desertstars
Reged: 11/05/03
Posts: 41911
Loc: Tucson, AZ
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I'm finally reading Deep Sky Wonders by Walter Scott Houston, and in one discussion he tosses in a brief mention of a correspondent's sketching technique. The subject, by the way, was an open cluster. The idea was to defocus the image until only the brightest stars could still be seen (albeit as blobs) and to make a "skeleton" sketch that included only these stars. I assume the idea is to seed the sketch with landmarks, so to speak. The image would then be focused and the faint stars marked in around the major players.
I'll have to try this before I call it a major head-slapper, but the idea has caught my fancy. Have I just missed mention of this idea in my frantic effort to keep up with CN? Or is this not a common technique at all?
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Thomas Watson
Author of Mr. Olcott's Skies. Available in paperback and ebook from Amazon and Barnes & Noble.
@desertstarsbks
Under Desert StarsEither Way, It's Reading
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Harry Pulley
professor emeritus
Reged: 08/17/05
Posts: 506
Loc: Guelph, Ontario, Canada
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I have read it before. The late Fr. Lucien Kemble (for whom the asterism Kemble's Cascade is named) mentioned this technique on many occasions. He was a member of the Royal Astronomical Society of Canada and it was mentioned in its publications but I've never gone back to see how far back it can be found. Much of the Journal is now online so it might be possible to find it on google scholar but I haven't found any articles by him that mention it there, though they have been scanned back to the early eighties. He mentioned it on the RASC mailing list many times 
Harry
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Vixen VC200L/GP/SS2K-PC, Up-Swing for Omcon 308, Glory 7x50mm, Skyline 7x35mm
Canon FD manual focus bodies (AE-1, TX, FTbN), circular fisheye to 300mm lenses
Starlight Xpress MX716 (you will be tempted by the dark side of the force)
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Michael Morris
Member
Reged: 01/05/05
Posts: 1518
Loc: Worcestershire, UK
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I too have recently discovered this. I've tried it once so far and it seems to work really well.
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Michael Morris
8" LX200 classic with piggy-backed Orion 80ED and Revelation 66mm Apo
Skywatcher HEQ5 Pro (portable mount for Orion 80ED and Revelation 66mm Apo)
Observatory Almira Observatory Website
Co-author of NightCal Astronomical Observing Calendar Software http://www.nightcal.co.uk
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desertstars
Reged: 11/05/03
Posts: 41911
Loc: Tucson, AZ
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Quote:
I have read it before. The late Fr. Lucien Kemble (for whom the asterism Kemble's Cascade is named) mentioned this technique on many occasions.
As happens, this was the correspondent. (Slipped my mind while I was typing up the first post.)
I'll almost certainly be sketching a few things at the AASP on Saturday night. I'll give it a try and see what comes of it.
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Thomas Watson
Author of Mr. Olcott's Skies. Available in paperback and ebook from Amazon and Barnes & Noble.
@desertstarsbks
Under Desert StarsEither Way, It's Reading
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Tim2723
The Moon Guy
Reged: 02/19/04
Posts: 5762
Loc: Northern New Jersey
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I recall Carol L. using that technique for Sinus Iridum (I think). Perhaps she'll chime in.
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Intes MK-66 Deluxe (6" f/12 Maksutov)
Celestron C-102HD (4" f/10 achromat)
Celestron C-102AZ (4" f/5 achromat)
Orion 6LT (6" f/8 classic Newtonian)
Orion Apex 90 (90mm Mak spotter/grab-n-go/little fun scope)
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WadeVC
Carpal Tunnel
Reged: 12/02/05
Posts: 2834
Loc: Lodi, California,
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Here again, I stumbled across this post from a while back, and thought it to be an interesting technique to share with others. Read the first post to see what I am referring to.
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Orion XTi10 f/4.7
Orion XTi8 f/5.9
Meade NGC 70mm f/10
Orion UltraView 10x50 Wide-Angle Binoculars
My Sketch Gallery
My Astronomy Blog
A wise man can see more from the bottom of a well than a fool can from a mountain top.
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rodelaet
Post Laureate
Reged: 04/28/06
Posts: 3185
Loc: 50°56' N - 4°58' E (Belgium)
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It really works. I've used it many times. If a field is really crowded, I'll defocus to concentrate on the brighter stars.
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Rony
'The Casual Sky Observer's Guide.'
My Astronomical Sketches
My Binocular Sketches
Callibrate your Monitor with this little strip.
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WadeVC
Carpal Tunnel
Reged: 12/02/05
Posts: 2834
Loc: Lodi, California,
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I think I shall give this a try this weekend and see how it works out.
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Orion XTi10 f/4.7
Orion XTi8 f/5.9
Meade NGC 70mm f/10
Orion UltraView 10x50 Wide-Angle Binoculars
My Sketch Gallery
My Astronomy Blog
A wise man can see more from the bottom of a well than a fool can from a mountain top.
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Jeff Young
Post Laureate
Reged: 08/04/05
Posts: 4491
Loc: Ireland
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What a great idea! I'll bet it would work particularly well in a nebula-swamped field such as M42 or the Rosette.
-- Jeff.
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Nikon 18x70s / UA Millennium Colorado:
Solarscope SF70 / TV Pronto / AP400QMD Coronado SolarMax40 DS / Bogen 055+3130
APM MC1610 / Tak FC-125 / AP1200GTO Tak Mewlon 250 / AP600EGTO
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frank5817
Postmaster
Reged: 06/13/06
Posts: 7212
Loc: Illinois
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Another use for this technique is in estimating visual magnitudes for long period and irregular variable stars. On some of the more difficult variables it can be helpful.
Frank
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My Gallery
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markseibold
Pooh-Bah
Reged: 01/19/08
Posts: 1493
Loc: Portland Oregon
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Tom
The situation was forced upon me by nature as a child. I was a tremendously nearsighted astronomer as a child. I could not understand it nor my parents when I racked the binoculars way out of focus (in focus for me) compared to those others in the family with 20/20 vision.
Although our parents first home was nearly 7 miles east out of Portland Oregon in 1955, the Milky Way and Amdromeda were easy naked eye objects, I was so nearsighted as a child before the teachers discovered that I squinted at the blackboard in 4th grade, I saw the skies as only a few bright cotton puffs, the moon was a big bright blob, until I first got eyeglasses as a 9 year old.
What a new world! To see the sky and discover so many thousands of more stars for the first time! It was a new universe to a 9 year old! As already established as a left handed artist then, can you imagine the new visual graphics?
Mark
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Carol L
Reged: 07/05/04
Posts: 6968
Loc: Tomahawk, WI 45N//89W
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I found out about the de-focus technique by accident (changing eyepieces) while teaching myself to sketch, and used it quite a bit back then but haven't used it in quite a while now.
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Carol Lakomiak, Tomahawk WI
Writing Sky at Night magazine's astrosketch page since June 2009
Moon Sketch Tutorial
Sun/DSO Sketch Tutorial
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