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nitegeezer
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Reged: 11/27/07

PEC training
      #6027189 - 08/15/13 01:31 PM

I am trying to do some astrophotograpy in the northern sky. I am set up and don't want to move for a while, but I think I may have a PEC issue. The manual instructions say that when training RA to pick a star in the southern sky which is currently a wall and roof. Since I am on a wedge and in polar mode, what would happen if I trained RA on a star in western sky? I don't want to mess the scope up but I after all the work to get alignment where it is I really don't want to move it. The reason I suspect PEC is that some exposures come through perfect and others have a bit of star drift. Are there other things that I should check first?

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Lorence
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Reged: 09/15/08

Re: PEC training new [Re: nitegeezer]
      #6027450 - 08/15/13 03:32 PM

It's a Meade not a Paramount. Have you tried Guiding? Now that I think about it, doesn't a Paramount have a guiding port?

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nitegeezer
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Reged: 11/27/07

Re: PEC training new [Re: Lorence]
      #6027486 - 08/15/13 03:49 PM

Guiding is on my list of improvements, but I have been taking this slow and learning everything about each step that I can. For me, I want to take the pictures, but understanding all the issues is more important. I would like to get my tracking to the best I can before I add a guider, that will probably happen next spring.

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Cliff Hipsher
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Reged: 12/31/08

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Re: PEC training new [Re: nitegeezer]
      #6027706 - 08/15/13 05:35 PM

Quote:

Guiding is on my list of improvements, but I have been taking this slow and learning everything about each step that I can. For me, I want to take the pictures, but understanding all the issues is more important. I would like to get my tracking to the best I can before I add a guider, that will probably happen next spring.




You have the proper attitude, that's for danged certain.


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nitegeezer
scholastic sledgehammer
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Reged: 11/27/07

Re: PEC training new [Re: Cliff Hipsher]
      #6028139 - 08/15/13 10:09 PM

I do get tired of people wanting everything to work the first night and have pictures that would make the Hubble jealous!!

This has been a long process for me that makes me appreciate each improvement. I am just wondering what would happen if I try to adjust PEC on the RA drive using a western star. Since I am wedge mounted it seems this would work fine, and southern stars would be a pain even if I had a view of the southern sky. I would just like additional opinions before I make that step.


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nitegeezer
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Reged: 11/27/07

Re: PEC training new [Re: nitegeezer]
      #6029987 - 08/16/13 10:07 PM

I have been searching the web for information before I jump in and make a big mistake!!

Does anybody know what happens if you do repeated pec training runs? I found one site that suggested that multiple runs are better, but that would mean that they are using the old pec data as they run a new pass. This sounds pretty useful, but if the pec data is thrown out with each new pass I would not bother with the multiple runs.

Any comments?

Thanks much


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OzAndrewJ
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Reged: 11/30/10

Re: PEC training new [Re: nitegeezer]
      #6030001 - 08/16/13 10:22 PM

Gday NightGeezer

If you do multiple "trains", each train will overwrite the previous.
You can do this if you want to export the PEC files after each run and externally average/sum the data, ( after excluding any data that looks suspicious ).
In polar, if you train and then update, each update is actually done with PEC off, so is essentially a fresh train, but the firmware then uses proportional averaging as you go.
Ie first update uses new value = old data + new data / 2
second update uses new = (2*old + new )/3
third update uses new = (3*old + new )/4
This is designed to ensure one bad update doesnt have a huge effect on a refined model, but you never know if you had a bad run in between.
I prefer the former method as you get to decide what data to use.

Andrew Johansen Melbourne Australia


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P26
Vendor - Peterson Engineering


Reged: 05/02/12

Loc: RI, USA
Re: PEC training new [Re: OzAndrewJ]
      #6030722 - 08/17/13 11:13 AM

I defer to Andrew on this one as he's gone into Meade's software extensively. I haven't redone my PEC for several years now. When I did do it I was using PemPro, and clearly recall being very impressed how each successive training iteration seemed to reduce the error by 50%. With 3 iterations my 2003 14" Meade LX200GPS was running about 6 arc seconds.

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OzAndrewJ
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Reged: 11/30/10

Re: PEC training new [Re: P26]
      #6031453 - 08/17/13 05:52 PM

If you are using PEMPro, then i agree, doing PEC ON refinements is the best way to "tweak" the data.
If you are using native Meade firmware, i still suggest doing multiple trains with external processing of the data,
as there is a large variability in the Meade generated data,
and the firmware also has a quirk that it "saves on fail".
ie if you mode out part way through, it still saves and processes what it has, which can really upset an update process.

Andrew Johansen Melbourne Australia


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nitegeezer
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Reged: 11/27/07

Re: PEC training new [Re: OzAndrewJ]
      #6031943 - 08/17/13 11:14 PM

Thanks for all this information. I think I will try to train tonight, but I will not really see the benefits for a couple of weeks when we lose the moon and I can image again. This whole process has been a great learning experience for me, I just hope that someday I have the photos to show what I have learned.

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svdwal
super member


Reged: 03/10/13

Loc: Leiden, The Netherlands
Re: PEC training new [Re: nitegeezer]
      #6080427 - 09/14/13 01:39 PM

I think (but am not a 100% sure) that training PEC on a star in the West (or East) will introduce some error into the training. The problem is refraction, stars are lifted up a bit, and the higher they are, the less they are lifted up. So stars in the west appear to move down more slowly than they really are.

Looking south stars move more or less parallel to the horizon, so the lifting effect is a constant.


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nitegeezer
scholastic sledgehammer
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Reged: 11/27/07

Re: PEC training new [Re: svdwal]
      #6080486 - 09/14/13 02:08 PM

Well I may have messed things up a bit because I used Arcturus the other night. From my current location where I want to spend the winter, I do not access to the southern sky. I will try imaging the next time we have a clear night, and if it does not go well I will take everything apart and move so I do have the southern sky. I am still learning so I will just add that to my lessons learned. Now that you mention it, I think this is also the reason the Moon looks larger at the horizon than when straight up. Thanks for the info.

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