Olivier Biot
Amused
Reged: 04/25/05
Posts: 14328
Loc: 51°N (Belgium)
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How about sharing some DSO observing techniques?
Let's start with the easiest technique: averted vision.
Technique: averted vision
Applicable to: all deep-sky objects
Ease: very easy
Effect: significant to dramatic improvement
Equipment: none
Averted vision is a visual observing technique that makes use of the fact that our eyes are not as sensitive to light where we see the best detail. When looking directly at an object, more detail can be seen, but when looking a bit away from the target you trade in resolving power for brightness. Every eye being different, the direction in which you have to look for perceiving this brightening at best is different. To find it, roll your eyes while observing a DSO - a bright globular usually shows a very dramatic improvement.
The technique of averted vision is the most widely used technique for observing faint targets. It can be used in combination with virtually every other visual observing technique.
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Tal-200K (#199) with JMI NGF-Mini2M focuser on GEM3 • Astro-Tech AT80ED on Orion Sirius EQ-G with EQDIR & home made wireless EQDIRECT • Celestron Regal LX 8x42 & 10x42 • Helios 15x70
ATM 14" f/5 (designing mirror cell and filter wheel/focuser) • ATM 10" f/6 Portable Truss (polishing) • ATM 10" f/25 Dall-Kirkham (primary: polishing, secondary: #120 grit)
AstroForecast
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Josh U
member
Reged: 07/10/07
Posts: 41
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Well, I'm not sure if it's a technique or not, but I always use my star chart to see EXACTLY where I'm supposed to be looking. "Lawn Mowing" always frustrates me. I like to zoom in from Telrad, to finder, to low power telescopic views. It's a little system I've developed for myself, and it works great for me!
Then there's always the slight movement of the scope (bumping it) to make the target stand out.
Steve O'Mera says it's important to breathe deeply!
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"How you do anything is how you do everything."
Zhumell 10" dob
80mm Refractor
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John Kocijanski
Pooh-Bah
Reged: 08/22/03
Posts: 1487
Loc: Monticello, NY
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Nice start. Averted vision is very important. How about using higher power to darken the sky a bit to make some DSOs stand out better. Another tip from Sue French in the August Sky and Telescope is to use higher power on globular clusters and planetary nebula to bring out more detail.
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John
Deep Space Observer 10 * SPC-8 * C102 HD f/10 * XT 4.5 * AT1010N * PST *
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rodelaet
Carpal Tunnel
Reged: 04/28/06
Posts: 2642
Loc: 50°56' N - 4°58' E (Belgium)
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Here is a picture I made to represent the sweet spot of averted vision, for a right eye observer, followed by a picture to represent the sweet spot for binocular users. ( Here is the whole post. ) A left eye observer can mirror the picture. To keep things simple : put the object between your center of view and your nose. While using the sweet spot, one can see up to 3 magnitudes fainter than with direct vision.
I did not find it an easy technique when I started observing. I had to learn to use averted vision to its full potential.
About the diagram : it represents the distribution of the optical receptors on the human retina; the yellow zone represents the density of the cones. The blue zone shows the density of the rods. The white zone is the blind spot, and should be avoided. The grey oval shows the sweet spot. Bear in mind that each observer can have other results, but in general , the diagram works for most people.
To give you an idea of the angular distances : your hand with fingers open measures about 20° at arms length. A simple test : stretch your right arm, and open your hand (like when waving hello) so that thumb and little finger are at max separation. Close your left eye (no, the other left eye  ). Look with your right eye at your little finger. Your averted vision sweet spot is now where the thumb is. Now look at your thumb. Your little finger is now where the blind spot is, and can dissapear when you wiggle your hand a little bit. If you keep these angular distances in mind while you observe, averted vision can be easier to learn.
Binocular and binoviewer users build up an image of both eyes with two blind spots and two grey ovals. These observers can shift their gaze above or under the center of view, so that the object of interest is positioned in one of the two gray ovals, thus avoiding the blind spot in each eye. See the right diagram.
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Rony
My Astronomy Sketches
My Binocular Sketches
Edited by rodelaet (07/13/08 01:44 PM)
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galaxyman
Pooh-Bah
Reged: 04/04/05
Posts: 1171
Loc: Limerick, Pa
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Quote:
Nice start. Averted vision is very important. How about using higher power to darken the sky a bit to make some DSOs stand out better. Another tip from Sue French in the August Sky and Telescope is to use higher power on globular clusters and planetary nebula to bring out more detail.
Yep...averted vision (even scanning) is one technique.
Also be a pirate...meaning use a eye patch. Makes it much easier and more comfortable to view. Helps in baffling fatigue also.
Don’t be a one-eyed pirate…meaning alternate eyes. If you have fairly decent vision in both eyes, switch eyes at the eyepiece. This will also battle fatigue.
Be a one-eyed hooded pirate...meaning baffling stray light around you and the eyepiece. Some use this technique with great results, though fogging the eyepiece can happen with this.
Be a one-eyed hooded pirate that likes to travel…if necessary. Meaning finding or observing from the darkest site possible, will be a huge advantage on deep sky observing. Even slightly darker skies then your backyard will produce big dividends.
Yes, higher power is something I been saying for years and years (actually decades and decades).
DSO’s as a whole should not be subject to what some might call “optimum magnification”, for many variables exist. Such as sky conditions (both seeing and transparency), scope condition (optics, collimation), object (size, magnitude, surface brightness), and of course the observer himself.
I like to push the power for most objects...particularly galaxies, planetary nebula, tight globs. Even large nebula like M-42 can reveal great detail using more than just low power.
Know that each object has its own character. For instance one galaxy may look best (detail included) in my 22” at 200x, while another may require 400x or more.
So when a certain galaxy per say is in view, I will continue step by step to push the power. In many instances detail will start to emerge. Even on nights where seeing is only fair, I’ll still push the power a bit.
Many times on these type of nights, seeing will settle for moments of time, this is where patience is good to have at the eyepiece (heck, that should apply at all times). So when those moments come, many times detail will pop or emerge.
My two main scopes are the 22” dob, and the 8” refractor. Both scopes I have (and will) continue to push the envelope. In fact last year, I really pushed the big refractor while observing many ARP’s.
I was amazed on the detail I could see on many of them, so technique can go a long way on what can be seen.
Oh, I need to say some of my best views ever was with the 22” dob on M-82 and M-104 at 715x to 1002x, using Naglers 3.5mm and 2.5mm respectively. The views were Hubblesque!!!
Karl
E.O.H.
Chesmont Astronomical Society
Telekit (Swayze optics) 22" F/4.5 Dob
Homemade (Parks Optics) 12.5" F/4.8 Dob
TMB 8" F/9 Refractor(The Beast)
Astrozap 6" f/8 Refractor
Orion 4" f/6 Refractor
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So many galaxies, so little time!
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SaberScorpX
Post Laureate
Reged: 01/12/05
Posts: 4121
Loc: illinois, usa
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re: breathe deeply...
Deeply and slowly. In addition, take time to stretch or go for a short walk at least every hour. Keeping the blood and oxygen pumping increases eye/brain performance at the eyepiece.
Wearing sunglasses during the day gives a major boost to expedite full dark adaptation before a big hunt. Many nights when fainter targets appear to leap out from the EP start with this simple pre-game preparation.
Saber Does The Stars at
www.astronomyblogs.com/member/saberscorpx/
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Mr Q
sage
Reged: 02/25/08
Posts: 351
Loc: N Central New Mexico
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I heard of this tip and have tried it with success -
Before going to the eyepiece, take several deep breaths, which pushes extra O2 to the brain, which enhances vision.
On the same account, try not to stop breathing when straining to see a detail or faint fuzzy. Breath but exhale slowly while trying for the object.
Should go without saying - no smoking or alcohol consuption for several hours before observing.
Be careful not to hyperventilate while using the above tip otherwise dizziness or possible fainting can occur. The o2 saturation point is easily reached and any further deep breathing would be counter-productive.
Mr Q
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What goes around, comes around, eventually.
Meade DS-10(10" newt)
10x50, 10x70 binos
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moron392
scholastic sledgehammer
Reged: 08/20/07
Posts: 808
Loc: Charlotte, NC
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use controlled, slow breathing to concentrate on your target more fully
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"If you've done something right, people won't be sure you've done anything at all."
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60mm meade ngc60 refractor.
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starblast4.5EQ
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Phillip Creed
Idiot Seeking Village
Reged: 07/25/06
Posts: 1032
Loc: NE Ohio
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One of my best investments was buying a pair of overcorrected eyeglasses. This is because if you have myopia, it becomes slightly worse during nighttime vs. daylight hours. These "O'Meara" glasses give me about an extra 0.3-mag boost with the naked-eye, and seem to help a bit at the eyepiece, too, though not as much.
Clear Skies,
Phil
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"Why suffer from insanity when you can revel in it?"
Wilderness Center Astronomy Club member since 1995
ICQ Comet Observer Code: CRE01
*****
16" f/4.5 Truss Dobsonian (FOR SALE!!)
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galaxyman
Pooh-Bah
Reged: 04/04/05
Posts: 1171
Loc: Limerick, Pa
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Quote:
Wearing sunglasses during the day gives a major boost to expedite full dark adaptation before a big hunt. Many nights when fainter targets appear to leap out from the EP start with this simple pre-game preparation.
Yep, everyone should wear a decent pair of sunglasses when outside during the day 
Karl
E.O.H.
Chesmont Astronomical Society
Telekit (Swayze optics) 22" F/4.5 Dob
Homemade (Parks Optics) 12.5" F/4.8 Dob
TMB 8" F/9 Refractor(The Beast)
Astrozap 6" f/8 Refractor
Orion 4" f/6 Refractor
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So many galaxies, so little time!
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stevek
Pooh-Bah
Reged: 04/16/06
Posts: 1229
Loc: west michigan
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Averted vision... I use it so much/so readily, I dont even know I do it any more  ...
When I am really studying a DSO, I will change EPs frequently. I tend to run the circuit from 40X-56X-92X-200X-300X back and forth, spending 3-5 minutes at each mag, often trying several EPs a 2nd & 3rd time. Then I will revert to the one that gave me my fav view and stay there for another 5 minutes or so. Sometimes I will add and then remove the narrowband filter also. I think this process helps me get a better perspective and helps me build a clearer picture of what I am looking at. FWIW, I do this on large targets like M17 and M31 as well as small ones like M104 & NGC 6543.
Steve
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DSO 8" f6 DOB w/ 8x50 RACI & 2"Crayford
1958 Sears Discoverer 76mm Refractor
GSO SV 30mm 2",21mm Hyp,13mm Strat,BO/TMB ver2-6mm & 4mm
1.25"Filters: DGM-NPB, 25%ND
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Orion 2X Shorty Barlow
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"What is that burning in the sky? Tell me y'all..." Jeff Beck/Jan Hammer
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dengwer
super member
Reged: 02/14/06
Posts: 113
Loc: Texas
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EYEPATCH OVER OBSERVING EYE WHEN NOT AT SCOPE. I use the "eyepatch-hood" technique when at the scope. Before getting out of the hood I switch the patch to my oberving eye to conserve the dark adaption and then can look at charts or whatever without worrying about too much light. I put my glasses over the eyepatch and can read the charts very well with one eye. I put the patch on the observing eye an hour before observing to get dark adapted.
David
Edited by dengwer (07/14/08 12:06 PM)
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Jeff Morgan
Carpal Tunnel
Reged: 09/28/03
Posts: 1531
Loc: Prescott, AZ
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A couple of techniques I use for the low surface brightness objects:
- Rock the tube slightly when over the suspected target. The motion helps to identify.
- Check your atlas to see if there are stars that lay along or near the edge of the target. Also, look for stars that can define an area or box that contain the target.
- My favorite is to try and find dark nebula or just dark areas that define edges of the object. After spending several minutes focused on the the darkest part(s) of the field, all of the sudden the object becomes obvious and sometimes easy.
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Jeff Morgan
Prescott, AZ
Wile E. Coyote School of Telescope Making
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Jeff Young
Post Laureate
Reged: 08/04/05
Posts: 3164
Loc: Ireland
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More on motion...
For really difficult targets, try different types of motion. Sometimes slewing slowing over the field will highlight a brightness gradient, while sometimes a more vibratory motion will help more (I used to tap the side of the tube, but my current instrument is so heavy that tapping the tube doesn't do much so I now tap the side of the diagonal).
I *think* I've found that slow motion usually works better with well-extended targets, while vibratory works better with smaller targets or very dim point sources. But more study is needed.
Orientation
Some targets will appear in averted vision seldom enough that you're not sure if you're seeing something or not. Try rotating the diagonal to change the orientation of the image and see if the object pops in/out at the same location. (Obviously this one doesn't work so well for Newts.)
Magnification, seeing, and "the wait"
I'm not a huge planetary observer, but I have developed a particular style. First I determine what magnification the current seeing will support. Then I bump it up one or two steps (25 - 40%). The image gets rather mushy. Next, I stare at the image for about 10 minutes. (I find this much easier to do with a binoviewer, and quite hard with a single eyepiece.) During that 10 minutes, if I bumped one step then I'm likely to get 3 or 4 moments, each perhaps 1/2 second to 2 seconds, in which the seeing settles and the image gets very crisp. If I bumped two steps, I'm about 50/50 likely to get a single moment. Then I take a break and do it all over again.
It's time-consuming, but the detail available in those few moments is well beyond what is available more-or-less constantly with lower magnification.
Cheers,
-- 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-100 / AP1200GTO Tak Mewlon 250 / AP600EGTO
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MessierScott
super member
Reged: 06/18/07
Posts: 187
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Most of you have already covered my helpful ideas.
-averted vision
-wearing an eyepatch over the non-observing eye
-wear good dark sunglasses during the daytime
-use a little scope-shake
-high magnification
-a good detailed atlas
-keep breathing and don't hold your breath straining to see an object
-keep hydrated
-take breaks to walk around and refresh your body
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Scott Kranz
20-inch f/4.3 Starmaster w/Zambuto mirror, Feathertouch focuser, GO TO & tracking
7-inch Starmaster
H-alpha Coronado PST
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astrokido
sage
Reged: 06/09/08
Posts: 269
Loc: Phoenix, AZ
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There's also astrophotography, you can always bring out more with film or ccd than a retina.
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- Gill C. - All opinions subject to a speed limit of 299,792,458 m/s unless noted otherwise.
Nikon D40 Bushnell 10x25 Zhumell 20x80 Celestron Cometron CO-100 binochair CN gallery
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Mr. Bill
Carpal Tunnel
Reged: 02/09/05
Posts: 2759
Loc: Just passing through.....
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Make sure that Happy Hour ends early....say 4 o'clock when you plan on observing that night and a nap also helps.
After new moon, I generally catch a nap in the evening and get up after moonset. The best seeing and darkness is around 2:00 AM out my way, so this works out great.
I try to stay on two hours either side of the meridian as this is putting objects in the best position and out of the muck.
Also, my observing technique is sweeping the area of interest alternately in both directions using an alt azimuth mount and when something of interest shows up, I look at the position through the Telrad and then look it up on the SkyAtlas or Uranometria if I don't know what it is.
I've "discovered" several comets this way which made for momentary excitement until they were identified.
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10x50 Fujinon FMT-SX binos
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JohanK
super member
Reged: 05/21/07
Posts: 163
Loc: Ghent, Belgium
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Another useful technique is observing with a bunch of uninterested teenagers. If you're lucky they will blow cigarette smoke over the telescope's opening to assist in seeing nebulosity.
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Johan
Orion XT10
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xfile101
professor emeritus
Reged: 12/08/07
Posts: 739
Loc: Ocean Gate, NJ
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Before I got my Dob I really didn't know how much this "technique" really helped viewing but.............SIT DOWN (preferable in a chair  ) while observing. Your back will thank you and you are much steadier in a seated position as opposed to standing. Actually standing is the least stable of all positions (anybody who hunts will tell you this).
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Jeff Young
Post Laureate
Reged: 08/04/05
Posts: 3164
Loc: Ireland
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Yeah, I forgot that one: for me sitting down is second in importance to averted vision (and #1 for planetary).
-- 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-100 / AP1200GTO Tak Mewlon 250 / AP600EGTO
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