From: "Dwight K. Elvey" 
To: atm{at}shore.net
Reply-To: "Dwight K. Elvey" 


Hi
 Should you decide to use a larger tube, you can always
mount the focuser on a flat board and cut a cordial notch in the tube to mount it.
 Small tubes usually have more issue with tube current
than reflected light ( the Moon being an exception ). Dwight


>From: "Dennis Woos" 
>
>My young son Tim (11 years old) and I are making a 5" f/11.4 newtonian.  We
>have acquired a .8" secondary, a very low profile 1.25"
helical focuser, and
>a 5.5" I.D. sonotube.  Our three remaining challenges are to 1) get the
>mirror coated with a short turn-around, 2) build a secondary holder and
>spider, and 3) decide on the tube.
>
>Our concern on the tube stems from its small diameter, and concerns that
>stray light will reflect off of the tube walls and enter the optical path.
>We are concerned that even ProtoStar flocking paper will not prevent this.
>However, we do want to stay as close to the secondary as is reasonably
>possible, as he wants a planet scope with small secondary.  Will the
>flocking paper do the job?  If not, we can use the 5.5" tube at the top end
>to mount the secondary and focuser, and then step up to a larger diameter
>tube (we have some 8").  What do folks think about the tube issue?
>
>How about a quick coating - any good sources?
>
>And finally, I have make seconday holders and spiders, but never one this
>tiny.  Any Ideas?  Thanks.
>
>Dennis
>
>
>
>

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