Cassini Division

A couple of nights ago I had some fairly decent seeing. Looking at Saturn at 310x with my C-11 I could just detect the Cassini division where the ring crosses in front of the globe of Saturn. It was clearly seen at 400x as a high contrast thin black line. Seeing 6-8/10. Has anyone else seen the Cassini division of the ring where it crosses in front of the globe of Saturn (current tilt 13.46 deg.)? If so, what instrument were you using and what was the magnification you were running. Honest answers only please.

Keith

As long as seeing cooperates, I see it quite often in my 10"f5 dob with tracking. It is especially noticable when Saturn is near opposition as the rings are brightened by the Seliger Effect.

Keith,
Since I posted in your thread, I have taken quite a few looks trying to see the CD in front of the disk using my 10" reflecor. Surprisingly, even on nights of really good seeing I have failed to observe it all the way around! So,I must say that my initial answer to your question was a bit impulsive. My scope has great optics and tracks, so this challenge is one that I will continue to observe with what lasts of this apparition.

Keith,

What an excellent observation and challenge! I figured I would give it a go with my 4" APO. Was a very interesting experience. At about 200x the CD was clearly visible until about 20 degrees of arc from the planet's orb on the back side of the rings, and maybe around 25-30 degrees from the planet's orb on the front side. Bumping the magnification up to 340x the CD was clearly visible completely on the back side of the rings. So was able to see it right up to where they vanished around the back of the planet. On the front side of the rings could clearly make it out right up to the point where it crossed the front of the planet, but not on the portion that was in front of the planet. My last bump in magnification was up to 400x. At this point the exit pupil was getting dim at only 0.25mm and this was working against me so less of the CD visible at that low exit pupil.

Was an interesting exercise since as I varied the magnification between 200x to 340x in different amounts, gradually more of the CD would become visible arcing around the rings. Interesting to see this happen and also another good validation that there is no such thing as "empty" magnification if you know where and what to look at on each target. One day soon will try this exercise with my 10" Newt since I will be able to sustain higher mags with better brightness to see if I can catch it entirely around front.

-Bill