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Old 16-09-2017, 01:52 PM
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Farewell Cassini

Though I knew there was essentially no chance of capturing the impact flash, I set up to image Saturn as Cassini made its farewell. The main image is a composite of two 5-minute exposures in quite poor seeing - one for Saturn at f/15 and a longer exposure stack for 5 of the moons at f/10. The methane image is built from 10 minutes around the time of impact.
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Old 16-09-2017, 01:58 PM
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Nice photo!

As long as you have a photo from the night where Cassini crashed into Saturn, doesn't matter if you can't see it.

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Old 16-09-2017, 02:01 PM
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Nice shot indeed, ah well nothing last forever.

Leon
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Old 17-09-2017, 06:59 PM
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You could just photoshop in Cassini on final descent
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Old 17-09-2017, 07:43 PM
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This would be EXTREMELY DIFFICULT to capture such a relatively small (a few meters across) device so far away.
It has an angualr size of 0.00000041". Only the burn could be bright enough to be detected by only the largest telescope currently on Earth (E-ELT) or in space (the JWST).
Forget about amateur telescopes.
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Old 17-09-2017, 08:28 PM
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As NASA pointed out in the Live Feed, there could be no burning up of Cassini as there is no oxygen in the atmosphere to support combustion. Signal loss occured at 1000 miles above the cloud top, and the vehicle would break up and be vapourised by atmo friction. The only observable evidence might be an infrared flare if you were imaging in IR at that time.
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Old 18-09-2017, 12:54 PM
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Thanks Leon and Stefan!

Quote:
Originally Posted by skysurfer View Post
This would be EXTREMELY DIFFICULT to capture such a relatively small (a few meters across) device so far away.
It has an angualr size of 0.00000041". Only the burn could be bright enough to be detected by only the largest telescope currently on Earth (E-ELT) or in space (the JWST).
Forget about amateur telescopes.
Err, the angular size is totally irrelevant, it's not about the angular size of the bolide, but its brightness (similar to bolides imaged on Jupiter). And nobody was trying to image the probe before its crash!! You're also wrong about the feasibility of imaging the impact - a call went out from the Cassini team to amateurs on this side of the world for us to try and record the impact in the methane band - see these posts by top planetary imagers Marc Delcroix and Christopher Go. Both thought the impact beyond the capability of small-medium amateur scopes (including Chris' own one). But they encouraged imaging anyway even though the estimate was that it might be detectable in a scope closer to 1m in aperture, of which there were v few in sight of the event, so using something was better than nothing. So the event was much more achievable than you suggest, but also I was very well aware it was basically sure to be beyond me. It's fun to be part of efforts like these, as it means for a while I'm not the only planetary scientist in my family!

Quote:
Originally Posted by glend View Post
As NASA pointed out in the Live Feed, there could be no burning up of Cassini as there is no oxygen in the atmosphere to support combustion. Signal loss occured at 1000 miles above the cloud top, and the vehicle would break up and be vapourised by atmo friction. The only observable evidence might be an infrared flare if you were imaging in IR at that time.
Who mentioned burning? I'm well aware of how objects enter atmospheres.
And you mean, in the IR like I was doing (850-900nm) as in the image I posted?! And as requested by Chris and Marc (see above) as contrast in IR would be quite high?

Last edited by andyc; 18-09-2017 at 01:08 PM.
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