Cassini Division in small scope?

[AndyWB]

Last night I got my first view of Saturn through my Skywatcher 130p. Though small at x130, it was crisp and perfectly formed, with rings and a band across it, and I could see Titan and Rhea nearby. Also, I think in good moments I was able to make out the Cassini division at east and west of the rings, but I'm not sure; I didn't expect to be able to see that at all. After all, the 130p isn't a big scope.

Is that possible, or merely a product of wishful thinking?

[John]

It's quite possible with the rings open as they are. I can see it clearly with my 4" refractor and I've seen the division with an 80mm refractor when the rings were wide open a few years back.

[wookie1965]

Ive seen the division in my six inch scope you may be able to see it with good seeing conditions.

[AndyWB]

That is so cool. I hadn't expected to be able to see that. It was serendipitous the angle of the rings are open like that.

Speaking of which, with what periodicity do the rings go through their cycle? Once every solar orbit (i.e. every 29 years)?

[wookie1965]

http://www.lunarplanner.com/HCpages/Synodic-Saturn.html

Have a read of this your 29 years is right in one respect but that's only when we are closest.

[Merlin66]

With good seeing conditions, Cassini Division should be visible in an ED80 - I've even seen it with a 3" refractor many years ago.....

[Moonshane]

I read once that you cannot theoretically resolve the Cassini Division with smaller scopes (cannot remember the figures) as it is less that the limit of seeing in terms of 'width' i.e. arc second width. however, you do see the contrast created by the gap which leads to the same effect so as far as I am concerned we are seeing it!

it was easily resolved in my 6" scopes and therefore I'd expect you to see it in good moments as you say. well done and enjoy!

[AndyWB]

Thanks! Yes, that sounds more like what I saw - in good moments it was like a darkness in the disc of the rings. It wasn't crisp, so I think you're right - it was the contrast of the gap. And yup, for me that counts as seeing!

[michael.h.f.wilkinson]

There was a discussion about this before. We can see things of sufficient contrast even if we cannot resolve them (like stars ). I gave an example here:

[AndyWB]

Ah, thank you. I did try a search! That's an interesting thread.

[Naemeth]

Congrats Andy! I've not managed it yet, but once I next get a view of Saturn I'll have a go

[Red Shift]

Saturn will be in OPPOSITION ( the Sun is on one side of Earth, and Saturn is on the opposite side of Earth )

in April 2013, with a magnificent tilt of the rings.

http://saturn.jpl.nasa.gov/education/saturnobservation/viewingsaturn/

[cs1cjc]

My experience of seeing the cassini division is much less positive than much of what is reported here. Yes I have *thought* I have seen it, but I am unconvinced that I would have seen it if I did not know it was already there. My fellow observer has been even less convinced than me...

[Stargazer_00]

In your 14"? In my 10" last night it was only for fleeting moments that the division wasn't visible. For all the other time it was a clear feature along with 2 greenish bands on the planets disc. I swear I even saw vague hints of some inner lines (a pair) inside the ring of the cassini division. This may have been wishful thinking or just some optica abberation caused by the atmosphere so I'm not counting it, I did see something though.

[Moonshane]

I would class the Cassini division as easy on decent nights and when the planet is at a reasonable elevation, especially with the current angle. it's currently tricky unless you stay up late / get up early as it's in the murk. it was straight forward with my 6" f5 even at about 120x.

[nightfisher]

I was viewing saturn through a huge mak cass last night, could not see the cassini div due saturn being so low, but if i could have left it a few hours it would have been easy

[chiltonstar]

Fairly easy with my ED80 two nights ago, whereas my 5" Mak took half an hour to cool before it would show the ring clearly. Should be easy with your scope at x130 if its cooled and the seeing ok.

I've seen the crepe ring once as well with the Mak when the seeing was really excellent.

Chris

[Moonshane]

aperture really helps with the crepe ring. I have seen it a couple of times with my 6" and on those same nights I fortunately had a larger scope (12" or 16") which allowed me to confirm it. as Chris said, the seeing needs to be excellent.

[LukeSkywatcher]

I read once that you cannot theoretically resolve the Cassini Division with smaller scopes (cannot remember the figures) as it is less that the limit of seeing in terms of 'width' i.e. arc second width. however, you do see the contrast created by the gap which leads to the same effect so as far as I am concerned we are seeing it!

it was easily resolved in my 6" scopes and therefore I'd expect you to see it in good moments as you say. well done and enjoy!

I have to agree. In small scopes, it is more likely to be the contrast created by the gap which tricks the brain into thinking it sees the actual division. In my mind also, its as good as seeing the actual division. I "saw" it with a 90mm refractor.

[cs1cjc]

I am not sure I have ever used the 14" on Saturn and while it should help, my 61 year old eyes get no younger...

Last night it was clear here and there was little wind but Saturn was still shimmering and showing little detail in the 120mm at 1pm (GMT). An hour later it might have been a bit better, but I was driven inside by tiredness and cold to find frost on some metal surfaces.

Regards

Chris C

[Stargazer_00]

frost on the OTA is usually the sign to pack up for me. I'm hardy-ish and can stomach cold reasonably well but I wont suffer a frozen scope nor a runny nose. Either of those sends me inside.

[Stargazer_00]

Since making that post I've been out with just my grab and go 150p. Wanted a short and purely from memory session. Got two hours in and came in its still absolutely clear or there but I'm tired and satisfied after last night's marathon still.

Ive come to the realisation that a cold wind will also drive me indoors. The chill on the wind tonight went through my 4 layers like I was in my birthday suit and my face was frozen after an hour. Brrrrr. Ask fun though saw 15 galaxies 8 globs 4 open 4 doubles including m40 I'd not bothered to find before and Jupiter and Saturn. Both planets not well placed at those times but observed nonetheless. Not bad all from memory

[chiltonstar]

I have to agree. In small scopes, it is more likely to be the contrast created by the gap which tricks the brain into thinking it sees the actual division. In my mind also, its as good as seeing the actual division. I "saw" it with a 90mm refractor.

Agreed.

IMHO, whatever the scope aperture, the true width of the Cassini Division is broadened (convolved) by the Airy disk and the seeing limitation, so what we are seeing is always broader than the actual division (0.5 arcsec). A small scope just broadens it a bit more than a 24" monster.......

It's a beautiful sight though, even through a 4", so maybe arguing about whether it's "resolved" or not may be nit-picking....

Chris