Affiliation
American Association of Variable Star Observers (AAVSO)
Thu, 01/31/2019 - 05:40
The Ferguson Observatory in Kenwood, California needs a new flat screen for the new 0.5m F8 RC telescope.
The screen will be attached to the wall which is 10 feet from the telescope. The planned screen will have a white circular center surrounded by a wide, flat black border ( in order to decrease scattered light from entering the light path).
How do we decide the size of the central white reflecting area?
Phil
My rule of thumb is: min (diameter of primary mirror, diameter of front aperture) + (distance to screen) * tan(field of view width + uncertainty in pointing)
That 10 foot distance screen-to-telescope is likely to add several inches to the required screen size, though it should help a lot with scattered light.
Is there a new source for large panel screens for flat calibration? That would be welcome news. Alnitak has had their production stopped, I hear.