I have seen a few posts about photometry with the Origin and thought I would post my notes on that subject in case they help someone.
There are three types of images produced. The most highly processed ones are those that go to the phone or tablet running the Origin app. These are not useful for photometry. The other two are described in section 12 of the manual. The ones named “Lightxxxxx.fits” are the individual sub-exposures. These are bayered images and have not had bias, dark or flat applied. You will find those calibration masters in the image subdirectory. The other file in the same subdirectory is named FinalStackedMaster.tiff. As the name implies this is a debayered and stacked combination of the “Lights”. It has been calibrated with the bias, dark and flat.
Taking the path of maximum laziness, I work with the TIFF file. The image is 16 bits per pixel and in the order red (TR), green (TG) and blue(TB) inside the 3-D array. You can split this into individual FITS files with any number of programs. Pixinsight and MaximDL are two I know of. Some conversions will allow all three images to be placed in a single FITS file which VPhot will plate solve and split apart for you if that is how you do photometry.
I chose to use a personal python script to perform conversion for a number of reasons. One is that I could adjust the FITS header. The values for the header are contained both in the TIFF file in the form of TAGS and in the info.json file you will find in the image subdirectory. The header keys to watch out for are the following:
DATE-OBS - this is the time of the first sub exposure in the info.json specified with the timezone offset. In the individual “Lights” it it the local time of that exposure with the timezone offset in a separate header - “TIMEZONE”.
EXPOSURE - this is the exposure time for the sub exposures. For the stacked image it needs to be multiplied by the number of exposures stacked in order for the mid exposure time to be calculated correctly.
In order to get the best calculations of airmass and HJD you want the latitude, longitude and altitude. The altitude in the FITS header of the “Lights” and the info.json seems to be set to zero.
FILTER - you should set these to “TR”, TG” and TB”.
It is best to replace the Origin’s clear filter with an IR cutoff filter to limit the long wavelengths impacting the TR measurements.
For the stacked images I have found that 25,000 ADU is the point where saturation sets in. I do not know what to advise about saturation on the “Lights”. Other than that I think photometry is pretty much business as usual. If you use webobs to submit data specify “DSLR” as the sensor type.