Jump to content


Photo

1st Jupiter this Apparition with Callisto Surprise

  • Please log in to reply
19 replies to this topic

#1 David Gray

David Gray

    Viking 1

  • *****
  • Posts: 575
  • Joined: 06 Aug 2012
  • Loc: Nr. Scotland.

Posted 06 August 2013 - 10:04 AM

Almost missed it: but suddenly realised that Jupiter was attainable above the fence. Some initial excitement (impact-wise) when I spotted the 'indentation' in the south limb. I had not realised that Callisto's shadow was again starting to cast on the disk after a long absence. The satellite was a way off and not readily apparent in the lighter sky - and initially some of the aperture obscured by the fence. WinJUPOS confirmed my 'impact scar' was indeed it's shadow - tho' shows it further into the disk than I made it.

Attached Files



#2 Jef De Wit

Jef De Wit

    Mercury-Atlas

  • *****
  • Posts: 2785
  • Joined: 06 Mar 2009
  • Loc: Hove, Belgium

Posted 06 August 2013 - 10:54 AM

Nice catch! Never heard of the multi-aperture mask before...

#3 David Gray

David Gray

    Viking 1

  • *****
  • Posts: 575
  • Joined: 06 Aug 2012
  • Loc: Nr. Scotland.

Posted 06 August 2013 - 11:07 AM

Thanks.

Multi-Aperture Mask: I first read of this (7-aperture) in S&T many years back. But recently found this on Google: being a 4-aperture version.

http://www.cloudynig...php?item_id=548

#4 kenrenard

kenrenard

    Surveyor 1

  • -----
  • Posts: 1562
  • Joined: 13 Dec 2012
  • Loc: Dunmore, PA

Posted 06 August 2013 - 01:06 PM

David,
Nice work as usual. Good to see one of your sketches again. That is some beautiful work.


Ken

#5 frank5817

frank5817

    Cosmos

  • *****
  • Posts: 8496
  • Joined: 13 Jun 2006
  • Loc: Illinois

Posted 06 August 2013 - 09:19 PM

David,

Nice capture of the Callisto shadow and fine sketch of the cloud top detail.

Frank

#6 niteskystargazer

niteskystargazer

    Gemini

  • *****
  • Posts: 3140
  • Joined: 05 Oct 2009
  • Loc: 41-43'-28" N 87-42'-39" W

Posted 06 August 2013 - 11:16 PM

David,

Nice capture of Callisto and Jupiter :).

CS,KLU,

:thanx:,

Tom

#7 Asbytec

Asbytec

    Guy in a furry hat

  • *****
  • Posts: 8335
  • Joined: 08 Aug 2007
  • Loc: La Union, PI

Posted 07 August 2013 - 06:39 AM

David, almost missed it, too. See my avatar, "Ganymede Rising." Jupiter offers up some wonderful observations.

Well done. Been reading on the multi aperture mask. It's not something I would do, but how do you like it?

#8 David Gray

David Gray

    Viking 1

  • *****
  • Posts: 575
  • Joined: 06 Aug 2012
  • Loc: Nr. Scotland.

Posted 07 August 2013 - 11:21 AM

Thanks all.

Seems I caught the second Callisto shadow transit of its new phenomena-‘season’. Given the longer orbital period not always easy to catch these timing-wise; and here I got it quite by chance!

Norme: I can’t say I use the mask a lot (often gets cobwebby!) but it certainly helps with objects in a bright sky, contrary to the impression I get from the guy in the link I gave. Maybe because I am using a Cassegrain type setup (baffle tubes/sky-flooding factors). I suspect it may be of advantage in larger SCT’s with their relatively larger COs for contrast considerations, mine is only 19%. In my case the mask gives the combined effect of 7 unobstructed 120mm scopes. Not a huge odd-shaped CO as one visitor heatedly insisted – sheesh!! I often find Jupiter too glary even with the apodizer and have applied the mask in addition with good advantage – suck-it-and-see!

Thanks again.
Cheers.
David.

#9 idp

idp

    Messenger

  • -----
  • Posts: 454
  • Joined: 21 Aug 2009
  • Loc: New Haven, CT

Posted 07 August 2013 - 11:32 AM

Nice drawing, and nice device. I guess it starts making sense for 12" reflecting telescopes and up?

I'm curious though, about what does "the combined effect of 7 unobstructed 120mm scopes" exactly mean? Does it refer to light gathering alone? Is the resolving power that of a 120mm scope?

Ivano

#10 David Gray

David Gray

    Viking 1

  • *****
  • Posts: 575
  • Joined: 06 Aug 2012
  • Loc: Nr. Scotland.

Posted 07 August 2013 - 11:49 AM

Is the resolving power that of a 120mm scope?


No! You have to think of extreme edge to edge spacing (of near-opposite apertures). In my case 398mm - I begrudge even 1mm but tolerable here!!

Perhaps think in regard to such as the twin Kecks working combined getting the resolution of one huge 65m(?) scope.

#11 Asbytec

Asbytec

    Guy in a furry hat

  • *****
  • Posts: 8335
  • Joined: 08 Aug 2007
  • Loc: La Union, PI

Posted 07 August 2013 - 01:46 PM

Thanks, David. I was just interested in your impressions and don't want to stray from the topic of observing Jupiter. But, the concept interests me.

#12 Tommy5

Tommy5

    Mercury-Atlas

  • -----
  • Posts: 2814
  • Joined: 28 Mar 2004
  • Loc: Chicagoland

Posted 07 August 2013 - 01:54 PM

Nice sketch, amateurs are often able to catch new stuff on Jupiter as Jup comes out from behind the sun to start another observation season , I think GRSJr. was discovered this way.Great sketch again.

#13 David Gray

David Gray

    Viking 1

  • *****
  • Posts: 575
  • Joined: 06 Aug 2012
  • Loc: Nr. Scotland.

Posted 07 August 2013 - 02:26 PM

Thanks, David. I was just interested in your impressions and don't want to stray from the topic of observing Jupiter. But, the concept interests me.


Yes Norme: I almost put this on the Planetary...... Forum. But I will have to respond to anyones' further queries on the mask via PMs, or I risk hypocrisy!! :o ;)

Cheers.

#14 David Gray

David Gray

    Viking 1

  • *****
  • Posts: 575
  • Joined: 06 Aug 2012
  • Loc: Nr. Scotland.

Posted 07 August 2013 - 02:38 PM

Nice sketch, amateurs are often able to catch new stuff on Jupiter as Jup comes out from behind the sun to start another observation season , I think GRSJr. was discovered this way.Great sketch again.


Right on! Over the years I have found it almost uncanny how Jupiter puts on a show near conjunction or a quick-change in the transition.

My thanks.

Cheers,
David.

#15 Special Ed  Happy Birthday!

Special Ed

    Fly Me to the Moon

  • *****
  • Posts: 7064
  • Joined: 18 May 2003
  • Loc: Greenbrier County, WV 38N, 80W

Posted 08 August 2013 - 06:57 AM

David,

Very nice rendering of the King--also nice that you caught that glimpse of shadow. A good reward for going out and looking. It's great that ever-changing Jupiter is coming back. :)

#16 David Gray

David Gray

    Viking 1

  • *****
  • Posts: 575
  • Joined: 06 Aug 2012
  • Loc: Nr. Scotland.

Posted 09 August 2013 - 07:21 AM

Thanks Michael.

Next few nights look promising - fingers crossed for the Perseids; and better prepared for Jupiter now!

David.

#17 ericj

ericj

    Viking 1

  • -----
  • Posts: 663
  • Joined: 17 Feb 2005

Posted 09 August 2013 - 08:14 AM

Hi David,

Great sketch as always. :jump:

Best,

Eric

#18 azure1961p

azure1961p

    Voyager 1

  • *****
  • Posts: 10430
  • Joined: 17 Jan 2009
  • Loc: USA

Posted 09 August 2013 - 12:45 PM

A very unusual moon shadow placement and nicely rendered. I wonder though if the masks aren't reducing angular resolution as much as improving the image in other aspects. The details seem to stop at around 2 arc seconds roughly but of course the instrument can see a small fraction of that. I'm tempted to think the angular resolution is that for a given off axis mask aperture. Not to be too technical here as I didn't sitdown and measure anything but it would seem we are seeing approximately 2" resolution. Is the cost of improved contrast a loss of res in the angular sense then?

Pete

#19 David Gray

David Gray

    Viking 1

  • *****
  • Posts: 575
  • Joined: 06 Aug 2012
  • Loc: Nr. Scotland.

Posted 09 August 2013 - 03:16 PM

Pete.

I can promise you I would not countenance such a loss of res! Close doubles (below 0.5") are well within reach with this setup - it's aperture spacing (as indicated to Ivano earlier) that determines/maintains resolution. I am out observing in a couple of hours and will push it - seeing allowing - to get further evaluation.

Getting back to Jupiter given the ("surprise") circumstances I would not go too deeply for fine detail (and indeed some detail-inaccuracy/placement I have found - recent imagery) with the drawing; being more concerned with the shadow, which occupied some time (as indicated OP), getting it's reality, position etc determined; and in a brightening sky - then found attaching the mask kept things going - but even that eventually fails with Jupiter as the sky ever-brightens!

I well recall catching the GRS at the limb and separated from the RSH: this gap must have been pretty narrow at that angle also considering reduced contrast near the limb.

I should also mention that my observing clock was found to be 8 minutes slow (battery) when I went out the following night - so assuming the same at the drawing-time: rounding to the nearest 5 min. should be 04:25 UT. I try to be alert to time-accuracy/checking: but as I say the surprise-context - I thought I'd spotted an impact scar - but I'm too old a dog to dash off to excitedly report suchlike without considering other possibilities first.

Cheers.
Dave

#20 David Gray

David Gray

    Viking 1

  • *****
  • Posts: 575
  • Joined: 06 Aug 2012
  • Loc: Nr. Scotland.

Posted 10 August 2013 - 09:39 AM

I can promise you I would not countenance such a loss of res! Close doubles (below 0.5") are well within reach with this setup - it's aperture spacing (as indicated to Ivano earlier) that determines/maintains resolution. I am out observing in a couple of hours and will push it - seeing allowing - to get further evaluation.


Whist I appreciate the interest/comments re. the multi-mask this is not the right forum – my mistake including it with the drawing! :tonofbricks: Happily a thread has started on the Planetary and Solar System Observing Forum – where I almost posted this thread in the first place.

To close the matter; here just to point out that last night’s evaluating bore out totally my claim that resolution is virtually unaffected – tho’ would have wished for rather better seeing. There is a major difference here with the larger airy disks presented by my (single!) 152mm off-axis mask than the smaller/neater ones the combined 120mm apertures show.

Really I do not need to be jumping up and down about this as it is a very simple task constructing one of these and trying it out for oneself! Stiff paper/card etc.: I made a test one from heavyweight stencil paper which is easy to cut with a craft knife; and is durable and could be made more so with such as acrylic paint.

I lack the maths to thrash this out ‘on paper’- as I keep saying: suck-it-and-see: I’m an eye to the telescope guy, if it looks like I get a result with whatever then I will persevere with it; otherwise I’ll trash it – or maybe come back at it from another angle or simply other nights in case conditions were affecting the issue.






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics