Sponsored By:

Subject: [M]: RE: LX200: Optics Question
From: Heapy Chris CG
Reply To: mapug@shore.net
Date: Thu Sep 18 00:06:48 1997

My 10" LX200 sounds similar, with the exception perhaps that bright
stars
(for example, Vega) produce 3 or 4 definite faint diffraction rings. Try
using a higher
power (say, 300x). The components of e-Lyrae (double-double) produce a
single faint diffraction ring around each at 350x. The 'bright ring'
sounds like
dew or perhaps streaks on the mirror/corrector plate - or maybe
fingerprints
on the eyepiece. Whatever, it doesn't sound like anything to do with the
figuring of the optics.

Chris Heapy

>----------
>From: Don Tabbutt[SMTP:DonTabbutt@worldnet.att.net]
>Sent: 18 September 1997 04:17
>To: mapug@shore.net
>Subject: [M]: LX200: Optics Question
>
>
>On bright stars, say mag 4 or less, my scope focuses to a very tiny yet
>extremely bright spot. It is by no means an airy disk, with which I am very
>familiar, but more like a tiny, bright, symmetrical, point. No diffraction
>rings...not even a hint of them...but plenty of tiny symmetrical "daggers"
>emanating from the point...sort of like the classical artist's rendition of
>a star. I also get a large diameter, barely perceptible, brighter than the
>background field, "circle of light" around the star...up to 1/4 the field
>at 150X. Is this a secondary effect? Is it flare from inadequate coatings?
>Or is this in fact a "diffraction ring"?
>
[...]
>
>What have I got here...a dog, a gem, or what? This, again, is purely
>academic...I love the scope. But it's my first and only SCT, and I just
>wonder....
>
>Thanks,
>
>Don
>