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[APML]: OAG & Illuminated Reticule Causing Reflection

Michael,

<HTML><PRE><FONT  COLOR="#000000" SIZE=3>Subj:   RE: [APML]: OAG & Illuminated Reticule 
Causing Reflection
Date:   09/02/98  05:09:06
From:   mhart@netexpress.net (Michael Hart)
Sender: owner-astro-photo@nightsky.com
Reply-to:       astro-photo@nightsky.com
To:     astro-photo@nightsky.com ('astro-photo@nightsky.com')

Michael wrote:-

"The illuminated reticle must always be used at the absolute minimum
brightness; a pulsing control helps.  What happens is reticle light is transmitted
through the off-axis guider prism and onto the first reflective surface (probably
a focal reducer in your case) and onto your film."

Michael,
You are right about my focal reducer being directly in front of the OAG. I had already 
put some dark red nail varnish over the bulb of the guiding eyepiece to dim it, and 
tweaked the prism a little.

I don't use the tube, I place the camera directly on the OAG body.

I had not, however, considered any reflection from the reducer. I had put my deep-sky 
filter before the reducer because it works best with a parallel light source. But, maybe 
it would benefit my setup if I put the reducer first, then the filter, to move the 
reducer a little further in front of the OAG body. What do you think ?

Another thought, do you know if the prisms on the Meade CCD OAG are lower into the light 
path ? I would have thought that the only difference would be that they provide the 
extension tube.

Thanks for the help.

Steve


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