[AZ-Observing] Re: Observing Weather this Weekend

Stan,
I had the same thing happen on my 10" LXD55, it caused me to freak out. 
happened about a week after I got the scope. At first I thought it was 
something on the corrector, as i had got it dewed up pretty good. Then upon 
closer inspection the next morning I realized it was actually on the primary. 
Funny thing is I have no clue what caused it. 3 days later the optics were 
clear & it has never happened again.

Stan Clark
webmaster
saguaroastro.org

---------- Original Message ----------------------------------
From: "Stanley A. Gorodenski" <stan_gorodenski@xxxxxxxxxxxxx>
Reply-To: az-observing@xxxxxxxxxxxxx
Date: Tue, 31 May 2005 15:45:26 -0800

>If the weather is good this weekend it is because I just purchased a 10" 
>LXD75 at RTMC this last Sunday. If the weather is not good it is because 
>of what someone else purchased. :-)
>
>I have a question about the optics. When I looked through the scope at 
>RTMC, unless I kept my eye close to the eyepiece (a plossel) it appeared 
>the field of view got brighter toward the center. When I backed off and 
>rotated my eyeball socket (i.e., I moved my head around as opposed to 
>just rotating my eyeball), I could see a small lighter disk of light 
>following my movement. I know achromatic refractors have the problem of 
>a brightness increase toward the center but I do not know if this could 
>also be a characteristic of Schmidt-Newtonians. At first I thought dust 
>on the secondary might be the cuprit, but it looks good upon closer 
>inspection. However, the primary does not look so good. It appears to be 
>dusty, but I do not think it is dust. I beleive it is either a bad 
>aluminization, or a bad wash job if this is done at Meade after a mirror 
>is aluminized. This could cause the field to be brighter because of 
>dispersion of the light, and the increase toward the center could be the 
>result of vignetting. Does anyone have any insight on what could be 
>causing this? I just got back from RTMC yesterday and haven't had a 
>chance to set it up outside and investigate this more but will do so 
>tonight.
>Stan
>
>
>
>--
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>
>
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