Dome offsets and flat fields » History » Version 3

William Wester, 12/27/2013 11:14 AM

1 1 William Wester
h1. Dome offsets and flat fields
2 1 William Wester
3 1 William Wester
Introduction: pre-March 2013 it was noticed that there could be small mis-alignments when the dome was moved into position
4 1 William Wester
for daily flat fields and/or DECal scans. A piece of safety tape was placed so that it would show proper alignment when
5 2 William Wester
the dome was moved into proper position. The telescope operator, as part of the procedures, now checks for this proper
6 2 William Wester
alignment. Indeed, some of the early daily flat fields (before the procedure) show a "rim" about 1/3 of a CCD wide
7 1 William Wester
with response lower by about a percent.
8 1 William Wester
9 1 William Wester
It is difficult to diagnose whether the observation might be due to dome mis-alignment as the screen illumination comes from
10 1 William Wester
four discrete stations mounted on the outer ring and the screen itself is nearly a perfect Lambertian reflector (brightness
11 1 William Wester
is the same no matter the view onto the focal plane). This series of studies attempts to look at the effect of the dome flats
12 2 William Wester
versus small offsets in the dome position to see whether the illumination pattern matches some of the early problematic daily flats.
13 3 William Wester
14 3 William Wester
"DocDB 7024": (Mar 2013 study)