Hi there,
This is my first time posting. I am starting to explore photometry and trying to work out the instrumental performance of my set up. I have an 8" SCT and using a ZWO-120MM-S (i.e. entry level monochrome planetary camera). A couple of nights ago I took about 1300 unfiltered frames of the Jewel Box as my testing target. I applied dark and bias (no flats). Processed using Siril and AstroimageJ. I undertook multi aperture photometry on two stars (K Cru and a dimmer 9.65 mag star (Stellarium doesn't give me an identifier - it is possibly Gaia DR2 6056408189581442944). Photometry was undertaken with similar magnitude reference stars (3 different reference stars in each case) to provide relative flux (which was normalised). The results are in the attached file. The x and y pixel drift was +/- 1 pixel in both axes over about ten minutes. There is virtually no correlation between pixel and relative flux.
The two stars both vary somewhat - but the second has a more distinct pattern (standard deviation of 0.16 mag for fainter star). I am wondering if it is possible it is real, or just wishful thinking.
To my surprise there are variable stars that vary on a timescale of minutes. I have attached graph of relative flux (for both K Crucis and the 9.65 mag star) and location of star in jewel box.
Nothing like a good walk to clear the mind. Likely rookie error spotted. The x and y pixel values that I tested for correlation against are the aligned x and y values reported by Astroimagej. There was quite a bit of drift over the imaging run - but the number threw me off. x drifted from 856 to 1034 over the run and y drifted from 645 to 611 (comparing first and last images). At low threshhold levels the image has a pronounced grid appearance (even after dark and bias subtracted). I expect the peaks and troughs represent running over these parts of the image frame for the fainter star. I'm hoping doing flats callibration may fix that problem.
Hey, complete another newbie here. I'm trying to apply flats calibration to the result but x and y still show Astroimagej. Trying to solve the problem by improvising but nothing helps. I will try to do one more observation from scratch when I go back to my real estate in Budva.