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INDI Library v1.9.1 Released (26 Jun 2021)

Bi-monthly INDI Library v1.9.1 is released bringing a few new drivers and improvements to existing drivers.

Progressive "Refocus every" in EKOS

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My 10" RC has a habit of losing focus very quickly at the beginning of the session.
I guess it is caused by a quick cooldown by the fans.
One way to solve this would be to set up "Refocus every" at a very short interval, but the problem is that once the telescope is thermally stable, refocusing would be taking time without good reason.
So suggestion is to have progressive "Refocus every", where the following parameters can be setup:
1. Initial duration - how long to wait till 1st refocus (default 10 min)
2. Progressive factor - a multiplying factor, which will be used for calculating next refocus period (default x2)
3. Maximum duration - no longer increase duration, after this value reached (default 120 min)

Alex
1 year 1 month ago #55693

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Hello,
If your focus issue is indeed due to the temperature, I think it could be solved by the feature I recently developed : trigger autofocus on temperature change. It uses the focuser probe, if available, to compare the last focus temperature to the current temperature, and triggers the autofocus in case it reaches the specified limit.

The feature should be delivered in the next release, but you can test it with the nightly.

Clear skies!
1 year 1 month ago #55703

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Florian,
I saw this feature in the nightly.
Problem is that I don't have a temperature sensor and also I don't know how effective it would be - my understanding is that different components come to temperature equilibrium at different speeds.
My suggested feature should solve the problem without any additional hardware.
I might just implement this feature myself, but if anyone wants to do it, please post here.
Alex
1 year 1 month ago #55740

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Florian,
I saw this feature in the nightly.
Problem is that I don't have a temperature sensor and also I don't know how effective it would be - my understanding is that different components come to temperature equilibrium at different speeds.
My suggested feature should solve the problem without any additional hardware.
I might just implement this feature myself, but if anyone wants to do it, please post here.
Alex
1 year 1 month ago #55741

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@Alex, If you use a Pegasus PowerBox, or V2, or any other sensor that reports temperature via "WEATHER_TEMPERATURE", (i.e. if you see temperature reported in the dome tab), then you will likely be able to use the autofocus delta-T feature that florian mentions. You might give it a try if you have a temperature sensor and see if it works. cheers, Doug
RASA11, Celestron CGX-L, ASI183mc Pro, 60mm guider + ASI290mm mini, ASI EAF focuser, PPB, Rpi4-4Gb+SSD, Powered USB3 hub, hardwire Ethernet.
1 year 1 month ago #55743

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That is most likely not going to do the trick, since the reflector is cooled down by the fans, so the temperature of the reflector is going to cool at a different rate than ambient.
My personal opinion is, you will have to wait until the telescope is equilibrated, then just use refocusing after a specified interval, depending on the temperature forecast for the night.
Atlas Pro AZ-EQ, ASI1600MM-Pro, ASI120MM-S, ES102ED, WO-Z61, Nikon D3300, ASI-EFW, ZWO LRGB,Ha,O3,S2 filter set
1 year 1 month ago #55746

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What Alex described (as I understand it) is a (warm) telescope adapting to a (colder) outside temperature. A sensor would be of limited help in this scenario as the telescope's focus shift occurs even if the outside temperature doesn't change at all. Also, the telescope's focus shift decreases over time as it approaches the outside temperature. The feature that Alex proposes in his original posting would deal with the problem well IMO.
1 year 1 month ago #55747

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Agreed, Alfred. Trouble is, the fans will cool the telescope not only quickly, but also generate a lot of seeing variability within the tube itself, besides refocus being necessary every few minutes anyway. I don't think one can get good images during that cooldown period anyway, so I would say, wait until equilibrated.
Atlas Pro AZ-EQ, ASI1600MM-Pro, ASI120MM-S, ES102ED, WO-Z61, Nikon D3300, ASI-EFW, ZWO LRGB,Ha,O3,S2 filter set
1 year 1 month ago #55748

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Absolutely. Without a doubt it's best practice to allow the telescope to cool down and adapt to the outside temperature before taking pictures.
1 year 1 month ago #55749

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Hello, this is unfortunately not true. Only the focuser temperature will work. Not the observatory one. The weather temperature was added after my feature implementation, and was not made available to it.

I would also advise, like others, to start telescope cooling more in advance, so that it gets more stable sooner.

Clear skies.
1 year 1 month ago #55758

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Avarakin, you will be far better implementing this rather complex algorithm yourself, that way you will get what you want - or at least be more likely to.

But starting the cool down process a bit earlier may be as effective, maybe this could require little more than a change in the order in which you set thigs up.

Or if you have an observtory do what the professionals do - air condition the observatory to the predicted night time temperature :)

Would an alternative way to determine the interval between refocuses be to look at the amount of change made? For example if it's changed by 100 in 10 minutes you do the next refocus in 10 minutes, it it's only changed by 10 you wait, say 30 minutes.
1 year 1 month ago #55761

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Hi Alex,
there is an option triggering refocus based on HFR changes. Have you tried this option?

Wolfgang
TSA-120 + FSQ-85 + GSO 150/750 | Avalon Linear + M-zero | Moravian G2-8300 + ASI 1600mm pro | KStars/INDI on Raspberry Pi 4 with Raspbian 10
1 year 1 month ago #56073

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