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27 Feb 2017
INDI development team is happy to announce the release of INDI Library v1.4.0. This new exciting release builds on the maturity of INDI Library and comes with many new supported devices and fixes for existing drivers. Several improvements and enhancements are included in this release including native support for Cygwin and MacOS platforms in addition to Linux, BSD, and Windows (Client only).
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TOPIC: Auto-Slew To Bright Star For Autofocus Routine.

Auto-Slew To Bright Star For Autofocus Routine. 1 month 2 weeks ago #14948

  • Ihoujin
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I have talked some friends into trying KStars and one has brought up a feature that he uses and is reluctant to give up. I could be wrong, I haven't personally explored autofocus much, but I don't believe this is in KStars at this time.
Essentially during his autofocus routine, the software he uses will slew to a nearby bright star, ~4th mag to focus on before returning to the target. It can do this periodically or when temperature changes exceed a set value. This procedure should help anybody attempting to image a region with few or dim stars and I suppose a brighter star can be more accurately focused with. Could such a feature be implemented in the future?

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Auto-Slew To Bright Star For Autofocus Routine. 1 month 2 weeks ago #14996

What sort of telescope + filter + conditions is he using? I have a C11 at f6.3 and I've never needed to slew to a bright star to focus. My FOV is about 27x30arc min and Ekos aut-focus never has any problems finding a star with 2/3 sec exposures. I guess if your friend has a much narrower FOV and under light polluted conditions then it could be different.

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Celestron CPC1100 Atik 383L
HP8300 Elite i5 running Xubuntu, Indi, Kstars & Ekos
Roll off roof observatory
Battling Irish weather
github.com/dokeeffe
twitter.com/BallyhouraStars

Auto-Slew To Bright Star For Autofocus Routine. 1 month 2 weeks ago #15000

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I can't comment on his reasons, as I expect his equipment will have no issues finding a suitable star. But he owns a Celestron HD 1100 @F/10 and Takahashi FSQ106 @ F/3.64, on a Losmandy G11. Plus, SBIG ST-8300M, Starlight Xpress SXVR-H18 cameras, and a comprehensive filter set.

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Auto-Slew To Bright Star For Autofocus Routine. 1 month 2 weeks ago #15001

Ihoujin wrote: I can't comment on his reasons, as I expect his equipment will have no issues finding a suitable star. But he owns a Celestron HD 1100 @F/10 and Takahashi FSQ106 @ F/3.64, on a Losmandy G11. Plus, SBIG ST-8300M, Starlight Xpress SXVR-H18 cameras, and a comprehensive filter set.


KStars will autofocus on a filter change, and when the HFR (Half Flux Radius) exceeds a given threshold. No slew is needed in order to do this. That would be a waste of imaging time to slew away, focus, then slew back, center, etc. The sensor on the camera you mentioned is sensitive enough that this action is unnecessary. The telescopes in question are both good enough that this also should not be necessary. This feature should not be added, as I think there are more important things in their backlog.

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Auto-Slew To Bright Star For Autofocus Routine. 1 month 2 days ago #15437

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I had a chance to ask him why he finds it necessary to spend the time focusing on a bright star. And the reason was he is imaging with very fine, 3nm narrow band filters.

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Auto-Slew To Bright Star For Autofocus Routine. 1 month 2 days ago #15438

You don't need to slew to a bright star to do that.

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Auto-Slew To Bright Star For Autofocus Routine. 1 month 2 days ago #15439

Same here with a 7nm HA filter. I just use a longer exposure, like 6 or 7 seconds or so, the ekos focuser has no problem.

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Celestron CPC1100 Atik 383L
HP8300 Elite i5 running Xubuntu, Indi, Kstars & Ekos
Roll off roof observatory
Battling Irish weather
github.com/dokeeffe
twitter.com/BallyhouraStars
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