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Saturn's Moons

Started by EdZ, 09/18/2002 07:22PM
Posted 09/18/2002 07:22PM Opening Post
Last Friday night, I left my 5” SCT out to acclimate and planned to get up at 4am to view Saturn. The sky I awoke too was a sky most people never see. It was brilliant. The winds had died down and the temp was just under 50.

I started out with a wide-field ep viewing a few clusters in Auriga. I easily saw NGC1907 as a diffuse hazy glow that looked like a nebula in the same field as M38. After stopping at M36, then M37, I settled on M35 and could see the faint NGC 2158 close-by.

Then I turned the scope to Saturn. Too my surprise, right away I noticed a few moons. I was using my 9mm UO ortho at 152x. I’m sure I could have gone higher, the seeing was so good, but I had the focus nats on and the view was so pleasing I didn’t want to take the eyepiece out, so I stuck with it. Turned out to be very productive as I did a nice sketch and plotted the moons I saw. I labeled the moons as b1= pa195 2ringL, f1=pa15,3/4ringL, f2=pa255,1diskD, suspected f3=pa165,1diskD.

Afterwards the key would be to verify if those were moons and which moons they were. You can do this by projecting the curved lines from the chart in S&T magazine up to the ellipses in the diagram at the top of the chart. Go to the curved lines chart, figure your correct UT and at that point, for each curved line project a parallel line up to the ellipse diagram. The point at which you hit the ellipse for that moon is the spot it is at in it’s orbit. See the dots S&T has placed for the example time as an indicator for whether you should be in front of or behind the disk.

Within 10*pa and at the correct distances, I had plotted b1=Titan mag8.4, f1=Rhea mag9.7, f2=Dione mag10.4 and suspected f3=Enceladus mag11.8. Tethys mag 10.3, as it turns out was pretty close to Dione and I missed it.

Last night again I left a scope out, this time my CR150. Similar conditions this morning led to similar results, I noticed 3 moons right away with a 17mmNagler at 71x. In fact the moons showed up easier with the 17mm than they did at any other higher power I used. I recorded many notes on the disk and rings, notably seeing Cassini all the way around except where the disk hid it and seeing the C ring especially at the north where it passed in front of the disk. The disk appeared as 3 dimensional and the A ring appeared as stripes. The best view of the disk and rings was with a 6mm UO ortho at 200x, but the best view of the moons was with the 17mm nagler at 70x. I verified that I saw Rhea, Tethys and Dione. Titan was 5 ring lengths to the east in starfields and Enceladus was very close to Dione, I missed it.

Looking back thru my old notebooks, all I had ever recorded was spotting Titan and one other moon in closer. Not a bad two nights for identifying Saturn’s moons. Somewhere it was said recently, part of the enjoyment is doing your homework. I really believe in that.

Posted 09/19/2002 01:45AM #1
Good stuff. you sound like you have had good seeing.

Did you see the C ring /B ring boundary was not clear cut. (Read some of the recent saturn posts)

Also did you notice any white spots????

the stripes?? Did you see hints od other ring divisions in the A ring???

Best wishes, weather has hampered any viewing from my neck of the woods.

Kevin B

Posted 09/19/2002 07:45AM #2
Hi Edz,

If you managed to spot Enceladus than Iapatus should also have been visible. It is an interesting moon to hunt down. Quite some distance from Saturn and with a large magnitude variation depending on which side of Saturn it is on.

Keep looking up.


* Teach a man to fish and you feed him for a day.
* Teach a man to use the internet and he won't bother you for weeks.
Posted 09/24/2002 09:44PM #3
Here are some sketches IMO from one of the best sketcher of our time, Eric Jamison.
While there, please do look around; there are wealth of info there.

Ron B[ee]