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Hi Dean,
The aperture of the scope and the magnitude of the star are important. Also the "seeing" or the transparency of the sky; all these things go into the determination of frame rate.
The optimisation also has to use signal to noise ratio as an input, because sometimes for an occultation the target star is much brighter than the occulting body, so it's just an on / off signal; but other times it's a step change in brightness (because the two objects have similar brightness levels).
In the case of PHEMU observations (mutual occultations by Jupiter's satellites) the light curve is a very gradual diminution over tens of seconds to minutes, rather than a step change.
The gain of the camera can be an influencer - at high gain, the light curve is noisier than at lower gain (pretty obvious), so dropping gain, and reducing frame rate may provide a cleaner output, with a reduction in temporal accuracy as a trade off.
The last thing in the mix is the tiredness of the operator. I've found that at 3am my mind is working at about 50%, and my rig has to be **very** easy to use, and hard to get wrong. So anything that gets done easily is good.
Regards,
Tony Barry
WSAAG
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