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Jupiter 20/4/17

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niallk    1,628

I just caught Io as it approached the limb, followed by its shadow from 10:45pm last night - GRS also on show :)

As Io reached the limb, there was a strong '3D' effect with the slight limb darkening and the trailing shadow: Io looked like a sharp ball - when far off disk I don't see it so sharply defined.  It was a really captivating sight.  One can really see the moon orbit Jupiter clearly in real time as it crosses the limb - just beautiful to observe!

I observed until ~12:30am, and tried a variety of mags - from 65x to 560x.  Conditions were good: jetstream was way north of Ireland, and it wasn't cold- I cooled my 15" scope for 3hrs in preparation and it paid off.  There was some mist and dew, but thankfully no problems with the secondary - I tweaked the potentiometer setting on my Dew Guard and it seems to be helping these last few sessions. The scope was dripping wet by the end.

For mono viewing, I settled on my 8E plus 2x PM for about 420x.  There was some turbulence, but with patience, there were moments of stunning clarity that kept me coming back for more.  Later on I got my binoviewer - 15mm TV plossls plus a 2.5x PM instead of a GPC, giving 250x or so...  It was very interesting to compare the Ethos vs binoviewer: it seemed to me that colours were a little stronger in the plossls - especially the brown of the cloud belts. The blue-grey festoons (I saw two) from the NEB arcing down to the equatorial zone were more visible in the Ethos.  The binoviewer seemed to show a barge in the northern edge of the NEB.  In past years, I've seen very obvious dark maroon barges; this was more subtly dark brown to my eye.

The NTB was visible, and the zone above it showed a yellowish banding - more obvious in the binos I found.

The GRS was prominently visible, seeming a little darker to its southern edge at times. Nice turbulence visible following it in the SEB, and a 'v' shaped light area around the margins of the GRS and the SEB.  The strongly brown band that angled up at the GRS that I recall from last year seems to have faded.

The STB was also visible, but I didn't see any white ovals last night - I did last week on the 'other side' of Jupiter.  No sign of the little red spot or whatever it is called.

All in all, a wonderful night out on a single target - delighted to get the scope out.



Edited by niallk
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mikeDnight    4,016

Superb report! You sound like you had much better seeing than I did, but I managed to see much of what you describes through the wobbly seeing. I'm glad you mentioned the dark southern edge to the GRS as I sketched it in my wonky, rapid eyepiece sketch before the clouds headed in again.

Mike :icon_biggrin:

2017-04-21 08.45.14.jpg

2017-04-21 08.46.07.jpg

Edited by mikeDnight
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Natty Bumpo    18

Great report. Great observations both. Was able to observe the same from the Midwest USA. The drawings are very beautiful. Thank you. 

My view was through an 80 millimeter F6 scope. I couldn't go over 96 x before I lost definition. Transparency was wonky here.

Edited by Natty Bumpo
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