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HFR DSLR & FWHM

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HFR DSLR & FWHM was created by pauledd

Hi

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! :)
Last edit: 6 years 6 months ago by pauledd.
6 years 6 months ago #19390

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Replied by Jasem Mutlaq on topic HFR DSLR & FWHM

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 :D
6 years 6 months ago #19391

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Replied by pauledd on topic HFR DSLR & FWHM

Thanks, I found a good short explanation:
www.diffractionlimited.com/help/maximdl/Half-Flux.htm
--= human, without Windows™ =--
pls excuse my bad english! :)
6 years 6 months ago #19392

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Replied by nMAC on topic HFR DSLR & FWHM


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.
Last edit: 6 years 6 months ago by nMAC.
6 years 6 months ago #19395

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Replied by pauledd on topic HFR DSLR & FWHM

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 :)
--= human, without Windows™ =--
pls excuse my bad english! :)
Last edit: 6 years 6 months ago by pauledd.
6 years 6 months ago #19400

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Replied by nMAC on topic HFR DSLR & FWHM

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.


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Last edit: 6 years 6 months ago by nMAC.
6 years 6 months ago #19420
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Replied by pauledd on topic HFR DSLR & FWHM

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! :)
6 years 6 months ago #19509

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Replied by nMAC on topic HFR DSLR & FWHM

Yes I had to do that on mine as I had too much steps and I could not find the center spot.
Try to do it cutting the current steps in half and so on.
6 years 6 months ago #19535

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