Polar Align - Auto-rotation of RA axis

[Fir Chlis]

I don't know if this has been suggested or considered (I didn't find any previous postings) but something I would find useful would be automated rotation during the polar alignment procedure, something like this.

Start polar align, and, at the stage when I have to rotate the RA axis have an option to specify an angle, and Sharpcap then rotates the mount the specified amount (as an alternative to the current manual rotation). This could also be automated if the option to proceed to the next stage is checked.

I think it might want a pause in frame capture during rotation until the mount has settled as I sometimes get an error message about rotation being detected and I have to restart the procedure. This *may* be a timing issue, as I think I see Sharpcap having detected the polar align error before the mount has settled (or at least before a settled frame has been captured).

I find that the manual rotation stage can be a bit fiddly - rotate, have I gone far enough, rotate, sometimes I then get a message that rotation has been detected (as described above), and I have to start again.

A nice to have, that would save a bit of time during setup, but once it works I do always get very low polar alignment errors. On my HEQ5 Pro, I can easily get to less than 1min error with little effort.

Cheers

Geoff

[admin]

Hi Geoff,

interesting idea - I recently added the slew buttons to the polar alignment that you can press and hold to rotate, but you still need to stop after the right rotation with those.

Thinking about it, I would not want to use GOTO movements to rotate, since the mount might also move in DEC as part of the GOTO (for instance to approach from a consistent direction or take up backlash). Dec movement would throw off the calculations. Anyway, some mounts may not be able to GOTO before star alignment, which is often done *after* polar align... So, it would have to be a version of the current movement buttons that rotate the axis but stop after a particular rotation is reached.

One thing to be aware of is that the angle isn't particularly critical... Although 90 degrees is ideal, anywhere from 30 to 120 should work fine. Some people even use 15 degrees or less when working with dobsonians mounted on an EQ platform.

cheers,

Robin

[Fir Chlis]

Hi Robin

Thanks for the reply. With hindsight, I probably meant some form of automation on the slew buttons.

My workflow is:
Set up scope in daylight, then come indoors and VNC onto the laptop which controls the scope.
Start Polar Align as dusk is coming in and check for the first frame solve every so often, while I'm doing other things.
Once the first frame is solved, I use the scope control RA buttons to rotate the RA axis (having set the rate to 2 or 3 degrees per sec), while watching the RA position in the scope control area until it looks like it's gone far enough, but I have to keep stopping and starting to make sure it hasn't gone too far, or not far enough. It usually takes a few mouse depressions to get far enough.
Then I nip outside to adjust the alt/az bolts on the tripod, watching the error via VNC on my phone.

If I could press a slew button once, and tell it to rotate, say, 30 degrees, that would be nice to have, in order to avoid the uncertainty of when to stop pressing on the slew button with the current behaviour.

When I get the rotation detected /restart message, I wonder if a valid frame has been captured and the polar align error calculated, but I'm still pressing the move in RA button, causing movement after the polar align error has been detected - but that's speculation on my part. Next time I'll try using the slew buttons (which I had forgotten about).

Cheers


Geoff

[admin]

Hi Geoff,

right, I think I see where your unerlying issue is anyway - do you have the 'auto advance' option ticked in polar align? If so, it may be advancing to the adjustment stage as soon as it detects enough rotation, but if you are still rotating at that point then it may move to the adjustment stage, detect more rotation and then give you the 'restart' message.

If I can fix the flow of the tool with auto-advance so that it (for instance) waits for a few seconds with no new rotation before advancing, then I think the problem of needing the right amount of rotation goes away... Let me think about that one for a bit.

cheers,

Robin

[Fir Chlis]

Yes - I have had auto advance set, as I tend to start the polar align process before it’s properly dark, then potter around in the house doing other things until I see on my indoors laptop that the first solve has been completed.

I’ll leave this for now, but will try without auto advance, and using the slew buttons rather than the telescope control pane.

Thanks for looking at this.


Geoff

[Fir Chlis]

Hi Robin

I’ve finally had a clear night to try this out with the latest build of V4.1. The polar align went fine with auto advance switched off…

…but I’m not sure that the slew buttons are honouring the selected slew speed. I’d set the speed to 2deg/sec, but the slew buttons moved the mount VERY slowly, so I gave up and used the RA direction buttons in the telescope control panel.

Sorry to bring up another little ‘feature’.

Cheers

Geoff

[admin]

Hi Geoff,

that's interesting...

What rates does your mount offer via the normal rate selection dropdown in SharpCap? The east/west buttons do not use the rate selected in the dropdown, instead they should choose the fastest rate that is less than 10 degrees per second. For most mounts, I would have thought that would be the fastest rate anyway...

cheers,

Robin

[Fir Chlis]

It's a Skywatcher HEQ5Pro mount, and in the normal dropdown it offers from 1x up to 3 deg/sec - and these do work when using the scope controls in the scope control pane of Sharpcap. 1x is very slow, and I normally use 2 or 3 deg/sec when slewing for polar align.

The laptop is connected to the mount via an EQDIR cable supplied by FLO.

Would a logfile help? Or let me know if I can do any testing.

Cheers

Geoff

[admin]

Hi Geoff,

unfortunately it currently doesn't log the rate chosen, since I didn't expect that to go wrong - I will add the logging for the next update and we can see what is going on.

cheers,

Robin

[Fir Chlis]

Hi Robin

After 10 cloudy ones, I had a clear night last night, so I was able to gather some more information on the Slew buttons in the Polar Align dialog.
I can see that the Rotate East/West buttons highlight when pressed but, even though the mouse button is held down, the button immediately dims again, as though the button has been released, and the mount fails to rotate. This seems at variance with what I saw last time where the mount just appeared to rotate very slowly, whatever the selected speed.

I did wonder if this is an artefact of me connecting to the telescope laptop via VNC, but if I press and hold the mouse on the RA movement buttons in the telescope control pane (which is what I have to do), the mount rotates at the selected speed.

I could test directly on the telescope laptop, but is it possible to do this using the mount and a test camera, then I wouldn’t need to wait for a clear night? I wouldn’t need to go through the full polar align process, just far enough that I can test the mount rotation.

I’ve attached my log file from last night in case this is of use. The polar alignment process starts at 19:14.

Cheers

Geoff