While I was imaging Saturn last night, I found the best focus practice was to use planetary live-stacking feature while focusing. Repeatedly bump focus and reset the live-stack buffer. And tune for most/clearest features in the image. Here are the steps I took with my Celestron telescope:
1. Tune focus 100 ticks below where the image is obviously below focus.
2. Start and setup planetary live-stacking.
3. Increase focus by 10 ticks.
4. Press 'reset' button in the live-stack area to start a fresh live-stack.
5. Repeat steps 3 and 4 until best live-stack image is achieved.
I am wondering if this procedure could be added and automated into the focusing tool set?
Thanks for providing such a great Astrophotography tool and continually making it better.
Planet Focus with Live-Stacking
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Re: Planet Focus with Live-Stacking
Hi,
yes, that's a good technique and I've used similar to do focus for solar in the past. I was also setting a relatively low stack length (50-100 frames) as there is no real need to reset then - the stack will quickly adjust to the new quality as the old data is flushed out over a few seconds. Of course the big enemy of auto focus on the sun/moon/planets is seeing variability, which can be easily mistaken for focus related quality changes
Were you using the 'display frame contrast' score that's shown on the left in planetary live stacking to judge good focus, or were you doing it by eye?
cheers,
Robin
yes, that's a good technique and I've used similar to do focus for solar in the past. I was also setting a relatively low stack length (50-100 frames) as there is no real need to reset then - the stack will quickly adjust to the new quality as the old data is flushed out over a few seconds. Of course the big enemy of auto focus on the sun/moon/planets is seeing variability, which can be easily mistaken for focus related quality changes
Were you using the 'display frame contrast' score that's shown on the left in planetary live stacking to judge good focus, or were you doing it by eye?
cheers,
Robin
Re: Planet Focus with Live-Stacking
The autofocus tool already does something like that under the hood, except there is no need to stack frames when you can just average scores. SharpCap's autofocus works great for planetary, lunar, and solar imaging.
https://youtu.be/s-hopclh2no?feature=shared&t=849
https://youtu.be/s-hopclh2no?feature=shared&t=849
Re: Planet Focus with Live-Stacking
Hi Robin,
I was focusing by eye, on Saturn, as the focus tool wasn't giving good results. I messed with shortening the stack length also. I am still learning. One challenge that was making it difficult was using a very short exposure, 1ms, with high gain. Image was quite noisy.
In the future, I will focus with longer exposure, then capture with short exposure and high gain to get rid of any motion blur.
Thanks for the support. This S/W is a great tool.
I was focusing by eye, on Saturn, as the focus tool wasn't giving good results. I messed with shortening the stack length also. I am still learning. One challenge that was making it difficult was using a very short exposure, 1ms, with high gain. Image was quite noisy.
In the future, I will focus with longer exposure, then capture with short exposure and high gain to get rid of any motion blur.
Thanks for the support. This S/W is a great tool.
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admin
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Re: Planet Focus with Live-Stacking
Hi,
glad you found a technique that works
Out of interest, why use 1ms exposures? My understanding is that longer exposures (10-20ms) will generally 'freeze' the seeing quite nicely, so hitting 50 to 100fps with those sort of exposures usually works out well. With 1ms exposures, in theory you could hit nearly 1000fps, but in practice you won't due to camera data rate limits, so you would be losing a large fractions of the available photons...
cheers,
Robin
glad you found a technique that works
Out of interest, why use 1ms exposures? My understanding is that longer exposures (10-20ms) will generally 'freeze' the seeing quite nicely, so hitting 50 to 100fps with those sort of exposures usually works out well. With 1ms exposures, in theory you could hit nearly 1000fps, but in practice you won't due to camera data rate limits, so you would be losing a large fractions of the available photons...
cheers,
Robin