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CGEM PHD Guide Log April 21 09

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#1 donsinger1

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Posted 23 April 2009 - 07:35 PM

All:

Seen some requests to look at some info on the CGEM, so I enabled the guide log in PHD the other night and saved it as a PHD Log and some additional PEAS output that can be looked at in PECPrep. I have attached the PHD file and some PEAS output for everyone to have a look at.

Used PHD Version 1.10.0; I guided for close to 3 hours (the log is for about an hour and a half) using with standard out of the box settings (100% Agressiveness, 10% Hystersis, Dec Guide Mode set to Auto and Dec Algorithm set to Resist Switching).

I opened up the PHD Log using PHD Analyzer (you need Version 3 which can be had at the Stark Labs Yahoo Group under Files/Supplemental Files folders).....checked it out, and have no idea what it means. I guided from my back porch, which is wood framed and is slightly affected by
cars going by or by myself walking away from the mount once everything is set...you can see those anomolies at the beginning and close to the end of the graphs...otherwise I have no idea what any of this info means...maybe someone
could clarify this information for us?

I was imagining using an AT90EDT (great scope) and SXVF H9C; Guidescope was a 50mm Miniborg of 250mm focal length and an Orion Starshoot Autoguider which has 5.2 micron square pixels. On this imaging run, I was taking 150second lights and stars came out nice and round (90%).

I have not fussed with PEC much as guiding has always seemed to mask things, but was kind of interested in what my new CGEM does. My CGEM is sure accurate in it's pointing and tracking...and, used the AllStar Polar Align routine which seems to work well.

Don

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#2 donsinger1

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Posted 23 April 2009 - 07:37 PM

Here is PEAS output 1 of 3 attached

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#3 donsinger1

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Posted 23 April 2009 - 07:39 PM

Here is PEAS Output 2 of 3

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#4 donsinger1

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Posted 23 April 2009 - 07:43 PM

Here is PEAS output 3 of 3

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#5 Moggi1964

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Posted 23 April 2009 - 08:55 PM

Can someone summarize for the weak of mind :)

Thanks.

#6 Jerry3672

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Posted 24 April 2009 - 08:16 AM

Thanks for the post, I am interested in your results because I am thinking about one of these mounts.

Did something happen 323 seconds into you test? I see the star was out 10 pixels for about 6 seconds. Other than that I see PHD was working hard to keep you on track.

Could you post a log of about 10 minuets with the output to mount control disabled? I would like to see how the P.E. is with no corrections from PHD.

#7 donsinger1

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Posted 24 April 2009 - 09:28 AM

Thanks for the post, I am interested in your results because I am thinking about one of these mounts.

Did something happen 323 seconds into you test? I see the star was out 10 pixels for about 6 seconds. Other than that I see PHD was working hard to keep you on track.

Could you post a log of about 10 minuets with the output to mount control disabled? I would like to see how the P.E. is with no corrections from PHD.


About 5 minutes into my imaging run my 5 year old slammed the porch door shut and that probably shook the mount, so that is most likely what you are seeing as 323.

I have never used PHD to just record output with no guiding input, but will try tonight and post tonight or tomorrow.

D

#8 Jerry3672

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Posted 24 April 2009 - 12:39 PM

I used PHD recently to evaluate how much PE I was getting with a homemade worm gear for my LXD75. It works great, just hit the brain and check the box that disconects corrections.

I ended up with 20 arc seconds of error. Not too bad, but I think I will do better on my next gear, or I may just upgrade to the CGEM mount. I have a C11 on that LXD75, and that is a bit much weight.


Thanks for taking the time to log your mount data. It is good information for the group.

On the good side of your mount- It didn't take very long for PHD to get your star back in the center after to door slam. Sometimes things just happen. I have kids too.

#9 famax

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Posted 24 April 2009 - 03:58 PM

As i said on the cgem yahoo group i made a peas analysis
of your file. A screen is attached to this post :



here are my though (sorry for my bad english...)

I made a screen shot of the peas analysis under the file folder , it is call :
Don_cgem_log 2.JPG

We can see some bumps (walking around the mount ) but the usual
guiding graph shows a +/- 1.5 arc sec guiding efficiency.
This is not a very good guiding but quite ok if your imager focal is under 1000
mm.

THe +/-1.5 arc sec is somehow wave form so it seems ther is something
that drive the guiding this way.
-I dont think it is due to the mount since it is very repeatable.
(i can be wrong on this point since mechanical transimistion can lead to a kind
of "noise" in guiding, but not as so repeatable...)

-I think more like to much agressiveness in the guiding properties :
I don't know well PHD guider but on guidmaster , to much agressiveness
can lead to theses oscillations, it never should exceed 80/90 %...

-The seeing can be a source of errors too: you should stack more frames to pass
over the seeing...

-In my opinion 250 mm seems pretty low focal lengh for guiding.
By the way this question is still open.

A good idea if you want to test your mount is to make a guiding session of about
20 mn , putting your camera at the main focus of your imager, and to save a log.
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