Mike Hosea
Post Laureate
Reged: 09/24/03
Posts: 3226
Loc: "Metrowest" Boston
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I recently picked up another 5mm Tak LE. I've always rather liked this eyepiece, but it suffers from a glare issue due to the way the field group is mounted. In lunar viewing I get illuminated arcs showing up in the view. Looking at the eyepiece, I can easily see that these arcs are due to light reflected off the flanges that hold in the field lens. I fixed the same sort of problem in the 4mm and 5mm Burgess/TMB Planetaries that I had, so today I decided to go ahead and give it a try. I used an ordinary countersink drill bit to bevel the upper flange from the inside. The bit wouldn't quite fit to bevel the bottom flange (retaining ring, actually), so I had to wing it with a small dremmel tool bit and some fine grit sandpaper. The illustration shows (in somewhat idealized fashion) what I did. The glare seems much reduced, but I'll know better how I did next time I can get it out for viewing the moon.
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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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andydj5xp
sage
Reged: 05/27/04
Posts: 372
Loc: 52.269 N/10.571 E
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Just as a reminder. You will have noticed most certainly this:
TAK LE glare
Andreas
--------------------
TEC140 (#216)
Leica 22...7.3mm zoom, barlowed 1.75x (12.6...4.2mm)
Zeiss AbbeII set with Barlow 2x
WO UWAN16, also barlowed 1.78x (9mm)
WO UWAN28
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Ed Kessler
professor emeritus
Reged: 05/17/06
Posts: 748
Loc: Millersburg, PA
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Hi Mike,
This is the reason why I no longer own TAK LE eyepieces. The glare was quite annoying and slightly deteriorated sharpness and contrast.
I always called it "light scatter" and didn't really know its source. Thanks for the interesting post.
Clear Skies,
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Ed Kessler
sic itur ad astra (Just to look profound!)
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wprince
professor emeritus
Reged: 02/26/06
Posts: 533
Loc: Atlanta, GA
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I greatly appreciate Mike's and Andreas's skill in fixing the glare problem, but it's a shame that it Takahashi hasn't addressed it first. Didn't Burgess Optical fix a similar problem with the 6mm Planetary?
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Wade
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leonard
member
Reged: 10/19/07
Posts: 81
Loc: West Virginia
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Hi Mike ,
This is off topic ,but I have been wanting to ask you about your scope for sometime now . Would you please tell us about your 7 inch F6.7 scope . I would be interested in what makes it a planetary scope and not just a newtonion ,small secondary ,etc., etc..
Any pic. or info. would be of interest to me .
BTW its nice of you to share this kind of information about eyepiece problems .
Thanks Mike , Leonard
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Mike Hosea
Post Laureate
Reged: 09/24/03
Posts: 3226
Loc: "Metrowest" Boston
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Leonard, I created a thread in the ATM forum.
Thread about my scope.
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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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Mike Hosea
Post Laureate
Reged: 09/24/03
Posts: 3226
Loc: "Metrowest" Boston
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Quote:
Didn't Burgess Optical fix a similar problem with the 6mm Planetary?
Some of it. They substantially reduced the problem on the inside of the field group with a threaded retaining ring, but the outside wasn't changed. However, from looking at the 20mm Stellar Series, it does appear that Burgess understands the problem and how to fix it. I have high expectations for the Planetary versions to come out soon.
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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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Mike Hosea
Post Laureate
Reged: 09/24/03
Posts: 3226
Loc: "Metrowest" Boston
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Quote:
Just as a reminder. You will have noticed most certainly this:
TAK LE glare
Andreas
At first I thought it wasn't a large enough baffle, but on second thought, it should be OK.
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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
Edited by Mike Hosea (10/11/08 04:19 PM)
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davidmcgo
sage
Reged: 10/09/04
Posts: 445
Loc: San Diego, CA
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On a couple of LE 5mm's I tried which both gave bad results on the Moon, I found the problem was worse than just the edge of the cell and retainer being not beveled. The field group has been flat ground around the edge and the resulting "frosted" surface is not completely covered by the retainer nor blackened well. This is pretty close to the focal plane when in the scope and any bright moon falling on the edge of the field lens lit up the whole field of view.
My 7.5mm on the other hand is nearly perfect.
Dave
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Mike Hosea
Post Laureate
Reged: 09/24/03
Posts: 3226
Loc: "Metrowest" Boston
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Dave, here's a photo taken through the eyepiece with a bright background (no telescope). You can see the part of the lens that you're referring to as a thin hair of light surrounding the exit pupil. This is extremely minor compared to the specular reflections off the flanges. I'm hopeful that it will turn out to be as insignificant in practice as it looks here, but I'll have to test it and let you know. If not, I may try to create a baffle that is just barely large enough to cover it and insert that under the retaining ring.
--------------------
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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leonard
member
Reged: 10/19/07
Posts: 81
Loc: West Virginia
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Hi Mike ,
Thanks ! 
Leonard
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Mike Hosea
Post Laureate
Reged: 09/24/03
Posts: 3226
Loc: "Metrowest" Boston
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Well, it turned out that I needed the 8mm baffle to finish it off.
--------------------
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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andydj5xp
sage
Reged: 05/27/04
Posts: 372
Loc: 52.269 N/10.571 E
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Quote:
Well, it turned out that I needed the 8mm baffle to finish it off.
I'm glad you could fix it.
The 8mm baffle positioned 16mm ahead of the effective field stop (4.5mm diameter) should work without vignetting down to below f/5 (actually f/4.57).
Andreas
--------------------
TEC140 (#216)
Leica 22...7.3mm zoom, barlowed 1.75x (12.6...4.2mm)
Zeiss AbbeII set with Barlow 2x
WO UWAN16, also barlowed 1.78x (9mm)
WO UWAN28
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