automatic refocus for planets

[dmead]

Hi guys

it would be super awesome if i could refocus between planetary captures.

I'm in the practice of automating planet tracking with phd2 and then using feature tracking with camera ROI in sharpcap to keep on a planet.

my goal is to automate as much of the process as possible, so having a timed refocus (or even using the time between captures for a refocus) would be super awesome.

is there a another feature i should be using for this? maybe seeing monitor?

Screenshot 2022-12-27 183328.png (16.73 KiB) Viewed 796 times

[admin]

Hi,

you can probably do this using the sequence editor in advanced mode. If you have the SharpCap autofocus working for planets then the 'Refocus' step in the sequence editor should do what you want (it will re-run the settings used for your most recent successful autofocus scan/goto best focus). See https://docs.sharpcap.co.uk/4.0/#The%20 ... e%20Editor

I am considering a planetary/solar/lunar sequence planner tool as a companion to the existing deep sky sequence planner, and this would be the sort of thign that it would have in it. Other suggestions welcome.

cheers,

Robin

[dmead]

I will try that and report back.

I have some feature requests that could go in a planetary sequencer.

Do you want them here or another thread?

[admin]

Hi,

here will be fine

thanks,

Robin

[dmead]

ok here goes

1) per channel focus method readout

I'm shooting planetary on a 12 inch lx-200 gps at f/25 with the 2.5x powermate etc.

my scope has pretty severe chromatic aberration (especially at this focal length). In this post I show examples of the issue in detail.

https://www.cloudynights.com/topic/8516 ... s-12-inch/

I've found that it's not just camera effects or seeing for the blue vs red channels. In sharpcap i can select blue channel -> mono and get good focus by eyeballing it.

I can also do the same for green and red channels.

What I would like is a per-channel readout so i can judge the focus level of each channel and make tradeoffs based on the target in question.

For mars, i can get a lot of detail and not care about blue. not the same for jupiter or saturn.

I would imagine, for instance that the focus graph could drop a triangle to indicate where the red green and blue channel are in terms of their score, along with maybe a white triangle to show the mean or median (we should also be able to focus on the mean of median of the channels as well). Or maybe show a lone grah so the different channels are easy to read? Per channels stuff is happening in the histogram tool, so I assume this is possible to implement.

My current solution to this is just run fourier detail detector, while tracking with camera ROI. My level of details has gone way up by using the baader fringe killer, but I'd still like a way to not just throw away all that information.

Also worth mentioning that the amount of CA that I'm dealing with makes it hard for SC to identify best focus because there is not a steep incline around the actual perfect focus (because there is none). What I end up with is a smooth arch shaped graph over the entire range of the focuser. The behavior that SC is looking for the identify a perfect focus spot never happens. I would be happy to provide graphs/logs for this.

my insta for examples:

https://www.instagram.com/mead_observatory/


2) automatic refocus between captures.

I get what you're saying about the sequence planner, which i will try. But i don't think it would be too much scope creep to use the intervals between captures to maintain focus.

Aside from a sequence feature, it would be cool if the focus tool could trigger it's own refocus if the value drifts too far.

3) focus tools should follow the target

Focus methods should follow targets the same way the ADC alignment tool does. This is a pretty straightforward ask and I don't think it would be hard to implement. I've found that scores are very different if i select a large area for my planet vs cropping in to just include the disk plus some wiggle room.

It would also be cool if the focus tool could stay tracking *inside* the planets disk, so that all the data going to the tool is a planet feature. I've done this manually with tight tracking and with phd2 and the feature tracking with camera ROI help. this would be helpful with jupiter's cloud bands.

the zeitgeist in the /r/astrophotography discord is that you should eyeball jupiter and mars to get perfect focus. I don't accept this and maintain automatic tools can find it if applied properly =)


4) mono/not wideband plantery sequences

if you design a planetary sequencer with mono work in mind, i think it will probably end up being more solid and full featured than if you targeted OSC cameras only. a bunch of nerds in the discord are converting the the daimann peach method and starting to do uv pass/uv-ir cut/ir cut/methane combinations.

I myself am converting my scope to a mono camera with an EFW and LRGB (where L is a fringe killer) to sidestep the CA issue entirely. it would be cool if i could design sequences for this in SC to keep doing DSO and planetary and not change to something else.

thanks for considering!

[dmead]

oh side note!

when i use center mass feature tracking and a focus tool, the selector for the focus tool influences what the center mass is for the frame.

this is clearly a bug and probably not intentional.

[admin]

Hi,

thanks very much for the feedback.

For the colour channel/focus thing, I think the first step would be to allow you to pick the channel to be used for the focus measurements - that would be realtively easy to implement and give the chance to do some manual measurements before taking it any further.

Automatic refocus would definitely be a thing to have in the planetary planner, although it always relies on the refocus procedure being reliable, so any feedback on whether or not it works nicely is also valuable, since there are so many possible variations in setup of camera/scope/focuser/etc. This also applies to a series of captures in different filters (filter wheel automation, etc).

For the focus tools following target, that makes sense - can you not get the equivalent of this already using the 'planet/disk stabilization' control from the preprocessing controls on the right? This offsets the image of each frame to try to keep the center of brightness steady. In SharpCap 4.0 it also adds a dark grey border to indicate the parts of the image that were outside the camera sensor (which can cause stacking issues), but in SharpCap 4.1, that indication is just drawn on the display and doesn't end up in the saved file. Not an ideal approach, but it should work, which would prove the concept (or not).

Finally, on the feature tracking/focus issue - I thought I had fixed that by changing the order of processing - is your SharpCap version right up to date?

cheers,

Robin