Re: mirror flop on a celestron c 9.25

Joe Zeglinski

Hi Georgio,

Is there any chance that the weight of the Pentax is causing the OTA to
sag or shift , depending on the mount position? If you use an autoguider, on a
different finder than the OTA, it might try to compensate the sag,
incorrectly. Everything on the plate has to be tight, flex free.


----- Original Message -----
From: "lupodima" <>
To: <>
Sent: Sunday, April 15, 2007 3:12 PM
Subject: [ap-gto] Re: mirror flop on a celestron c 9.25

Hi Tom thanks for your input
Sorry to all the users here but i make a error i post on the group
rather than send a email to Mr John .
Anyway , Tom , is intresting the focuser and i will check it !
The mount 900 gto is perfectly orthogonal but this commercial OTA have
some problems.... first of all i have measured whit a digital calliper
the thickness of the corrector ring and the rear cell ring ( primary
mirror ) and the difference is almost 2 mm (0,079 inch )...i have
shimmed the ota with some piece of soda can (coca cola) .But following
the istruction for check the orthogonality issue from the 900 gto
manual t(the meridian delay) i have still a noticeable error and of
course the quality of goto is very low ...
For focusing i have a Microfocuser analog pc who is very precise and
is fully controllable remotely from my PC thru ascom driver
I have 2 losmandy dovetail one for match the OTA to the 900 gto and
another (the equal model) as accessory tray (now i have on a Pentax
sdhf 75 with 2 rings to grab it).
The advice of mr John is very intresting ,because is possible to do it
without disassemble the c9 totally can find it here :

thanks again

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