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Schmidt Cassegrain Telescope onboard the ISS

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#1 PhilCo126

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Posted 14 June 2013 - 03:29 AM

Celestron's 9.25” diffraction limited Schmidt-Cassegrain telescope is positioned within the Destiny module’s Earth-facing window. While remotely controlled from the planet’s surface, ISERV will monitor and assess environmental disasters, climate change, rainforest destruction, and air quality in various locations around the globe. It will also aid in short-term weather prediction.

See:
http://ut-images.s3....lfOCYAIJQkF.jpg

#2 dickbill

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Posted 14 June 2013 - 08:22 AM

behind the glass?

#3 Otto Piechowski

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Posted 14 June 2013 - 08:43 AM

If I understand duckbill's question, I have the same. Isn't the 9.25 sct a waste of aperture since one has to look through the thick glass panes on ISS? Also, what about thermal disequilibrium between the air temp inside ISS and the temperature differentials and changes on the outside of the glass window?

My question then; wouldn't a much simpler and lighter scope accomplish as much as they hope to accomplish? Or is the 9.25 a good tool for what is hoped to be accomplished? If not, just how much did it cost in fuel to get the weight of the 9.25 to orbit?

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#4 WaterMaster

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Posted 14 June 2013 - 08:45 AM

Hey, you have to admit, whether it's entirely practical or not, it's pretty cool.
I would like to see a pic of it mounted, though. :cool:

#5 Jarad

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Posted 14 June 2013 - 09:13 AM

As for thermals, I think the temperature in the ISS is pretty stable, so that shouldn't be an issue. The temperature outside the glass doesn't matter - it's a vacuum, so no thermal turbulence.

The purpose of the scope is to monitor stuff on earth, so I presume someone went through the exercise of matching CCD field to desired FOV, used that to determine what focal length they wanted, and found a reasonable matching scope. An SCT makes sense since it is very compact for the focal length, and space is at a premium on the ISS.

Jarad

#6 Ravenous

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Posted 14 June 2013 - 09:18 AM

I would think the windows in the ISS are of a pretty high specification. I dimly remember reading something about Apollo spacecraft windows being specified with the intention of doing high quality photography through them. (Afraid I can't remember which module it was, maybe even both.) Surely the ISS windows are along similar lines.

Mounting the scope inside does prevent a spacewalk if some vital adjustment needs to be made, so maybe that's why it was done. Also the thing can be taken out and returned if it isn't up there for permanent use, freeing up that area for other work.

The mount looks non-standard to me - though I'm not an expert on Celestron's product lines. I'm sure the whole scope is a lightened version tweaked and set-up for the job.

Maybe it'll appear on the CN classified one day! :)

#7 dickbill

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Posted 14 June 2013 - 09:47 AM

They could have put it outside the iss, on fork with wifi control, a filter wheel, a motorized focus and a ccd (It is already fork mounted in the picture). Wasn't worth the trouble apparently.
Good publicity for celestron anyways.

#8 dickbill

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Posted 14 June 2013 - 09:56 AM

Please, admire a successfull realization in terms of bangs for the buck spent.
Even CCCP was more financially efficiernt than American ISS, that says it all.

http://en.wikipedia.org/wiki/Salyut

#9 groz

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Posted 14 June 2013 - 10:32 AM

It's down looking, ie, at the earth, not out into space, so, it's not being used as a 'telescope' per se, but more as a 'very long fixed telephoto lens' for a dslr camera.

The dslr is mounted in hyperstar configuration.

There is a fair amount of detail on the customizations done over on the starizona website, including some tidbits about the quality of the glass its looking thru.

#10 Otto Piechowski

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Posted 14 June 2013 - 04:44 PM

I take it we are all of the opinion that since NASA etc. took 9.25 inches of aperture into space, that they made sure that aperture and focal length and photographic characteristics were the idea match for the scientific needs?

#11 Jay_Bird

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Posted 14 June 2013 - 07:11 PM

If used as a prime-focus Hyperstar setup, this is a full frame equivalent from 35mm film days to ~ 500mm f/2.0 telephoto lens, and it's optimized for use 'wide open' unlike many traditional camera lenses. It might work closer to f/2.8 transmission with DSLR body in front, but that's still a great big photographically 'fast' lens. That aspect might help for imaging from orbit - allowing faster shutter speed in low light, or slower ISO setting.

Used this way it's an 18-20 inch focal length f/2 or so telescope - don't think of it as 92.5 inch focal length f/10 telescope.

#12 Kevdog

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Posted 19 June 2013 - 03:25 PM

IIRC from watching lots and lots of the Nasa channel, the earth facing window is over very high quality glass. And they also have a protective glass layer they put over it when they are not doing high quality imaging. So when the astronauts are just looking, they have the protective glass in place, but when they want to do imaging, they move it aside.

#13 Matthew Ota

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Posted 29 June 2013 - 12:49 PM

Not cost effective. It would need insulation to keep the temperatures stabilized, and grease that is rated for vacuum conditions. As a matter of fact there would have to be a LOT of engineering to make the telescope work reliably in a harsh space environment.

They could have put it outside the iss, on fork with wifi control, a filter wheel, a motorized focus and a ccd (It is already fork mounted in the picture). Wasn't worth the trouble apparently.
Good publicity for celestron anyways.



#14 Ravenous

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Posted 01 July 2013 - 11:16 AM

As a matter of fact there would have to be a LOT of engineering to make the telescope work reliably in a harsh space environment.

Definitely. I'm not an expert in such things, but at the very least a motorised focus would be needed (vacuum rated) as well as the mount's motors.

Even worse, the camera itself appears to be an off the shelf DSLR - can you imagine the hassle of getting one of those to work in vacuum and heat/cold for prolonged periods?

(At least it wouldn't get much dust on the sensor!)

The cost of organising a single spacewalk to carry out any unscheduled adjustments would, I am guessing, far exceed the from-the-store total cost of the system. The real benefit of the ISS (or any such manned station) is the system can be used for a few months, or a few years, and people are up there in shirt sleeves to fix it.






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