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Paz

Jupiter and Saturn - Comparison Session

18 posts in this topic

Having missed a number of good weather opportunities to observe recently because of being busy, I made a last-minute decision to go for it last night and get out there for a short session. I think the whole of this session lasted about 30 minutes from when I decided to go out to when I was back in and packed away.

I took out the MC-127 Maksutov and Porta 2 mount and just an RDF finder, the objective being to have a look at Saturn, Jupiter and some double stars so no need for a finder scope.

I focused on Jupiter, and figured out that a 10mm eyepiece was about right for the conditions (190x magnification), and I decided to stick with this for the whole session as I didn't have much time. After the session, in hindsight I think I would have been better off with a bit less magnification.  Jupiter was at about 23° in the south west and not too close to any rooftops which was good, but I have no time to wait for the scope to cool down (or should I say warm up - it was hotter outside and it was indoors!). I could see a number of bands, and the 4 big moons blazing away.

After only a minute or so I swung across to Saturn which was about 12° in the south-east. Saturn was not far away from an annoying lamppost, the light from which didn't help. The thing which made this session really interesting was, because I had an easy point-and-look set up, the gap between being at the eyepiece looking at Jupiter, and being the eyepiece looking at Saturn was literally less than a count of five.

I was immediately taken by how different Saturn looked, when compared directly to Jupiter. Looking at double stars, or anything else went out of the window, and I spent the next 15-20 minutes going directly back and forth between Saturn and Jupiter, spending a minute on one and then going back to the other, looking at, comparing, and thinking about the differences.

First of all, the difference in (apparent) size is stark when you know you are using the same magnification. Jupiter simply does look much bigger. It has the advantage of being closer at this point in time (762 million kilometres compared to 1353 million kilometres) as well as being bigger. Saturn's rings take its size to perhaps a similar apparent size to Jupiter's disc (this is my best guess being objective) but Jupiter "felt" bigger.

Jupiter looked significantly brighter, which makes sense being bigger and closer - Jupiter was magnitude -2.1 compared to Saturn at magnitude 0.0. when switching between the two, the darker brown colours of Jupiter becomes more obvious, compared to the white/grey of Saturn. Jupiter's big 4 moons were all really bright - magnitude 5.8-6.8. I could only see two moons near Saturn, I think Titan ( magnitude 8.7) and Rhea (magnitude 9.9). I know there were some others around magnitude 10.5 or so but I couldn't see them at all, I think due to the street light. Rhea was averted vision only, and even then only just spotted.

I didn't see the Cassini division, the only thing I noticed about the rings was that the outer third looked dimmer than the inner two thirds.

Looking at the pure/featureless surface of Saturn seem to result in the features of Jupiter jumping out more clearly as soon as I moved back to Jupiter.

If using the planet to get focus, I found Saturn easier to focus on than Jupiter. Whenever I look at Jupiter, I always have to look at a moon to set my focus.

I did a quick start test on Altair before packing up to get a feel for the conditions, they looked pretty good to me (and collimation was right in the middle, as always with the Maksutov).

This was a really unusual and memorable session and I am going to keep in mind trying this newly discovered observing trick on other objects.

I was playing around with sky Safari afterwards, and noticed that around about Christmas time in 2020 Saturn and Jupiter will be very close - passing within about 6 arc minutes  of each other. This will put them in literally the same field of view even at high magnification, but they will be fairly low in the south-west. This is once put in the diary!

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Great report Paz :thumbsup:

Closest approach looks to be very low altitude for me! Might have to get aligned during daylight ;)

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Very interesting writing! 

Jupiter and Saturn are two very different beasts, each with its own list of interesting features to spot. Unfortunately, the current altitude of Saturn complicates things quite a lot. They are amazing targets though. :) 

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Nice one. Des

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Paz - great report of an interesting and memorable session.  The points about observing these wondrous sights certainly strike a chord!

And Yes, they are indeed small in the EP, yet can still reveal features and fascination.

Doug.

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Nice report. I use the moons of Jupiter rather than Jupiter to get focus as well.

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Great Planets to observe.. thanks for the heads up about 2020.

 

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Great report, just interested if you have been able to pick out the Great Red Spot with your 127. I've not managed that myself but may be down to timing.

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Posted (edited)

On 7/14/2017 at 07:52, Wpit said:

Great report, just interested if you have been able to pick out the Great Red Spot with your 127. I've not managed that myself but may be down to timing.

I haven`t seen the GRS yet as well . When I asked the question recently about magnification for detail to open up on these two planets , Jupiter and Saturn , the consensus was anywhere from X130 - X200 magnification , and conditions , light pollution , etc . also being a factor ... 

I think the secret is to just keep trying and that`s what I intend to do .

Browsing SGL I came cross this link and info of the Great Red Spot https://drive.google.com/open?id=0B9NIdVS1knefYzlLTUhIZ1F5bGc 

Here is a screen cap of the relevant section ...

 

capture-20170716-023314.jpg

Edited by Red Dwarfer
Link and screen cap
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5 minutes ago, Red Dwarfer said:

and conditions , light pollution , etc . also being a factor ... 

I think the secret is to just keep trying and that`s what I intend to do . 

Light pollution is not so much a factor in planetary observing, seeing conditions are much more important as well as the cooling and collimation of your scope.

Absolutely right on the last sentence, keep trying and sooner or later the conditions will be good and you will catch some great views.

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On 14/07/2017 at 07:52, Wpit said:

Great report, just interested if you have been able to pick out the Great Red Spot with your 127. I've not managed that myself but may be down to timing.

I've had a look back through my notes and I've recorded seeing the grs well with the vx14, and also with a 10" reflector. I've not got a record of seeing it with the maksutov or my st120 but I think it's more to do with conditions. Ive seen some details on the bands in good conditions with the maksutov so I'm guessing the spot is doable with it when everything comes together.

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36 minutes ago, Paz said:

I've had a look back through my notes and I've recorded seeing the grs well with the vx14, and also with a 10" reflector. I've not got a record of seeing it with the maksutov or my st120 but I think it's more to do with conditions. Ive seen some details on the bands in good conditions with the maksutov so I'm guessing the spot is doable with it when everything comes together.

It's visible in really quite small scopes. I've seen it in a 66mm William Optics SD66mm and a Tak FS60C. Not easy necessarily but certainly doable at around x120 provided the conditions are pretty good.

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It is certainly easily visible with my 127 Mak; It is more saturated with my ED80, but less detailed of course (x150).

With my 180 Mak, the GRS is visible even with poor conditions, and once or twice this season has been really intensely coloured, although it is often paler, a sort of salmon pink colour.

Chris

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I missed your original post Paz, very interesting comparison. Not long after I first started observing back in 1999, Jupiter and Saturn were high in the sky and quite close together. The views, even in the rather rubbish 150mm reflector I had at the time were amazing. I do wish I had both the scopes and the experience I have now, back then as I would have got far more out of it.

2020 might be a date to head south as far as possible to get some decent views!

IMG_2944.PNG

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Posted (edited)

Re size and detail: these four were taken in the last few months with a Mak (180 although the 127 Mak showed only a little less detail). Although they are stacks, they represent fairly well the view though the scope in moments of excellent seeing - they are not exactly matched for colour, although the scale should be the same. As you can see, the GRS should be fairly obvious when visible.

The view in 2020 should be amazing - I'm on the lookout for a location for a site in S Spain with good seeing!

Chris

satandjup.jpg

Edited by chiltonstar
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I reckon if you have the screen maybe 6-8 feet away you'd get the view through the eyepiece depending on magnification.

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Very nice. That Mak 180 really gives some good results. Keep thinking about buying one 

to put on my CG-5 mount for imaging , because of the 2.8 f/l . 

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9 hours ago, Moonshane said:

I reckon if you have the screen maybe 6-8 feet away you'd get the view through the eyepiece depending on magnification.

I'd reduced the file size to roughly match my fov with a Baader 10mm ortho, which works with my 38cm laptop screen, but obviously won't work with other mags or different laptop (or phone) sizes.

Chris

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