generally speaking, beginner astrophotography telescopes will have a focal ratio of around f/6, and intermediate and advanced astrophotography telescopes will have a focal ratio as high as f/8 or f/9.