While playing with my focuser and my Canon 700D I wonder what the "HFR" value actually means?
Is it related somehow with the "FWHM" that I can analyse on stars in my postprocessing
software?
What HFR values would you expect with your DSLR similar to my Canon700D?
My best HFR on my 150/600 Newton with the Canon was ~3.6.
--= human, without Windows™ =--
pls excuse my bad english!
Half-Flux-Radius. It is generally between than FWHM and does not fluctuate as much due to seeing..etc. It is pixel based as well. Google would help as well
It depends on the star you are trying to focus and focus accuracy (motor / manual). In autofocus my 550D usually has values around 1.2 - 1.5. Sometimes more than that. Usually I make a motorized (accufocus) manual focus and can achieve 0.8 to 1.0. But only on very steady nights.
Try to manually select a not too bright star, medim to small sized, and then use autofocus or manual focus. Also do not push the ISO as it tends to "burn" out the star. ISO800/ISO1600 should do it but it also depends on model/make of the camera.
1.2 - 1.5 ... wow okay. I usually use ISO400 and 0.5seconds to focus and as you wrote medium to small stars. But I live in a slight valley in a mid-big city with a river in front of my telescope, so I would not expect a much lower HFR here dye to atmospheric conditions but I am still practizing all the stuff
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pls excuse my bad english!
I am just making a session right now and I got 1.4 on focus. That's the best for tonight, the sky is not very steady. Also I live in a suburban area so I have some light pollution adding to that.
Well having a river near can be kind of problematic because of ascending water heat currents. They tend to mess up images.
My HFR did also improve the last session to 2.3, but I had to focus manually. I think I need to tweak the step size in ekos and/or if possible, smaller step size in the astroberry focuser code, my stepper currently run at 1/2 step size...
--= human, without Windows™ =--
pls excuse my bad english!