Quote:
Originally Posted by DavidTrap
Surprised about needing longer exposures.
What Mag star are you aiming at? I centre up a mag 5-6 star and with luminance, my exposure times are ~1sec or shorter with Bin 1x1. I've not gone much longer for fear of saturating the pixels. This is an f7, 130mm refractor. I might have to try longer exposures and have a good look at the histogram.
DT
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Hi David,
With SGP you stay on the target (do not slew to a bright star) and that's why longer exposures are often needed, in particular with narrowband. SGP also looks at the entire image and calculates HFR for many stars (bright and dim) and uses that for calculating optimal focus. That's why I think you do not need many focus runs with SGP, as in each focus-step it uses an average for hundreds of stars.
A few times I rerun autofocus routine to check if SGP calculates the same focus, and it always has been to within one or two focuser steps.