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Voyager Focusing Experiences

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#1 rockstarbill

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Posted 09 October 2019 - 11:26 PM

Hello, 

 

Wanted to open a thread up for folks to share their experiences with Voyager focus. This is not a thread to discuss SGP, SkyX, FocusMax, etc... It is to talk about and share experiences with Voyager focus.

 

I'll kick it off by showing my most recent focus tonight. This was taken with a FLI ML16200 camera, AP 92mm refractor, with the G filter, in 86%-ish moon. Unguided, using APCC Pro/APPM.

 

Voyager_G_filter_focus.png

 

Thats in HFD, so the HFR of this was 0.835.

 

Very, very impressive. The focuser is a 2.5" Feathertouch focuser using a Starlight Instruments Handy Stepper Motor. I have no backlash compensation enabled (even though the focus motor does have backlash). The controller here is the Pegasus Astro Powerbox v2 with a custom cable I made. The lack of care about backlash compensation comes from my familiarity with the ML alg used in Voyager focus. In my experience, over time, you dont need to bother. It will figure it out on its own.

 

laugh.gif

 

Result?

 

Result.JPG

 

 

More Results.JPG


Edited by rockstarbill, 09 October 2019 - 11:35 PM.

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#2 Peter in Reno

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Posted 09 October 2019 - 11:41 PM

Very nice. Please note that the HFR/HFD measurement is in pixels, not arcseconds. It's probably likely HFR/HFD in pixels will be larger as the image scale gets larger (but actual FWHM will get smaller in arcseconds), correct?

 

I too use Voyager but so far I have been using LocalField to avoid Meridian Flipping when I was imaging an object at Southern sky but I don't remember what the HFR/HFD was but it resulted very nice focus curve. I used backlash compensation of 200 steps which may be an overkill but it does not matter if backlash compensation setting is larger than actual backlash size. If the focuser actually has backlash mechanically then it's a good idea to have backlash compensation set in Voyager and Leo recommended it regardless of the result of Voyager's VCurve First Light Wizard.

 

Voyager does a wonderful job of auto focusing.

 

Peter



#3 Peter in Reno

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Posted 09 October 2019 - 11:46 PM

BTW, I noticed you are using Voyager Web Dashboard, where can I find my IP/Hostname to fill it in?

 

Sorry to be slightly off topic.

 

Thanks,

Peter



#4 rockstarbill

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Posted 09 October 2019 - 11:46 PM

Very nice. Please note that the HFR/HFD measurement is in pixels, not arcseconds. It's probably likely HFR/HFD in pixels will be larger as the image scale gets larger (but actual FWHM will get smaller in arcseconds), correct?

 

I too use Voyager but so far I have been using LocalField to avoid Meridian Flipping when I was imaging an object at Southern sky but I don't remember what the HFR/HFD was but it resulted very nice focus curve. I used backlash compensation of 200 steps which may be an overkill but it does not matter if backlash compensation setting is larger than actual backlash size. If the focuser actually has backlash mechanically then it's a good idea to have backlash compensation set in Voyager and Leo recommended it regardless of the result of Voyager's VCurve First Light Wizard.

 

Voyager does a wonderful job of auto focusing.

 

Peter

Correct. 

 

Robostar will not execute close to the meridian. It will wait for the flip to focus. Considering how deadly accurate it is, the extra time shouldn't matter. 

 

Here is a frame taken, with the same focus run, 20 mins later:

 

https://drive.google...5ZuCUDHyqpWzKEe

 

I have tested using Backlash comp, and not using it, and I have found that over time, not using it is better. But if you like the results you get, keep on keeping on. cool.gif

 

Download that frame though. That is ridiculous focus. We have a 86% moon, and I have 50 m/s jet stream overhead. The frame is 3 mins, unguided. :D



#5 rockstarbill

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Posted 09 October 2019 - 11:47 PM

BTW, I noticed you are using Voyager Web Dashboard, where can I find my IP/Hostname to fill it in?

 

Sorry to be slightly off topic.

 

Thanks,

Peter

Local IP from your router. Whatever local IP the device uses, you input that and connect. 

 

Go here: 

http://www.starkeeper.it/wdash/

 

Plug in the local IP, and hit connect. :D



#6 Peter in Reno

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Posted 10 October 2019 - 12:08 AM

Does Voyager need to connect to astro gears first before using Dashboard? Is there anything I have to do first before using Dashboard?

 

Is there a documentation for Dashboard?

 

Peter



#7 rockstarbill

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Posted 10 October 2019 - 12:16 AM

It does not need to be connected first, you can use the dashboard to connect gear, load a sequence file, and load a dragscript file, if they exist on the machine running Voyager with the server component enabled. smile.gif

 

I think the documentation is still WIP -- this is a beta after all.

 

You have to have Voyager open, and the server component enabled.


Edited by rockstarbill, 10 October 2019 - 12:21 AM.


#8 Peter in Reno

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Posted 10 October 2019 - 12:57 AM

Finally got it working. It turned out the IP address is for my laptop where Voyager resides.

 

Thanks,

Peter


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#9 Peter in Reno

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Posted 10 October 2019 - 01:08 AM

I am testing the Dashboard indoors and my laptop is connected to astro gears. What a wicked software to be able to control my astro gears with my Android tablet!!!!!

 

Peter


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#10 rockstarbill

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Posted 10 October 2019 - 01:10 AM

I am testing the Dashboard indoors and my laptop is connected to astro gears. What a wicked software to be able to control my astro gears with my Android tablet!!!!!

 

Peter

Use the zoom function on the last image that came in. It uses the PixInisght STF, and lets you zoom and pan around. So cool. cool.gif


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#11 Peter in Reno

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Posted 10 October 2019 - 10:50 AM

I found out if you are using your setup locally, you can enter "localhost" instead of IP address, it also works. 

 

Peter 



#12 elmiko

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Posted 10 October 2019 - 01:28 PM

Neat presentation Rockstarbill! Which mount were you using?


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#13 rockstarbill

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Posted 10 October 2019 - 01:39 PM

My experience with Voyager focusing is it's quick but not super accurate and the application has stability issues. Also I've heard some horror stories about their customer support. 

 

HFR isn't useful without knowing the image scale. But I'm glad you're happy with it! :-)

I shared an image file so folks could do as they wish with it. I have had no application stability issues, and no issues with customer support. I spoke with Leo for two hours the other night to get more insight on some of the comments here on CN in other threads, and there are some misunderstandings, and false narratives being spread. 

 

That is not what this thread is about though. :) The focusing has been wonderful. 

 

Neat presentation Rockstarbill! Which mount were you using?

AP1100, I have not used my MyT in a bit. Soon though!


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#14 ArkabPriorSol

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Posted 10 October 2019 - 01:43 PM

Thank you for the data Bill. It's good to have many experiences and reference points.



#15 elmiko

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Posted 10 October 2019 - 01:52 PM

I shared an image file so folks could do as they wish with it. I have had no application stability issues, and no issues with customer support. I spoke with Leo for two hours the other night to get more insight on some of the comments here on CN in other threads, and there are some misunderstandings, and false narratives being spread. 

 

That is not what this thread is about though. smile.gif The focusing has been wonderful. 

 

AP1100, I have not used my MyT in a bit. Soon though!

Sweet mount! Thanks



#16 rathijit

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Posted 10 October 2019 - 04:13 PM

Quite impressive, Bill. How many seconds does it take for an AF run on your setup? I clocked my MoonLite focuser + EdgeHD w/ 0.x7 reducer + ASI1600MM camera setup to take 22 seconds on average with Voyager local field and RoboStar @ position. That's blazing fast compared to anything I have experienced.


Edited by rathijit, 10 October 2019 - 04:13 PM.

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#17 rockstarbill

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Posted 10 October 2019 - 04:46 PM

There are two AF modes, each have different characteristics. I use RoboStar focus, which will slew to a bright star, center it (via solving), and run focus, then slew back to my target, solve and center, then resumes imaging. This will not finish in 22 seconds, obviously. This focus method is optimized on quality, not speed. This gives me the best focus results and images.

 

There is LocalField focus, which will focus on the field you are imaging. This runs very quickly, I dont have any numbers on me but its pretty fast. I dont see why it would take any longer than 20-25 seconds or so. I do not use this when I am in sequence though.


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#18 rathijit

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Posted 10 October 2019 - 04:53 PM

There are two AF modes, each have different characteristics. I use RoboStar focus, which will slew to a bright star, center it (via solving), and run focus, then slew back to my target, solve and center, then resumes imaging. This will not finish in 22 seconds, obviously. This focus method is optimized on quality, not speed. This gives me the best focus results and images.

There is LocalField focus, which will focus on the field you are imaging. This runs very quickly, I dont have any numbers on me but its pretty fast. I dont see why it would take any longer than 20-25 seconds or so. I do not use this when I am in sequence though.

There is an option on the “on the fly” tab to run RobotStar @ actual position... this is what I tried without slewing. Luckily Voyager found a suitable star in the field of view to focus with. The other option I clocked was local field. Both methods did not slew my telescope, so both took about 22 seconds on my setup and ran quite consistently for me.

#19 rockstarbill

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Posted 10 October 2019 - 04:56 PM

There is an option on the “on the fly” tab to run RobotStar @ actual position... this is what I tried without slewing. Luckily Voyager found a suitable star in the field of view to focus with. The other option I clocked was local field. Both methods did not slew my telescope, so both took about 22 seconds on my setup and ran quite consistently for me.

I have used the actual position option, but only in the case where a bright star was in the center of my frame. I do not want it focusing off to the edge of my frame, as the overall frame focus can be impacted if you do that on systems with any slight field issues, etc. But yes, that is an option and it runs very, very quickly. 

 

Speed is only one aspect of focus though. Quality is another. Voyager's focus quality is great in my experience. 


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#20 rathijit

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Posted 10 October 2019 - 04:58 PM

I have used the actual position option, but only in the case where a bright star was in the center of my frame. I do not want it focusing off to the edge of my frame, as the overall frame focus can be impacted if you do that on systems with any slight field issues, etc. But yes, that is an option and it runs very, very quickly.

Speed is only one aspect of focus though. Quality is another. Voyager's focus quality is great in my experience.

Yes, I agree about the center of frame aspect of it and the quality.

#21 jhayes_tucson

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Posted 10 October 2019 - 05:05 PM

Hello, 

 

Wanted to open a thread up for folks to share their experiences with Voyager focus. This is not a thread to discuss SGP, SkyX, FocusMax, etc... It is to talk about and share experiences with Voyager focus.

 

I'll kick it off by showing my most recent focus tonight. This was taken with a FLI ML16200 camera, AP 92mm refractor, with the G filter, in 86%-ish moon. Unguided, using APCC Pro/APPM.

 

attachicon.gif Voyager_G_filter_focus.png

 

Thats in HFD, so the HFR of this was 0.835.

 

Very, very impressive. The focuser is a 2.5" Feathertouch focuser using a Starlight Instruments Handy Stepper Motor. I have no backlash compensation enabled (even though the focus motor does have backlash). The controller here is the Pegasus Astro Powerbox v2 with a custom cable I made. The lack of care about backlash compensation comes from my familiarity with the ML alg used in Voyager focus. In my experience, over time, you dont need to bother. It will figure it out on its own.

 

laugh.gif

 

Result?

 

attachicon.gif Result.JPG

 

 

attachicon.gif More Results.JPG

 

 

Bill,

The focus does indeed look very good but I'm scratching my head over your numbers here.  The Airy disk size for your 92 mm, F/6.65 scope is 8.93 microns in the focal plane, which is 1.48 pixels on your camera and 3" in the sky (@ 550 nm.)  You are sampling at a rate of 2"/px with your camera.  The number that concerns me is the medial FWHM of 1.584 pixels using a Moffet4 fit.  That number is right at the limit of your optical system, which would be pretty good (and maybe possible with a 92 mm scope;) but, it's a red flag--even considering the HFD value of 1.67 px computed by Voyager.  The Moffet4 fit is a pretty good model for a stack of very high quality data and for for star images taken under pretty poor seeing; however, it is a poor indicator of FWHM on high quality star images.  So, your data jumps out as suspect--in more than one way, which I'll discuss next.  

 

In order to achieve an accurate measure of FWHM, it's important to fit to the correct Moffet order.  You can find the nearest Moffet order by using the DynamicPSF tool in PI.  Sample a number of well exposed stars and look at the "beta" value for each star.  That's the exact "best least squares fit" Moffet order needed to minimize the fitting errors shown in the MAD (Mean Average Deviation) column.  The higher order Moffet functions tend to be less sharply peaked with a much wider "base".  When you use the FWHMEccentricity tool, you can't use the best fit order so you have to use one of those provided.  In your case, I suspect that the best fit Moffet order might be either 2.5 or maybe even 1.5.  When you get the fit right, you'll find that the FWHM as measured by the FWHMEccentricity tool will decrease a bit.  In your case, I bet that you'll find that you'll see FWHM measures somewhere between 1.1 and maybe 1.3 pixels.  Combine that estimate with the fact that you have the Upper Limit set at 1.00 and that you measured 4042 stars tells me that you are most likely measuring mostly hot pixels due to dark current.  Setting the Upper Limit to say 0.8 excludes using over-exposed stars, which will bias the results toward too large of a value as well as eliminating saturated hot pixels.  Setting the star detection sensitivity to a higher value will prevent including too many extremely faint "blimps" in the data.  You have a lot of stars in that image but using over 4,000 stars is red flag that the algorithm is picking up too much garbage in the image.  Try adjusting that value until you get 300-500 stars with the upper limit set to 0.8.  More is not better!  You want a good sample of properly exposed stars only.  Then examine the support image to make sure that you aren't picking up warm/hot pixels.  That's how to get a more accurate reading of the performance of your system.

 

I'll be really impressed if you are indeed operating at the diffraction limit of your system but don't be surprised if the FWHM is closer to 4" or 5".  The HFD number shown by Voyager looks really good but it does not represent the final result in your image.

 

Finally, I have one other comment.  Seeing a good result from any autofocus routine is great but it's always a good idea to cross check the result against another method.  The simplest way to confirm both the accuracy and repeatability of autofocus is to cross-check it using a Bahtinov mask.  It's not hard to judge focus to within about 1/10 wave using a B-mask and that's a very good way to make sure that the final focus is spot on.  Run the autofocus routine say 10 times and carefully check it each time with the B-mask.  If it's good each time, you have very high confidence of the result--both in terms of accuracy and repeatability.

 

John


Edited by jhayes_tucson, 10 October 2019 - 08:37 PM.

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#22 rockstarbill

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Posted 10 October 2019 - 05:11 PM

Great comments, John. I will have a look at these suggestions this evening while my system is running. I've bookmarked this as well, as this is great information on how to dig into data quality more.

 

I will post an update this evening with what I find.


Edited by rockstarbill, 10 October 2019 - 05:13 PM.

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#23 tjugo

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Posted 10 October 2019 - 05:13 PM

Pure HDF figures are not very useful, for instance I have 2 systems with very different image scales, during the same night one system in focus produces an HDF of 2 and the other an HDF of 0.8

 

In my experience Voyager is as accurate as FocusMax (sorry to bring up a comparison, but FocusMax IMO is the the gold standard for autofocus), however Voyager is way faster than FM. Another nice feature of Voyagers autofocus routine is that all the platesolves are done with the L filter, doing the solves with the clear filter makes focusing with the norrowband filters a practical reality. No need to use offsets.

 

The LocalField routine is also very accurate and convenient but I prefer the single star routine (I feel more in control).

 

Cheers,

 

Jose


Edited by tjugo, 10 October 2019 - 05:38 PM.

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#24 rockstarbill

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Posted 10 October 2019 - 05:27 PM

Pure HDF figures are not very useful, for instance I have 2 systems with very different image scales, during the same night one system in focus produces an HDF of 2 and the other an HDF of 0.8

 

In my experience Voyager is as accurate as FocusMax (sorry to bring up a comparison, but FocusMax IMO is the the gold standard for autofocus), however Voyager is way faster than FM. Another nice feature of Voyagers autofocus routine is that all the platesolves are done with the L filter, doing the solves with the clear filter makes focusing with the norrowband filters a practical reality. No need to use offsets.

 

The reason you don't need backlash compensation to achieve good focus is because Voyagers (and FocusMax) only moves the focuser in one direction during the run, they only walk one side of the VCurve so no backlash compensation is needed at all.

 

The LocalField routine is also very accurate and convenient but I prefer the single star routine (I feel more in control).

 

Cheers,

 

Jose

Agreed. In this case I was providing all of the data for folks to see, poke at, etc.

 

Focus Max isnt off topic though, as Voyager supports the use of Focus Max.



#25 freestar8n

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Posted 10 October 2019 - 05:35 PM

I don’t know how voyager finds focus but if it makes multiple measurements as it goes through focus, the actual measurements it made would be helpful to know how confidently it worked.

As for backlash compensation - any system that measures focus in one direction will need to apply compensation because it will need to go to the extreme position and then reverse. As a result it will need to overshoot that spot and come back.

But all these systems need to do that only once to find focus - and then again to return to focus. This is a mechanical limitation and there is no way around it.

Frank


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