Guiding Rates

[mlewis...@gmail.com]

I have read "How to ask for help with PHD". I would love to post logs but I can't find them. I move all data from a night of imaging off of the mini PCs that I control my systems with. I am currently setting up 2 new imaging systems with 3 cameras and 3 PCs. I have the logs.... somewhere. For the time being I think we can get on with it without the logs.

I always use all of the various wizards and assistants to set up PHD2. It's worked out well for me that way over the years. Setting up the systems I'm workng witth now is no exception.

One of the systems I'm setting up now uses a Software Bisque MyT Mount. I have owned the mount for a couple of years. Up until now I have been using the Autoguiding app included with The SkyX Pro. I think there is something to be said for using a single source software provider in systems that are as complex as imaging systems can be. Except in this case. The SkyX is just too fragile for my taste. So I'm moving on to NINA and back to good old trusted, dependable PHD2.

My results with PHD2 are...I'm not sure. I guided this scope on a Celestron CGE Pro using the same guide camera as this and got much better guiding graphs. So I've started to try to tune things. Still I'm not certain that I have as much of a problem as it appears.

When I guided this scope previously I was using a Baader Vario Finder Scope (10x60, 250mm fl). Now I'm using the same camera (Starlight Xpress LodeStar Pro Mono) but on the off axis guider port of my QSI 683. Now My guide scope fl is 980mm. So I am not confident that identical guiding at the different focal lengths would display the same graphs. In other words, would the nice smooth graph I had at 250mm look not so good at 980mm even though the stars would be as round? I just don't know. I tend to tune systems until I get them as smooth as I can and no smoother. I think I have work to do here.

When I started using the Calibration assistant it reported to me that my mount guide rate was set to 50% and needs to be at least 50% to work effectively. I am a big believer in not putting a limiter on things and letting the guiding software decide how much to push the mount around. I've decided to go down this path to start smoothing things out.

Looking into how to adjust that setting for the MyT Mount I found the setting in TCS Settings. In the manual, where it discusses this setting it says;

"The general rule of thumb is that the fewer number of corrections to the mount’s position that are made during autoguided exposures, the better the resulting star profile. So, a the guide rate of 0.5 sidereal rate (the default setting) is the optimal value to achieve this goal."

So this creates a dilemma for me. My inclination is to follow the advice of the Calibration Assistant. My basic assumption is that Software Bisque's preferred settings would likely work well with their autoguiding routine, but it might not work best with PHD2. As I've decided PHD2 is the preferable routine, your recommendation will prevail in my decision making.

On the other hand I note that there are allowances  in PHD2 for Direct Guiding. I can see a possibility that might be a difference in guide rate settings. In the end I figure it's just best to ask the expert. If this were your equipment and you were setting it up to use with PHD2 what would you set the MyT Mount's Guide Rate to as a starting point?

The clouds will clear in a few days and I'll be at it again. I'll make sure to keep tabs on the logs and post if needed at that time.

Thank you,

Mike

[Brian Valente]

Hi Mike,

Actually the logs give us exactly what we need to give you feedback. I think you might be jumping the gun looking for solutions to problems you don't (yet?) have. 

Use the built-in log uploader feature in PHD under the Help menu. You don't have to know where the logs are, just follow the prompts and post the resulting link.

Regarding guidespeed, a higher guidespeed (i.e., closer to 1x) makes the system more responsive, but not all mounts can do that. The minimum you want is 0.5x sidereal. For something like a MyT that is a relatively well behaving mount, I wouldn't sweat this too much, certainly not at this point.

The calibration assistant offers good general advice to get things working and avoid common mistakes. How you tune it from there really depends on your results (i.e., the guidelogs)

For bisque mounts, you just need to make sure it's setup properly, following this guide https://github.com/OpenPHDGuiding/phd2/wiki/SkyX-Settings

Brian

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Brian Valente

astronomy portfolio https://www.astrobin.com/users/bvalente/ 

[Bruce Waddington]

The complaint from the Calibration Assistant about the guide speed doesn't matter in your case, it's because the SB driver doesn't report it correctly.  In the 2.6.13dev7 release, you won't see this message unless the mount guide speed is substantially below 0.5x sidereal.  If you're guiding a Paramount, you should also avoid slewing the scope while guiding is active - doing so will run you afoul of a different bug in the SB driver.

With regard to the appearance of the guiding graph, you should take a look at the Appendix of this document:

https://openphdguiding.org/tutorial-analyzing-phd2-guiding-results/

As Brian said, you're not going to get any accurate help on the forum if you can't post the correct log files.  Everything we do here is based on hard data because no two mounts or imaging setups are identical.  If you've chosen to move the PHD2 log files around, you now own the problem of where they are. :-)

Good luck,

Bruce

[mlewis...@gmail.com]

Well there are those pesky logs! Here’s the most recent.

[Bruce Waddington]

Please go back and read the 'Getting Help' instructions.  We need to see both the guide and matching debug log files which means you will need to upload them to our server rather than trying to use attachments.  If you have them stored on a different PC than the one you use for imaging, you can just install another copy of PHD2 over there just for the purpose of using the 'Update log files' menu function.

Bruce

[mlewis...@gmail.com]

Apologies, when I read "You need the log files" I took this literally. The "through the standard system." was implied. I really did read the If you need help.

Regardless, I have found both logs, downloaded PHD2 to my general porpoise PC, dropped the logs into the appropriate folder, and submitted. Here's the  Link .

And thank you for your patience and willingness to not only keep developing this software, but taking your time to help folks like me.

Clear skies and Cheers after

[Brian Valente]

Thanks Mike

FYI it looks like you are on an older dev release, make sure to update to dev7

(you can change update preferences in advanced settings to include dev releases)

The calibration looks pretty rough for a MyT. 

For now i would stick with shorter exposure of around 3 seconds until you get this dialed in

Can you say more about the status of the mount? Is this coming out of retirement? Can you describe the telescope setups including the guidescope setup - a few pictures of your setup at different angles often helps.

You didn't have much in the way of guided runs. However the longest 58 min run shows some concerning behavior in RA. This is with the corrections backed out. It shows some pretty significant excursions of 30-40" each. For a mount with absolute encoders, that's not at all expected. 

Brian

To view this discussion visit https://groups.google.com/d/msgid/open-phd-guiding/5dc285b4-63b8-4fb4-becf-be535dcd00dcn%40googlegroups.com.

[Brian Valente]

PS

I also recommend you do a longer guiding assistant run (15-20 mins at least) following a calibration assistant run to see what the unguided results look like

[mlewis...@gmail.com]

Thank you for the advice.

The mount is just a few years old and has been used irregularly. It is due for lubrication and I'm researching that. As this mount sits I can get guided subs 30 minutes long with stars that work well enough with Deconvolution. My goal is to get 30 minute guided stars that are pinpoint without Deconvolution. But at this point this is the rig that I can collect data with. I have 2 other systems that are not yet completely commissioned. I really don't want to risk making this mount worse by doing a maintenance task for the first time before I have something else to work with until I fix that problem. So the lube job will have to wait.

There is no guide scope, the guide camera is on the off axis guider port  of the camera. The camera is threaded on to the 2.156" female adapter on the Astro-Physics field flattener with a precise parts adapter. So the guiding system is very rigid. Unfortunately I can't get any pictures until Tuesday night.

The night that these logs came from was dedicated to getting NINA set up. The long exposures on the calibration were due to NINA settings. I have since rectified this. When guiding with The Sky's guiding routine I was getting really smooth guiding with 5 second guide exposures with a 2 second pause. Effectively in PHD terms I was doing 8 second guide exposures with the saturation of a 6 second exposure. Since my PHD Guiding is not yet tamed I was working with 6 second exposures. When re-calibrating I neglected to reset the exposure to something reasonable. My typical best practice for calibration exposure is to use the shortest exposure that gives an adequate SNR for calibration. As it was a night for NINA set up there were a lot of irregularities in my system. In fact I might have been trying to slew while guiding. I also don't know the state of the PEC, or the quality of the PEC training run as it was the first time I'd done it. So I consider this log less relevant. Too many unknowns to place much value in.

Tuesday is forecast to be clear here. I plan to go out, set up early, and make sure that all of my balance repeatability techniques are working correctly. I noticed while disassembling for the night that I had a slight Dec imbalance. So I'm going to verify everything is as close to perfect as possible.

Then I'm going to redo the T-Point (the sky model in Software Bisque speak). Then I'll redo PEC Training and apply it. Then I'll re-calibrate PHD2 and run the guiding assistant, then I'll run the Guiding Assistant for half an hour. I think that will get a valid data set to get going with. Then, if nothing else ends the show early, I'll do a few hours of Luminance.

Are there other data points I can collect that would help?

The question of the guide rate is, I think, well answered. With this mount 50% is likely adequate. So going forward with the rest of these questions I'll just submit the logs and post on this forum if it seems like something others can learn something from.

[Brian Valente]

For diagnostic purposes, it's a good idea to complete a baseline guidelog following the steps attached to this email. This is our routine "get to know your equipment" type of diagnostic run

Brian

To view this discussion visit https://groups.google.com/d/msgid/open-phd-guiding/5d2a49ae-af3c-4b15-95c3-d2ea31e8cc46n%40googlegroups.com.

[mlewis...@gmail.com]

Thank you very much to all who advised! I’m sitting here in the field, or parking lot, doing a 30 minute run of 5 second guide exposures. I did all of the things that were suggested including the Software Bisque things I said I was going to do first. I’ve never seen the Baseline Measurement Doc, though most of the information was familiar, It was still helpful and I saved it in my Books folder for future reference and sharing. Anyway I’m sitting here 23 minutes into the run thinking about posting again. I think I know how to interpret the graph, but after the other night I find 1.01” in RA and 0.57 in Dec hard to believe. I remember my old guidescope days and those numbers would make me really happy. But maybe this OAG business is different somehow, though I can’t think of how. Oh, what’s this “Trendlines” button. ……..Oh, it’s as flat as the flat parts of pool tables in Kansas.”

 I think I can do with this. Thanks for your patience and advice.

[mlewis...@gmail.com]

I was getting pretty good results using 5 second exposures. I'm a little concerned because the star profile was a bit flat on the top sometimes. Software Bisque has an autoguiding app included in their suite. I used it while I was using The Sky for controlling the system. In the SB Autoguiding app there is an option to capture an exposure length x and pause for time y seconds giving the equivalent of an exposure of x+y exposure time with the ability to control saturation. SO I could do a 5 second exposure then pause 5 seconds and make a guiding adjustment every 10 seconds with the saturation level of a 5 second exposure. This worked out pretty well for me, and in fact I was using 4 second exposures with a 2 swecond pause to get really smooth guiding.

Is there a way to do this in PHD2?

[Brian Valente]

Yes the variable delay option

In fact, it’s even a little better than that. You can set the short delay for tasks like dithering and calibration, and then set the long delay when you’re guiding. That’s the delay between exposures.

Brian 

Brian Valente

astronomy portfolio https://www.astrobin.com/users/bvalente/ 

To view this discussion visit https://groups.google.com/d/msgid/open-phd-guiding/671b4676-bbe6-43b9-b7be-d922f112887dn%40googlegroups.com.

[mlewis...@gmail.com]

Ooh that’s a great option! I’ll have to fiddle with that. Thank you for the information.

 I assume that’s documented somewhere. Do you know where so I can read about it more?

[Brian Valente]

yes it's in the documentation, right there if you look:

https://openphdguiding.org/man/Supplemental_Info.htm#Variable_delay_guiding

You may also find this video helpful (it's an Astro-Physics video but it covers basic exposure delay principles) https://youtu.be/wCu8PKjDZ20

Brian

To view this discussion visit https://groups.google.com/d/msgid/open-phd-guiding/3cde6359-454d-4f96-9640-97a8d31a1cb2n%40googlegroups.com.

[mlewis...@gmail.com]

Thank you very much. Exactly what I need, the delay function and the reference material. This should work great.