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Polemaster or PHD drift - which is right?

Skipper Billy

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Skipper Billy

Skipper Billy

Posted
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I recently bought the QHY Polemaster setup as I find the drift routine in PHD2 a bit tedious.

They give different results !!!

The error is repeatable too - I can set up with Polemaster and then drift align in PHD2 and it requires a half turn clockwise of the altitude bolt  to get the drift right - back to Polemaster it needs half a turn back anticlockwise to get the crosses lined up - I can repeat this ad infinitum.

So which one is right ??!!!

Stars are round with either setting but the guiding seems to have less work to do when drift aligned in PHD2 than with Polemaster.

This is in an observatory so tripod movement etc can be ruled out.

Any ideas ??

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  • 1 month later...
Jannis

Jannis

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Were you able to find out which of them was correct? And, how much difference is there actually?

From what I've heard the polemaster can quickly achieve more accurate polar alignment then most others have been able to before, but for a permanent setup i would also assume a long and time-consuming drift align would be the most accurate.

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KyleStoke

KyleStoke

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I used the polemaster for the first time a few weeks back checked the results with PHD2 and it gave me an error of 10+ arc minuets i ignored this and got round stars on 15 min subs.

Could be whatever settings are in PHD are incorrect, giving a false result.

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Tiny Small

Tiny Small

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I've found that PHD is very inaccurate with it's drift align. I did an actual drift align using DARV and got a straight line on both axes at 10 minute subs. I can image unguided for a number of minutes with no trailing and on 900 second subs, no rotation, so I know it's decent. PHD reports it as substantially out and the guiding assistant recommends 4s subs. With this alignment, I am consistently drifting within +-0.5" with RMS errors ranging from about 0.08 to 0.14 in each axis and a total of under 0.2 usually. Until a gust catches the scope or something then I might get a spike of 1". So I wouldn't trust the PHD drift align that much.

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  • 1 year later...
swag72

swag72

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1 hour ago, emyliano2000 said:

Sorry to bring back this thread but last night I aligned perfectly with my polemaster and the error in phd2 was huge. What alignment method gives you better result in the end?

Emil

Interesting......I found the Polemaster gave me a pretty poor PA on my mount when checked in PHD2

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emyliano2000

emyliano2000

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The problem is that my visibility is quite restricted up to 25 degrees above horizon to the east and the west so I can't go close to the horizon. It's the first time I had a go at phd2 and I really wasn't expecting such a huge error. So far I've been using the lacerta standalone autoguider.

I think I did the polemester alignment better than I ever did.

I would also like to add that my mount has been hypertuned.

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Davey-T

Davey-T

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You can drift align on pretty much any star, the further from the pole the faster the drift will be which is the reason for using the horizon but then the nearer the horizon the more the atmospheric dispersion, you need to get the "crosshairs " at right angles to RA /Dec movement and as mentioned if it takes too long to reach a conclusion mechanical issues will interfere with the results.

Best not to get too OCD about PA if it's near enough then guiding should sort it, you may get a bit of field rotation but stacking should sort that.

Drift aligning using an illuminated graduated reticle eyepiece is good on a permanent setup but not worth messing about with every time on a mobile setup, time is better spent gathering data rather than wasting time drift aligning.

The DARV method is pretty good in terms of results vis time taken, not used Polemaster but is seems an expensive sledge hammer to crack a nut, just my opinion may be talking rubbish and not for the first time :grin:

Dave

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Davey-T

Davey-T

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1 minute ago, emyliano2000 said:

I will try DARV next time to see how the drift is.

I want to use phd to see the errors in the mount.

I'd hope a hypertuned EQ6 would have no problems imaging guided when PAd within 30arc secs, why do you want to see the errors in the mount ?

Dave

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