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Seeing the shadow of Titania

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#1 Spaceman Spiff

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Posted 25 January 2021 - 02:39 PM

I know it sounds impossible, since Titania is only 0.1 arcseconds wide, but the encke gap is only 0.05 arcseconds wide, and it's barley visible in great seeing. Does this mean that the shadow might be visible under ideal circumstances? Thanks.


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#2 StarBurger

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Posted 25 January 2021 - 04:01 PM

Titania is a satellite of Uranus not Saturn. To see anything on Uranus itself (much further away than Saturn) is really not possible with any earth bound telescope so not a snow ball's (slight pun here) chance in hell of seeing a teeny-weeny shadow transit.


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#3 Spaceman Spiff

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Posted 25 January 2021 - 04:27 PM

Titania is a satellite of Uranus not Saturn. To see anything on Uranus itself (much further away than Saturn) is really not possible with any earth bound telescope so not a snow ball's (slight pun here) chance in hell of seeing a teeny-weeny shadow transit.

Yeah, I know. I should've been clearer. I was using the encke gap as an example, since it's so small that it shouldn't be resolvable, but it's still visible. When I was looking at the angular diameters, I realized titania's shadow on Uranus was larger than the encke gap, so I was wondering if it was visible, even if unresolvable. 


Edited by Spaceman Spiff, 25 January 2021 - 04:32 PM.


#4 StarBurger

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Posted 25 January 2021 - 05:29 PM

Thanks for the clarification. There have been discussions before on the visibility of Encke's gap and although not "theoretically" visible it appears the eye/mind can make assumptions with linear features rendering detectability possible. Obviously or Encke would not have seen it.

How visible a diffuse shadow of twice the angular diameter on Uranus's cloudy surface is happily open for debate. Hubble would certainly pick it up, but when?

The high inclination of the orbital plane of the satellites of Uranus and the axis of rotation itself would imply transits of satellites are very rare. Most of the time we see them orbiting around Uranus like a bulls eye and not transiting the planet.

A long shot but this might be an interesting challenge for observers with larger scopes, perfect seeing and perfect optics.

Most of us have trouble seeing Uranus as a disc let alone shadow transits on it!


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#5 Redbetter

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Posted 26 January 2021 - 12:38 AM

As I understand it, the last time that Uranus was aligned to allow shadow transits was 2007.  There are 42 years between its equinoxes when the shadows should be aligned with the planet, so check back around in 2048/9.

 

In good seeing one can watch Galilean moon shadow transits of 1+ arc second moons with a 60mm scope without difficulty.  The contrast of shadow transits is quite good, so with very large aperture the primary problem for something 10x smaller with similar contrast will likely be seeing.  


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#6 Pcbessa

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Posted 17 February 2021 - 02:49 PM

How about Titan transits? Are they easy to see?
I never considered those.

#7 Mirzam

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Posted 18 February 2021 - 05:43 PM

Titan transits are only visible when the rings are close to edge on.  I think such transits are visible in a medium sized amateur scope of good quality, but have not observed one myself. 

https://www.cloudyni...-saturns-moons/

 

JimC


Edited by Mirzam, 18 February 2021 - 05:48 PM.



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