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INDI Library v1.9.5 Released (08 Mar 2022)

Bi-monthly INDI Library released with new drivers and bug fixes.

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I first want to express my thanks to all who are involved with the StellarMate/KStars/EKOS/INDI technology.  The current StellarMate 1.61 version has been rock solid on my two mounts.  I haven't had a crash or abort of any kind since I upgraded.  Well done!

The one "fly in the ointment" for me is auto-focus.  I continue to use polynomial, but the results have been inconsistent.  For instance, last night it focused perfectly on the initial operation, but focused badly for the next three through the night.  Unfortunately, it wasted a great above average seeing night.  Bummer.

I'm not sure what is happening... It's like it is focusing on different objects (spots?) at each iteration and gets misled into thinking the focus is better (I use darks).  I'm sure that backlash is also contributing to the problem, but I've worked carefully to get the best number to use.  Bottom line... I'm going to abandon polynomial focusing in the short term and go back to linear.

So... I could use some recommendations and/or best practices for linear focusing.  I'm using a 80mm refractor with an ASI EAF focuser.  My focal setting is usually around 14,900 with my ASI183MC Pro.  What are good settings for the "Mechanics" tab, particularly Initial Step Size and "Out Step Multiple"?

Thanks!

Ron
Mounts: Sky-Watcher EQ6-R Pro, Meade LX85, Celestron NexStar Evolution Alt/Az
OTAs: Celestron 8" Edge HD w/Celestron Focus Motor, Meade 80mm APO Triplet Refractor w/ZWO EAF
Cameras: ASI533MC Pro, ASI183MC Pro, ASI224MC, ASI120MC-S, ZWO ASI290MM
Raspberry Pi 4 with Stellarmate OS, MacBook Pro
5 months 2 weeks ago #78219

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Ron,

I designed Linear to help with focusers with backlash (probably most focusers have that). It isn't as fast as polynomial, but is more tolerant to backlash.

The key parameter for you is probably step size, which is totally dependent on the motorized focus hardware you're using.
I'm attaching below the parameters I use for my refractor, but, really they depend on the fact that I'm using a f/5.6 105mm refractor with a moonlight v2 focuser.

 

 

 

The step size parameter is important to get in the right ballpark, but don't sweat the difference between 20 and 18, or something of that nature.

The other parameter is important is tolerance.  For me, too tight a tolerance can be problematic, as seeing or whatever can introduce noise into the focus measurements. I use 10%, you can experiment with 5% too, but I'd stay away from very tight tolerances.

I like full-field with an annulus to reduce the HFR noise, but I don't bother with multiple samples.

I use SEP for the star detection. If you don't see reasonable star-detection, you need to play with the SEP profile.

Bottom line, to find a decent step-size parameter, set your system to pretty well focused, then start the Linear algorithm. It will move outside focus and start stepping inward. You want to see a reasonable sampling size. Perhaps each sample gives a small improvement or degradation as it moves near the optimal focus. You don't want to see large jumps near the focus point (too large a step size), and you don't want to see several samples with the same focus (too small a step size). You will see a second inward pass after the system establishes a v-curve where your original step size is halved, and finally some fine-tuning for the final focus at the end once the solution is pending.

Hy
AP1100 & Orion Atlas Pro, WO/ZS105 w/Moonlight V2 focus, GSO RC10 w/RSF focus
ZWO ASI1600, Astronomik Filters, ST80, QHY 5L-IIm.
KStars/Ekos/Indi on NUC10 & RPi4 w/SSD -- Ubuntu
Projects: Greedy Scheduler, Terrain, Polar Align, Analyze, Linear Focuser, SEP MultiStar & GPG Guide, FITS autostretch.
The following user(s) said Thank You: Ron Clanton, Rafael Schlegel
5 months 2 weeks ago #78223
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Hy,

Thanks!  Very helpful.

A couple of questions:
  • What is the percent tolerance measuring?  Is it the percent difference in the final HFR from the best HFR?
  • Why do you use "Small Sized Stars" in the SEP Profile?
  • Also, noticed that you didn't check "dark".  Wouldn't darks help?
Thanks a lot.  Hopefully I can try it out in the next couple of days.  Unfortunately, it's cloudy tonight.  :-(

Ron
Mounts: Sky-Watcher EQ6-R Pro, Meade LX85, Celestron NexStar Evolution Alt/Az
OTAs: Celestron 8" Edge HD w/Celestron Focus Motor, Meade 80mm APO Triplet Refractor w/ZWO EAF
Cameras: ASI533MC Pro, ASI183MC Pro, ASI224MC, ASI120MC-S, ZWO ASI290MM
Raspberry Pi 4 with Stellarmate OS, MacBook Pro
Last edit: 5 months 2 weeks ago by Ron Clanton.
5 months 2 weeks ago #78225

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1) The first pass finds a v-curve with a "best HFR" at the minimum. The 2nd pass is successful if it finds a position within tolerance of that minimum. E.g. if the min HFR is 1.0, and tolerance is 10%, then it will accept an HFR of 1.1 or less as a solution, though if the HFR is falling during the 2nd pass, it will continue to sample and move in until the HFR stops falling.

2) Don't recall how I wound up with that profile. I guess I tried the different ones and saw which seemed to detect stars the best. Again, I don't think one needs to optimize too much, just make sure that star detection is decent. I may have adjusted some of the parameters in the profiles.

3) I haven't experimented with darks yet. No good reason why not, but I believe my focus is working reasonably well without them.

Hy
AP1100 & Orion Atlas Pro, WO/ZS105 w/Moonlight V2 focus, GSO RC10 w/RSF focus
ZWO ASI1600, Astronomik Filters, ST80, QHY 5L-IIm.
KStars/Ekos/Indi on NUC10 & RPi4 w/SSD -- Ubuntu
Projects: Greedy Scheduler, Terrain, Polar Align, Analyze, Linear Focuser, SEP MultiStar & GPG Guide, FITS autostretch.
The following user(s) said Thank You: Ron Clanton
Last edit: 5 months 2 weeks ago by Hy Murveit.
5 months 2 weeks ago #78227

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Thanks!

Ron
Mounts: Sky-Watcher EQ6-R Pro, Meade LX85, Celestron NexStar Evolution Alt/Az
OTAs: Celestron 8" Edge HD w/Celestron Focus Motor, Meade 80mm APO Triplet Refractor w/ZWO EAF
Cameras: ASI533MC Pro, ASI183MC Pro, ASI224MC, ASI120MC-S, ZWO ASI290MM
Raspberry Pi 4 with Stellarmate OS, MacBook Pro
5 months 2 weeks ago #78229

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Hi Ron, Hy's given you what amounts to some coarse rules of thumb. If you are interested in precision (to avoid wasted time), I suggest you become familiar with and calculate your critical focus zone size, and measure your focuser drawtube travel. The 3rd important variable is your motor counts per revolution (focuser motor). You don't want to set a step size larger than the CFZ (otherwise, you'll just jump over best focus). Too small and you'll waste time walking through several measurements in the same CFZ.
The CFZ topic and calculation (don't be scared by the math...it's easy enough) are covered here:
www.goldastro.com/goldfocus/ncfz.php
Some minor time spent reading another related topic can help too (starting at the link):
indilib.org/forum/ekos/8963-question-abo...e.html?start=0#68078
You'll then be in position to set that step size properly and with confidence that your V curve will be sized right. In an ideal world, the step size setting should be automatic (based on other system parameters), but it's not too hard to set manually. You'll also have a better handle on how seeing affects needed precision.
Good luck and happy readings, Doug
RASA11, Celestron CGX-L, ASI183mc Pro, 60mm guider + ASI290mm mini, ASI EAF focuser, PPB, Rpi4-4Gb+SSD, Powered USB3 hub, hardwire Ethernet.
The following user(s) said Thank You: Ron Clanton
5 months 2 weeks ago #78233

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Doug,

Okay... I think I understand the concept of NCFZ. I'll get the calculator out and give it a whirl! Man, this is cool stuff!  So... just a couple of questions:
  • Once I have calculated the NCFZ and translated that length into EAF focus clicks, what step size should I put into EKOS?  For example, if the NCFZ calculates to 100 steps... would you use 50?
  • I understand the concept of seeing limits, but how/where do I get that measurement for a particularly night?
  • Since seeing is a variable, do you change your step size every night?
Thanks for the education!

Ron
Mounts: Sky-Watcher EQ6-R Pro, Meade LX85, Celestron NexStar Evolution Alt/Az
OTAs: Celestron 8" Edge HD w/Celestron Focus Motor, Meade 80mm APO Triplet Refractor w/ZWO EAF
Cameras: ASI533MC Pro, ASI183MC Pro, ASI224MC, ASI120MC-S, ZWO ASI290MM
Raspberry Pi 4 with Stellarmate OS, MacBook Pro
5 months 2 weeks ago #78235

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Yes, a 1/2 size setting should do the trick pretty well. On very rare occasion, you might land at the extreme edge of the CFZ, so if you wanted to short that 1/2 by a tad, that would give a bit of insurance that you're always going to be in the zone.

Seeing is often estimated by double star separations (visual observers do this regularly). You can get a coarse feel for seeing over time by watching HFR floor values during focus runs too.

Generally, I don't change my step size. I know my site, and it's nominal seeing spread. I factor the step size for good/very good conditions, leave it there, and accept that the "actual" CFZ for a lesser seeing condition will be larger. I accept some wasted measurements in those conditions (while praying for seeing to improve!) ;-)
RASA11, Celestron CGX-L, ASI183mc Pro, 60mm guider + ASI290mm mini, ASI EAF focuser, PPB, Rpi4-4Gb+SSD, Powered USB3 hub, hardwire Ethernet.
The following user(s) said Thank You: Ron Clanton
5 months 2 weeks ago #78240

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Doug,

Okay... I'm working on getting all the information/measurements to calculate the CFZ for my setups.  However, I'm having difficulty finding an estimate of "seeing" for various conditions.  I use Astrospheric to monitor and predict conditions in my area.  Is there a rough equivalent for their ratings of excellent, good, average, etc. to seeing arc-seconds?  I read some articles about measuring double stars... but wow.  I've looked for other sources on how to estimate the seeing in arc-seconds, but am not coming up with anything.

Thanks,

Ron
Mounts: Sky-Watcher EQ6-R Pro, Meade LX85, Celestron NexStar Evolution Alt/Az
OTAs: Celestron 8" Edge HD w/Celestron Focus Motor, Meade 80mm APO Triplet Refractor w/ZWO EAF
Cameras: ASI533MC Pro, ASI183MC Pro, ASI224MC, ASI120MC-S, ZWO ASI290MM
Raspberry Pi 4 with Stellarmate OS, MacBook Pro
5 months 2 weeks ago #78268

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Replied by Doug S on topic ~

Hi Ron, no need to spend too much time on the seeing issue. Unless you live on a mountain top, you won't experience 1 arcsecond seeing very often (and possibly never). Most amateur sites are in the 1.5 (best) to 3 (or worse) arcsec seeing regime. If you set up CFZ for ~2 arcsecs seeing, you'll be fine with that 1/2 mark discussed previously. Then, if by chance you get lucky and get 1.5 arcsecs or better on that rare occasion, you're still likely to be fine. Hope that helps, Doug
RASA11, Celestron CGX-L, ASI183mc Pro, 60mm guider + ASI290mm mini, ASI EAF focuser, PPB, Rpi4-4Gb+SSD, Powered USB3 hub, hardwire Ethernet.
The following user(s) said Thank You: Ron Clanton
5 months 2 weeks ago #78270

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Replied by Ron Clanton on topic ~

Thanks!
Mounts: Sky-Watcher EQ6-R Pro, Meade LX85, Celestron NexStar Evolution Alt/Az
OTAs: Celestron 8" Edge HD w/Celestron Focus Motor, Meade 80mm APO Triplet Refractor w/ZWO EAF
Cameras: ASI533MC Pro, ASI183MC Pro, ASI224MC, ASI120MC-S, ZWO ASI290MM
Raspberry Pi 4 with Stellarmate OS, MacBook Pro
5 months 2 weeks ago #78284

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