EAA Telescope Options
Below are some general guidelines for picking a telescope for EAA. For a more in depth discussion check out my Blog "Choosing a Telescope for EAA".
A new class of telescopes has appeared over the last 4-5 years called Smart Telescopes. These are highly automated telescopes which make it a lot easier for a beginner to do EAA. I recently bought the Seestar S50 Smart Telescope from ZWO because it is extremely low cost, $500, yet very capable and, I think, an good choice for an EAA beginner.
There are many different options for the choice of optics to use for EAA. Perhaps the most common telescopes used are Schmidt-Cassegrains (SCTs) with primary mirrors in sizes from 5" to 14". The large back-focus capabilities of SCTs makes it very easy to achieve focus with them. Because they are typically native f/10, i.e. very long focal length, a focal reducer is most commonly used to reduce the focal ratio to f/5 or lower. With faster focal ratios, much shorter exposures are needed which, in turn, makes observing have more of a "live" feel and also reduces the tracking requirements on the mount and the required precision of polar alignment. For really fast optics, add a Hyperstar to get to f/2.
Refractors, especially wide field ones are also commonly used for EAA. These may need extenders to put the focal plane at the right distance to achieve focus with the camera, but extenders are plentiful and not expensive. Often 60mm to 80mm scopes are used to achieve wide FOVs at reasonably low cost. But there is really no size limit to the type of refractor that can be used. Since they commonly have focal ratios of f/5 to f/7.5 they may not require focal reduction.
Newtonians offer the largest apertures at the lowest cost. It is common to find 6" and 8" versions used for EAA. Anything larger than that requires a larger, heavier and more expensive mount. However, because of the very limited in-focus travel of these designs, some will require modification to achieve focus. This may require a low profile focuser or moving the primary mirror closer to the secondary. To avoid this problem look for Newtonians labeled as imaging Newtonians or astrographs as they are designed to come to focus with a camera without modification.
Below are some general guidelines for picking a telescope for EAA. For a more in depth discussion check out my Blog "Choosing a Telescope for EAA".
A new class of telescopes has appeared over the last 4-5 years called Smart Telescopes. These are highly automated telescopes which make it a lot easier for a beginner to do EAA. I recently bought the Seestar S50 Smart Telescope from ZWO because it is extremely low cost, $500, yet very capable and, I think, an good choice for an EAA beginner.
There are many different options for the choice of optics to use for EAA. Perhaps the most common telescopes used are Schmidt-Cassegrains (SCTs) with primary mirrors in sizes from 5" to 14". The large back-focus capabilities of SCTs makes it very easy to achieve focus with them. Because they are typically native f/10, i.e. very long focal length, a focal reducer is most commonly used to reduce the focal ratio to f/5 or lower. With faster focal ratios, much shorter exposures are needed which, in turn, makes observing have more of a "live" feel and also reduces the tracking requirements on the mount and the required precision of polar alignment. For really fast optics, add a Hyperstar to get to f/2.
Refractors, especially wide field ones are also commonly used for EAA. These may need extenders to put the focal plane at the right distance to achieve focus with the camera, but extenders are plentiful and not expensive. Often 60mm to 80mm scopes are used to achieve wide FOVs at reasonably low cost. But there is really no size limit to the type of refractor that can be used. Since they commonly have focal ratios of f/5 to f/7.5 they may not require focal reduction.
Newtonians offer the largest apertures at the lowest cost. It is common to find 6" and 8" versions used for EAA. Anything larger than that requires a larger, heavier and more expensive mount. However, because of the very limited in-focus travel of these designs, some will require modification to achieve focus. This may require a low profile focuser or moving the primary mirror closer to the secondary. To avoid this problem look for Newtonians labeled as imaging Newtonians or astrographs as they are designed to come to focus with a camera without modification.
Below are some of my telescopes
ZWO Seestar S50 Smart Telescope
Sharpstar 61EDPH III Refractor
Celestron C11 SCT with Hyperstar & ASI2600MC Camera
Orion ED80 f/6.25 Refractor
Newtonians can also be paired with a camera for EAA. However, because of the very limited in-focus travel of these designs, some will require modification to achieve focus. This may require a low profile focuser or moving the primary mirror closer to the secondary. Another option is the smaller form factor video cameras like the MC Micro, which can fit inside the barrel of a 2" focuser, allowing them to get closer to the secondary mirror without modification. There also is the Dob-Cam from Mallincam which has a cylindrical design no larger in diameter than a standard EP.
Any telescope including Maksutov-Cassegain, Astrographs, Ritchey-Chretien and more can also be used with a camera for EAA so long as it can come to focus. For really wide FOVs and a low cost setup, standard camera lenses (50mm, 100mm, 200mm et.) can be attached to the front of the camera with the proper adapter in place of a telescope.
Any telescope including Maksutov-Cassegain, Astrographs, Ritchey-Chretien and more can also be used with a camera for EAA so long as it can come to focus. For really wide FOVs and a low cost setup, standard camera lenses (50mm, 100mm, 200mm et.) can be attached to the front of the camera with the proper adapter in place of a telescope.
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