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#1 cildarith

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Posted 08 July 2005 - 09:49 AM

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.

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#2 cildarith

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Posted 08 July 2005 - 09:50 AM

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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#3 cildarith

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Posted 08 July 2005 - 09:50 AM

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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#4 cildarith

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Posted 08 July 2005 - 09:51 AM

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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#5 cildarith

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Posted 08 July 2005 - 09:52 AM

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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#6 ForgottenMObject

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Posted 08 July 2005 - 10:03 AM

That is so cool!

WOW!

#7 Ron B[ee]

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Posted 08 July 2005 - 10:14 AM

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

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

Ron B[ee]

#8 Tim2723

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Posted 08 July 2005 - 10:17 AM

Eric,

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

#9 cildarith

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Posted 08 July 2005 - 10:21 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.

#10 kraterkid

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Posted 08 July 2005 - 12:09 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

#11 Jeremy Perez

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Posted 08 July 2005 - 12:33 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.

#12 cildarith

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Posted 08 July 2005 - 12:37 PM

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

Here.

#13 cildarith

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Posted 08 July 2005 - 12:46 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.

#14 bicparker

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Posted 08 July 2005 - 12:55 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.

#15 oldsalt

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Posted 08 July 2005 - 01:10 PM

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

#16 cildarith

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Posted 08 July 2005 - 01:11 PM

Thanks David.

(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!

#17 cildarith

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Posted 08 July 2005 - 01:13 PM

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


Thanks Jim. Best of luck!
:)

#18 Erix

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Posted 08 July 2005 - 01:19 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!

#19 cildarith

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Posted 08 July 2005 - 01:30 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.
:)

#20 Erix

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Posted 08 July 2005 - 01:41 PM

Thanks, Eric. I appreciate your help. :rainbow:

#21 kraterkid

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Posted 09 July 2005 - 12:34 PM

Eric,

Stunning inverted image, just fantastic work delineating the nebulosity and the hallmark stellar associations.

Thanks,

Rich

#22 cildarith

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Posted 10 July 2005 - 06:53 PM

Erika: You're most welcome. :)

Rich: Thanks for the kind words.

#23 Erix

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Posted 10 July 2005 - 11:04 PM

Eric, I've put your tutorial to use last night. I tried to do the entire sketch by remembering your steps to see how I got along with it. Any pointers?

M71
M27

The bright blob around the star at the bottom of M27 was very apparent and I'm not sure if it was condensation on my EP, but sketched it anyway as it was what I saw.

#24 Ron B[ee]

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Posted 11 July 2005 - 09:23 AM

M71
M27


I don't have any pointers, only compliments ;). Those are awesome sketches, Erika :waytogo:! I knew you're an expert at lunar sketching and just found out you're an expert at DSO sketching as well. Eric is a great teacher indeed.

I look forward to see more.

Ron B[ee]

#25 cildarith

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Posted 11 July 2005 - 09:49 AM

Those are beautiful, Erika! Keep up the good work. :waytogo:






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