OAG tracking too coarse with ASIAIR

jbradsh

I am having grief with ASIAIR - looks great and most of it works (upgraded to 1.3x yesterday and firmware updated at first login). But I have yet to get a satisfactory set of exposures on ASAIR guiding despite a lot of trying.

For starters the guiding with my OAG/ZWO120Mini is too coarse with trailed stars even on 480mm refractor at 60 secs with pretty good polar alignment (ZWO 178MMC as main camera). I have aggressiveness at 5% RA and DEC and max pulse length at 1msec RA and DEC (calibration step 3ms) (Mount is HEQ5Pro connected through synscan handset) (Eqmod cable not recognised — leave that for another day). But tracking is +/- 4" or greater. Tonight is a very still night so it is not chasing seeing as far I can tell.

It feels like it would be good to have an option for even shorter max pulse length (even down to 0.1 mSec max) — is it possible? (Or is it even likely to be helpful?) - it feels like increased aggressively with gentler nudges (it goes from one +4" to further than -4" when it corrects) would be useful as an option.

I wanted to get a single module going (ASIAIR/Main Camera/EFW/OAG with tracking camera,ideally EQMOD permanently bolted together) that I could shift from one scope to another as my preferred scope is 1200mm, but that is a pipe dream with tracking like this. (But I can do it with my MGEN autoguider so its not impossible).

Anyone out there doing OAG? Any tips?

Is it possible to increase the range of Max Pulse length and aggressiveness available in the software?

jbradsh

PMTeam@ZWO

jbradsh wrote:

I am having grief with ASIAIR - looks great and most of it works (upgraded to 1.3x yesterday and firmware updated at first login). But I have yet to get a satisfactory set of exposures on ASAIR guiding despite a lot of trying.

For starters the guiding with my OAG/ZWO120Mini is too coarse with trailed stars even on 480mm refractor at 60 secs with pretty good polar alignment (ZWO 178MMC as main camera). I have aggressiveness at 5% RA and DEC and max pulse length at 1msec RA and DEC (calibration step 3ms) (Mount is HEQ5Pro connected through synscan handset) (Eqmod cable not recognised — leave that for another day). But tracking is +/- 4" or greater. Tonight is a very still night so it is not chasing seeing as far I can tell.

It feels like it would be good to have an option for even shorter max pulse length (even down to 0.1 mSec max) — is it possible? (Or is it even likely to be helpful?) - it feels like increased aggressively with gentler nudges (it goes from one +4" to further than -4" when it corrects) would be useful as an option.

I wanted to get a single module going (ASIAIR/Main Camera/EFW/OAG with tracking camera,ideally EQMOD permanently bolted together) that I could shift from one scope to another as my preferred scope is 1200mm, but that is a pipe dream with tracking like this. (But I can do it with my MGEN autoguider so its not impossible).

Anyone out there doing OAG? Any tips?

Is it possible to increase the range of Max Pulse length and aggressiveness available in the software?

jbradsh

Hello jbradsh,

I just a little confused about your questions, let's move on:

#1 You wanna shorter pulse for the calibration step of RA and DES, right?

#2 The Max Pulse length and aggressiveness can be adjusted in the app. What did you mean of increasing the range?

Thank you.

jbradsh

It appears that the only controls I have for guiding are 1) exposure time on guiding camera 2) max duration of guiding pulse in RA and DEC and 3) aggressiveness of guiding.

(I am curious to know if I change autoguider speed on my skywatcher synscan controller whether that will changes things as well as it was an option in ASIAIR, now removed it appears, and I hope to test this out tonight).

But control 2) above only goes down to 1mS and at this setting still kicks the mount 4 arc seconds or more which results in trailed stars. I would like the option to be able to send say 0.1-0.5mS pulse (if that is possible) so that the mount doesn't overcorrect so much.

So YES to question 1. I want a shorter pulse option in RA and DEC — but not for the calibration step, for the RA and DEC options just below that in asiair app.

(I assume the calibration step itself is only for when calibrating - I did have to drop calibration step as it lost star often during calibration at default but seemed ok at 2mS and 3mS).

I am aware max pulse and aggressiveness can be adjusted in the app - but the range of adjustment available in the shorter pulse direction for max pulse duration on RA and DEC seems not enough to get small corrections.

thanks for your reply.

jbradsh

PMTeam@ZWO

jbradsh wrote:

It appears that the only controls I have for guiding are 1) exposure time on guiding camera 2) max duration of guiding pulse in RA and DEC and 3) aggressiveness of guiding.

(I am curious to know if I change autoguider speed on my skywatcher synscan controller whether that will changes things as well as it was an option in ASIAIR, now removed it appears, and I hope to test this out tonight).

But control 2) above only goes down to 1mS and at this setting still kicks the mount 4 arc seconds or more which results in trailed stars. I would like the option to be able to send say 0.1-0.5mS pulse (if that is possible) so that the mount doesn't overcorrect so much.

So YES to question 1. I want a shorter pulse option in RA and DEC — but not for the calibration step, for the RA and DEC options just below that in asiair app.

(I assume the calibration step itself is only for when calibrating - I did have to drop calibration step as it lost star often during calibration at default but seemed ok at 2mS and 3mS).

I am aware max pulse and aggressiveness can be adjusted in the app - but the range of adjustment available in the shorter pulse direction for max pulse duration on RA and DEC seems not enough to get small corrections.

thanks for your reply.

jbradsh

Okay, it's so weird, let's check the last thing: how about your guiding rate (or speed)? Under the Guiding Settings page in-app.

jbradsh

Hi Ji,

It is set to 0.5x

I have been trying a few things so my setup has changed. I am now successfully using EQMOD (after finding that I have to support the weight of the cable to stop losing the connection from Skysafari pro. Unfortunately the weather has turned against me so I have not been able to test it under the stars though. I have also given up on OAG for the moment and am using your zwo60mm guidescope until I sort this out.

I also wondered it it was a backlash issue so I have done a mechanical tighten up on the HEQ5Pro but again have not had the weather to test it out on.

I wonder if it is too much weight for the HEQ5Pro (6kg load not counting counter weights is over the 50% of rated load people talk about but should be ok I thought on the still nights I had been having).

In the system I was using before changing to EQMOD -- asi120mm guiding through first oag (and then guidescope) with serial connection from asiair unit through synscan handset -- there was no option to set guiding rate in Telescope Settings. This has only appeared since I got EQMOD working.

(I did try setting Autoguider rate everything from 0.125x to 1x in synscan handset but that made no difference with the system above).

Jbradsh

PMTeam@ZWO

jbradsh wrote:

Hi Ji,

It is set to 0.5x

I have been trying a few things so my setup has changed. I am now successfully using EQMOD (after finding that I have to support the weight of the cable to stop losing the connection from Skysafari pro. Unfortunately the weather has turned against me so I have not been able to test it under the stars though. I have also given up on OAG for the moment and am using your zwo60mm guidescope until I sort this out.

I also wondered it it was a backlash issue so I have done a mechanical tighten up on the HEQ5Pro but again have not had the weather to test it out on.

I wonder if it is too much weight for the HEQ5Pro (6kg load not counting counter weights is over the 50% of rated load people talk about but should be ok I thought on the still nights I had been having).

In the system I was using before changing to EQMOD -- asi120mm guiding through first oag (and then guidescope) with serial connection from asiair unit through synscan handset -- there was no option to set guiding rate in Telescope Settings. This has only appeared since I got EQMOD working.

(I did try setting Autoguider rate everything from 0.125x to 1x in synscan handset but that made no difference with the system above).

Jbradsh

Hello Jbradsh,

Glad to hear that. Wish you have clear nights.

jbradsh

Clouds are against me so I don't know if I still have a problem — I suspect I do because EQMOD is limited to minimum 20mS guiding pulse in PHD as I understand it.

BUT

I would still be interested to know if anyone out there is successfully using OAG guiding with ASIAIR unit. and what gear they are using, at what settings, and what guiding quality they are getting.

(I can only find one web page mentioning the combination and they just dismiss the combination and say it doesnt work and go to PHD natively to try and sort out the tracking problem they have). The advantages -- in weight of gear and having a modular setup that can be shifted between telescopes easily and so on -- should be great if it can be done but I put a lot of work into serial connection guiding before I put this thread up and I can only say if it works it doesn't come easily with my gear (including small pixel size but still about 2 arcs/pixel which is fairly average ideal). But it looks like people expect 0.5-1" RMS guiding error with PHD, not +/- 4". And the error introduced can't be deconvoluted out because it looks like saturn in profile - big central blob and thin lines at each side protruding - nothing gaussian about that unfortunately.)

PMTeam@ZWO

jbradsh wrote:

Clouds are against me so I don't know if I still have a problem — I suspect I do because EQMOD is limited to minimum 20mS guiding pulse in PHD as I understand it.

BUT

I would still be interested to know if anyone out there is successfully using OAG guiding with ASIAIR unit. and what gear they are using, at what settings, and what guiding quality they are getting.

(I can only find one web page mentioning the combination and they just dismiss the combination and say it doesnt work and go to PHD natively to try and sort out the tracking problem they have). The advantages -- in weight of gear and having a modular setup that can be shifted between telescopes easily and so on -- should be great if it can be done but I put a lot of work into serial connection guiding before I put this thread up and I can only say if it works it doesn't come easily with my gear (including small pixel size but still about 2 arcs/pixel which is fairly average ideal). But it looks like people expect 0.5-1" RMS guiding error with PHD, not +/- 4". And the error introduced can't be deconvoluted out because it looks like saturn in profile - big central blob and thin lines at each side protruding - nothing gaussian about that unfortunately.)

Oh, the OAG guiding work great with ASIAIR, we dev team are using OAG for guiding in normal tests.

jbradsh

Thats good to know that it works for some people.

I'll keep working at it at my end then.

If I may ask what gear and what settings do you use when doing oag?

jbradsh

PMTeam@ZWO

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jsrj98

Hello,

I'm reopening this thread because I stopped using the ASIAir (even though I love so many of it's features) because I could never get the guiding to work optimally with my setup. I think the main issue is that I need to be able to control more PHD2 settings, particularly the MinMove for RA and DEC. Hard coding the MinMov to 0.20 pixels simply doesn't work for my setup. I need to change the MinMove to a much higher value because I have a longer FL than you're testing and I'm using the smaller pixel ASI290 as the guide camera. Below is what I'm using. With PHD2 I normally get about 0.6" to 0.8" RMS, whereas I can hardly get 1.0" RMS on the same night with ASIAir. My main camera arcsec/pixel is 1.02" and my guiding arcsec/pixel is 0.78". I love the setup I have so I'm going to continue use a Windows Laptop until ASIAir can provide more PHD2 configuration options.

Any thoughts to allow more PHD2 options?

Mount: HEQ5, Hypertuned, Belt-Modded, corrected residual error of about 8" or less

Main Scope: Intes MN55, 770mm, F5.5

Main Camera: ASI1600 Mono Pro, w/5p EFW

Guide Camera: ASI290Mini

Guiding w/: ZWO OAG + ZWO 1.25″ Helical Focuser

Focuser: ZWO EAF

Image Capture: N.I.N.A.

PMTeam@ZWO

jsrj98 wrote:

Hello,

I'm reopening this thread because I stopped using the ASIAir (even though I love so many of it's features) because I could never get the guiding to work optimally with my setup. I think the main issue is that I need to be able to control more PHD2 settings, particularly the MinMove for RA and DEC. Hard coding the MinMov to 0.20 pixels simply doesn't work for my setup. I need to change the MinMove to a much higher value because I have a longer FL than you're testing and I'm using the smaller pixel ASI290 as the guide camera. Below is what I'm using. With PHD2 I normally get about 0.6" to 0.8" RMS, whereas I can hardly get 1.0" RMS on the same night with ASIAir. My main camera arcsec/pixel is 1.02" and my guiding arcsec/pixel is 0.78". I love the setup I have so I'm going to continue use a Windows Laptop until ASIAir can provide more PHD2 configuration options.

Any thoughts to allow more PHD2 options?

Mount: HEQ5, Hypertuned, Belt-Modded, corrected residual error of about 8" or less

Main Scope: Intes MN55, 770mm, F5.5

Main Camera: ASI1600 Mono Pro, w/5p EFW

Guide Camera: ASI290Mini

Guiding w/: ZWO OAG + ZWO 1.25″ Helical Focuser

Focuser: ZWO EAF

Image Capture: N.I.N.A.

Hello,

We want to keep the ASIAIR simpler, so maybe we can't add more options to it. But, your advice will be feedback to our team.

w7ay

Ji xian sheng,

PHD2 Minimum Move (MinMo) and low pass filter (LPF) parameters are not just for advanced users, but also required by beginners who own mounts that have large periodic errors (PE), but with very long periods.

Because of the long periods (for example, 430.82 seconds for the Rainbow Astro RST-135), the large PE (40 to 50 arc seconds peak-to-peak with the RST-135) is actually correctable, but you either need a very small MinMo value, or guide scopes that have very long focal lengths, together with very short sampling time (guide scope exposure) .

Because of the short sampling time, you also need the PHD2 low pass filter so that when "seeing" becomes poor, you won't be tracking the seeing.

Examples of mounts that exhibit these behavior include mounts that incorporate strain wave gears ("harmonic drive") such as the RainbowAstro RST-135, 150h and the Hobym Crux 170HD. Additionally, the Avalon M-zero (belt drive) also has large PE, but long periods.

This Avalon web page has recommendations of MinMo, exposure, and lowpass mount guide algorithm:

https://www.avalon-instruments.com/13-troubleshooting/117-phd2-guide-suggested-parameters

You can see from the above that Avalon recommends a MinMo of zero (!), while using the Lowpass2 filter, and an exposure time of 0.5 to 1 second.

All that is needed is an Advance Button that allows the user to type in the MnMo value, and be able to select Lowpass2 or Default as the Mount Guide Algorithm. These parameters can then be sent to PHD2.

Best regards,

Chen

PMTeam@ZWO

W7AY wrote:

Ji xian sheng,

PHD2 Minimum Move (MinMo) and low pass filter (LPF) parameters are not just for advanced users, but also required by beginners who own mounts that have large periodic errors (PE), but with very long periods.

Because of the long periods (for example, 430.82 seconds for the Rainbow Astro RST-135), the large PE (40 to 50 arc seconds peak-to-peak with the RST-135) is actually correctable, but you either need a very small MinMo value, or guide scopes that have very long focal lengths, together with very short sampling time (guide scope exposure) .

Because of the short sampling time, you also need the PHD2 low pass filter so that when "seeing" becomes poor, you won't be tracking the seeing.

Examples of mounts that exhibit these behavior include mounts that incorporate strain wave gears ("harmonic drive") such as the RainbowAstro RST-135, 150h and the Hobym Crux 170HD. Additionally, the Avalon M-zero (belt drive) also has large PE, but long periods.

This Avalon web page has recommendations of MinMo, exposure, and lowpass mount guide algorithm:

https://www.avalon-instruments.com/13-troubleshooting/117-phd2-guide-suggested-parameters

You can see from the above that Avalon recommends a MinMo of zero (!), while using the Lowpass2 filter, and an exposure time of 0.5 to 1 second.

All that is needed is an Advance Button that allows the user to type in the MnMo value, and be able to select Lowpass2 or Default as the Mount Guide Algorithm. These parameters can then be sent to PHD2.

Best regards,

Chen

Hello Chen,

Got you, but I talked to our team, they said it's useless -- about the part. Also, I send them the . But I will keep an eye on it.

w7ay

>> Got you, but I talked to our team, they said it's useless -- about the part.

Make sure that they do simulations with short sampling periods, for the case when seeing is poor.

With my (indoor) experiments that has no "seeing" fluctuations, the optimal sampling period for the RainbowAstro RST-135 is 0.5 seconds. This proved out under real stars when seeing is good.

However, when seeing is poor with real stars, the sampling period has to be increased to 1 to 2 seconds. (If you take the time derivative of a sine wave with 50 arc second p-p that has a period of 432 seconds, you will see why short exposures and small MinMo are more optimal). The LPF filters allows you to keep using a short sampling time when seeing is poor, while still tracking the large PE slope (time derivative) near the start and end of a sine wave period, albeit with a lag (thus affects the Bode plot of the feedback loop).

Again, the missing PHD2 parameters are not a matter of how experienced the user is. It is a function of the mount and seeing conditions.

You can see that there is no way an M-zero user on ASIAIR could do what Avalon recommends for their mounts (no PHD2 recommendations so far from RainbowAstro). Some users are disappointed with ASIAIR guiding performance compared to the full PHD2, when it is simply a case that the default parameters in ASIAIR are not optimal.

Regards,

Chen

PMTeam@ZWO

W7AY wrote:

>> Got you, but I talked to our team, they said it's useless -- about the part.

Make sure that they do simulations with short sampling periods, for the case when seeing is poor.

With my (indoor) experiments that has no "seeing" fluctuations, the optimal sampling period for the RainbowAstro RST-135 is 0.5 seconds. This proved out under real stars when seeing is good.

However, when seeing is poor with real stars, the sampling period has to be increased to 1 to 2 seconds. (If you take the time derivative of a sine wave with 50 arc second p-p that has a period of 432 seconds, you will see why short exposures and small MinMo are more optimal). The LPF filters allows you to keep using a short sampling time when seeing is poor, while still tracking the large PE slope (time derivative) near the start and end of a sine wave period, albeit with a lag (thus affects the Bode plot of the feedback loop).

Again, the missing PHD2 parameters are not a matter of how experienced the user is. It is a function of the mount and seeing conditions.

You can see that there is no way an M-zero user on ASIAIR could do what Avalon recommends for their mounts (no PHD2 recommendations so far from RainbowAstro). Some users are disappointed with ASIAIR guiding performance compared to the full PHD2, when it is simply a case that the default parameters in ASIAIR are not optimal.

Regards,

Chen

Hello Chen,

Yes, I agree with you. I will feedback to the team again. Thank you so much.

jbradsh

Just an update on my progress. I did get equally good results with the "normal" settings on OAG and improved by about 50% with some mechanical work on my mount but am still getting RMS about the order of 1-2 secs. Unfortunately bushfire smoke looks like wiping me out for months so I haven't been able to test very much (2 nights only since last posting). Certainly larger steps for calibration seems to have fixed the failed calibration problem although still getting a warning that DEC and RA vary by a larger than expected amount.

jbradsh

jsrj98

In reference to my comment above about the MinMove, I always use the Analyze feature in PHD2 before starting a session. Generally, the recommendations are:

Improve polar alignment (covered in ASIAir)

Change the MinMove for both Dec and RA (for my setup that is generally in the range of 0.4 to 0.7 depending on seeing)

Apply Backlash Compensation (I think ASIAir has that, I don't recall; i have very little backlash with my mount the way i have it modified)

You can see that if I could change the MinMove, I'd feel like I could use ASIAir on a consistent basis. While I often use the Predictive algorithm in PHD2 with my laptop, I could definitely live with the normal algorithm in ASIAir.

If I go to a remote imaging site (which I do rarely, unfortunately), then I would use the ASIAir with a guidescope confutation to better match the MinMove rather than with the OAG.