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NGC 3532 Wishing Well Cluster, from Sydney

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#1 maroubra_boy

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Posted 02 May 2011 - 06:05 AM

Hi all,

Cloud sadly stopped another dark sky session, and last night was the first chance to get a scope out in a month, though it was from home - you take what you get I guess. High cloud rolled in by the time the 45 minute sketch was done.

The Wishing Well cluster is a naked eye DSO, just east of the Eta Carina nebula. It is often mistaken for Eta Carina through a finder. It is a big sucker, nearly 60' in size, nearly twice that of the Moon.

This immensly rich and bright cluster is best viewed through binoculars or a rich-field-telescope.

In this sketch too, I included a AFOV white ring to give a sense of the size of this cluster. With the eyepiece I used, the AFOV is 2.5deg!

This cluster also presented a common problem associated with sketching open clusters. They usually end up looking flat and lifeless - just a bunch of white dots on a page, and nothing like the bag of diamonds you see in the eyepiece. This first image shows the original picture - flat, and unimpressive, :(.

Object: NGC 3532, Wishing Well cluster
Telescope: 8", f/4 dobbie
Gear: GSO Superview 30mm (68deg), 27X
Date: 1st May 2011
Location: Sydney, Australia
Conditions: *BLEEP*, :rolling:
Media: White charcoal pencil, white and coloured ink, white chinagraph pencil, on black paper

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#2 maroubra_boy

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Posted 02 May 2011 - 06:22 AM

The cool light of day revealed the horrible truth. And the words of a fellow amateur rang in my ears - "most sketches don't excite me".

But how can you tart-up a bunch of dots?

ADD DIFFRACTION SPIKES!!

I don't really like to make bright stars as large blobs. Yet diffraction spikes seem to add the 'glare' you experience through the eyepiece, and adds the sparkle that the sketch needs.

What do you think?

Alex.

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#3 Jef De Wit

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Posted 02 May 2011 - 01:35 PM

I never tried adding spikes, but I have to agree: it makes the OC more alive.
Should be a mighty sight this "southern" cluster! Why is it called "wishing well"?

#4 JakeSaloranta

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Posted 02 May 2011 - 02:09 PM

A great sketch and I prefer the first one. Must have been quite a job to draw and a great view!

/Jake

#5 JayinUT

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Posted 02 May 2011 - 05:40 PM

Alex,

Well done! I really like this one.

#6 frank5817

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Posted 03 May 2011 - 09:55 AM

Alex,

I must respectfully disagree with you. I don't think that first sketch looks flat at all. You have kept the star points small but have variation in brightness to match the real sky. I for one like the sketches of open clusters.
In the second sketch the addition of diffraction spikes generated by the spider add realism to match the eyepiece view in a standard Newtonian scope.
I can't choose both are superb.

Frank :)

#7 maroubra_boy

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Posted 03 May 2011 - 10:28 PM

Mars, it's called "The Wishing Well Cluster" because the mass of bright stars resembles a mass of silver dollars glistening in the bottom of a well!

Jake & Frank, thank you for the critique. I do like to read these differences in opinion. They challenge and help to develop ideas, technique, and arguement (in the conversation sense, not in being nasty).

I've hesitated in sketching open clusters as I've always found it difficult to relate what is seen in the eyepiece to the page without resorting to large blobs for bright stars, and the impact of the cluster is lost without a mechanism by which to highlight their brilliance.

And to just limit the sketch to the cluster without relation to its surrounding bit of sky makes it loose context for me. It is the way it stands out from its surrounds that gives the cluster its impact. That's the reason I extend my sketches so far, and usually don't add the FOV ring. If I do, I still extend the sketch beyond the ring.

I might look at reducing the size of the spikes next time too. I don't want to make the spikes the feature, but an understated element. "Less is more" as they say.

This cluster is a true gem of the sky. An extraordinary collection of stars within a rich section of the Milky Way filled with so many. A binocular view of it is a marvel. Think of this cluster as M7 on steroids, :lol:.

#8 starquake

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Posted 04 May 2011 - 12:07 AM

Although both sketches I find just perfect, here's one more vote for the first sketch. :) Although diffraction spikes may add something to the realism, but for example, in my 12" newt I can only see spikes around _really_ bright stars (up to about 6m). In my 6" I have curved spider vanes, which also reduce spikes almost to zero. Somehow these spikes on a sketch often look a bit artificial for me - something like the fake colours of an astrophoto.

Anyway, seeing your sketches, I guess many astrophotographers start to cry over the thousands of dollars (euros/pounds/etc) of equipment they had to buy to produce an image you can do with a pencil. :D

Congrats, Ferenc

#9 Livelongnprosper

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Posted 30 May 2011 - 06:21 PM

Simply, wow- thanks for sharing these.

#10 niteskystargazer

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Posted 31 May 2011 - 07:13 AM

Alex.

Very good sketch of NGC 3532 :).

CS,KLU,

:thanx:,

Tom






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