Tried visual astronomy yesterday - challenged seeing the Cassini division

[g__day]

Hey folk,

Yesterday I tried some visual astronomy for the first time in ages on the smaller of my 3 scopes (80mm Williams Optics Megrez refractor and 127mm Skywatcher MAK). I wanted to have a look at Saturn and check my mounts alignment after little use in the past 6 months.

I focused my smaller OTAs using a Bhatinov mask on Spica, then locked on Saturn. I was using a 8mm Vixen LWV eye piece on the Megrez (60x magnification) and a 22mm then 13mm LWV eyepiece on the MAK (68 and 115x magnification respectively).

My C9.25 is set up for imaging - so I didn't touch it. Now I noticed Saturn was reasonably sharp for 20 - 30 minutes until the clouds rolled in - so seeing was only average and we had a 1/3 moon. But focused correctly neither scope (or my eyes) would see the Cassini division.

So to my question - is it most likely that this is:

1. Seeing related
2. The angle Saturn is inclined at present makes it hard to split the Cassini division in poor seeing at low magnification
3. An optical alignment issue with my smaller OTAs
4. My eyes - getting old!

Many thanks for your help.

Matthew

[mental4astro]

Answer: 1, seeing.

You might be hard pressed to make out the Casini division in the 80mm, but in the Mak it should be a cake-walk. My C5 never had a problem with it at its current angle, except in poor seeing.

Try the Mak again, but with the 8mm. If seeing is good you should have no problem with it. It had sufficient resolution to make it out ok. I had a C9.25 up until a month ago, and it too struggled, but only when seeing was poor.

[g__day]

Thank you! How big in arc seconds is our view of the Cassini gap at its widest point right now - anyone know?

[dannat]

I have never really appreciated what it's like for the city folk, now I'm using the melb obs scoes, 8" refrac & 12" reflect I see the massive effect light pollution has. They are quality scopes but you need real good nights to see it

I don't feel bad though when I walk out my back door, pull out the 80 mm f15 let it cool for 2mins then immed go above 150x, does it quickly & easily

[alocky]

I have often seen a figure of .7" (arc seconds) quoted for Cassini's division. Of interest is the difference between resolving a point source and a line, as that is below the Dawe's limit for a 4", yet I have no trouble seeing the division in any of my 4" scopes. Encke's division has eluded me in anything under 10", in comparison.
Cheers,
Andrew.

[sopticals]

Cassini:thumbsup: discovered the division in 1675 using 90x magnification in a 2.5" refractor. Quite amazing considering the division is only around 0.5" arc. I find for me 200x-300x using my binoviewer, is the ideal for easily seeing the CD, and the pastel coloured bands on the planet itself. I really think that for most of us with normal/near normal eyesight 120x plus is needed to magnify the CD enough to clearly pull it out of the bright background of the rings. At the present "orientation" it should be an easy:eyepop: target for a 6" to 8" reflector at 150x.(seeing allowing).

[ColHut]

You got it. Seeing was awful for me last night, and it certainly wasn't visible to me in my 10" F5 at x125 or x250. The local seeing was ghastly.

[HCR32]

Saturn is a planet that is in a sense forgiving in bad seeing conditions, but the division is one part of the planet that needs seeing to be fair. Your scopes aperture would add to the challenge. Planetary work comes to life with at least a four inch.