Quote:
|
Originally Posted by ving
I use a single disk that sits between the vanes. no obstruction then 
its only 80mm but thats plenty on really bright objects, which is what i use it for |
Hi Ving, you might not need the light, but you might need the aperture to get the resolution needed to split very close doubles. You know how they quote theoretical minimum arc second (another technical term) resolving power for different diameter objectives. Your 80mm disk will give you the resolving power of an 80mm scope - not sure what that is, but it's way more than an 8 inch scope - whereas a thin annular mask that exposes only a small amount of the outer edge of your mirror of equivalent area to an 80mm objective should "theoretically" still provide the full resolving power of your 8 inch scope while only utilising the same amount of light as the 80mm. Make sense?
Of course whether you can get a good focus with such an annular mask (Asi?) and the greater impact of atmospheric turbulence etc on the larger mask might over-ride such advantages.
Just a thought
cheers,