FAQs - Alignment

FAQs - Alignment

How do you pick a good star for 1-Point alignment.

Assuming that the mount is polar aligned and there is minimal cone error, choose any star from eastern or western side at least 45 degrees from the ground.

If you click the [Stop] button do you lose alignment?

No, it will not lose alignment. Position computation is time based. If you stop tracking and re-initiate tracking 30mins later, the driver will simply compute the new position and apply the GOTO.

If the mount stops because an RA limit has been reached, does it lose alignment?

No, it will not lose alignment. (see the reference to the [Stop] button above). Simply move the mount away from the limit using slew controls and restart tracking.

Clear sync data vs Clear align data

To remove all pointing correction you must clear both the alignment data and sync data.

  • Clear align data deletes all your current alignment points.
  • Clear Sync data removes any sync shift that is currently active. When operating in “dialog mode” for alignment, a sync will act to shift the entire model rather than add a new point. Once assigned a sync shift will be applied to the  pointing model irrespective of whether “append on sync” or “dialog” mode is subsequently used. You can tell if there is a sync shift active as the DXSA and/or the DXSB values will be non zero. 

Note: Alignment points can be created by append on sync, dialog mode or a mixture of both.

Does unclamping and moving mount move ring counters?

Unclamping will not move the ring counters. However you will lose alignment if you loosen the RA/DEC clutches. This can be fixed by:

  • initiating a GOTO to a bright object (assuming the 3-Point data is still active)
  • manually centering the object through the scope eyepiece FOV after the GOTO by loosening
  • the RA/DEC clutch and pushing the tube to bright object's position.
Why a GOTO on a previously aligned object might not work after 6 hours.

When you “append on sync” all that happens is a new alignment point is added to the model - the model isn't shifted at all (so a true “sync” in the traditional sense hasn't really been performed). Only when in “dialog mode” is a received ASCOM sync used to shift the model. If you always operate in “append” mode then the likelihood is that no sync shift would have been present.

It is important to appreciate that the pointing transformations are applied not only in moving to goto targets but also whenever EQASCOM updates its reported position. In light of this is really no surprise that after 6 hours of tracking the EQASCOM position /reticule has drifted off your initially aligned object.

If initially you added three alignment points around an object, your goto would have had a three point transformation applied to it to take you accurately to the object. So long as the object remains in the triangle the position reported by EQASCOM will be subject to the same 3Point transformation. As soon as the object drifts outside of the alignment triangle, EQASCOM will switch to using a Nearest Point transformation for it's reported position. When you're six hours away and over the meridian EQASCOM will still be trying to apply that nearest Point transformation even though the point is a long long way away. If you have the “Pierside points only” option checked then once you cross the meridian you will loose all correction as there are no points defined on the current side.

/home/welshdra/public_html/eqmod/data/pages/faqs_-_alignment.txt · Last modified: 2012/07/13 21:55 by jon
 
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