In an attempt to find a way for the IPP to identify which exposures show moon glints, I examined a series of Three Pi exposures that had small moon angles and had visible glint features. All exposures are in the i filter.

exp_name exp_id dateobs moon_angle moon_phase
o5080g0156o 94818 2009-09-06 10:02:30 19.9828 0.547319


exp_name exp_id dateobs moon_angle moon_phase
o5080g0160o 94822 2009-09-06 10:08:51 24.5752 0.547387


exp_name exp_id dateobs moon_angle moon_phase
o5080g0164o 94826 2009-09-06 10:15:03 32.6811 0.547452


exp_name exp_id dateobs moon_angle moon_phase
o5080g0166o 94828 2009-09-06 10:18:16 19.8979 0.547486


exp_name exp_id dateobs moon_angle moon_phase
o5080g0171o 94833 2009-09-06 10:26:19 36.004 0.547569

Note that the bright glint in ota41 has a peak level of ~18k counts in 60 sec, while the nominal background in that image is ~11k counts in 60 sec (16.3 mags per asec2)


exp_name exp_id dateobs moon_angle moon_phase
o5080g0173o 94835 2009-09-06 10:29:37 31.0689 0.547603


Sky brightness levels for matched pairs of ISP and GPC1 images as a function of airmass and moon angle. The ISP data is consistent with airmass effects. The GPC1 data shows strong glints at moon angles ~ 30-35 degrees.

The same data, now plotted as differences in sky brightness. The pairing mitigates the airmass trends, showing that GPC1 gradually becomes brighter relative to the ISP, with the glints influencing the ~ 30-35 degree range. All "GPC1 bright" pairs with moon angle > 50 degrees all come from the same night, and the observing logs note clouds. Therefore, these points are likely not to be related to the telescope, but to variations in cloud cover.

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