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I see a few problems with your approach, specifically the use of Sync instead of Align

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Here's my take on what should happen using your procedure, along with additional comments.?

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SETUP

- Cold start at CWD position erases the model

- polar align is important for good tracking (as always)

- CWD position accuracy is really only for the first goto, as you pointed out. i wouldn't sweat it too hard

- slew speed setting should not impact accuracy for gotos

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FIRST GOTO, Altair in eastern sky

- no model means the first slew will be the least accurate, that's expected

- Doesn't matter how you center the target: use slew/move/center, Although typically if the goto is farther out, you start the centering routine with slew, then move, then center, and perhaps guiding if you are fine tuning the position. There's no hard and fast rule here

- Then Menu-> Align ->Align.? ?You don't need to add Sync at this point, you aren't syncing a model yet, you just started your first model point

- "It worked very well!? Everything I told it to go to was reasonably well centered." WIth an Altair Align, you have one point model, so that's surprising it was that good but hey, who's arguing if it's accurate. If you needed to refine the goto accuracy for any of the subsequent goto targets in the eastern sky, you would goto, center (with hand controller, etc.) and then Menu->Align->Align. Typically a 3 point model is what I would consider a baseline, but i've often done 1 point as well. You can see this if you go to Menu->Align-> Model Parameters. It should show model terms for the first two (HA and DEC) only.?

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NEXT GOTOs - Western Sky

- this is where i think part of your issue is happening. The Sky Model is actually two separate models, one for the eastern sky, one for the western sky. If you go back to the Model Parameters and press Switch, you will see it Building a model on one side does not do anything for the opposite side. So we are back to the "first goto will be the least accurate"

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- Goto Mizar as the first western goto in an ampty?western sky model. This goto will therefore be as inaccurate as Altair, your first goto in the eastern sky.??

- At this point, you would repeat the same procedure for Altair, goto, center and ALIGN. Sync won't do anything at this point because there's no western sky model you are syncing to.?

- I would also add two more Goto/center/aligns on this side, but at a minimum one Align.?

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NEXT - Gotos returning to eastern sky

- at this point things should be fairly accurate on both sides

- if you goto back to the eastern sky and it's slightly off, you would center and then SYNC to get your existing eastern sky model back in line with where the mount is pointing

- why would eastern sky be slightly off when it was spot on earlier? equipment shift, polar misalignment (which is accounted for in the model only when you have 3+1 alignment points), mirror flop, ground shifting, etc. many things could impact the move from one side of the sky to the other. If you are using an SCT mirror flop can and will play a major role here

- this will be the case anytime you switch sides of the sky

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I appreciate how important understanding this is, because I am doing planetary imaging with a miniscule fov (0.06 x 0.03 degrees) and a modest finder scope with a cmos camera attached (2.18"/pixel). I am not using any eyepieces so I can't just switch magnifications, it has to be really accurate to get it into the fov. With my Edge HD 11" my rough calculation of the difference in position when switching between sides of the sky is 2-4 arcmin? I'm estimating based on my memory of things but I will look closer next time. I attribute this primarily to equipment shifting and possibly mirror movement, even though I have mirror locks on the 11"

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So i would say if you give the above a go, i hope and expect things will improve for you

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Brian

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On Wed, Aug 17, 2022 at 8:58 AM Mark de Regt <deregt@...> wrote:

Brian?