To stack or not to stack, which is best?

[John Coffin]

Hi, I am learning how to do photometry in order to flux calibrate my spectra. I am using an 80 mm refractor and an Atik 460 with a field flattener.

I have been using ASTAP to plate solve and calibrate the individual images. I wanted more control over the process so changed from using ASTAP’s photometry facility and am now using Astroimage J.

I can’t image for more than 10 seconds before my target is saturated. I collected 20 frames. I found that processing the frames individually or after stacking them made very little difference to the result.

A typical spectroscopy session lasts for an hour, and I aim to measure the magnitude of the target during this time.

How many frames should I collect to get an accurate result? I suppose the advantage of processing the frames separately is that I could spot any major fluctuations in the target’s magnitude.

Any thoughts?

[Robin Leadbeater]

The nice thing with the individual measurements (both in photometry and spectroscopy) is you can use them to make a true estimate of the stochastic uncertainty (though not any systematic errors)

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