RE: ATM 10" Problems

["Fearon, Gary" <gary.fearon@wapl.com.au>]

Rare is the night that offers pin point images at
higher powers of magnification. (But sweet they are
when you catch them).
Gary 

> -----Original Message-----
> From: The Silent Observer [SMTP:silent1@ix.netcom.com]
> Sent: 31 July 1999 11:48
> To:   ATM List
> Subject:      Re: ATM 10" Problems
> 
> 
> > 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
> Rocket Pages             http://members.aol.com/silntobsvr/launches.htm
> 
> Opinions expressed are my own -- take them for what they're worth
> and don't expect them to be perfect.