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bbcoltrane
journeyman
Reged: 05/07/08
Posts: 5
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While viewing bright planets or any bright star, I've noticed a hazing phenomenon.
I've used my Antares 5mm Plossl and my Meade QX 15mm w/a 2.25x barlow. Both are similar magnification with my 5" Achromat, but the QX has a greater FOV, which helped me figure out what was happing here.
I don't believe it's dew or moisture. What I've noticed is that the bright Jupiter disc actually reflects off of my own cornea and back onto the EP glass. If I keep Jupiter off center in the EP, the affect goes away. But, if I center Jupiter and move my eye around, I notice that when the reflection converges with the disc, the haze appears. The 5mm Plossl has such a small opening that I can't really get Jupiter off center enough to negate the affect, so the EP is kind of useless (same problem with Saturn & Mars @ opposition, and bright stars)
So, the real question here is... what EP's have better anti reflective coatings on the top glass?
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Mr. Mike
scholastic sledgehammer
Reged: 11/08/05
Posts: 855
Loc: Churchville, NY
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Hmmm... this is the third thread about this. I started one and so did someone else. It does seem that most replies blame moisture or humidity issues as the major culprit. maybe you are onto something though. My similar problem happened with a pretty expensive, high-end eyepiece that I would assume had REALLY good coatings so I dunno if thats the problem.
This happened to me on Jupiter as well. I have to try out the planet with a few other high-power EPs to confirm it was the eyepiece and/or the viewing conditions.
The cornea reflection thing is an interesting concept though.... 
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Stellarvue NG 80mm ED
Meade 7x50 Binos
Pentax XW 5mm
Meade 5K UWA 8.8mm
Vixen LVW 13mm
Vixen LVW 22mm
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Mike Hosea
Post Laureate
Reged: 09/24/03
Posts: 3226
Loc: "Metrowest" Boston
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Quote:
So, the real question here is... what EP's have better anti reflective coatings on the top glass?
Good luck with that. It never helped me that much. You may find some relief from specific designs, although I don't know which--maybe if the eye lens is convex, since this will spread the reflection out rather than concentrate it. Also shorter eye relief may help.
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Mike
- 7" f/6.7 home-built planetary Newt
- 35mm Panoptic
- 13mm Ethos
- 5mm Tak LE
- 2x TV Barlow
- Canon 10x30IS Binoculars
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Bill Weir
scholastic sledgehammer
Reged: 06/01/04
Posts: 880
Loc: Metchosin (Victoria), Canada
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A variable polarizing filter can help to some degree. So can an apodizing screen.
Mostly, it just is, what it is.
Bill
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6'' Orion SkyQuest
12.5'' f/5 Custom Truss Dob
William Optics 80mm ZenithStar II ED Doublet
f/5 25" newtonian on a giant GEM, any time I want
Observing sessions grand total for 2007, 171.
So far in 2008, 111
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escaner
member
Reged: 09/25/07
Posts: 22
Loc: Barcelona, Spain
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This phenomenon has happened to me with a Kokusai Kohki 6mm Ortho. Very frustrating. I tried to clean the outer lens and still the same, so perhaps it was reflection as you say.
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GlennLeDrew
professor emeritus
Reged: 06/18/08
Posts: 575
Loc: Ottawa, Ontario, Canada
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Have you tried moving your eye closer and farther from the eye lens? This would help identify the source of the ghosting...
I would think that a lens surface--and not necessarily the rear-most and hence closest to the eye--of the right curvature could send back to the observer just such a reflection of a bright source. I wonder how visible such a ghost image might be? Let's throw some numbers into the mix...
First, the emergent light bundle would have to reflect off the cornea, which would then be, say, at around the 4% level of intensity. Then that redirected light has to reflect off a (nominally) coated surface where the intensity is reduced to less than 1% of the 4%, or no greater than 0.004 of the brightness of the direct image. That's 1 part in 2,500, or a brightness difference of 8.5 magnitudes. Let's take Jupiter, which is near -2.5m. In a typical 'scope it'll be brightened by, say, 8 magnitudes, to -10.5m. So a ghost image, even if out-of-focus, will have an integrated magnitude 8.5 magnitudes fainter, or -2 (if *really* de-focused, its surface brightness will probably render it insignificant.)
So it would seem that eyepiece designers should take into account image ghosting caused by both internal reflections within the eyepiece AND reflected light from the observer's eye when placed at the correct eye point.
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Home-made 11X50 right angle bino, 8.1 deg. FOV
Modified 26X100 bino, 3.5 deg. FOV
Mediocre minds discuss people. Good minds discuss events. Great minds discuss ideas.
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Brooklyn
scholastic sledgehammer
Reged: 07/24/08
Posts: 870
Loc: Central New Jersey
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ive heard many say that its dew or moisture getting into the eyepiece, and thus since jupiter and other bright objects are so illuminating, it possibly causes a ghost, or copy of the jupiter circle of light.
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Meade 8.25"(209.55mm) LX-90 EMC (SCT)
Albert Einstein =>
“Intellectual growth should commence at birth and cease only at death.”
“If you can't explain it simply, you don't understand it well enough.”
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naglertized
Carpal Tunnel
Reged: 01/10/07
Posts: 1515
Loc: Jacksonville Florida
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I noticed this aberration a couple of nights ago while looking at Jove using my 15mm. TV Wide Field. I came to three conclusions. I noticed the EP had some finger print marks (thanks kids!). Two, I noticed some odd reflections caused by my specs. Three, it was humid, with an EP with ~10mm. ER there probably was some minor fogging.
I'm beginning to think that Jupiter is the ultimate test of an EP's light handling capabilities.
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Clinton
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