Imaging Saturn’s moons

[David Swan]

Hello,

Just wondering if anyone is willing to give advice on getting Mimas as a distinct point in an image of Saturn and its moons. Is it a question of using a longer focal length and judicious choice of exposure time? I have at my disposal a 200mm f/10 SCT, 3x barlow, ADC and ASI178MC camera.

Thanks – David Swan

[Martin Mobberley]

Hello David,

I can’t claim to be an expert on this subject but I did take quite a few Saturn images from the 1990s up to about 2011. These were, typically, at a scale of about 6 pixels per arcsecond and 10 – 15 frames per second, using 10 and 12 inch Newts. I don’t ever recall recording Mimas, but I did sometimes just get Enceladus, which is about a magnitude brighter. Like everything in planetary work, it largely boils down to the seeing. In perfect seeing I’m sure Mimas could be recorded without resorting to long exposures of a second or so. In fact I’m sure it must have been recorded on quite a few of Damian’s excellent  images.

Expert visual observers (like David Gray, using a 415mm Dall-Kirkham) have seen Mimas when the rings are edge-on and there is less dazzle.

Regards,
Martin

[David Swan]

Thanks Martin. Visually I could make out Titan easily, not so much the dimmer trio (it doesn’t help being so close to the summer solstice of course!). The camera makes light work of them. I’ll keep trying with Mimas: it’s a long wait till the rings are edge on! I’m pretty sure I’ve got a positive on Enceladus – there’s a definite concentration of signal (see my posted observation, and please give an honest opinion) where it is predicted to be by my planetarium application. I’ll have to be patient for a favourable elongation for Mimas – if there is such a thing!

[Damian Peach]

Hi David.

I’ve captured it many times. You’ll need good seeing for a start (as Martin mentions.) With thousands of frames averaged under good seeing it should show up as a faint spot (at least it does in the 14″ scope.) Exposures of 1 second or so will certainly show it up as its not really that faint. Using an R or IR filter will help with Saturn from the low altitude we have in the UK. You already have an ADC which is essential. Its just making sure collimation, focus are good….and then catching steady seeing. I do warn you though – at just 17deg altitude you may be in for a long wait!

Damian

[David Swan]

Thanks Damian. David

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