Re: 900 mount in Antarctica at Dome C


Nov 29, 2004

 


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

#11222 Nov 29, 2004

Hi folks,



One of our French dealers sent me this link showing the French research team

down under with two of our 900 mounts getting ready to track the Sun and stars

with a pair of specially made C11 scopes. These mounts already spent last

season down there in weather as cold as -60C doing research on seeing at Dome C.



Interesting that the platform and tripods were made from wood. I was told

that they resist the cold better than metal and won't twist with the temperature.



Some pictures:



pleiades.unice.fr/~agabi/galerie/Agabi_DSCN9206_m.jpg

pleiades.unice.fr/~agabi/galerie/Agabi_DSCN7818_m.jpg

pleiades.unice.fr/~agabi/galerie/Agabi_DSCN9370_m.jpg

pleiades.unice.fr/~agabi/galerie/Agabi_DSCN9219_m.jpg



Home page: pleiades.unice.fr/~agabi/



Roland Christen





[Non-text portions of this message have been removed]



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

#11223 Nov 29, 2004

Roland wrote: > One of our French dealers sent me this link showing the French research team

> down under with two of our 900 mounts getting ready to track the Sun and stars

> with a pair of specially made C11 scopes. These mounts already spent last

> season down there in weather as cold as -60C doing research on seeing at Dome C.



Wow, and I thought I was bordering on abusive leaving my 900 mount outside (covered, of course) in the mild California winters...:)



You build 'em tough, Roland, no doubt. Wouldn't trade mine for anything.



Paul



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#11225 Nov 29, 2004

Roland,



Those do not look like any 900's I've ever seen. The location

that the counterweight shaft bolts in to looks a lot beefier.

What's the large metalic doodad where the polar scope cover

would go?



Did you have to do any special hardening of the electronics to

deal with the brutal cold down there?



- Vince

--- In ap-gto@yahoogroups.com, chris1011@a... wrote:

> Hi folks,

>

> One of our French dealers sent me this link showing the French

research team

> down under with two of our 900 mounts getting ready to track the Sun

and stars

> with a pair of specially made C11 scopes. These mounts already spent

last

> season down there in weather as cold as -60C doing research on

seeing at Dome C.

>

> Interesting that the platform and tripods were made from wood. I was

told

> that they resist the cold better than metal and won't twist with the

temperature.

>

> Some pictures:

>

> pleiades.unice.fr/~agabi/galerie/Agabi_DSCN9206_m.jpg

> pleiades.unice.fr/~agabi/galerie/Agabi_DSCN7818_m.jpg

> pleiades.unice.fr/~agabi/galerie/Agabi_DSCN9370_m.jpg

> pleiades.unice.fr/~agabi/galerie/Agabi_DSCN9219_m.jpg

>

> Home page: pleiades.unice.fr/~agabi/

>

> Roland Christen

>

>

> [Non-text portions of this message have been removed]



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

#11227 Nov 29, 2004

In a message dated 11/29/2004 7:57:25 PM Central Standard Time,

astronaughty2002@... writes:



>

> Those do not look like any 900's I've ever seen. The location

> that the counterweight shaft bolts in to looks a lot beefier.

> What's the large metalic doodad where the polar scope cover

> would go?



The mount was modified slightly by the French team. I don't know what they

did for the counterweight end or the polar scope opening.

>

> Did you have to do any special hardening of the electronics to

> deal with the brutal cold down there?

>



The electronics are pure stock. Nothing was done to them. The entire mount

was tested in a special cold chamber at -70C before sending it down there. The

only thing they did to the drive train was to remove all the lubricants from

all bearings and gears. Only the gear wheel has a light coating of a very thin

grease applied, which remained soft to -70C. After 1 year of operation, the

mounts were disassembled by Frank, the Ovision technician and new worms were

fitted for this year's project.



That's the only thing I know, unless Gilles from Ovision would like to add

something to this.



Roland Christen





[Non-text portions of this message have been removed]



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

#11228 Nov 29, 2004

Roland,

This is really neat to see. I particularly enjoyed seeing the polar

axis' pointing almost straight-up! Thanks for sharing.



- Steve



-----Original Message-----

From: chris1011@... [mailto:chris1011@...]

Sent: Monday, November 29, 2004 4:10 PM

To: ap-ug@yahoogroups.com

Cc: ap-gto@yahoogroups.com

Subject: [ap-gto] 900 mount in Antarctica at Dome C





Hi folks,



One of our French dealers sent me this link showing the French research

team

down under with two of our 900 mounts getting ready to track the Sun and

stars

with a pair of specially made C11 scopes. These mounts already spent

last

season down there in weather as cold as -60C doing research on seeing at

Dome C.



Interesting that the platform and tripods were made from wood. I was

told

that they resist the cold better than metal and won't twist with the

temperature.



Some pictures:



pleiades.unice.fr/~agabi/galerie/Agabi_DSCN9206_m.jpg

pleiades.unice.fr/~agabi/galerie/Agabi_DSCN7818_m.jpg

pleiades.unice.fr/~agabi/galerie/Agabi_DSCN9370_m.jpg

pleiades.unice.fr/~agabi/galerie/Agabi_DSCN9219_m.jpg



Home page: pleiades.unice.fr/~agabi/



Roland Christen





[Non-text portions of this message have been removed]







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#11232 Nov 30, 2004

> That's the only thing I know, unless Gilles from Ovision would

like to add > something to this.

>

> Roland Christen

>



Hi Roland,



Franck will post soon his reply.

He will also post some interesting images of the mounts "low

temperatures" modifications.



Gilles



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

#11250 Dec 2, 2004

--- In ap-gto@yahoogroups.com, "astronaughty2002"

astronaughty2002@y...> wrote: >

> Roland,

>

> Those do not look like any 900's I've ever seen. The location

> that the counterweight shaft bolts in to looks a lot beefier.

> What's the large metalic doodad where the polar scope cover

> would go?

>

> Did you have to do any special hardening of the electronics to

> deal with the brutal cold down there?

>



my name is Franck one of the author of the modify on those mounts



the "doodad" on the axis are absolute encoder positioning system,

in the case there is a total cut of the communication on the mount(of

course special process to warm it and measure it before restart the

mount).

The mounts are located 30 m away from the CP for winter (-74.), the

CP are on the mount during summer (only -42.).It is not possible to

send some body during winter to verify the position.



Those encoder are coupled with electronic finder (warmed also)to

final calibrate the position.



We are very surprise of the way the electronics resist for exemple

one keypad had been forget during 15 days on the platform with -58 .

at the lowest !! it still working!

There is some mechanical modify on the mount specialy on dec axis and

for this year we added a warming system inside the motor housing with

temperature detection because the mounts will work for one year even

in winter at -74.c. The main pb is to anticipate the retract of the

alloy between worm and gear.

All grease everywere had been remove and replace by another one even

in all the ballbearing that the only way to have motor starting at

the coming out of the climate chamber.

Same type of work had been done on optics and camera.



the quality of the mount is so good that the periodic error, tested

before sending it this autumn, is less than 4 arc sec after 3 summer

on the base.

Eric said " how it is well done, we have runs of 25 days

uninterrupted tracking with much less than 1' error with all the 50

meridians pass over, we have good measures!" of course he find this

absolute nominal! you know how astrophysician could find things

classical!



hope this will interrested

clear skies

Franck Valbousquet



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