Feature Tracking fails calibration with Sky-Watcher HEQ5 Pro

[cydonia]

Hi Robin,

I have been trying to get Feature Tracking working on the moon's surface with my Sky-Watcher HEQ5 Pro mount but without success. I can't seem to get it to calibrate correctly.

The equipment I am using is:

Sky-Watcher HEQ5 Pro mount using SynScan Mobile wireless ASCOM driver
Sky-Watcher Skymax 180 scope
ZWO ASI290MC camera

If I leave the default settings for "Initial Step Size" (0.5) it fails calibration quickly whereas if I change the value to 0.1 it takes longer to fail but that may just be that it takes longer to get to the point at which it fails.

The errors below are recorded in the logs although the errors shown on screen were slightly different but along the same lines (I didn't note them down as thought they would be the same in the log anyway):

"Failed to produce a good measurement of scale/direction from RA +ve (or-ve) mount movements".

"Inconsistent angles of -153.45687888231 and -170.832451651025 from the two x measurements".

When it fails it seems to keep moving the mount and I have to then use the SynScan app to return to the moon and start tracking again as it quickly moves out of view. Any initial drifting before attempting calibration is tiny and so I don't think it's excessive initial drifting causing issues.

I have included several logs showing the errors below.

GuidingLog_2020-06-01T23_03_47-12648.log

(7.62 KiB) Downloaded 98 times

GuidingLog_2020-06-01T22_32_18-11556.log

(46.39 KiB) Downloaded 100 times

GuidingLog_2020-06-01T22_19_31-10160.log

(28.21 KiB) Downloaded 90 times

GuidingLog_2020-06-01T22_09_22-4568.log

(3.13 KiB) Downloaded 97 times

I'd like to use the feature tracking to eliminate any small drifting when shooting the moon's surface as I often shoot 3 minutes or so of video and at such a high magnification with the Skymax 180 any drift at all can cause me to have to manual correct during that time.

Thanks in advance for any help with this and keep up the good work as apart from this issue (I understand the feature is still experimental) I have found SharpCap extremely reliable and use it all the time for DSOs.

James

[admin]

Hi James,


Which mount movement speed are you choosing from the drop-down? I'd suggest trying the option of using the guiding rate – if you use that option then pulse guiding commands are sent to the mount which should make it move relative to the normal tracking rate. If you choose one of the other options then SharpCap asks the mount to move its axis at a particular speed. The poem with that is that some Ascom driver/mount combinations keep tracking and move at the same time and others stop tracking, then move, then start tracking again. If you have a slow rate as a multiple, this stop tracking restart behaviour can easily mess up the entire movement in the RA direction.

Cheers, Robin

[cydonia]

Hi Robin,

I had tried 1x speed and guiding speed but with no success. I'll do more testing when the clouds clear again and see if I can nail down the issue and feedback details if I can.

I have had the mount failing to return to tracking speed a few times lately when using SharpCap's telescope controls rather than the SynScan app so I dont know if that could be related at all?

James

[admin]

Hi,


If the mount is sometimes failing to go back to tracking then it could certainly mess up the alignment routine as the object in view would suddenly start drifting without SharpCap having asked the mount to move.

[cydonia]

Hi Robin,

I've been trying again to get Feature Tracking working but without success. I have however had more success setting the mount movement speed to x16 although ultimately it still fails calibration but just takes a lot longer to do so.

The errors I get are:

WARN tracking - Failed to produce a good measurement of scale/direction from RA +ve mount movements

and

WARN tracking - Inconsistent angles of 173.230829829898 and 172.77385314462 from the two x measurements

I was wondering if the fact I am using a high magnification (Skymax 180 Mak which is 2700mm) would make any difference to calibration? I really want to try and get this working if I can as sometimes I have a very small drift that this would hopefully correct for. the drift is not significant but over 3 -5 minutes I sometimes have to make a few small adjustments to keep the framing how I want it. I doubt this tiny drift is enough to throw off the calibration though as it usually takes a while to start showing.

Is there anything else you can suggest to try please?

Thanks in advance.

[admin]

Hi,

the biggest problems are typically related to backlash - running at high magnifications will probably make that more significant because the mount movements are smaller and therefore more likely to be within the backlash zone. If SharpCap can't get the mount to clearly move in two different directions for each axis, then the calibration will fail in the way that you are seeing (or something close to it).

Try switching between the different options for the mount movement speed and see if any work correctly for you. In particular the 'Guiding Rate' option will use the mounts pulse guide functionality if it's available, which may suffer from less backlash.

Cheers, Robin

[cydonia]

Thanks, I'll experiment more next time I get a chance.