Where's Cassini?

[JohnSadlerAstro]

Hi guys,

I spent lots of time looking at Saturn during and after May's opposition, but I never once saw the Cassini Division, and none of my photos showed it either. I've been told that it can be seen with a 76mm refractor, and my 'scope is a 130mm reflector. Does anyone know why I'm not seeing this? Could it be that my mirrors need collimation?

John

[alexbb]

Hi John,

You should have seen it with a 130mm aperture, provided you had a high enough magnification. It is most probably that your mirrors need collimation.

Best regards,

Alex

[John]

It's not actually easy to see even with the right aperture, if the seeing conditions are not pretty good. Your scope needs to be properly cooled and collimated and a decent quality eyepiece plus some experience can help too !

Here is a diagram of the main Saturnian features. Visually, with a small scope under moderate seeing conditions things like the Cassini Division and the Crepe Ring can be really challenging to pick out despite their clarity in the diagram !:

[laudropb]

It's not that easy to see, even in an 8 inch scope. The seeing has to be good and you have to spend a bit of time observing to get your eyes used to the view.

[hgjevans]

Saturn is also pretty low down for UK latitudes at the moment (<20 degrees, and getting worse for the next few years), and that makes it all the more awkward for seeing things like the Cassini division. I only managed it on a couple of the better nights back in the summer with an 8" scope - mostly it was all far too mushy. Should be peachy in about 15 years' time though.

[alexbb]

Indeed, I didn't take into account that it's lower in UK. This summer it was above 25 degrees where I live and I could easily see the division with the heritage 130.

[JohnSadlerAstro]

Thanks Guys,

I'm glad that it wasn't because my scope's gone wrong! I never realized that you had to have such good seeing to see it, all the books make it sound easy!   

John