Jupiter and a shadow?

[seiko]

Hi Guys,

Used my new Nexstar 5i last night to view Jupiter, UK, approximately 00:30 to 01:40. At times the seeing was very good and using the stock 25mm plossl I was convinced I could see what appeared to be a very small but clear shadow on it's surface from it's closest right side moon?

Not that it's important as the views were very pleasing anyway for a small scope but is this possible or was I simply seeing a trick of viewing conditions?

[mike.brightmore]

I saw two small round dark shadows slowly moving across the face of Jupiter. This was obviously due to the transit of one of Jupiter's moons (Callisto). Details on the earlier thread below - 'Five planets and a Jupiter Transit'.

[seiko]

Thanks Mike, I only saw one of the shadows and yes I believe it was Callisto's shadow.

Really chuffed that my little 5i managed to show me such a great site!

[David Galvin]

Indeed, there was a shadow transit of Callisto at 00:30 U.T. Does the attached computer simulation look familiar?

[mike.brightmore]

Yes David it does but at that time (0330 hrs) I could see both Callisto and its shadow as dark spots against Jupiter's disc. Just noticed that your computer diagram is at 03.30 p.m.

[seiko]

Yep, I saw it a little earlier so the shadow was a little closer to the planets edge.

Thanks for posting.

[Leedsgreen]

All,

Attached is my first image of Jupiter that I took last night around 2am (Skymax 127, 2.5x Powermate, SPC900NC). I was curious about the dark spot, so it has been interesting to read this thread.

Cheers,

Nick

[David Galvin]

I am not sure what happened with the time on that but this should be correct. All times are in UT and not BST.

Ah I have just found out that the programme stamps the time that I saved the file at plus the observation data. I will have to check up on that as it is confusing.

[Leedsgreen]

It must have been closer to mid-night then, when I captured the images. With the speed of the change, does anyone know how long an image train can be, before the moons (and Jupiter) start to blur?

Cheers,

Nick

[brianb]

With the speed of the change, does anyone know how long an image train can be, before the moons (and Jupiter) start to blur?

How long is a piece of string? It depends on seeing conditions & the resolution of your scope: trying to complete within 2 mins is supposed to be the rule for Jupiter but it took me almost 4 mins to capture the following & it seems to be prettry well motion blur free.

2009 Aug 09, 0125 UT +/- 2 min

[Leedsgreen]

Brian,

Thanks for answer. Yes, four mins seems fine for your image. I imagine you have better resolved scope as well. With my Skymax 127 (and 2.5x powermate and SPC900NC), I wonder if I could up it to 5mins, even 10? One prblem is that my old laptop only has USB1.1 and the webcam runs at a paltry 3.5fps.

Anymore advice welcome etc. Thanks again,

Nick

[seiko]

Great picture Nick. Thanks for posting.

[mike.brightmore]

There will be more shadows on Jupiter tonight (Wednesday) in case you get fed up of meteors. Between 9.00 p.m. and midnight Ganymede and Europa will transit across Jupiter's disc. Io will also be eclipsed by Jupiter's shadow.

[Kokatha man]

Brian,

Thanks for answer. Yes, four mins seems fine for your image. I imagine you have better resolved scope as well. With my Skymax 127 (and 2.5x powermate and SPC900NC), I wonder if I could up it to 5mins, even 10? One prblem is that my old laptop only has USB1.1 and the webcam runs at a paltry 3.5fps.

Anymore advice welcome etc. Thanks again,

Nick

Hi Nick - there are well-established "rules of thumb" for planetary imaging times per single avi.....2&1/2 minutes for Jupiter and Saturn, although in the case of Saturn where cloud structure and other details (eg storms) are very difficult to pick up with smaller scopes people can let the image run for as long as they wish to produce "aesthetically" pleasing Saturn images with belts/banding well-defined in these longer exposures.....

To get any sharp details in cloud structures etc on Jupiter the 2.5 mins (150 secs) is pretty well a requirement, although of course if the image scale is small and detail is not clearly resolved then images that are not really "sharp and crisp" may appear so - it is a "trick" you can utilise to make poorer images "better".....try it with a clearly poor image by opening it in P/shop and clicking on the magnifying glass icon, then - one up the top (+ or -) and shrink your image up or down to see what happens....!

Jupiter rotates so fast on its axis and this is why the limited avi time is necessary.....also why Jupiter appears to "bulge" at the equator and is "flattened" at the poles.

I haven't used my Toucam for quite some time (have a DBK now that can operate at up to 60fps) and mine was an 840k but I am positive you can run at better than 3.5fps.....at the faster framerates with usb1 there is compression and artefacts may be a slight nuisance but 5 and even 10 or 15fps should certainly be achievable with good results!!!:D

[Talitha]

I caught the last of Io's shadow transit last night just as Jupiter was clearing the low trees to the SE, and was surprised how good the seeing was despite the low altitude. The GRS's central darker spot was even visible.. haven't seen that for a while. Within about 30 minutes of seeing the shadow, Io cleared the bright limb and was floating in the darkness.. looked like a tiny white pearl on a black sand beach.

[mike.brightmore]

Hi Carol, missed Io (and meteors) last night due to cloud. Looking forward to seeing a double shadow transit (and meteors) tonight.