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Astrophotography and Sketching >> Sketching

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David Gray
sage
*****

Reged: 08/06/12

Loc: Co. Durham UK
1st Jupiter this Apparition with Callisto Surprise
      #6009182 - 08/06/13 11:04 AM Attachment (40 downloads)

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.

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Jef De Wit
Carpal Tunnel


Reged: 03/06/09

Loc: Hove, Belgium
Re: 1st Jupiter this Apparition with Callisto Surprise new [Re: David Gray]
      #6009274 - 08/06/13 11:54 AM

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

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David Gray
sage
*****

Reged: 08/06/12

Loc: Co. Durham UK
Re: 1st Jupiter this Apparition with Callisto Surprise new [Re: Jef De Wit]
      #6009303 - 08/06/13 12:07 PM

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.cloudynights.com/item.php?item_id=548


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kenrenard
Carpal Tunnel


Reged: 12/13/12

Loc: Dunmore, PA
Re: 1st Jupiter this Apparition with Callisto Surprise new [Re: David Gray]
      #6009559 - 08/06/13 02:06 PM

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


Ken


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frank5817
Postmaster
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Reged: 06/13/06

Loc: Illinois
Re: 1st Jupiter this Apparition with Callisto Surprise new [Re: kenrenard]
      #6010449 - 08/06/13 10:19 PM

David,

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

Frank


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niteskystargazer
Carpal Tunnel
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Reged: 10/05/09

Loc: 41-43'-28" N 87-42'-39" W
Re: 1st Jupiter this Apparition with Callisto Surprise new [Re: David Gray]
      #6010662 - 08/07/13 12:16 AM

David,

Nice capture of Callisto and Jupiter .

CS,KLU,

,

Tom


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Asbytec
Guy in a furry hat
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Reged: 08/08/07

Loc: La Union, PI
Re: 1st Jupiter this Apparition with Callisto Surprise new [Re: niteskystargazer]
      #6010957 - 08/07/13 07:39 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?


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David Gray
sage
*****

Reged: 08/06/12

Loc: Co. Durham UK
Re: 1st Jupiter this Apparition with Callisto Surprise new [Re: Asbytec]
      #6011382 - 08/07/13 12:21 PM

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.


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idp
sage


Reged: 08/21/09

Loc: New Haven, CT
Re: 1st Jupiter this Apparition with Callisto Surprise new [Re: David Gray]
      #6011408 - 08/07/13 12:32 PM

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


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David Gray
sage
*****

Reged: 08/06/12

Loc: Co. Durham UK
Re: 1st Jupiter this Apparition with Callisto Surprise new [Re: idp]
      #6011442 - 08/07/13 12:49 PM

Quote:

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.


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Asbytec
Guy in a furry hat
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Reged: 08/08/07

Loc: La Union, PI
Re: 1st Jupiter this Apparition with Callisto Surprise new [Re: David Gray]
      #6011640 - 08/07/13 02:46 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.

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Tommy5
Carpal Tunnel


Reged: 03/28/04

Loc: Chicagoland
Re: 1st Jupiter this Apparition with Callisto Surprise new [Re: Asbytec]
      #6011651 - 08/07/13 02:54 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.

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David Gray
sage
*****

Reged: 08/06/12

Loc: Co. Durham UK
Re: 1st Jupiter this Apparition with Callisto Surprise new [Re: Asbytec]
      #6011707 - 08/07/13 03:26 PM

Quote:

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!!

Cheers.


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David Gray
sage
*****

Reged: 08/06/12

Loc: Co. Durham UK
Re: 1st Jupiter this Apparition with Callisto Surprise new [Re: Tommy5]
      #6011728 - 08/07/13 03:38 PM

Quote:

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.


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Special Ed
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Reged: 05/18/03

Loc: Greenbrier Co., WV 38N, 80W
Re: 1st Jupiter this Apparition with Callisto Surprise new [Re: David Gray]
      #6013021 - 08/08/13 07:57 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.


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David Gray
sage
*****

Reged: 08/06/12

Loc: Co. Durham UK
Re: 1st Jupiter this Apparition with Callisto Surprise new [Re: Special Ed]
      #6015284 - 08/09/13 08:21 AM

Thanks Michael.

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

David.


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ericj
professor emeritus


Reged: 02/17/05

Re: 1st Jupiter this Apparition with Callisto Surprise new [Re: David Gray]
      #6015356 - 08/09/13 09:14 AM

Hi David,

Great sketch as always.

Best,

Eric


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azure1961p
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Reged: 01/17/09

Loc: USA
Re: 1st Jupiter this Apparition with Callisto Surprise new [Re: ericj]
      #6015885 - 08/09/13 01:45 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


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David Gray
sage
*****

Reged: 08/06/12

Loc: Co. Durham UK
Re: 1st Jupiter this Apparition with Callisto Surprise new [Re: azure1961p]
      #6016167 - 08/09/13 04:16 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


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David Gray
sage
*****

Reged: 08/06/12

Loc: Co. Durham UK
Re: 1st Jupiter this Apparition with Callisto Surprise new [Re: David Gray]
      #6017346 - 08/10/13 10:39 AM

Quote:

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! 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.

Edited by David Gray (08/10/13 10:40 AM)


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