[Aavso-photometry] Focal Reducer

[Walt Cooney]

Greg,

I have used the Celestron 0.63 focal reducer and the Astro-physics 0.68 focal
reducer on my 12" LX-200 with an AP-7.  Using the 0.63 focal reducer and Ted
Agos's variable distance adapter, I had some troubles.  There was a large
circular area in the middle of my images in flats that was a couple of percent
off.  It looked like a scattered light phenomenon.  I was never able to pin it
down.  I have since swapped to the AP reducer operating at about 0.74x and have
not seen the problem.  The 0.33x reduction is pretty extreme.  I have not used
one but would not be surprised if there aren't some issues with it.  Really good
flat fielding techniques will hopefully solve any issues.  If you have a
scattered light phenomenon as I did with the 0.63 Celestron, you won't be able
to flat out that problem.

Clearest skies,
Walt Cooney
http://members.cox.net/waltc/BLACKBERRY_OBSERVATORY.htm

-----Original Message-----
From: aavso-photometry-bounces at mira.aavso.org
[mailto:aavso-photometry-bounces at mira.aavso.org]On Behalf Of Greg Spear
Sent: Saturday, January 22, 2005 12:45 PM
To: aavso-photometry at mira.aavso.org
Subject: [Aavso-photometry] Focal Reducer



I am in the process of configuring a setup for Transit Search which
consists of an Meade LX-200GPS and a SBIG ST-7XME. I'm looking for a
good focal reducer suitable for high precision photometry (< .01 mag)

So far, I've found:
   Optec NextGEN MAXfield 0.33x
   Meade Series 4000 Focal Reducer .33x

Does anyone have any recommendations or other reducers?
Does anyone have any experience with these or comparison information?
I have found some information on the Internet but would like to hear
something from those doing photometry.

Thanks

Greg Spear
gspear at ucolick.org


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