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Measuring PE with PHD Logs and PECPrep

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#1 orlyandico

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Posted 15 November 2011 - 12:04 PM

Hi all

As it's really cloudy here, all I'm doing now is looking for holes in the clouds and running PHD (with guiding turned off) to get some PE graphs.

I have a question - the declination of the star matters, but PECPrep has no way of specifying it. I can't use a star on the meridian because the clouds get in the way, and the light pollution means only Mag2 stars or brighter are visible.

(and yes I have an evaluation version of PEMPro, but I'm used to PHD)

#2 orlyandico

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Posted 15 November 2011 - 12:43 PM

Output of PECPrep given my PHD log file. +34/-32 arc-seconds (a lot of PE!)

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PECPrep took the PHD log file and turned it into something that PEMPro could digest..

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+29/-31 arc-seconds.

This is a Vixen Great Polaris. The only saving grace seems to be that the PE curve is fairly clean. I used to think this thing could do +/- 10 arc-seconds.. but that was with guiding turned on. Doh!

#3 Kolenka

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Posted 15 November 2011 - 07:37 PM

Even with the size, it is extremely clean. The vast majority of the PE is even in the fundamental which is good. I'd wager that you can get a lot better than +/-10 arc seconds guided with that curve, even without PEC. If you are having trouble, flex and the settings used are your likely culprits.

#4 orlyandico

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Posted 15 November 2011 - 07:44 PM

Hi Kolenka,

My thoughts as well. It used to be noisier because the RA spur gear was not centered on the RA worm shaft, but a tiny metal shim (cut from a sardine can!) seems to have fixed that..

But I'm not sure if the measurement is correct! because the star's declination is 45 degrees (Capella). There is no dialog in PECPrep to input the declination so I have suspicions about the accuracy of this measurement.

There is no PEC possible here, it's a "dumb" Vixen GP with the DD-1 stepper controller and two MT-1's. I'm just measuring the PE because I have nothing better to do..

I measured the PE of my CGEM a couple weeks ago, and got +/- 10 arc-seconds, but the graph was noisier than the above. Again, not sure how accurate due to declination, and I wasn't very well polar-aligned that time. Could not use ASPA because my balcony restricts the view across the meridian, hence could not add calibration stars.

As an aside, I'm using WCS DSI - http://wcs.ruthner.at/index-en.php - for polar alignment, couldn't be easier.

#5 Kolenka

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Posted 15 November 2011 - 10:01 PM

PECPrep's dialog for importing PHD logs does have a way to specify the declination. Try re-importing the log. It will show up as a "Dec adjust" or similar in the dialog where you also specify your pixel size.

Although the smoothness of the curve won't really change a ton from Declination, just amplitude.

#6 ccdmaker

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Posted 25 May 2013 - 02:13 PM

Hi Orlayndico,

I am in the process of characterizing my Vixen GP with MT-1. Can you post your PECPREP results so I can compare notes? I do not see them in your post, perhaps because the forum software recovers storage space by deleting image attachments from older posts.
Thanks
RK

#7 orlyandico

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Posted 25 May 2013 - 11:07 PM

hi RK, unfortunately the GP is long gone (and so are the data files).






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