Feature Tracking Calibration "Failed due to inconsistent scales from Axis X"

[Borodog]

PS the focus box affecting feature tracking is apparently not in fact fixed in 4.1.

[admin]

Hi,

I don't think I have released a version with that change in yet

cheers,

Robin

[Borodog]

Well no wonder then!

[Borodog]

Back to not working. At all. Changed absolutely nothing, used the same small initial step size, back to "Failed due to inconsistent scales from Axis 1."

I eventually gave up imaging completely because it was just too cumbersome that none of the features seemed to work. Feature tracking via the mount, didn't work. Feature tracking via ROI, also didn't seem to work. The planet still kept drifting to the edge of the ROI anyway. Planet stabilization with a reasonably small ROI isn't useful because the ROI doesn't track with it. Feature tracking and planet stabilization don't work together.

[admin]

Hi,

from the look of the logs and the description it sounds like you had quite a bit of drift of the target going on even without moving the mount. If that was true then it's possible that the drift was causing the calibration failures - both the logs show errors due to inconsistent angles rather than scales - that can happen if the movement of the planet caused by the calibration is superimposed on top of an existing drift across the view. Basically, instead of finding that the directions that the planet moves for +Dec and -Dec are opposite, SharpCap finds that they might be only 90 degrees apart or something, which the code can't cope with.

cheers,

Robin

[Borodog]

So are you saying rough polar alignment is not good enough for feature tracking to work properly?

[admin]

Hi,

it depends on how rough, and also the luck of the draw on which part of the sky you are pointing at compared to the misalignment of the pole. If your polar alignment is out in the N/S direction then you will see relatively little drift imaging to the north and south, but declination drift imaging to the east and west.

Basically the drift rate from misalignment has to be small compared to rate that the object moves when calibrating - the drift rate should probably be at least 5 times smaller than the calibration movement rate, ideally even less.

cheers,

Robin

[Borodog]

It's definitely much smaller than that. The planet drifts over time; it doesn't race across the field.

Basically, I am virtually certain SharpCap simply does not allow enough time to take up the declination backlash. If I manually take up the dec backlash in the direction SharpCap starts testing, the first part of the test is fine. But then it tries to switch, nothing moves for a while, it finally starts to move, and SharpCap declares failure. I wish there was a user setting for this. All I need is for the calibration to not fail, and then it will never have to take up dec backlash more than once. Precisely because the polar alignment is rough, drift only occurs in one direction.

[admin]

Hi,

in the latest versions, the code should pay attention to the calibration 'Required Movement (Pixels)' setting when calibrating. Each direction (RA +/-, Dec +/-) should continue to move until either

1) The movement of the image exceeds the required movement level and there is a good correlation calculated between mount movement distance and screen movement (an initial backlash area is allowed) or
2) The movement of the image exceeds 5 times the required movement level (if this happens calibration fails)

It may be worth increasing that setting if you think you are having backlash issues.

Once two opposing directions have been measured, SharpCap checks that the directions that the image moved are approximately opposite (within 30 degrees) and that the apparent speeds of movement are roughly the same (to within 25%).

Once all four have been measured, SharpCap checks that the directions moved due to RA are roughly at right angles to those moved due to dec (within 25 degrees).

If you see log messages about 'inconsistent angles' or 'inconsistent scales' then the individual direction calibrations are working to some extent, but the later checks are not being satisfied.

If you see messages about 'failed due to a bad measurement correlation from' or 'failed to produce a good measurement of scale/direction ...' in the log then it is the individual direction calibrations that are failing.

Hope this helps,

Robin

[Borodog]

Ok. I'll give it a shot. Failing that I'll probably just have to install a guide scope and let PHD2 do it, guiding on the planet. I'm not sure if it would be able to guide on the Moon, though.