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== Choosing a Telescope == Since there are so many telescopes out there, it can be difficult to choose your first OTA. There are three main types of OTA commonly sold, these are Newtonian Reflectors, Apochromatic Refractors, and Schmidt-Cassegrains (SCTs). Each have their advantages and disadvantages, and are best suited to different aspects of astrophotography. ====== Apochromatic Refractors: ====== ----Pros: Refractors are very convenient. They don't need collimation and are small making them portable. Their light weight makes them resistant to wind and their short focal lengths make them easy to guide with. Cons: The small aperture makes them unusable for serious planetary imaging, and most are F/7 in focal ratio which is "slow", meaning you dont collect as much light per unit of aperture compared to other scopes. Smaller refractors tend to have shorter focal lengths, so are only really good if you want to image large targets. Larger refractors become increasingly expensive quite quickly. '''Best suited for: Deep sky imaging.''' ====== Newtonian Reflectors: ====== ----Pros: Fast focal ratio, most are F/4 or F/5 which allows the collection of a lot of light in a short amount of time. Cheap compared to refractors. Can be had in a nice array of apertures and focal lengths. Cons: Size. For 8" or above you will probably need an Orion Atlas mount or better. They are not very portable at all. They also need collimation every imaging session, the faster the f/ratio the more difficult a precise collimation is. They also can suffer from changes in air temperature, where a warmer pocket of air can sit on top of your primary mirror causing blurriness. Its recommended to let your telescope acclimate to outside temperatures before you begin imaging. Adding a fan on the back of your primary mirror, or just manually circulating air inside the scope can help with this. '''Best suited for: Planetary or Deep sky imaging depending on mount and aperture.''' ====== Schmidt-Cassegrains: ====== ----Pros: More compact than newtonians while still maintaining that large aperture. Cons: Requires collimation (which can be difficult on SCT's), very slow focal ratio (F/10), front corrector is very prone to dewing over. Large central obstruction (compared to newtonians) can reduce contrast on planets. Not recommended for deep sky imaging, but it is possible with a high quality mount. '''Best suited for: Planetary imaging.'''
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