mirror flop on a celestron c 9.25


T.A. Meneghini <t.tamen@...>
 

Giorgio,

I am also an owner of a C9.25. Most of your problem is, obviously,
orthogonality of the telescope and mount. If you believe there is a residual
problem from mirror flop, there is a product that will help minimize (but
not eliminate entirely) the effect. It is a Hutech focuser lock. This is not
a mirror lock, but a mechanism that replaces your SCT focus knob. It employs
a long set screw through the knob that is used to lock the internal focus
mechanism. I've found that it removes about 80% of the mirror flop in my
C9.25. The unit sells for about $55.00 US.

Best regards,
Tom Meneghini

-----Original Message-----
From: ap-gto@yahoogroups.com [mailto:ap-gto@yahoogroups.com] On Behalf Of
lupodima
Sent: Sunday, April 15, 2007 8:38 AM
To: ap-gto@yahoogroups.com
Subject: [ap-gto] mirror flop on a celestron c 9.25



Hello John
i read the your post on astrophysics yahoo group regarding the
adjustment of your Celestron c11 mirror flop
here the link were i read your intresting advice
http://tech.
<http://tech.groups.yahoo.com/group/ap-gto/messages/5619?threaded=1&m=e&var=
1&tidx=1>
groups.yahoo.com/group/ap-gto/messages/5619?threaded=1&m=e&var=1&tidx=1

I have 900 gto cp3 from astrophysics and my Celestron c9.25 have a
very large error in orthogonality as well mirror flop
i read also your pdf downloaded from your site
and i will try your advice (seem to be not to much difficult)
Have you upgraded this advice or i can follow your pdf litterally ?
i have to dissassemble my c9.25 and i think is the same way of a c 11 ...
when i told about the orthogonality error i mean if i point to Vega
and then point on a star on the other side of the meridian i notice
the error also in the finderscope ( 9x60 )who is attached on the main
OTA c9.25
i have shimmed it but with a lot of piece soda can i havent get the
good result

thanks for your precious advice
im waiting for your responce
my best regards
Giorgio Ospici
Italy

my email address is
lupo.di.mare@ <mailto:lupo.di.mare%40virgilio.it> virgilio.it


lupodima <lupo.di.mare@...>
 

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 ....you can find it here :
http://tech.groups.yahoo.com/group/ap-gto/message/5619

thanks again
Cheers
Giorgio


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.

Joe

----- Original Message -----
From: "lupodima" <lupo.di.mare@virgilio.it>
To: <ap-gto@yahoogroups.com>
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 ....you can find it here :
http://tech.groups.yahoo.com/group/ap-gto/message/5619

thanks again
Cheers
Giorgio



To UNSUBSCRIBE, or for general information on the ap-gto list
see http://groups.yahoo.com/group/ap-gto
Yahoo! Groups Links




lupodima <lupo.di.mare@...>
 

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.

Joe

------------------------------------------------------------------------

Hi Joe
I think about and had removed the Pentax sdhf 75 from the c9 but i
still have this problem.
Anyway the rings and the losmandy dovetail on the Pentax was firmly
blocked.
at this point i hope who i have only an error of orthogonality of the
OTA in one direction ( i mean up and down so i can fight with shimming
the ota) and not in right left
cheers
Giorgio