Annotation off center

[donboy]

When doing a plate solve the annotation centers on the objects found position and not on the centered position; thus requiring another plate solve.

Don

[admin]

Hi Don,

can you let me know the exact sequence of steps that you have used to see this effect? As long as you have your ASCOM mount connected in SharpCap then any small movements since the last plate solve should be accounted for (SharpCap can tell how much you have moved the mount since the plate solve and therefore correct for that offset). This does fall apart rather if you are very close to the north or south celestial poles though...

cheers,

Robin

[donboy]

I slew to the target and select plate solve in the Scope Controls. After the plate solve recenters (usually under .02 deg) I look at the Annotation and it is off center by the offset. I then do another plate solve and the annotation centering is correct. Some times i wait to do the second plate solve while livestacking and use the Plate Solve(solve only).

Don

[admin]

Hi Don,

remind me... what action have you set up to happen after plate solving in this section of the settings?

Capture.JPG (24.63 KiB) Viewed 535 times

The default is Sync mount and recentre, which is what I usually use (and I'm pretty certain it is fine - will check the next time I have clear skies, since it's not easy to test this one without a real sky). If you have set up offset goto then maybe it is something to do with that?

cheers,

Robin

[donboy]

I use Sync mount and recentre.


Also happens when one uses Goto- Catalog Target / Coordinates

Don

[Menno555]

Hi Don

This can happen but as far as I know it's because of the mount and not SharpCap.
It can happen that the mount has a tiny deviation. Be it in position, polar alignment, mechanical, software, and so on. The deviation is too small to have an effect during tracking or guiding.
With my Ioptron mount for example I have the same what you describe, especially when the mount has to move a long way. For that, the Ioptron software has an option called Sync to target: you GoTo to an object or coordinates and if the object is not in the center, you can manually slew the object in the center and use the Sync to target. Now the mount software is re-calibrated. Call it finetuning.
The plate solve & sync function of SharpCap does essentially the same: GoTo an object and re-center and when it's not in the center, do the plate solve & sync again. The mount now is re-calibrated for the exact position.

Menno

[admin]

Hi,

it could be something like that, but given that Don has just done a solve + sync, it would have to mean that the offset the mount makes after the solve+sync is not reflected in the mount co-ordinates as read by SharpCap.

Another possibility is if the ASCOM driver has a complex pointing model (sky mapping) - in that case it may interpret the sync as just another data point for the pointing model rather than a firm 'this is the co-ordinates' message.

I will give it a try myself (EQMOD, NEQ6 with belt mod) and see if I get it. If I get it then I will fix, if not I will need to look at Don's logs to see exactly what is going on.

cheers,

Robin

[admin]

Just to update...

we had some clear intervals (or at least fairly clear), so I tried this out. Seems to work OK for me - I recorded a video just in case watching it lets you spot something that perhaps I do differently that might explain the failure on your setup.

Let's see if this works...



cheers,

Robin

[donboy]

I don't see any difference in what you do. As long as I've used Annotation it has always required a second iteration. The amount annotation is off on the first go is directly related to the goto error. Gotos on the same side of the Meridian have very little error like .01 to .02 degree's while gotos that require a meridian flip are much greater .1 to .5 degrees off. It's a mystery.

Thanks for going through the trouble of generating a video.'

Don

[admin]

Hi Don,

when you get the chance, can you try using the latest SharpCap 4.1 beta version - just in case this is something that is fixed in the latest beta but not in the version you are using... That might explain it.

cheers,

Robin