VintageBigBlue.org

 

Re: PEC & GM-8 question....again.


Mar 29, 2005

 


----------------------------

#24915 Mar 29, 2005

Hi all,



I have a GM8 which I am still learning to use and have a question.



I'm interested in using a 12cm f/5 achromat for prime focus CCD

imaging and wonder at what magnification I should do the PEC run

through before actually imaing at prime focus? I have used a 3x

Barlow with the CCD camera to do the PEC run and after the 8 min

recording period the mount seems to track pretty well with the 3x

Barlow, efr f/15. But when I go to prime focus and try to record for

1 minute, the stars are shifting with each 60 second iteration. Is

this seeing? Or is there something I am missing utilizing the PEC?



I am doing the PEC run near the object of interest and do not turn

off the mount between the PEC run and actual imaging with the CCD

camera.



Any thougts?



Thanks,

Jim

www.lafterhall.com/2hs.html



----------------------------

#24917 Mar 29, 2005

Hi Jim,



You can train PEC at the same or slightly greater magnification as

the one you'll use for imaging. Ideally, you don't want too much

magnification, as you are then more likely to correct for seeing

fluctuations instead of PE.



If the motion you see is repeatable, it is periodic by definition :-)

If you see the same motion every 60 seconds, PEC will likely help.



If you will be auto-guiding, I'd suggest you try guiding without

training PEC first, just to see if it'll be sufficient. In many

cases, especially with shorter focal lengths, you're likely not to

need PEC when guiding -- this can save you extra time and effort.



Regards,



-paul



--- In Losmandy_users@yahoogroups.com, "Jim Ferreira" bakerst@c...>

wrote: >

> Hi all,

>

> I have a GM8 which I am still learning to use and have a question.

>

> I'm interested in using a 12cm f/5 achromat for prime focus CCD

> imaging and wonder at what magnification I should do the PEC run

> through before actually imaing at prime focus? I have used a 3x

> Barlow with the CCD camera to do the PEC run and after the 8 min

> recording period the mount seems to track pretty well with the 3x

> Barlow, efr f/15. But when I go to prime focus and try to record for

> 1 minute, the stars are shifting with each 60 second iteration. Is

> this seeing? Or is there something I am missing utilizing the PEC?

>

> I am doing the PEC run near the object of interest and do not turn

> off the mount between the PEC run and actual imaging with the CCD

> camera.

>

> Any thougts?

>

> Thanks,

> Jim

> www.lafterhall.com/2hs.html



----------------------------

#24922 Mar 30, 2005

Hey, Paul, thanks for the info. Good point about possibly correcting

for seeing rather than PE when training the PEC at high

magnification. Seeing at my observing site is typically turbulent to

some degree as I am in a valley surrounded by homes with a major

metropolitan area up wind from me...



Eventually I will add a guide scope and a second camera for auto

guiding, but for now I am hoping to do some good imaging unguided.

Some results, thus far, have been most encouraging.



Cheers,

Jim

www.lafterhall.com/2hs.html







--- In Losmandy_users@yahoogroups.com, "Paul K" pkane2001@h...>

wrote: >

> Hi Jim,

>

> You can train PEC at the same or slightly greater magnification as

> the one you'll use for imaging. Ideally, you don't want too much

> magnification, as you are then more likely to correct for seeing

> fluctuations instead of PE.

>

> If the motion you see is repeatable, it is periodic by definition :-

) > If you see the same motion every 60 seconds, PEC will likely help.

>

> If you will be auto-guiding, I'd suggest you try guiding without

> training PEC first, just to see if it'll be sufficient. In many

> cases, especially with shorter focal lengths, you're likely not to

> need PEC when guiding -- this can save you extra time and effort.

>

> Regards,

>

> -paul

>

> --- In Losmandy_users@yahoogroups.com, "Jim Ferreira"

bakerst@c...> > wrote:

> >

> > Hi all,

> >

> > I have a GM8 which I am still learning to use and have a question.

> >

> > I'm interested in using a 12cm f/5 achromat for prime focus CCD

> > imaging and wonder at what magnification I should do the PEC run

> > through before actually imaing at prime focus? I have used a 3x

> > Barlow with the CCD camera to do the PEC run and after the 8 min

> > recording period the mount seems to track pretty well with the 3x

> > Barlow, efr f/15. But when I go to prime focus and try to record

for > > 1 minute, the stars are shifting with each 60 second iteration. Is

> > this seeing? Or is there something I am missing utilizing the PEC?

> >

> > I am doing the PEC run near the object of interest and do not turn

> > off the mount between the PEC run and actual imaging with the CCD

> > camera.

> >

> > Any thougts?

> >

> > Thanks,

> > Jim

> > www.lafterhall.com/2hs.html







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