Help with Dithering Settings within NINA

[Richard Sauerbrun]

I have been using PHD2 for about a year now and am ready to get serious about improving my guiding. Last night I built a new profile with the wizard, then ran the Guiding Assistant to get things set up as close as possible. I use NINA for my image sequences and it is directing PHD2 for the dithering.

The attached screen shot from the log analyzer and the guiding log from last night show a series of "Settling Failed" errors. I assume that I have a setting in NINA that is incorrect, and your help will be appreciated.

Here are my settings in NINA ...

[wave...@talktalk.net]

Hello Richard, I'm not yet advanced enough to even try dithering, but looking at the plot it seems the Dec axis isn't returning fast enough, especially after the Dec dither changes direction (dither N, then dither S). Consecutive dithers in the same direction seem to settle faster. To my amateur's eye I'd say backlash is the cause. I guess you could verify that by selecting the 'Dither RA only' to 'ON'.

I'm sure one of the gurus will be along soon to provide more insight.

Cheers,

=-Jack

[bw_msgboard]

Hi Richard, this is a somewhat unusual problem.  Look at the RA data points in the graph – do you see that they never return to the zero-point but instead are offset to the west?  When you add this offset to the natural tracking error of the Dec points, you aren’t able to meet your settling criterion of a 1.5px total offset.  This RA offset won’t hurt your guiding in terms of producing round stars but it interferes with the settling criteria.  All of the RA guide commands are trying to move the mount east with the scope on the east side of the pier.  One possibility is that you have an imbalance with a nose-heavy OTA and perhaps a loose clutch, both of which would cause the OTA to “fall” toward the west.  Or, since you’re probably using a separate guide scope, the guiding assembly may be moving around and letting the guide scope “fall west”. Even when you get this sorted out, your mount shows a very sluggish response with direction reversals and settling often fails for that reason.  Have you used the GA to measure the backlash/reversal-delay?   If you’re satisfied with the images you’re getting and you just want to mow ahead, you’ll have to loosen the settling criterion – probably to 2.0 px or even higher.

 

Good luck,

Bruce

 

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[bval...@gmail.com]

Richard you might also consider dithering in RA only - it won't solve all your problems but it will address the big challenge of getting DEC back inline