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Old 28-08-2016, 04:51 PM
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OneCosmos (Chris)
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Join Date: Apr 2010
Location: Brisbane
Posts: 355
Guiding problem with PHD settings?

Hi thanks for the details.

I'm having a problem. My main imaging scope has a focal length of 900mm and I'm guiding using the lodestar attached to an Orion ST80 with a focal length of 480mm. It is currently attached using a prism diagonal because I don't have an extension tube, but I have ordered one to remove that.

Typically I have done 10 minute subs and for the most part they guide successfully (i.e. no trail), but 20 minute subs do seem to trail although it seems worse pointing east for some reason.

I am using PHD 2 and it has done an auto calculation of my step/ms size based on 0.3 x guide speed in both RA and DEC which is also configured in EQMOD.

Mechanically it all seems pretty firm, but I do know that one of the screws bolting the top bar on to the main rings broke and so it is only secured with three. I will certainly correct that but it is hard to believe it is causing the problem because there are still three.

Just wondering then about some of the other settings in PHD, like agressivness etc. They are currently at default settings. The PHD graph also seems to show a lot of corrections - like all the time and the peaks and troughs do seem to be far from the centre line although the RMS is typically around 14 which is as low as it ever is.

Any advice/thoughts on what to try are most welcome.

Chris
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