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cildarithModerator
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Sketching Globs
      #507976 - 07/08/05 10:49 AM Attachment (569 downloads)

I have always found sketching globular star clusters to be a bit more challenging and time consuming than any other type of deep-sky object. What follows is the method I currently use. I would be happy to hear of your own methods for dealing with these objects. The example cluster is M-13.

Step 1: Bright field stars. These are the most prominent stars in the field of view. They serve to anchor the drawing and are the reference points from which all additional details may be positioned. Their positions therefore should be as accurate as possible.

Attachment

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Eric
6" f/6 Parks Newtonian
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cildarithModerator
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Re: Sketching Globs new [Re: cildarith]
      #507977 - 07/08/05 10:50 AM Attachment (454 downloads)

Step 2: Background haze. This step involves rendering the cluster strictly as a nebulous cloud. It may be necessary to slightly defocus your eyes (or your scope) to get the proper effect. The purpose of the step is to produce a brightness gradient for the cluster. If the cluster has no hint of resolution or mottling go directly to Step 5.

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Eric
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cildarithModerator
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Re: Sketching Globs new [Re: cildarith]
      #507979 - 07/08/05 10:50 AM Attachment (432 downloads)

Step 3: Stippling. This step involves the semi-random placement of small dots to represent the mottled appearance of many globular clusters and to render the teaming mass of stars hovering just beyond full resolution. Stippling should follow closely the brightness gradient established in the previous step, generally concentrated toward the center unless specific features suggest otherwise. If a cluster has a mottled appearance, but no true resolution, go directly to Step 5.

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Eric
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cildarithModerator
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Re: Sketching Globs new [Re: cildarith]
      #507980 - 07/08/05 10:51 AM Attachment (420 downloads)

Step 4: Placement of resolvable cluster members. This step involves the placement of those stars clearly seen as distinct members of the cluster, with intensity or size proportional to their brightness. Place them to the best of your ability based on distance from the center of the cluster and position angle, paying attention also to their relationship with the bright field stars.

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Eric
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cildarithModerator
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Re: Sketching Globs new [Re: cildarith]
      #507981 - 07/08/05 10:52 AM Attachment (452 downloads)

Step 5: Placement of faint field stars and final touchup. This final step involves the placement of minor field stars, primarily with respect to the bright field stars and the subject of the sketch. Carefully re-examine the object in the eyepiece, noting any additional details and eliminating any stray streaks and smudges with an eraser.

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Eric
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ForgottenMObject
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Reged: 09/11/04
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Re: Sketching Globs new [Re: cildarith]
      #507993 - 07/08/05 11:03 AM

That is so cool!

WOW!

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Matthew
IDA member
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Ron B[ee]
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Re: Sketching Globs new [Re: cildarith]
      #508007 - 07/08/05 11:14 AM

Thank Eric for the tutorial ! DSO sketching has always been really hard on me , so anything tips are always appreciated.

Please keep up your good work and please give us more tips .

Ron B[ee]

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Tim2723
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Re: Sketching Globs new [Re: ForgottenMObject]
      #508010 - 07/08/05 11:17 AM

Eric,

Great work and a wonderful piece of tutorial! Do you use any specific tools for the different steps, such as certain pencils?

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cildarithModerator
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Re: Sketching Globs new [Re: Tim2723]
      #508019 - 07/08/05 11:21 AM

Thanks guys, I hope you find it useful.

Tim, the entire sketch was done with a #2 pencil and a blending stump. Black ink was used on the eight brightest stars to make them stand out a little more. Nothing fancy here in terms of materials used.

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Eric
6" f/6 Parks Newtonian
10x50 Bushnell Binocs


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kraterkid
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Re: Sketching Globs new [Re: cildarith]
      #508158 - 07/08/05 01:09 PM

Hi Eric,

Wonderful tutorial! Do you convert your images to white on a black field? Could you do that and post it as well? I'd sure enjoy seeing this drawing displayed that way. Lovely sketch.

Thanks for sharing,
Rich Handy

Rich Handy

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Rich



My CN Gallery




Edited by kraterkid (07/08/05 01:14 PM)


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Jeremy Perez
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Re: Sketching Globs new [Re: kraterkid]
      #508192 - 07/08/05 01:33 PM

Niiiice. Thanks for the great step-by-step Eric. I couldn't have hoped for a better subject for you to approach than that sketch of M13.

Your process is essentially the same thing I was doing when I rendered M92 and M56. Although, geeze, not with the same level of intricacy as you gathered from M13.

Maybe something I was doing a bit different--for the random mottling, I applied some of it in the central regions of the cluster using the tip of the blending stump for a softer lumpiness. Then used the pencil after that for the more sprinkly appearance. After scanning and inverting, I applied a light sharpening brush to pop some of that granularity out, since the scanner--and my own technique--weren't doing justice to the pile of stars I saw. That seemed to help too.

Any time you want to tutorialize any of your sketches, I'm all eyes man. Thanks.

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cildarithModerator
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Re: Sketching Globs new [Re: kraterkid]
      #508199 - 07/08/05 01:37 PM

Thanks Rich, the inverted view (actually a different sketch, but based on the same observation) is in my CN gallery.

Here.

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Eric
6" f/6 Parks Newtonian
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cildarithModerator
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Re: Sketching Globs new [Re: cildarith]
      #508210 - 07/08/05 01:46 PM

Thanks Jeremy. You technique sounds interesting and is very effective. I haven't tried too much manipulation on the computer after scanning (other than removing artifacts, inverting, applying a mat and labeling).

I have found that you can tweak the scanner settings until it will reproduce subtle shadings just about as faithfully as they appear on paper, however, so don't be afraid to experiment with the custom settings on your scanning software.

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Eric
6" f/6 Parks Newtonian
10x50 Bushnell Binocs


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bicparker
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Re: Sketching Globs new [Re: cildarith]
      #508226 - 07/08/05 01:55 PM

Eric,

That was an excellent presentation. I agree that the globs are probably the most challenging object.

I think your point about getting the brightest field stars in first as your anchors for the sketch can't be overstated. I use that as my initial starting point for almost every sketch I can.

However, since I am working on tiny galaxies at higher magnifications right now, for the most part, I sometimes have few, if any field stars to anchor the drawing. This just adds to the challenge, though.

I usually add the nebulous blur/hazing last on my sketches instead of before the stippling as you do. I do this partly for overall blended effects (it's the watercolor guy in me). I let the stippling set the boundaries for the blur instead of the other way around. But I think I am going to change all of that now that I am looking at your methodology.

Great tutorial guide! Thanks.

David M.

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David Moody, FRAS
17.5" f/5 dob
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Plus a few others out of the rotation

Edited by bicparker (07/08/05 02:03 PM)


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oldsalt
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Reged: 02/12/05
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Re: Sketching Globs new [Re: bicparker]
      #508254 - 07/08/05 02:10 PM

Very nice Eric, I'll have to give it a try.

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There are no winners in war, only bigger losers.

"Duty is the most sublime word in our language. Do your duty in all things. You cannot do more. You should never wish to do less. Rober E Lee

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Jim


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cildarithModerator
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Re: Sketching Globs new [Re: bicparker]
      #508255 - 07/08/05 02:11 PM

Thanks David.

Quote:

(it's the watercolor guy in me).




LOL. I'm sure its the oil painter in me leads me to do it the other way around.



Cheers!

--------------------
Eric
6" f/6 Parks Newtonian
10x50 Bushnell Binocs


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cildarithModerator
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Re: Sketching Globs new [Re: oldsalt]
      #508259 - 07/08/05 02:13 PM

Quote:

Very nice Eric, I'll have to give it a try.




Thanks Jim. Best of luck!


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Eric
6" f/6 Parks Newtonian
10x50 Bushnell Binocs


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Erix
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Reged: 12/25/04
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Re: Sketching Globs new [Re: cildarith]
      #508266 - 07/08/05 02:19 PM

What size circle do you use for the sketch. I have trouble getting nice round stars and wondering if the area I use for the sketch is too small to begin with (just shy of 2" in diameter).

Any pointers on getting nice clean dots instead of oblong?

Your tutorial is terrific...many thanks!

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Erika
Automatic doors make me feel like a Jedi.

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cildarithModerator
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Re: Sketching Globs new [Re: Erix]
      #508278 - 07/08/05 02:30 PM

Thanks, Erika.

I use a circle 3 5/16 inches (8.4 cm) in diameter for nearly all of my sketches. One recommendation I remember (from the Webb Society Handbooks, I think) is to use a 4" circle for low-power, a 3" circle for medium power, and a 2" circle for high power.

As far as achieving round star images is concerned, that is always a bit of a challenge and is one of the main reasons I usually do a re-drawing of my field sketch after the observing session, seated at a table, with good lighting, etc. Keeping the pencil as close to perpendicular to page as possible is the best way to keep your stars in the proper shape.


--------------------
Eric
6" f/6 Parks Newtonian
10x50 Bushnell Binocs


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Erix
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Re: Sketching Globs new [Re: cildarith]
      #508301 - 07/08/05 02:41 PM

Thanks, Eric. I appreciate your help.

--------------------
Erika
Automatic doors make me feel like a Jedi.

Zhumell 16", 10" LX200 Classic,Celestron 102 XLT, ETX70-AT, DS Maxscope 60mm, AT6RC
PCW Memorial Observatory


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