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Equipment Discussions >> Mounts

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korborh
scholastic sledgehammer
*****

Reged: 01/29/11

Loc: Arizona
AP1200GTO PE curves
      #5708142 - 03/02/13 03:08 AM Attachment (47 downloads)

My AP1200GTO is now almost 2 years old.
I Ran some PE curves tonight when the moon was up. Sampling at 0.48"/px using C11 EdgeHD and Atik 314L+.
Seeing was less than average.

First, the raw captured data before PEC. Shows a smooth and clean sine wave.


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korborh
scholastic sledgehammer
*****

Reged: 01/29/11

Loc: Arizona
Re: AP1200GTO PE curves new [Re: korborh]
      #5708143 - 03/02/13 03:09 AM Attachment (30 downloads)

The raw PE calculated just under 4" p-p.

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korborh
scholastic sledgehammer
*****

Reged: 01/29/11

Loc: Arizona
Re: AP1200GTO PE curves new [Re: korborh]
      #5708144 - 03/02/13 03:09 AM Attachment (29 downloads)

Here is the frequency spectrum of the capture. Note how large is the fundamental relative to the other frequencies indicating a nice sinusoidal and easily correctable PE.

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korborh
scholastic sledgehammer
*****

Reged: 01/29/11

Loc: Arizona
Re: AP1200GTO PE curves new [Re: korborh]
      #5708145 - 03/02/13 03:10 AM Attachment (31 downloads)

Data captured after uploading the measured PEC to the mount. Virtually flat line!

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korborh
scholastic sledgehammer
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Reged: 01/29/11

Loc: Arizona
Re: AP1200GTO PE curves new [Re: korborh]
      #5708146 - 03/02/13 03:11 AM Attachment (27 downloads)

The resulting PE - no period found. Good!

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korborh
scholastic sledgehammer
*****

Reged: 01/29/11

Loc: Arizona
Re: AP1200GTO PE curves new [Re: korborh]
      #5708147 - 03/02/13 03:12 AM Attachment (21 downloads)

Frequency spectrum - just noise. PE has been anhilated.

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orlyandico
Postmaster
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Reged: 08/10/09

Loc: Singapore
Re: AP1200GTO PE curves new [Re: korborh]
      #5708191 - 03/02/13 05:02 AM

Did you only use the fundamental for the PEM curve?

On my Mach1 i use the 1, 2, and 3rd harmonics. There is still a residual of about 0.4" after PEM...


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korborh
scholastic sledgehammer
*****

Reged: 01/29/11

Loc: Arizona
Re: AP1200GTO PE curves new [Re: orlyandico]
      #5708735 - 03/02/13 12:33 PM Attachment (15 downloads)

I used linear fit in PemPro which selected 1,2,3 and 4 harmonics as below. You can see the 2,3,4 are insignificant. I used this default selection to program so all four were used.

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orlyandico
Postmaster
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Reged: 08/10/09

Loc: Singapore
Re: AP1200GTO PE curves new [Re: korborh]
      #5708877 - 03/02/13 01:56 PM

hmmm.. i'm always using quadratic or cubic fit. maybe i should use linear fit..

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korborh
scholastic sledgehammer
*****

Reged: 01/29/11

Loc: Arizona
Re: AP1200GTO PE curves new [Re: orlyandico]
      #5708913 - 03/02/13 02:22 PM

I usually start with linear fit and check the fit quality using the RMS and scrolling through the whole data in the above dialog box. If the RMS does not change much going to quadratic, I just use linear.
The quadratic fit is usually ok and may work better but higher order fitting can be artificial and not useful for smooth AP mounts.
Your 0.4" corrected (after PEM) seems pretty good to me. Depending on balance and side of pier, I see somewhat different results and corrected PE of 0-0.5".


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orlyandico
Postmaster
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Reged: 08/10/09

Loc: Singapore
Re: AP1200GTO PE curves new [Re: korborh]
      #5708917 - 03/02/13 02:25 PM

i'm at 0.4" when east heavy and 0.8" west heavy.

uncorrected is 3.5" east heavy and 6" west heavy.


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korborh
scholastic sledgehammer
*****

Reged: 01/29/11

Loc: Arizona
Re: AP1200GTO PE curves new [Re: orlyandico]
      #5708944 - 03/02/13 02:47 PM

That sounds quite good and sub-arcsec. I found it best to have it well balanced but the difference is insignificant when its all under 1". I see no difference with these PE figures with or without correction on my guided images. I usually do PE once in a while to check if nothing sudden is happening to tracking making sure mechanics of the mount are good.

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andysea
Pooh-Bah
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Reged: 09/03/10

Loc: Seattle, WA
Re: AP1200GTO PE curves new [Re: korborh]
      #5709065 - 03/02/13 04:09 PM

You guys! I never checked the PE on my mounts but your posts make want to dig into it. So far I just look at my subs and if they look good I don't worry:)
I wonder how my 2005 vintage NJP would compare.


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Tom and Beth
Post Laureate


Reged: 01/08/07

Loc: Tucson, AZ
Re: AP1200GTO PE curves new [Re: korborh]
      #5709330 - 03/02/13 06:35 PM

Like you, I'm just starting to use PEMpro. Didn't need it when I was 100% visual, but now as I tune the mount I find visual use is even MORE enjoyable. Still have a bit more to do in order to get long exposures with a 3 Meter FL scope,

Edited by Tom and Beth (03/02/13 06:36 PM)


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Mike Clemens
Frozen to Eyepiece
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Reged: 11/26/05

Loc: Alaska, USA
Re: AP1200GTO PE curves new [Re: Tom and Beth]
      #5709621 - 03/02/13 09:46 PM

PemPro fixed my AP1200 GTO right up
http://www.pbase.com/mclemens1969/image/94812800


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korborh
scholastic sledgehammer
*****

Reged: 01/29/11

Loc: Arizona
Re: AP1200GTO PE curves new [Re: Mike Clemens]
      #5709626 - 03/02/13 09:55 PM

That looks so much like the the PE curve on mine! Yeah the zero PE is cool.

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andysea
Pooh-Bah
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Reged: 09/03/10

Loc: Seattle, WA
Re: AP1200GTO PE curves new [Re: korborh]
      #5709760 - 03/02/13 11:42 PM

hmm I've been wanting to get an AP900 but looking at your results with the 1200 makes me wonder if I should shift gears and keep an eye out for a good used 1200.

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korborh
scholastic sledgehammer
*****

Reged: 01/29/11

Loc: Arizona
Re: AP1200GTO PE curves new [Re: andysea]
      #5709769 - 03/02/13 11:50 PM

Andysea, I would not recommend you make the choice between the 1200 and 900 based on PE. With the (not very old) AP mounts, the PE is guaranteed to be low and smooth and will <1" pp corrected out of the box.
I would recommend the 1200 if you can pick and move 50lbs without issue. Its a really strong and overbuilt mount, conservatively rated for 140lb payload. They are coming up on Amart used at good prices.


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orlyandico
Postmaster
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Reged: 08/10/09

Loc: Singapore
Re: AP1200GTO PE curves new [Re: andysea]
      #5709770 - 03/02/13 11:50 PM

Andy, I don't think there's much different between the Mach1, 900, and 1200. I think it's when you get to the 1600 that you get a smaller native PE (somebody else posted about 1.6" before PEM). But these usual suspects are all in the 3.5" range before PEM.

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andysea
Pooh-Bah
*****

Reged: 09/03/10

Loc: Seattle, WA
Re: AP1200GTO PE curves new [Re: orlyandico]
      #5709885 - 03/03/13 02:43 AM

True and true! The more I think about it the more the 1200 makes sense given that I already have a 45lb. and a 70lb. mounts.
I do see them come up used for very good prices.


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