Cassini "Kodak Moments" |
Cassini "Kodak Moments" |
Mar 4 2007, 07:47 PM
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#61
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Dublin Correspondent Group: Admin Posts: 1799 Joined: 28-March 05 From: Celbridge, Ireland Member No.: 220 |
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Mar 4 2007, 07:59 PM
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#62
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Senior Member Group: Moderator Posts: 3225 Joined: 11-February 04 From: Tucson, AZ Member No.: 23 |
(Celestia's great and all, but I stopped trusting it for this sort of thing when I saw what a cop-out Epimetheus/Janus were ) I'm working on a public version of an add-on I've been using that will drastically improve the positions of Cassini and Saturn's moons for the time period of the Cassini mission.
-------------------- &@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io |
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Mar 4 2007, 09:49 PM
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#63
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Member Group: Members Posts: 199 Joined: 20-November 05 From: Mare Desiderii Member No.: 563 |
I see your point - if I run things forward though by about 12 hours I get this which must be Titan then, possibly the timing I got for the transit is wrong or there is some issue with Celestia handling dates back in the 19th Century. I think the times Lord Lindsay gives must be p.m. -- xephem says Saturn would have been below the horizon from the UK at 5:46 a.m. (these observations appear to be from Aberdeen). (BTW, on p98 there's mention of Titan shadow transit observations on Oct 22 and Nov 23.) |
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Mar 11 2007, 05:42 PM
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#64
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Senior Member Group: Members Posts: 1621 Joined: 5-March 05 From: Boulder, CO Member No.: 184 |
Greetings,
It appears Helvick has shown that Celestia can render both Titan and at least one smaller satellite in shadow transit. Looking at the case from this month at the appropriate time (Mar 2 1700-1800UT) I was unable to see any shadow transit from Mimas even though it was in front of Saturn as seen in a solar perspective. I used Celestia 1.3.2. The sun centered view also showed Enceladus near that time passing just south of the limb, so it's unclear to me which satellite (Mimas or Enceladus) would have been in more of a position for this type of grazing shadow transit. So I wonder which smaller satellite Helvick was showing and whether Celestia will show shadow transits for satellites as small as Mimas & Enceladus? Perhaps I'll try running Celestia near solar ring plane crossing time and see how the shadow transits look with more regularity. -------------------- Steve [ my home page and planetary maps page ]
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Mar 11 2007, 06:03 PM
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#65
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Senior Member Group: Members Posts: 1621 Joined: 5-March 05 From: Boulder, CO Member No.: 184 |
I found on the Celestia forum that at least Iapetus can be shown. If I have this link correct, it should show a 1980 shadow transit from Iapetus where its shadow falls within the rings' shadow. This version of Celestia would not however show Iapetus' shadow on the rings itself. The inclination of Iapetus means its shadow can be less elongated on the rings. I wonder if there will be a similar event in the coming 2009 season?
http://www.lns.cornell.edu/~seb/celestia/gallery-001.html#5a -------------------- Steve [ my home page and planetary maps page ]
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Mar 11 2007, 06:03 PM
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#66
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Senior Member Group: Moderator Posts: 3225 Joined: 11-February 04 From: Tucson, AZ Member No.: 23 |
Here is what I was able to get with Celestia 1.5pre2:
Tethys transit (2009-03-16) I couldn't see Mimas or Enceladus... -------------------- &@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io |
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Mar 11 2007, 06:37 PM
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#67
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Dublin Correspondent Group: Admin Posts: 1799 Joined: 28-March 05 From: Celbridge, Ireland Member No.: 220 |
Scalbers - I used Celestia 1.5 pre release for the screen caps I posted but I also am unable to find the March 2 Mimas shadow so I don't think the newer version is the reason we can't see it. By my calculations the umbral shadow will only be around 60km across so it will be hard to find unless you know precisely where to look and can zoom in appropriately. I'm pretty sure the shadow will be rendered if the zoom level is sufficient but catching it is beyond me at the moment.
This may have been noted before but I found out that the Ciclops team used Celestia to render the views for the Rev 29 lookahead page while looking for more information on the eclipse shadow rendering. |
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Mar 11 2007, 06:43 PM
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#68
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Senior Member Group: Moderator Posts: 3225 Joined: 11-February 04 From: Tucson, AZ Member No.: 23 |
Yeah, although I have discovered a bug in my custom .ssc file that means that the Titan map isn't displayed correctly on Titan. I think the rotation offset is off, but it is odd to characterize.
-------------------- &@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io |
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Mar 12 2007, 07:19 PM
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#69
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Junior Member Group: Members Posts: 73 Joined: 14-June 05 From: Cambridge, MA Member No.: 411 |
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Mar 19 2007, 06:40 PM
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#70
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Member Group: Members Posts: 146 Joined: 23-August 06 From: Vriezenveen, Netherlands Member No.: 1067 |
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Mar 20 2007, 05:37 PM
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#71
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Member Group: Members Posts: 648 Joined: 9-May 05 From: Subotica Member No.: 384 |
There are 3 new Saturn animations on HST site. Some old transits animated...nice.
-------------------- The scientist does not study nature because it is useful; he studies it because he delights in it, and he delights in it because it is beautiful.
Jules H. Poincare My "Astrophotos" gallery on flickr... |
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Mar 20 2007, 06:05 PM
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#72
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
Very nice animations, but the captions for 1 and 3 appear to have been swapped.
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Mar 20 2007, 07:10 PM
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#73
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Member Group: Members Posts: 117 Joined: 7-December 06 From: Sheffield UK Member No.: 1462 |
-------------------- It's a funny old world - A man's lucky if he gets out of it alive. - W.C. Fields.
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Jul 8 2008, 08:58 PM
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#74
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Member Group: Members Posts: 237 Joined: 22-December 07 From: Alice Springs, N.T. Australia Member No.: 3989 |
Check out video of Carloyn Porco at 8th July New Scientist talking about her favourite images of the Cassini primary mission. http://space.newscientist.com/article/dn14...ini-images.html
Even though you may have seen these images before it's fascinating to hear what makes them her favourites. For me - the hi phase shot of the crescent of Titan is something special. The last pic of a back lit Saturn with an eclipsed sun peaking out on the edge of the disc with a clear view of the G ring and E (Enceladus jet created) ring and the blue orb of the earth at 10 o'clock next to the G ring is awe inspiring. |
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Jul 20 2008, 09:39 PM
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#75
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Member Group: Members Posts: 146 Joined: 23-August 06 From: Vriezenveen, Netherlands Member No.: 1067 |
I was playing with Celestia to find out when Titan's shadow will be passing Saturn when the rings are nearly edge on, so Titan's shadow is bigger than the ring's shadow. Or, better said, when Titan's shadow will fall directly on the rings, which should be a weird sighting.
Unfortunately Celestia can't cast the shadow of Titan on the rings itself, but Titan's passage on 2/3 august should be spectacular! At this time (around 5 am UTC) Cassini will be able to watch Titan's shadow cross the rings from a distance of about 2 million kilometers (phase angle of Saturn is 113 degrees). |
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