Glints in PS1 / GPC1

(Back up to IPP for PS1)

Sample Images

The plot above shows 4 GPC1 images placed on the sky in relation to nearby bright stars. The largest circles are 6th magnitude, while the smallest are 10th magnitude in i-band. The sequence of four exposures start with 108o oriented north-south, shown in black. The next exposure (109) is in red; the next (110) is in black and rotated further; the last (111) is shown in blue.

For these exposures, the chips are arranged with 00 in the upper-right corner, 70 in the lower-right corner, 77 in the lower-left, 07 in the upper-right.

The following 4 images show the greyscale version of the exposures shown above. Update: I've rotated the images for convenience -- the first image (108) now has the same orientation as the plot above. The rest are slightly rotated, as can be seen above. The images have chip 00 in the upper-right corner, and 70 in the lower-right. It is possible to identify the stars that are causing the main glints, as discussed below.

There are three vertical glints in this image: one on the top (entering about the middle of chip 40) and two on the bottom, on either side of the boundary between chips 27 and 37. The three stars that are responsible for these three glints are marked with a red square. Notice that in this exposure, these three stars are lined up with the observed location of the glints (after correctly adjusting for the relative orientations). In the following three images, the same stars continue to generate glints, but since the camera is rotating, their relative positions change. It is possible to predict the position for the glints from these stars by drawing a line parallel to the chip boundaries that intersects the stars for each exposure. There are also fainter glints that can be seen in the full-scale jpeg parallel to the cell rows coming from stars that can be identified on the north and south.

It is a bit worrying that the position of these stars relative to the edge of the focal plane is changing quite a bit between exposures. It appears (though I have not measured this carefully yet) that the boundary (in camera coordinates) in which a star may cause a glint is fairly wide.

For this exposure, the three glints are found at: 1) chip 40, at the boundary with chip 30; 2) chip 37 between cell columns 1 & 2; 3) chip 37 between cell columns 4 & 5.

For this exposure, the three glints are found at: 1) chip 30, between cell columns 3 & 4; 2) chip 47, on cell column 5; 3) chip 37 on column 0.

For this exposure, the three glints are found at: 1) chip 30, column 7; 2) chip 47, column 2; 3) chip 47, column 5.

Attachments