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Old 01-08-2011, 04:30 PM
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PHD Settings when using 50mm Finder scope

Can anone who uses PHD with a 50mm guide scope share thier settings they use.

Especially Minimum motion. Given the short focal length I have read this minimum motion needs to be very small but not sure how small.

Also what dec algorithm do you use ? Resist or Low Pass ?

I have been messing around with my Starshoot Autoguider attached to my SBIG E-Finder. Bu getting very mixed results so far. Seem to be better off with unguided.

Was mucking about Sat night between clouds getting 2 min unguided at 900mm FL on the MI250 without guiding and getting perfectly round stars. Naturaly I was VERY happy with this, but wanting to autoguide on longer exposures so need to sort it out.

Cheers
Chris
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Old 01-08-2011, 05:00 PM
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multiweb (Marc)
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Quote:
Originally Posted by cventer View Post
Can anone who uses PHD with a 50mm guide scope share thier settings they use.

Especially Minimum motion. Given the short focal length I have read this minimum motion needs to be very small but not sure how small.

Also what dec algorithm do you use ? Resist or Low Pass ?

I have been messing around with my Starshoot Autoguider attached to my SBIG E-Finder. Bu getting very mixed results so far. Seem to be better off with unguided.

Was mucking about Sat night between clouds getting 2 min unguided at 900mm FL on the MI250 without guiding and getting perfectly round stars. Naturaly I was VERY happy with this, but wanting to autoguide on longer exposures so need to sort it out.

Cheers
Chris
I always left the PHD default settings. When using 50mmFL though set your calibration steps to 2-3s. Other than that resist-switch. If you have loads of backlash in DEC try to guide against the drift, north or south and unbalance your scope slighty.
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Old 02-08-2011, 11:54 AM
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Logieberra (Logan)
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Go into the "Brain" icon, I forget the exact heading / settking name - and bump up the timing from 700 (the stock settings) and experiment up to around 1,500

That will do the trick for ya
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Old 02-08-2011, 12:05 PM
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Yes did that. That sorts out the calibration issue but I am more curious about min motion settings in the brain for 50 mm type scopes.
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Old 02-08-2011, 12:41 PM
dynobolt (Dave)
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Hi Chris,

I have a friend with a Borg45 guidescope who uses 0.25 for minimum motion setting very successfully.

Cheers,

Dave
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Old 02-08-2011, 05:46 PM
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Interesting.

Everything I am reading says to make that number MUCH smaller ie .05 or even 0 when using a 50mm guide scope.


I can see the logic of making it smaller as a larger move on a 50mm guidescope translates to a VERY large move on a 1000mm focal length main scope.

I guess its a balancing act between making this number small but not too small to cause oscillation.

See craigs starks post on this here:
http://www.cloudynights.com/ubbarchi...sed/sb/5/o/all

Here is what he said

"Well, I've guided with an 8x50 finderscope and am the author of PHD http://www.cloudynights.com/ubbthrea...lins/smile.gif

The trick is that you need to drop the minimum pixel motion parameter way down. For most (reasonable, non-insane) guide setups, the default of 0.25 pixels works well. If you're on a very short setup, this may correspond to a few pixels on your image rig. I run this at 0.05 when using the guide scope as the guider.

The M27 and M57 shots near the top here were done on just such a rig:

http://picasaweb.google.com/celstark/Astrophotos

Craig "
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