Joe Ogiba
Postmaster
Reged: 02/14/02
Posts: 5446
Loc: NJ USA
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I just received my BT-80 45 today and tried several pairs of eyepieces between the rain showers and it does not show any vignetting with any 1.25" eyepiece. The 20mm Widescan III's have 84 deg AFOV and show the full unvignetted 84 deg AFOV but do not focus to infinity . That is ok since my 20mm Pentax XW's with 70 deg AFOV and 20mm eye relief do.  But it looks like it will be a week before we get clear skies in the NE. 
BTW the 26.05mm Oberwerk eyepieces that come with the BT-80 45 have the same AFOV as my pair of 26mm Meade 4000 Super Plossl's (50-52deg) and that compares to my pair 26mm Meade 5000's that have 60 deg AFOV that work great with it.
Joe
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Pentax PF-80ED,Meade 102ED APO,Orion EON 72,120ST
Apex 127,C6 XLT,CR150,C9.25,XT10 ,Celestron Regal 100 F-ED, CT152
Zeiss 7x42 FL,Canon 10x42L IS WP,15x50 IS
12x36 IS II , Pentax 8x32 ED
Garrett Optical 28x110 HD-WP Signature Series
Oberwerk BT-80 45, Apogee RA-88-SA
Denk II Power x Switch binoviewer w/13mm Ethos, 20mm Pentax XW's, 20mm Widescan III's.
21mm Ethos,17mm Ethos, 22mm Nagler, 40mm Pentax XW, 14mm Pentax XL, 5.2mm Pentax XL, 8-24mm Pentax XL Zoom, 31mm Axiom LX
Member #17
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Bob W6PU
Carpal Tunnel
Reged: 12/23/04
Posts: 2278
Loc: Springer-N.E.NM
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It looks beautifull, good luck with it Joe!
Bob in NM
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Joe Ogiba
Postmaster
Reged: 02/14/02
Posts: 5446
Loc: NJ USA
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Thanks Bob, I wish I had the great night skies that you get in NM.
Joe
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Pentax PF-80ED,Meade 102ED APO,Orion EON 72,120ST
Apex 127,C6 XLT,CR150,C9.25,XT10 ,Celestron Regal 100 F-ED, CT152
Zeiss 7x42 FL,Canon 10x42L IS WP,15x50 IS
12x36 IS II , Pentax 8x32 ED
Garrett Optical 28x110 HD-WP Signature Series
Oberwerk BT-80 45, Apogee RA-88-SA
Denk II Power x Switch binoviewer w/13mm Ethos, 20mm Pentax XW's, 20mm Widescan III's.
21mm Ethos,17mm Ethos, 22mm Nagler, 40mm Pentax XW, 14mm Pentax XL, 5.2mm Pentax XL, 8-24mm Pentax XL Zoom, 31mm Axiom LX
Member #17
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Glassthrower
Vendor - Galactic Stone & Ironworks
Reged: 04/07/05
Posts: 17931
Loc: Oort Cloud 9
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Joe -
Is there any way to determine in advance which eps will focus and which will not? Or is it a trial and error type of affair? You mention that the 20mm does not vignette, but what about a 25mm or perhaps a 30mm?
Clear dark skies...
MikeG
BTW - I ask because the BT-80 is almost within my price range and therefore I must examine it closely.
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Michael Gilmer - Member of the Meteoritical Society & Collector of Falling Stars.
☄ ⒼⒶⓁⒶⒸⓉⒾⒸ ⓈⓉⓄⓃⒺ ☞ www.galactic-stone.com
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Joe Ogiba
Postmaster
Reged: 02/14/02
Posts: 5446
Loc: NJ USA
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Mike,
The 20mm Widescan III's (84* AFOV) have the largest fieldstop of all my 1.25" eyepieces so there is no vignetting problem with the BT-80 45. The problem with the 20mm Widescan III is it needs alot of in-travel to reach infinity focus and it does not with the BT-80 45. The 20mm Widescan III have a wider TFOV than the 24mm Panoptic or my 40mm Plossl's that I also tried.
Any 1.25" eyepieces should reach infinty focus unless it's a special one like the 20mm Widescan III that requires extra in-travel.
Joe
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Pentax PF-80ED,Meade 102ED APO,Orion EON 72,120ST
Apex 127,C6 XLT,CR150,C9.25,XT10 ,Celestron Regal 100 F-ED, CT152
Zeiss 7x42 FL,Canon 10x42L IS WP,15x50 IS
12x36 IS II , Pentax 8x32 ED
Garrett Optical 28x110 HD-WP Signature Series
Oberwerk BT-80 45, Apogee RA-88-SA
Denk II Power x Switch binoviewer w/13mm Ethos, 20mm Pentax XW's, 20mm Widescan III's.
21mm Ethos,17mm Ethos, 22mm Nagler, 40mm Pentax XW, 14mm Pentax XL, 5.2mm Pentax XL, 8-24mm Pentax XL Zoom, 31mm Axiom LX
Member #17
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ZX12
super member
Reged: 12/29/05
Posts: 156
Loc: Rhode Island
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Hi Joe,
I've experimented with a number of wide field e.p.'s in both my BT 100/45 and Vixen BT125 and had the same problem that you describe with your BT 80's. The BT 100 has more focus travel than the Vixen, but neither could reach focus with any KK widescan that I tried. TV Nagler's came very close to focusing in the BT 100, but bottomed out just shy of it.
Ultimately I found that TV Radian's are the best performing e.p.'s overall. My 24mm Panoptics seem to have more flaring visible on bright objects, but with the addition of a minus violet filter they look nearly as good as the Radians.
If I was to pick one eyepiece as my overall favorite it would be the 18mm Radian. It has the sharpest stars, good TFOV, and excellent eye relief. I did have to machine off about 2mm's from the barrel to allow it to drop deeper in the Vixen.
For high power viewing, Vixen Lanthanum's have been fantastic. Also my TV 8-24mm zoom gets much use due to its good performance combined with a convenient power range to pull in some detail.
Clear Skies, Mike
--------------------
AP 160 Starfire/AP 1200GTO
Stellarvue SV809D
Kowa Highlander Prominar
Vixen BT 125 HFT-MA
Oberwerk BT 100/45
Tak 22x60 Astronomer
Nikon 10x70 FMT-SX
Leica 8-12x42 Duovid
WO 66mm SD
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Joe Ogiba
Postmaster
Reged: 02/14/02
Posts: 5446
Loc: NJ USA
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Hi Mike,
My favorite 26mm that will reach infinity focus and have maximum TFOV in the BT-80 45 are the 26mm Meade 5000's after I removed the rubber eyeguard's and metal inner sleeves that turned them into great bino eyepieces with 60 deg AFOV and 19mm eye relief. The 26mm Oberwerk eyepieces that ship with the BT-80's have the same 50-52 deg AFOV as my pair of 26mm Meade 4000 SP's.
I wonder if the Orion Stratus series of eyepieces that have 68 deg AFOV and 20mm eye relief would reach infinty focus in the BT's ?
Joe
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Pentax PF-80ED,Meade 102ED APO,Orion EON 72,120ST
Apex 127,C6 XLT,CR150,C9.25,XT10 ,Celestron Regal 100 F-ED, CT152
Zeiss 7x42 FL,Canon 10x42L IS WP,15x50 IS
12x36 IS II , Pentax 8x32 ED
Garrett Optical 28x110 HD-WP Signature Series
Oberwerk BT-80 45, Apogee RA-88-SA
Denk II Power x Switch binoviewer w/13mm Ethos, 20mm Pentax XW's, 20mm Widescan III's.
21mm Ethos,17mm Ethos, 22mm Nagler, 40mm Pentax XW, 14mm Pentax XL, 5.2mm Pentax XL, 8-24mm Pentax XL Zoom, 31mm Axiom LX
Member #17
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ZX12
super member
Reged: 12/29/05
Posts: 156
Loc: Rhode Island
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Hi Joe,
That's a good question. I have been looking at the Stratus series for my BT100. The eyepiece sheet that came with my Vixen's said that the Lanthanum Superwide series (similar to the Stratus) works in the BT125. From what I've tried so far, the Oberwerk has greater focus range than the Vixen so they should work.
I'm looking at trying the 22mm LVW, which will be 34.5x and 1.88 TFOV in the 125's.
It seems that the depth from the end of the e.p.'s barrel to the surface of the lower lens assembly determines whether there is enough focus range. Too deep and you run out of in focus, too shallow, not enough out focus. The KK Widescans had the most barrel depth that I've seen on any eyepiece. My 24 Pan's are on the opposite end of the travel range so they accept filters and have plenty of in focus.
Of course, all this is from my machinist's point of view, and I understand that there is more to the problem of making the wider field e.p.'s work in these giant binoculars.
After last night's observing session with the BT 125, I was again impressed with the 18mm Radian and it's sharpness across the field. This gives me 42x with a 1.4 TFOV. I spent at least an hour scanning the Milky Way and couldn't ask for a more spectacular view.
Mike
--------------------
AP 160 Starfire/AP 1200GTO
Stellarvue SV809D
Kowa Highlander Prominar
Vixen BT 125 HFT-MA
Oberwerk BT 100/45
Tak 22x60 Astronomer
Nikon 10x70 FMT-SX
Leica 8-12x42 Duovid
WO 66mm SD
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Joe Ogiba
Postmaster
Reged: 02/14/02
Posts: 5446
Loc: NJ USA
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Mike,
Another eyepiece I am looking at is the 18mm UWA Meade 5000's that have 82 deg AFOV and 17mm eye relief that would also need to be stripped of it's eyeguard system for bino use. I had the 16mm Nagler T5's but they had only 10mm eye relief and I did not see anymore than 70 deg AFOV when used in my binoviewer.
I also wish there was a 28mm with 55 deg AFOV and 20mm eye relief like the old Pentax XL but smaller for bino use.
Joe
--------------------
Pentax PF-80ED,Meade 102ED APO,Orion EON 72,120ST
Apex 127,C6 XLT,CR150,C9.25,XT10 ,Celestron Regal 100 F-ED, CT152
Zeiss 7x42 FL,Canon 10x42L IS WP,15x50 IS
12x36 IS II , Pentax 8x32 ED
Garrett Optical 28x110 HD-WP Signature Series
Oberwerk BT-80 45, Apogee RA-88-SA
Denk II Power x Switch binoviewer w/13mm Ethos, 20mm Pentax XW's, 20mm Widescan III's.
21mm Ethos,17mm Ethos, 22mm Nagler, 40mm Pentax XW, 14mm Pentax XL, 5.2mm Pentax XL, 8-24mm Pentax XL Zoom, 31mm Axiom LX
Member #17
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Joe Ogiba
Postmaster
Reged: 02/14/02
Posts: 5446
Loc: NJ USA
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Here are photos of the 26mm Meade 5000 Plossl's that have 60 deg AFOV before and after removing the eyeguard system for use in my Denk II and Oberwerk BT-80 45.
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Pentax PF-80ED,Meade 102ED APO,Orion EON 72,120ST
Apex 127,C6 XLT,CR150,C9.25,XT10 ,Celestron Regal 100 F-ED, CT152
Zeiss 7x42 FL,Canon 10x42L IS WP,15x50 IS
12x36 IS II , Pentax 8x32 ED
Garrett Optical 28x110 HD-WP Signature Series
Oberwerk BT-80 45, Apogee RA-88-SA
Denk II Power x Switch binoviewer w/13mm Ethos, 20mm Pentax XW's, 20mm Widescan III's.
21mm Ethos,17mm Ethos, 22mm Nagler, 40mm Pentax XW, 14mm Pentax XL, 5.2mm Pentax XL, 8-24mm Pentax XL Zoom, 31mm Axiom LX
Member #17
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ZX12
super member
Reged: 12/29/05
Posts: 156
Loc: Rhode Island
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Hi Joe,
I'm amazed at how thick the eyeguard is on the Meade 5000 series. I'm assuming that the IPD was not close enough with it in place. How do the 26mm's look for sharpness across the field?
The 18 UWA sounds like it would be fantastic if it comes to focus. Do you know anybody that would let you borrow one to find out? I would be interested to hear the results.
Mike
--------------------
AP 160 Starfire/AP 1200GTO
Stellarvue SV809D
Kowa Highlander Prominar
Vixen BT 125 HFT-MA
Oberwerk BT 100/45
Tak 22x60 Astronomer
Nikon 10x70 FMT-SX
Leica 8-12x42 Duovid
WO 66mm SD
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Joe Ogiba
Postmaster
Reged: 02/14/02
Posts: 5446
Loc: NJ USA
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Mike,
I just compared the 26mm 5000's to the 26mm 4000 SP's that have only 50-52 deg AFOV in the BT-80 45's in daylight and the 4000's are sharp in the center 40 deg AFOV with the last 5 deg at each edge not sharp. The 5000's have about the same 40 deg center AFOV sharp and the last 10 deg at each edge not sharp. So they show about the same amount of sharpness in the center but less sharpness at the edge than a normal 50 deg AFOV Plossl. For daytime use they are great since they give a very bright view and long eye relief. It has been overcast every night since I received the BT-80's but maybe tonight it might clear up.
The 18mm Meade 5000 UWA's look even larger than the 26mm 5000 Plossl's so they would also need the same mods to use in a binoviewer or BT. Meade specs say the 5000 series are parfocal so they should come to infinity focus in my BT-80 at least. I will purchase one when I catch up with my recent charges. 
Joe
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Joe Ogiba
Postmaster
Reged: 02/14/02
Posts: 5446
Loc: NJ USA
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Photo of BT-80 45 with 26mm Meade 5000 Plossl's.
--------------------
Pentax PF-80ED,Meade 102ED APO,Orion EON 72,120ST
Apex 127,C6 XLT,CR150,C9.25,XT10 ,Celestron Regal 100 F-ED, CT152
Zeiss 7x42 FL,Canon 10x42L IS WP,15x50 IS
12x36 IS II , Pentax 8x32 ED
Garrett Optical 28x110 HD-WP Signature Series
Oberwerk BT-80 45, Apogee RA-88-SA
Denk II Power x Switch binoviewer w/13mm Ethos, 20mm Pentax XW's, 20mm Widescan III's.
21mm Ethos,17mm Ethos, 22mm Nagler, 40mm Pentax XW, 14mm Pentax XL, 5.2mm Pentax XL, 8-24mm Pentax XL Zoom, 31mm Axiom LX
Member #17
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ZX12
super member
Reged: 12/29/05
Posts: 156
Loc: Rhode Island
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Hi Joe,
Nice setup. Much lighter than the BT100 I imagine. The Oberwerks are probably the best buy in bino telescopes right now. I'll have to get a hold of a pair of the new 5000 series to try in my own binos.
Have you tried higher magnifications to see how well they hold up? My BT100/45 was great up to 60x, but started to show a slight doubling of the image at 75x. Beyond that the image breakdown was significant enough not to push it any higher. Best power range is from 25x to 50x.
--------------------
AP 160 Starfire/AP 1200GTO
Stellarvue SV809D
Kowa Highlander Prominar
Vixen BT 125 HFT-MA
Oberwerk BT 100/45
Tak 22x60 Astronomer
Nikon 10x70 FMT-SX
Leica 8-12x42 Duovid
WO 66mm SD
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Joe Ogiba
Postmaster
Reged: 02/14/02
Posts: 5446
Loc: NJ USA
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Mike,
I have over ten pairs of eyepieces from 20mm to 40mm because my dual arm Denk II has up to a 6x multiplication when using a 3x Denk multiplier with 2x power x switch setting. But I plan on getting some eyepiece pairs between 12mm and 18mm. I guess the BT-80 is only 26x with 20mm eyepieces if the FL is 520mm. I have 32x eypieces for my Apogee RA-88-SA's and use my Denk II with my scopes for anything higher than 32x. If 25x to 50x is best for the BT-100's then I guess 20x to 40x would be best for the BT-80's and that would be 26mm to 13mm eyepieces. Hmmm, 13mm Nagler T6's might work. 
Joe
--------------------
Pentax PF-80ED,Meade 102ED APO,Orion EON 72,120ST
Apex 127,C6 XLT,CR150,C9.25,XT10 ,Celestron Regal 100 F-ED, CT152
Zeiss 7x42 FL,Canon 10x42L IS WP,15x50 IS
12x36 IS II , Pentax 8x32 ED
Garrett Optical 28x110 HD-WP Signature Series
Oberwerk BT-80 45, Apogee RA-88-SA
Denk II Power x Switch binoviewer w/13mm Ethos, 20mm Pentax XW's, 20mm Widescan III's.
21mm Ethos,17mm Ethos, 22mm Nagler, 40mm Pentax XW, 14mm Pentax XL, 5.2mm Pentax XL, 8-24mm Pentax XL Zoom, 31mm Axiom LX
Member #17
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ZX12
super member
Reged: 12/29/05
Posts: 156
Loc: Rhode Island
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Hi Joe,
I have tried the 7mm and 11mm Naglers in the BT 100. The 7mm doesn't even come close to focus, but the 11 is focused just as it runs out of travel. My guess is that the 13mm might be even better. It would be a great combo if it works. Might have to look from side to side to get it all in though.
Clear skies, Mike
--------------------
AP 160 Starfire/AP 1200GTO
Stellarvue SV809D
Kowa Highlander Prominar
Vixen BT 125 HFT-MA
Oberwerk BT 100/45
Tak 22x60 Astronomer
Nikon 10x70 FMT-SX
Leica 8-12x42 Duovid
WO 66mm SD
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Rick
Post Laureate
Reged: 04/12/05
Posts: 3285
Loc: Tokyo, Japan
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I have the 7,9 and 13mm Nagaler T6. The 13mm has a slightly longer barrel than others in the TV "B" parfocal group. If the eyepiece holder has a retaining ring in the bottom to prevent the barrel from touching the prism it will need more infocus travel than the 7mm.
clear skies,
Rick
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ZX12
super member
Reged: 12/29/05
Posts: 156
Loc: Rhode Island
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Hi Rick,
How deep is the lens assembly inside the barrel of the 13mm as compared to the 7mm and 9mm?
Mike
--------------------
AP 160 Starfire/AP 1200GTO
Stellarvue SV809D
Kowa Highlander Prominar
Vixen BT 125 HFT-MA
Oberwerk BT 100/45
Tak 22x60 Astronomer
Nikon 10x70 FMT-SX
Leica 8-12x42 Duovid
WO 66mm SD
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Rick
Post Laureate
Reged: 04/12/05
Posts: 3285
Loc: Tokyo, Japan
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The 7mm and 9mm both have 30mm long barrels. The 13mm is 33mm long.
-Rick
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Joe Ogiba
Postmaster
Reged: 02/14/02
Posts: 5446
Loc: NJ USA
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Hi Mike,
I might try a 18mm Meade UWA first since I would also like to use it in my Pentax PF-80ED spotting scope. It should also not have much vignetting with my Denk II with .66x focal reducer StarSweeper mode in my C9.25. I think the 13mm Nagler T6 would work better in the BT100's with their shorter FL that I think is in the F5+ range vs F6+ range of the BT80's.
Joe
--------------------
Pentax PF-80ED,Meade 102ED APO,Orion EON 72,120ST
Apex 127,C6 XLT,CR150,C9.25,XT10 ,Celestron Regal 100 F-ED, CT152
Zeiss 7x42 FL,Canon 10x42L IS WP,15x50 IS
12x36 IS II , Pentax 8x32 ED
Garrett Optical 28x110 HD-WP Signature Series
Oberwerk BT-80 45, Apogee RA-88-SA
Denk II Power x Switch binoviewer w/13mm Ethos, 20mm Pentax XW's, 20mm Widescan III's.
21mm Ethos,17mm Ethos, 22mm Nagler, 40mm Pentax XW, 14mm Pentax XL, 5.2mm Pentax XL, 8-24mm Pentax XL Zoom, 31mm Axiom LX
Member #17
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