Re: ATM 10" Problems

[The Silent Observer <silent1@ix.netcom.com>]

> Dale Schmitz wrote:
> 
> Greetings all.  Need some advice on a 10" scope I recently completed.
> I'm having problems getting a decent view from it.  There are a number
> of things I'd like to know about, but let me start with the quality of
> the view with a 21mm eyepice (my...largest?).  While I can focus
> things in relatively sharp (good enough for casual viewing), there are
> distinct flares of light from the larger stars and most stars have
> little "spikes" of light radiating from them in a direction that's
> dependent on my position over the eyepiece.  Also, with my smaller
> eyepiece (8mm) the degradation of the view is tremendous.
> 

I had (have) a similar problem with the views from my 4.5" f/9 Newtonian
-- I've been told that it's mostly due to tube currents, that is, air
moving up and down in the tube under convective impetus in a scope that
isn't fully cooled.  On top of that, my scope has a small amount of
astigmatism, most likely due to an unflat diagonal, and some periodic
errors in the primary that contribute -- but even if the optics were
perfect, I'd still get the spikes, changing slowly (on about a 1 minute
or faster scale) due to tube currents.

Have you tried leaving the scope out for several hours after sunset
before observing?  That will reduce or eliminate cooling related
problems, and give you a better chance of seeing what the optics are
really doing.

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Donald Qualls, aka The Silent Observer           NAR # 70141-SR Insured
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