|
Coma correction
Typical coma correctors do require in-focusing--at least this is true of the Lumicon and the TeleVue.
The lens you've linked seems to be threaded to attach to something (the bottom of the focuser drawtube?), which is interesting. It wouldn't work attached to the bottom of an eyepiece (too close to the eyepiece focal plane), though, even if it could be attached there.
Since the active part of a coma corrector is the lens, there's no reason to have a tube if it isn't necessary.
I believe this is a Ross corrector, so it's intended for photographic use. But, like the Baader MPCC, so long as you pay attention to maintaining the correct distance between the eyepiece's focal plane and the lens, it should be usable visually as well.
The eyepieces most likely to require more in-focusing would be your short focal length ones, which are probably 1-1/4". There are 2"to1-1/4" adapters that drop the eyepiece down 12+mm, so you might be able to achieve extra in-focusing without resorting to a shorter focuser. More the issue is whether you can achieve the correct distance between the camera's focal plane and the lens. It might require experimentation.
|