flat fielding screen

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

Affiliation
American Association of Variable Star Observers (AAVSO)
My rule of thumb is: min

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.