NOTE: I apologize if the message below is a repeat. I've just changed ISPs
and in the process missed out on about 36 hours worth of MAPUG mail. I
meant to send this yesterday - but I don't think it went through. If this
HAS already been sent to the list - I apologize. If anyone on the list has
already replied to this message, could you please forward your reply to me
directly, as I am only just now receiving messages directly from MAPUG
again.

Thanks - Tony L'Hotellier

In an attempt to more accurately assess the condition of my telescope
optics I purchased Suiter's book 2 months ago and have come up with the
following star test observations. I'd like to hear other observer's
interpretations of the results as I am considering selling the scope. I
want to know if I can sell it in good conscience (the scope is still
under warranty).

Telescope: 10" LX200 f/6.3 (40% sec. obstruction).

Defocusing aberration: approx. 10 wavelengths (slightly less than 1/4
turn of the focuser).

Results

Inside Focus: Very bright inner ring, two other faint rings - no outer
ring. Well defined secondary shadow that appeared almost instantly,
well within 1/16 of a turn, small at first progressively increasing in
size with rest of the image.

Outside Focus: Bright outer ring, other rings faint and progressively
fainter towards the centre. Border of secondary shadow is fuzzy and
indefinite. The secondary shadow does not appear until about 3/16 of a
turn of the focuser.

Suiter indicates that the secondary shadow ratio for a 40% obstruction
should be something less than 2:1.

Thanks, Tony

*******************
Cass & Tony L'Hotellier
+61 3 5133 9258
Australia

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