Variable star test images

Here you will find a series of calibrated images for photometry, that can be used for tests.


Calibrated images can be downloaded at this link.

The serie contains 431 CCD images taken in August 2011, somewhere in Cygnus.
Here is the first image.

More information

The images have been exposed 30 sec, and taken in binning 1x1.

The CCD camera is an Audine with a KAF0402-ME sensor (an Audine is a French camera purchased in kit, to be assembled at home: see here and there).
- sensor size is 512*768 pixels.
- read-out noise is about 25 electrons.
- the gain is 4.35 electrons/ADU, this value allows to match the full-well capacity of the pixels (around 130000 electrons) to the full dynamic of the ADC (32768 ADU).

Image statistics

The figure below shows the variations of star size. We see directly the impact of focusing drift and turbulence.
If we plot the minimum and maximum signals on the image (actually part of the image, to avoid the strongly saturated star on the right), we find a good correlation between the two curves.

We can also check the image uniformity by computing the differences between median values taken in the image corners and center.
The image uniformity is excellent.

Mount drift

Finally we can compute the image shifts with respect to the first image.