Difference: 20151310MsciPhotometryLab (1 vs. 8)

Here A is most likely a 'hot' pixel, around 4 magnitudes brighter than the background of the image. B is another bright spot, but this time more spread out, and around 2 magnitudes brighter than the background. The interesting feature at C was first thought to be a cosmic ray, as it appears to have moved over the image during exposure, however it appears to have curved in a noticable way, over a small distance, perhaps identifying it as a low momentum, charged particle. We have yet to acertain whether this is a result of natural radioactivity however.

Here A shows the largest of the rings, with an outer ring diameter of around 340 pixels, and an inner ring diameter of 130. B is the medium ring, with outer and inner ring diameters of 180 and 75 pixels respectively. Seen very faintly at C is one of the small rings, which due to its size, only one ring can be measured for, at around 12 pixels. D hghlights the cooling ring of the camera, which although much brighter looking, has around 1000-1500 additional ADU's.

Analysis

Temperature Control for CCD

We first tested the lowest temperature we could achieve for the CCD, whilst keeping the cooler power at around 90%, so that small changes in atmospheric conditions could be accounted for by the cooler, so the temperature of the camera could remain as fixed as possible.

Ambient Temperature today: 12 degrees celsius, and tested in the range -10 to -20 degrees, the results of which can be seen in the table below:

From this we concluded that the optimum temperature for today's observations is around -17 degrees, and was used throughout.

Thermal Noise

We then set about determining the thermal noise created by the system. For this the lens cap was left on, as we were only interested in seeing what images where produced due to thermal noise, not from outside sources. We took images at different exposure times, as seen in the attached zipped file (Exposure_test_lens_cover_on.zip), containing the FITs files.

CCD Faults (?)

Then we removed the lens cover and took images of a smooth side of the inside of the dome, and from this we identified two interesting properties of the camera. First several dust grains are visible in such conditions, marring the observed image. Below saturation an overbright cirular line is visible on the images, identified as perhaps a fault with the CCD chip, however when saturation is reached (~40 seconds), the image is warped considerably, and this line is no longer present. The full set of files can be seen in the zipped file titled Exposure_test_lens_cover_off.zip

-- Public.DavidHadden - 13 Oct 2015