15 replies to this topic

[rlmxracer]

This is a new one for me. My guiding in Dec is consistently above the 0 line of the guide graph. What is the fix? 

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[djbridges]

I would try increasing aggressiveness and/or your corrective duration. How close was your polar alignment?

[JF1960]

Weird that the text says your Dec is at 0.49” and the graph clearly shows it > 2.0”

[JF1960]

I’d also worry if your mount is even correcting in DEC cause the ASIAir corrections are aggressive and appear to have 0 effect on your graph.

[rlmxracer]

I did PA twice because I slightly bumped the mount during the first try. I set up on grass and firmly planted the tripod feet into the ground when I set up so I doubt it moved. I was just playing it safe. The PA was great on the second try at 05”

[rgsalinger]

Please post the log. My guess is that something is incorrectly set. Even the AA has a log. There are too many possibilities to even make a suggestion without a log. It has nothing to do with your polar alignment. Also, if the system was sagging, then the corrections wouldn't be so apparently even. If I had to guess that the minimum move is incorrectly set. This happens most often when someone changes out an OTA for a longer/shorter one. And you should set the graph scale to 2" not 4" if you want to be able to really see what's going on.  

Edited by rgsalinger, 14 June 2025 - 11:22 PM.

[rlmxracer]

Please post the log. My guess is that something is incorrectly set. Even the AA has a log. There are too many possibilities to even make a suggestion without a log. It has nothing to do with your polar alignment. Also, if the system was sagging, then the corrections wouldn't be so apparently even. If I had to guess that the minimum move is incorrectly set. This happens most often when someone changes out an OTA for a longer/shorter one. And you should set the graph scale to 2" not 4" if you want to be able to really see what's going on.  

I’ll try to post the log tomorrow. My subs seem to be fine as the stars are small and round. 

[rgsalinger]

In any case, without a log, it's all very speculative. When you say small and round, what is the scope? What is the FWHM? What is the eccentricity? 

[michael8554]

Yes the Dec error is about 2 arcsecs from the axis, but actual error is 0.49.

 

A quick stop/start of guiding would probably reset Dec to the axis.

 

As to why the guide pulses aren't effective, need the GuideLog.

[matt_astro_tx]

Did you run a guide calibration last night?

[DeepSky Di]

Ask yourself what changed.

 

I had this happen last September only in my case the DEC was showing 8 on the graph and sub 1 on the number. I assumed the number was correct and I was wrong!

 

Here's how I diagnosed and fixed.

 

First, it happened after an ASIAIR software update in Sept 2024 that was known bad and I had been avoiding. My iPad was not downloading updates so I thought all was well. However when I put the iPad on charge while turned on, it saw its chance and downloaded the update and there's no way to go back on the iPad.

 

Then I saw the problem with the chart vs number - initially no red line at all because it was off the chart at 8. After a lot of head scratching, I wondered if it was a polar alignment issue. I checked this by polar aligning, doing a Goto to the target and then doing a "mount go home". It was several minutes of arc away from the pole.

 

I had been using the newer 3 point polar alignment, although I didn't need to for the location. I switched to the old fashioned polar alignment, polar aligned and repeated the goto / mount go home. It was now correctly returning to the pole and the dec chart and guiding number were consistent.

 

I also deleted and repeated guiding calibration a lot during this experience, but the rule is if the guide camera rotates then calibration must be repeated. With an OAG, calibration must be redone if you rotate the main camera for framing as well as if you rotate the guide camera in the OAG for any reason, including accidentally. The recent ASIAIR updates to support the CAA can rotate guide calibration to suit the CAA rotation - an option that can be enabled or disabled. Symptoms of bad guide calibration are different though, just crazy behavior that does not settle down.

 

Here are my iPad screenshots from the event:

 

 

 

 

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[rgsalinger]

The first rule in troubleshooting guiding problems is to do a fresh calibration. Relying on one's memory in this hobby is a bad idea. Being a "few arc minutes" off the pole cannot cause a guiding error like the one that the OP's screenshot shows. A "bad" update that you can't get rid of sounds just awful, though. 

[DeepSky Di]

The first rule in troubleshooting guiding problems is to do a fresh calibration. Relying on one's memory in this hobby is a bad idea. Being a "few arc minutes" off the pole cannot cause a guiding error like the one that the OP's screenshot shows. A "bad" update that you can't get rid of sounds just awful, though. 

My guess is that one or two bad ASIAIR updates were due to providing for the CAA and its option to rotate calibration.

 

After I switched back to the old fashioned polar alignment, I stayed with it as I heard it was more accurate. But I should definitely check the all sky polar alignment again.

[dx_ron]

It sure looks like the mount is either not responding to Dec guide pulses or not even receiving them. A first obvious thing to do when something is suddenly totally whacked out is to park/home the mount and then power cycle everything.

 

If a hard reset doesn't fix it, then you need to start troubleshooting. It would seem that the Dec motor and controller-mount communication is working at some level, or you never could have left Park and reached your target. A re-calibration is in order. Aside from just being a good idea when you have trouble, calibration requires the mount to respond to Dec guide pulses. If you have the same lack of Dec response to pulses during calibration it will be obvious, because the calibration will fail to move the mount during the Dec steps. If calibration works, but Dec guiding fails again once on target then I have no idea what to suggest, but at least you can come back here with that info.

[AstroFromHome]

The DEC graph is shown relative to the calibration position.

You axis drifted off about 3 arcsec relative to the calibration position of the star. All those strong corrections barely keep your mount about 3 arcsec north of the position.

If the drift stays like this over the whole nicht everything is fina and the stars are round as there is not diviation in north- south direction while imaging.

 

Could you please share your values for the correction puls length? I expect the pulses to be too short that PHD2 can just keep the error at that point but is unable to bring the guide star into its initial position. The correction happen at every step in full length already. A hight aggression could also help to make the situation "better" over a duration of multiple corrections as the axis is pushed stronger into the desired direction.

[rlmxracer]

Did you run a guide calibration last night?

The first calibration seemed fine and before I changed targets I did another calibration. I didn’t really get to test the second calibration because clouds rolled in shortly afterwards.