Date   

Re: Tracking and guiding with and without encoders - Part2

Roland Christen
 


It seems you're not claiming guiding results, particularly Total RMS, will be improved with encoders. 
Yes, for sure guiding results will improve with the encoders. Dec response is instant, zero backlash. RA periodic error goes away, so no PE curve is required. Makes long term adjustment, tweaking, maintenance negligible, especially for remote mounts. RA guiding becomes relatively easy since you don't have to guide at rapid rates. You can take longer guide exposures without having the guide star wander due to short term tracking errors. The Mach2 tracks measurably better than the Mach1 for sure. By a factor of 2 on good nights. And even on poor nights there is less wander especially in the Dec axis.

Rolando


-----Original Message-----
From: badgerz49@... [ap-gto]
To: ap-gto
Sent: Tue, Sep 17, 2019 9:11 am
Subject: Re: [ap-gto] Re: Tracking and guiding with and without encoders - Part2



Roland,

It seems you're not claiming guiding results, particularly Total RMS, will be improved with encoders.  That's what I wanted to know.

It's never been in doubt whether encoders remove fast oscillations.  The oscillations in your graph are very small over a typical 2-3 second guide interval.  Whether they're detectable in guided images is a different topic.  I don't know what the seeing threshold is to notice them but I image it's beyond what most/all of us will ever have.

Chad



Re: Tracking and guiding with and without encoders - Part2

Chad A
 

Ray,

Yes, comparing FWHM seems like a good way to quantify the difference.  Rapid changes in seeing might make it difficult to test properly.  Any difference in results should be statistically confirmed over many samples and repeatable.  The test would be:

Guided encoder off FWHM vs. 1 second FWHM

against

Guided encoder on for same duration vs. 1 second FWHM

Chad







Re: Tracking and guiding with and without encoders - Part2

Ray Gralak
 

Hi Chad,

RMS guide error is the wrong measurement because it depends on the sampling of autoguider moves.

What you want to compare is average stellar FWHM and eccentricity of non-saturated stars in images. The image integrates light over the entire duration of an image and is the way to best determine guide quality. You want to compare the guided image's FWHM and eccentricity to those values in a very short duration image (e.g. 1 second duration).

-Ray Gralak
Author of APCC (Astro-Physics Command Center): http://www.astro-physics.com/index.htm?products/accessories/software/apcc/apcc
Author of PEMPro V3: https://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver

-----Original Message-----
From: ap-gto@yahoogroups.com [mailto:ap-gto@yahoogroups.com]
Sent: Tuesday, September 17, 2019 7:00 AM
To: ap-gto@yahoogroups.com
Subject: Re: [ap-gto] Re: Tracking and guiding with and without encoders - Part2



Roland,


It seems you're not claiming guiding results, particularly Total RMS, will be improved with encoders. That's what I
wanted to know.

It's never been in doubt whether encoders remove fast oscillations. The oscillations in your graph are very small
over a typical 2-3 second guide interval. Whether they're detectable in guided images is a different topic. I don't
know what the seeing threshold is to notice them but I image it's beyond what most/all of us will ever have.


Chad


Re: Tracking and guiding with and without encoders - Part2

Chad A
 

Roland,

It seems you're not claiming guiding results, particularly Total RMS, will be improved with encoders.  That's what I wanted to know.

It's never been in doubt whether encoders remove fast oscillations.  The oscillations in your graph are very small over a typical 2-3 second guide interval.  Whether they're detectable in guided images is a different topic.  I don't know what the seeing threshold is to notice them but I image it's beyond what most/all of us will ever have.

Chad


Re: New file uploaded to ap-gto

Bill Long
 

That image leaves no doubt. 


From: ap-gto@... Sent: Monday, September 16, 2019 3:17 PM
To: ap-gto@...
Subject: [ap-gto] New file uploaded to ap-gto
 
 

Hello,

This email message is a notification to let you know that
a file has been uploaded to the Files area of the ap-gto
group.

File : /Mach2 Dual Encoder Guided Imaging/TrackingComparison.jpg
Uploaded by : uncarollo2
Description : Encoder on vs encoder off - tracking test

You can access this file at the URL:
https://groups.yahoo.com/neo/groups/ap-gto/files/Mach2%20Dual%20Encoder%20Guided%20Imaging/TrackingComparison.jpg

To learn more about file sharing for your group, please visit:
https://help.yahoo.com/kb/index?page=content&y=PROD_GRPS&locale=en_US&id=SLN15398

Regards,

uncarollo2


New file uploaded to ap-gto

ap-gto@...
 

Hello,

This email message is a notification to let you know that
a file has been uploaded to the Files area of the ap-gto
group.

File : /Mach2 Dual Encoder Guided Imaging/TrackingResponse.jpg
Uploaded by : uncarollo2 <chris1011@aol.com>
Description : Mach 2 tracking response with encoders on. 0.5 sec sec move commands sent at various intervals.

You can access this file at the URL:
https://groups.yahoo.com/neo/groups/ap-gto/files/Mach2%20Dual%20Encoder%20Guided%20Imaging/TrackingResponse.jpg

To learn more about file sharing for your group, please visit:
https://help.yahoo.com/kb/index?page=content&y=PROD_GRPS&locale=en_US&id=SLN15398

Regards,

uncarollo2 <chris1011@aol.com>


New file uploaded to ap-gto

ap-gto@...
 

Hello,

This email message is a notification to let you know that
a file has been uploaded to the Files area of the ap-gto
group.

File : /Mach2 Dual Encoder Guided Imaging/TrackingComparison.jpg
Uploaded by : uncarollo2 <chris1011@aol.com>
Description : Encoder on vs encoder off - tracking test

You can access this file at the URL:
https://groups.yahoo.com/neo/groups/ap-gto/files/Mach2%20Dual%20Encoder%20Guided%20Imaging/TrackingComparison.jpg

To learn more about file sharing for your group, please visit:
https://help.yahoo.com/kb/index?page=content&y=PROD_GRPS&locale=en_US&id=SLN15398

Regards,

uncarollo2 <chris1011@aol.com>


Re: Using the GTO keypad with the Mach2

Roland Christen
 

We will always have a full functioning keypad - the one we sell now. I use it almost always, even if I am imaging with other software.

Rolando



-----Original Message-----
From: mike.hambrick@... [ap-gto]
To: ap-gto
Sent: Mon, Sep 16, 2019 4:43 pm
Subject: Re: [ap-gto] Using the GTO keypad with the Mach2



Not everyone uses just a PC for imaging. I still like having a fully functional keypad


Best Regards

Michael Hambrick
ARLANXEO
TSR Global Manufacturing Support
PO Box 2000
Orange, TX 77631-2000
Phone: +1 (409) 882-2799
email: mike.hambrick@...




From:        "chris1011@... [ap-gto]"
To:        ap-gto@...
Date:        09/14/2019 07:04 PM
Subject:        Re: [ap-gto] Using the GTO keypad with the Mach2
Sent by:        ap-gto@...




 
What we do need is a keypad we can see during the day when we're doing maintenance stuff.
I hear you. We actually are thinking of adding a minimalist keypad with Oleg screen that shows up in the daytime. One of our customers developed one and it is really nice. We just have to work out some things, but like you i do want this also.

Rolando


-----Original Message-----
From: 'Greg Salyer' astronutcase@... [ap-gto]
To: ap-gto
Sent: Sat, Sep 14, 2019 5:45 pm
Subject: RE: [ap-gto] Using the GTO keypad with the Mach2



Rolando, I don't mean to start anything, but most imagers have their mount connected to a PC and therefore don't need the keypad - at least at night. What we do need is a keypad we can see during the day when we're doing maintenance stuff. Your keypad is great but only at night. During the day it's a real pain. Every time I'm forced to use it I keep thinking of the easy to read in the daylight keypad on the cheap mount I use for visual stuff. Will we ever see an AP keypad usable during the day?
 
Greg
 
From: ap-gto@... [mailto:ap-gto@...]
Sent:
Saturday, September 14, 2019 5:47 PM
To:
ap-gto@...
Subject:
Re: [ap-gto] Using the GTO keypad with the Mach2

 
 
Nothing has changed on the keypad physically. Some of the buttons may change function. We don't have a final software set yet. We are adding in some things that will be very useful to imagers.
 
Rolando
 
 
 






Re: Using the GTO keypad with the Mach2

mike.hambrick@...
 

Not everyone uses just a PC for imaging. I still like having a fully functional keypad


Best Regards

Michael Hambrick
ARLANXEO
TSR Global Manufacturing Support
PO Box 2000
Orange, TX 77631-2000
Phone: +1 (409) 882-2799
email: mike.hambrick@...




From:        "chris1011@... [ap-gto]" <ap-gto@...>
To:        ap-gto@...
Date:        09/14/2019 07:04 PM
Subject:        Re: [ap-gto] Using the GTO keypad with the Mach2
Sent by:        ap-gto@...




 

What we do need is a keypad we can see during the day when we're doing maintenance stuff.
I hear you. We actually are thinking of adding a minimalist keypad with Oleg screen that shows up in the daytime. One of our customers developed one and it is really nice. We just have to work out some things, but like you i do want this also.

Rolando


-----Original Message-----
From: 'Greg Salyer' astronutcase@... [ap-gto] <ap-gto@...>
To: ap-gto <ap-gto@...>
Sent: Sat, Sep 14, 2019 5:45 pm
Subject: RE: [ap-gto] Using the GTO keypad with the Mach2



Rolando, I don't mean to start anything, but most imagers have their mount connected to a PC and therefore don't need the keypad - at least at night. What we do need is a keypad we can see during the day when we're doing maintenance stuff. Your keypad is great but only at night. During the day it's a real pain. Every time I'm forced to use it I keep thinking of the easy to read in the daylight keypad on the cheap mount I use for visual stuff. Will we ever see an AP keypad usable during the day?
 
Greg
 
From: ap-gto@... [mailto:ap-gto@...]
Sent:
Saturday, September 14, 2019 5:47 PM
To:
ap-gto@...
Subject:
Re: [ap-gto] Using the GTO keypad with the Mach2

 
 
Nothing has changed on the keypad physically. Some of the buttons may change function. We don't have a final software set yet. We are adding in some things that will be very useful to imagers.
 
Rolando
 
 
 




Re: Tracking and guiding with and without encoders - Part2

Roland Christen
 

You are mixing apples and oranges. No wonder there is so much confusion. When you do 2 to 4 second guide exposures you are certainly not going to see very fast RA oscillations in the guide data. These oscillations happen quickly and can only be seen when you actually look at a star at rates faster than a guider can record. In my graphs I used sample rates of 100msec. You can do this with video on a small guide camera, but not at normal guide sample rates. Therefore all mounts can bury small fluctuation in RA tracking rates simply because they do not show up at long integration times.
If you don't know what these oscillations look like, here is one of many examples:https://www.cloudynights.com/topic/676345-cem-60ec-tracking-oscillations/

In this particular case it shows up at long focal lengths and is completely buried in the tracking graph when using 3  - 4 second integration times. Even though the guide chart shows maybe sub-arc sec guiding, the stars with that focal length are always a bit oval due to these p-p variations. And again, a belt drive isn't what does this, it's a microstepper motor without shaft encoder that can produce these fast moving oscillations. No amount of guiding can eliminate these.

Also, your seeing in both your examples is not good, average maybe for your skies, but we have to build mounts that can perform their best at sites that have excellent seeing without introducing mount tracking errors that would spoil the best results that could be obtained. This guiding graph (below) is what I would want the mount to achieve under good seeing, which in our case happens maybe once per month, but in places like Tuscon may happen every clear night. And that's taken at fairly long focal length with a long refractor:

-----Original Message-----
From: badgerz49@yahoo.com [ap-gto] <ap-gto@yahoogroups.com>
To: ap-gto <ap-gto@yahoogroups.com>
Sent: Mon, Sep 16, 2019 3:13 pm
Subject: Re: [ap-gto] Re: Tracking and guiding with and without encoders - Part2

#yiv2559891291 #yiv2559891291 -- #yiv2559891291 .yiv2559891291ygrp-photo-title{ clear:both;font-size:smaller;min-height:15px;overflow:hidden;text-align:center;width:75px;} #yiv2559891291 div.yiv2559891291ygrp-photo{ background-position:center;background-repeat:no-repeat;background-color:white;border:1px solid black;min-height:62px;width:62px;} #yiv2559891291 div.yiv2559891291photo-title a, #yiv2559891291 div.yiv2559891291photo-title a:active, #yiv2559891291 div.yiv2559891291photo-title a:hover, #yiv2559891291 div.yiv2559891291photo-title a:visited { text-decoration:none; } #yiv2559891291 div.yiv2559891291attach-table div.yiv2559891291attach-row { clear:both;} #yiv2559891291 div.yiv2559891291attach-table div.yiv2559891291attach-row div { float:left;} #yiv2559891291 p { clear:both;padding:15px 0 3px 0;overflow:hidden;} #yiv2559891291 div.yiv2559891291ygrp-file { width:30px;} #yiv2559891291 div.yiv2559891291attach-table div.yiv2559891291attach-row div div a { text-decoration:none;} #yiv2559891291 div.yiv2559891291attach-table div.yiv2559891291attach-row div div span { font-weight:normal;} #yiv2559891291 div.yiv2559891291ygrp-file-title { font-weight:bold;} #yiv2559891291 #yiv2559891291 #yiv2559891291 #yiv2559891291 -- #yiv2559891291ygrp-mkp { border:1px solid #d8d8d8;font-family:Arial;margin:10px 0;padding:0 10px;} #yiv2559891291 #yiv2559891291ygrp-mkp hr { border:1px solid #d8d8d8;} #yiv2559891291 #yiv2559891291ygrp-mkp #yiv2559891291hd { color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px 0;} #yiv2559891291 #yiv2559891291ygrp-mkp #yiv2559891291ads { margin-bottom:10px;} #yiv2559891291 #yiv2559891291ygrp-mkp .yiv2559891291ad { padding:0 0;} #yiv2559891291 #yiv2559891291ygrp-mkp .yiv2559891291ad p { margin:0;} #yiv2559891291 #yiv2559891291ygrp-mkp .yiv2559891291ad a { color:#0000ff;text-decoration:none;} #yiv2559891291

Roland,
P-P excursions are rare even with my belt-driven Atlas Pro.  Here's an image of guiding with two AP1100s and an Atlas Pro (top left) all at the same time with PEC disabled.  Excursions above 1" are infrequent (approx. 1/100 samples) and they're quickly guided out by PHD2.  Virtually none go above 1.5".  Total RMS is usually around .3" but seeing was mediocre this night.  
https://imgur.com/a/RDhtTaI

A PHD2 test of encoders vs. non-encoders would show excursions in the Target window.   Encoders should instantly remove excursions but when guiding are they really necessary and do they make a difference in the final result?  Maybe the belt-driven Mach 2 is a different story as you've noted.
Chad


Re: Tracking and guiding with and without encoders - Part2

Chad A
 

Roland,

P-P excursions are rare even with my belt-driven Atlas Pro.  Here's an image of guiding with two AP1100s and an Atlas Pro (top left) all at the same time with PEC disabled.  Excursions above 1" are infrequent (approx. 1/100 samples) and they're quickly guided out by PHD2.  Virtually none go above 1.5".  Total RMS is usually around .3" but seeing was mediocre this night.  


A PHD2 test of encoders vs. non-encoders would show excursions in the Target window.   Encoders should instantly remove excursions but when guiding are they really necessary and do they make a difference in the final result?  Maybe the belt-driven Mach 2 is a different story as you've noted.

Chad



Re: Tracking and guiding with and without encoders - Part2

Rick Socarras
 

Thankyou!

Rick


Re: Tracking and guiding with and without encoders - Part2

Bill Long
 

That was a FLI ML16200 camera. 


From: ap-gto@... <ap-gto@...> on behalf of Miguel Morales miguelmjr14@... [ap-gto]
Sent: Monday, September 16, 2019 9:23 AM
To: ap-gto@...
Subject: Re: [ap-gto] Re: Tracking and guiding with and without encoders - Part2
 
 

 

Hey Bill,

 

Just interested in what camera was used to take those images.

 

 

Miguel   8-)

 

.

 


Re: Tracking and guiding with and without encoders - Part2

Miguel Morales <miguelmjr14@...>
 

 

Hey Bill,

 

Just interested in what camera was used to take those images.

 

 

Miguel   8-)

 

.

 


Re: Tracking and guiding with and without encoders - Part2

miguelmjr14@...
 

Hey Bill,

Just interested in what camera was used to take those images.


Miguel   8-)

.


Re: Congratulations Ignacio and Alan!

Karen Christen
 

Those are just tremendous.  Thanks so much for sharing, Keith.  And a great big congrats to Ignacio and Alan!!

Karen

 

From: ap-gto@... [mailto:ap-gto@...]
Sent: Sunday, September 15, 2019 11:25 AM
To: ap-gto@...
Subject: [ap-gto] Congratulations Ignacio and Alan!

 

 

Insight Investment Astronomy Photographer of the Year 2019 winners using Astro-Physics scopes and mounts, well done gentlemen!



https://www.rmg.co.uk/whats-on/astronomy-photographer-year/galleries/2019/overall-winners

 

Congratulations to all the winners and participants who submitted some phenomenal images.

 

Keith


Re: Tracking and guiding with and without encoders - Part2

Roland Christen
 


I can see by the graphs that these motors are constantly correcting and therefore working hard. 
No, they are not working hard while constantly correcting. This is a fallacy. Microsteppers get fed a constant current which varies not one iota whether they are moving or not. That is completely different from DC servo motors where the motor current is dependent on the load. The current that is sent to a microstepper is always the same whether they are at rest (not moving) or turning at various rates while tracking.

Rolando


-----Original Message-----
From: tgrick@... [ap-gto]
To: ap-gto
Sent: Sun, Sep 15, 2019 4:41 pm
Subject: [ap-gto] Re: Tracking and guiding with and without encoders - Part2



Roland,

I can see by the graphs that these motors are constantly correcting and therefore working hard.  I'm located in BOILING HOT south Florida and expect to receive a Mach 2 in December if all goes well.  My question is simple...is there any concern about the motors overheating?  I also have solar telescopes so the daytime temperatures can get really hot.  Thoughts?  Sorry, I just worry about things getting too hot - experience!

Rick Socarras



Re: Tracking and guiding with and without encoders - Part2

Roland Christen
 

The Mach2 mount needs the encoders to be on in order to produce smooth tracking. Without the encoders the error of the microstepper will dominate and you will have elongation of the stars in RA even though the rms guiding might be sub-arc seconds. The rms value does not take into account the peak to peak excursions of the guide star, which can be 5 times the rms value. It's a lot like sticking your head in the oven and your feet in the freezer. Your average rms body temp might indeed be very comfortable.

You all may not realize this but most of the inexpensive mounts being sold today with microsteppers and belt drives have these fast moving p-p excursions. That's because they don't have any kind of encoder feedback, either on the motor shafts or on the mount axes. It's a well known effect of microstepping where the individual step sizes are not constant but vary by 5% in a typical stepper motor. These are fast moving errors that occur between 1 to 3 times per second depending on pulley ratio. Without encoder feedback you simply won't get smooth tracking. These show up as fast oscillations in the RA direction when used with longer focal length scopes such as SCTs. They may not show up when using short wide field instruments and they certainly won't show up when guiding at 3 second frame rates.

That's why DC and AC servo motor drives with spur gear reduction have smooth tracking rates because they must use encoders on the motor shafts simply because these motors won't work without them. Microsteppers do work without encoders and have been the cheap solution for low end mount manufacturers, but the downside is tracking wiggles.

Rolando



-----Original Message-----
From: badgerz49@... [ap-gto]
To: ap-gto
Sent: Sun, Sep 15, 2019 3:11 pm
Subject: [ap-gto] Re: Tracking and guiding with and without encoders - Part2



Roland, 

Without encoders your mounts already guide up to the limit imposed by seeing.  How much will encoders improve the results of guided imaging?  No one is questioning whether encoder mounts track better or are superior for unguided imaging.

A test like this would be helpful:

- Have encoders on, calibrate PHD2, use default PHD2 settings, set a 3 second guide interval, run 200-400 samples .... check the total RMS error

- Turn encoders off, have PEM disabled, recalibrate PHD2, default PHD2 settings, 3 second guide interval, run 200-400 samples .... check the total RMS error

Repeat the test a few times and compare.  It would be best to use optimal PHD2 settings with both encoders on and off.  The above test would be simple and give at least some idea of the difference though.

Chad







SGP/APCC meridian limits vs. Homing/limits

Rodolphe G.
 

Hi,

A bit lost here, hope somebody can shed some light on it.

I run SGP for unattended imaging sessions.

Would like to wait up to 10 minutes AFTER the theoretical meridian flip, to give a chance to the current image capture to complete.

Note I have almost no risk of having the telescope hit the pier by accident during the imaging session.


What would be the simplest way of doing this?


To me it looks like simply indicating "10" in the RA Limit box of the "Home and Limits Configuration" dialog box is enough, and of course disable settings in the "Meridian" tab altogether.


Did I get it right?


Thanks in advance,

Rodolphe


Re: Tracking and guiding with and without encoders - Part2

Chad A
 

Ok, that explains it.  Yes, PEMPro works great.

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