Jump to content


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

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: 704
  • Joined: 06 Aug 2012
  • Loc: Ower Yonder, 01.5ºW. 55ºN.

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: 2995
  • 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: 704
  • Joined: 06 Aug 2012
  • Loc: Ower Yonder, 01.5ºW. 55ºN.

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: 1621
  • 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: 8897
  • 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: 3473
  • 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: 8595
  • Joined: 08 Aug 2007
  • Loc: Pampanga, 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: 704
  • Joined: 06 Aug 2012
  • Loc: Ower Yonder, 01.5ºW. 55ºN.

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: 704
  • Joined: 06 Aug 2012
  • Loc: Ower Yonder, 01.5ºW. 55ºN.

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: 8595
  • Joined: 08 Aug 2007
  • Loc: Pampanga, 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: 704
  • Joined: 06 Aug 2012
  • Loc: Ower Yonder, 01.5ºW. 55ºN.

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: 704
  • Joined: 06 Aug 2012
  • Loc: Ower Yonder, 01.5ºW. 55ºN.

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

Special Ed

    Fly Me to the Moon

  • *****
  • Posts: 7221
  • 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: 704
  • Joined: 06 Aug 2012
  • Loc: Ower Yonder, 01.5ºW. 55ºN.

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: 10651
  • Joined: 17 Jan 2009
  • Loc: Triton

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: 704
  • Joined: 06 Aug 2012
  • Loc: Ower Yonder, 01.5ºW. 55ºN.

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: 704
  • Joined: 06 Aug 2012
  • Loc: Ower Yonder, 01.5ºW. 55ºN.

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.


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.



Recent Reviews


Imaging/Sketching Contest






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics