Top 5 Most Recent Articles
Top 5 Most Popular Articles
Top 5 Most Emailed Articles
OBSERVING BLOG by Alan MacRobert
Spot Titan's Shadow on Saturn!
If you've looked at Saturn through a telescope recently, clearly the planet is not its usual gorgeous self. Those famous rings are angled nearly edge-on to our line of sight, appearing like a spear through Saturn's midsection.
Like the rings, the orbits of Saturn's major satellites are also seen nearly edge-on this year. As a result, the satellites now pass in front of and behind Saturn, casting their tiny shadows onto the planet's face and ducking in and out of its shadow, just like the moons of Jupiter do.
Saturn is about twice Jupiter's distance from us, however, and only Titan is a match for Jupiter's Galilean moons in terms of size. Nevertheless, notes Belgian astronomer Jean Meeus, the classic guidebook Saturn by A. F. O. Alexander describes Titan's shadow on Saturn being seen "quite easily" in a small refractor as early as 1862.
Meeus calculated the Titan timetable below so that you can try for yourself. The dates and times are in Universal Time. Oc refers to an occultation of Titan behind Saturn's limb. Ec means eclipse in Saturn's shadow. Tr is a transit of Titan across Saturn's face. Sh refers to Titan casting its shadow onto the planet.
An occultation or eclipse begins when Titan disappears (D) or reappears (R). A transit or shadow passage begins at ingress (I) and ends at egress (E). Each event is gradual, taking several minutes.
If you manage to snap a shot of Titan crossing Saturn's disk, please share it with other visitors by posting it to our online photo gallery.
Like the rings, the orbits of Saturn's major satellites are also seen nearly edge-on this year. As a result, the satellites now pass in front of and behind Saturn, casting their tiny shadows onto the planet's face and ducking in and out of its shadow, just like the moons of Jupiter do.
Saturn is about twice Jupiter's distance from us, however, and only Titan is a match for Jupiter's Galilean moons in terms of size. Nevertheless, notes Belgian astronomer Jean Meeus, the classic guidebook Saturn by A. F. O. Alexander describes Titan's shadow on Saturn being seen "quite easily" in a small refractor as early as 1862.
Meeus calculated the Titan timetable below so that you can try for yourself. The dates and times are in Universal Time. Oc refers to an occultation of Titan behind Saturn's limb. Ec means eclipse in Saturn's shadow. Tr is a transit of Titan across Saturn's face. Sh refers to Titan casting its shadow onto the planet.
An occultation or eclipse begins when Titan disappears (D) or reappears (R). A transit or shadow passage begins at ingress (I) and ends at egress (E). Each event is gradual, taking several minutes.
| Titan and Its Shadow on Saturn | ||||||
| Date | UT | Event | Date | UT | Event | |
| Apr. 5 | 9:21 | Ec. D. | May 23 | 6:30 | Ec. D. | |
| Apr. 5 | 13:37 | Ec. R. | May 23 | 12:06 | Ec. R. | |
| Apr. 13 | 7:22 | Sh. I. | May 31 | 4:32 | Sh. I. | |
| Apr. 13 | 11:51 | Sh. E. | May 31 | 10:00 | Sh. E. | |
| Apr. 21 | 8:20 | Ec. D. | June 8 | 5:39 | Ec. D. | |
| Apr. 21 | 13:10 | Ec. R. | June 8 | 11:31 | Ec. R. | |
| Apr. 29 | 6:22 | Sh. I. | June 16 | 3:40 | Sh. I. | |
| Apr. 29 | 11:16 | Sh. E. | June 16 | 9:18 | Sh. E. | |
| May 7 | 7:23 | Ec. D. | June 24 | 4:50 | Ec. D. | |
| May 7 | 12:40 | Ec. R. | June 24 | 10:53 | Ec. R. | |
| May 15 | 5:26 | Sh. I. | ||||
| May 15 | 10:39 | Sh. E. | ||||
If you manage to snap a shot of Titan crossing Saturn's disk, please share it with other visitors by posting it to our online photo gallery.
Posted by Alan MacRobert, April 13, 2009
The following comments do not necessarily reflect the opinions of Sky Publishing.
By posting a comment, you agree to our Rules of Conduct and Terms of Use.
By posting a comment, you agree to our Rules of Conduct and Terms of Use.
First comments (from 16)
Saturn on edge doesn't help
Posted by Nathaniel Sailor
April 18, 2009 At 06:37 PM PDT
Ok Titan shadow will be cast on Saturn because its rings are on edge. But for me, I don't really care. I want to see the individual rings. I got a 6 in. reflector in December and I want to see all the rings but I got to wait now. Great! I had some friends come over and that is what they saw. It kinda stinks not being able to see the rings.
P.S. Question for all with a 6 in. Newtonian. When I put scope magnifying power to 240x, it seem like it was no bigger than what it looked like in my 60mm refractor at 70x. Is because I was rushing when my friends were around or is that what it really looks like? E-mail is adm.x421@yahoo.com.
:]
Posted by W
April 19, 2009 At 10:10 PM PDT
Well the zoom lens makes it larger because you're getting closer to it, but the detail may lack depending on the focal length. is it 1000mm? more? Try using the calculator provided on the website, and it may tell you how far you can see with lens sizes.
6' reflector and saturn edgewise
Posted by snowstargazer
April 25, 2009 At 02:45 AM PDT
This is a response to Nathaniel Sailor.
Nathaniel, the rings are less edgewise than they were awhile back. I guess they will become more so again. But I had no trouble seeing the rings at any time, with my 6 inch reflector.
I wonder if you are allowing your mirror to cool properly? You can't rush viewing nature, it's not television. Try setting up your scope at least an hour early, don't let the sun shine on the mirror. A fan blowing on the mirror's back will help it cool faster, just make sure you are not blowing dust into the scope.
You also must make sure your optical train is collimated, that is aligned. Look it up. Even a pill bottle with a hole in the lid and the bottom cut off will help. Insert in the eyepiece holder and check for everything being centered. There are many ways, and it can be confusing, but even a rough job is better than none.
You can definitely get better images from a decent reflector if the aperture is bigger than your refractor. But it takes a bit of effort and time to get it set up properly.
Remember that it may be very clear but still can be poor "seeing", with turbulence making images terrible. You can't compare different nights with different instruments. Google Clear Sky Charts for seeing conditions.
I know how difficult it can be trying to show impatient people the pleasures of viewing the heavens. You need to use your new telescope by yourself or with other experienced people until you get used to it. It will work, and work fine. And you have to look at what is there, it's not like a photo album. It's ever changing.
Best wishes.
Respose to Snowstargazer
Posted by Nathaniel Sailor
April 26, 2009 At 06:35 PM PDT
I'm not trying to be mean but I'll say this. A. I'm in high school, I don't have the time to let the telescope cool. Plus I don't have cash for a fan. Nor can I make one right now. But also I was showing two of my friends so right there that's a problem B. I know the rings were on edge. I read my E-mail once a week. At least. C. I have collimater. I worked on my mirror heavy before I took my friends out to give them the best view I can give. D. I got it for my birthday in December. It was like early March when I showed my friends. So I have little to no time learning how to work my scope. As I said, I'm not trying to be mean but I want ya to understand that I don't have a lot of what ya'll have. Right now I'm my best to deal with. Want to talk to me, E-maill address is in the First response.
6" Saturn
Posted by Pete
May 20, 2009 At 04:49 AM PDT
That reflector ought to swamp the refractor on every front. Send the friends home and give yourself some quiet focused time with this instrument.
Pete
6" Saturn
Posted by Pete
May 20, 2009 At 04:49 AM PDT
That reflector ought to swamp the refractor on every front. Send the friends home and give yourself some quiet focused time with this instrument.
Pete
Pete needs a little respect
Posted by Nathaniel Sailor
May 28, 2009 At 06:20 PM PDT
Well Pete I wanted to show my friends some objects in the sky. Telling me to send my friends home I see as vary rude. Should spend some time looking at Saturn before they came? Won't hurt. But I find your comment rude. Also to add, they weren't noisy. They behaved themselves. And the observing part was my dealing with my state of mind, I wasn't paying attention.
Patience
Posted by astronig
May 29, 2009 At 11:26 AM PDT
The wonderful hobby of astronomy is one that takes patience . Time , money , travel to dark sky sites (unless you're lucky enough to live in one) & a little research doesn't hurt either .
Most of all patience & relaxation is what is needed & is the virtue of this hobby . If one cannot bring himself to appreciate these values , then it quite very well be time to find another hobby .
I relize patiance
Posted by Nathaniel Sailor
May 29, 2009 At 06:48 PM PDT
Astroning, you just cross the line with the find another hobby part. A. I am patiance, but when ya get to go tho bed at 10:00 it's a little hard not to rush. B. I watching auto racing. There is like no patiance in racing because when you slack off on the track and not fight to one -thousanth of a second, you lose.
When more shadows
Posted by Zoomit
May 30, 2009 At 08:51 PM PDT
Here's a topical question. Where can I find more Titan shadow dates after the ones in this article?
|
|
|
||
|
|
Date:
|
comments (16)