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#1 mikiek

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Posted 01 February 2009 - 09:34 PM

I've been enjoying some faint open clusters lately - quite a few in Perseus. You know the type - a few faint resolved stars, a few more that twinkle in and out of sight and then a lot of unresolved haze.

I'm really having trouble with the haze. I've tried tortillons, stumps and even my finger - trying to make the haze look more like unresolved stars rather than nebulousity (there's a definate difference between the two).

Any help would be appreciated.

#2 rodelaet

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Posted 02 February 2009 - 04:19 AM

I've tried tortillons, stumps and even my finger - trying to make the haze look more like unresolved stars rather than nebulousity (there's a definate difference between the two).



Mike, I see no difference between an unresolved haze of stars and nebulosity. But that's just me.

I use the same aproach to draw the Andromeda nebula ,M31 (people thought it was a nebula until prove was given), as I do to draw an unresolved globular or the Orion nebula. For my eyes, there are only two types of objects : pinpointed stars and 'glow'.
Astronomers once believed that every nebula would resolve if a powerful instrument would be used to observe it, so neither could they make a distinction between the two types of glow.
When I look with my bino's at an open cluster, the unresolved stars appear like a faint nebula. I have to look up books to find out if the nebula is real or unresolved starlight.

When we use our averted vision, we gain a few magnitudes on sensitivity of our vision, but loose on resolution. Most faint star clusters appear like unresolved glows, unless we use a high enough power to notice separate stars.

My reply will not help you in solving your drawing problem though. Here is my idea : first draw all the stars that you can detect, ignore the haze. Then concentrate on the haze. It might help to unfocus the scope a little to notice the glow better. :)

#3 varmint

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Posted 03 February 2009 - 02:56 AM

I read about a technique called stimpling, where you place random dots around the area where you discern the glow. If the glow is brighter you increase the density of the dots, if the glow is fainter you decrease the density of the dots. I would imagine that if you kept the stimpling dots a fainter shade of graphite you might better achieve the look you're after, a hint of resolved stars that aren't really discernible.

In the "Astronomical Sketching" book this is a technique used for Globulars, so maybe this wouldn't be a good suggestion for an open cluster.

(can you tell I haven't tried it. :grin: )

I'd suggest just experimenting with different techniques and softness/darkness of the graphite to achieve the look you find most appealing.

#4 Jeff Young

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Posted 03 February 2009 - 12:08 PM

The technique Jim refers to is "stippling" (swap the m for another p), but it is likely what you want. You can also smudge the stippling afterwards; the glow mixed with some smudged dots will give a different texture than just a glow. That's what I did with the attached open cluster (and is also the technique I use with globulars).

Cheers,
-- Jeff.

Attached Files



#5 Jeff Young

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Posted 03 February 2009 - 12:10 PM

And here's a globular:

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#6 varmint

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Posted 03 February 2009 - 09:51 PM

The technique Jim refers to is "stippling" (swap the m for another p), but it is likely what you want.
-- Jeff.


DOH! That's two misspells in one evening :foreheadslap: Thanks for the correction.

Great sketches, really shows off how the technique can bring out the texture as you say.

#7 Jeff Young

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Posted 04 February 2009 - 06:52 AM

Jim --

I had to look it up too -- in my field it's usually referred to as halftoning. Wikipedia, though, reserves "halftoning" for the photographic or digital application of the dots and specifies "stippling" for the manual application.

:shrug:

-- Jeff.






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