Mr. Bill
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Reged: 02/09/05
Loc: Northeastern Cal
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Re: MrBill's review of Gemini 25x100 IF MkII binos
[Re: Mr. Bill]
#5222160 - 05/14/12 03:34 PM
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Did my due diligence on these...unfortunately, I cannot recommend these because of the above problems and also because of off axis distortion and rapid decline of field illumination from on axis. I finally had a decent night with good seeing and fair transparency to evaluate what I bought them for....MW observing.
The on axis images are quite sharp...I cleanly split Beta Scorpius a pretty double with a 13.6 arc second separation.
However, things rapidly turn bad at about 20% out from center and by 50% the image is suffering from coma that becomes a smear at the edge of the field. Coma is a big problem with these...the 20x80 version does much better, perhaps due to the triplet objectives.
Reluctantly, I have requested a return authorization for refund from Garrett. I was really hoping these would fill the bill for Australia.
I guess it will be the Oberwerk 20x80s and my 120mm f/5 refractor going with me on that trip.
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Zdee
Carpal Tunnel
Reged: 09/20/10
Loc: North Carolina, USA
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Re: MrBill's review of Gemini 25x100 IF MkII binos
[Re: Mr. Bill]
#5222195 - 05/14/12 03:46 PM
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Sorry to hear that, Bill. I think we all had high hopes for these. 
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daniel_h
Carpal Tunnel
Reged: 03/08/08
Loc: VIC, Australia
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Re: MrBill's review of Gemini 25x100 IF MkII binos
[Re: Zdee]
#5222305 - 05/14/12 04:46 PM
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That's a bugger, beta Scorpio is a nice dbl, I look fr it in my clubs 20" when i Use it in Melb
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Mr. Bill
Postmaster
Reged: 02/09/05
Loc: Northeastern Cal
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Re: MrBill's review of Gemini 25x100 IF MkII binos
[Re: daniel_h]
#5222315 - 05/14/12 04:52 PM
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Daniel
OT.....do you have a copy of The Night Sky Observer's Guide Vol3 The Southern Skies?
Highly recommend and am "boning up" on your wonderful night sky sights getting ready for my trip.
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Gordon Rayner
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Reged: 03/24/07
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Re: MrBill's review of Gemini 25x100 IF MkII binos
[Re: Mr. Bill]
#5222371 - 05/14/12 05:26 PM
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Have you seen the article,with beautiful star photos , in the current issue of Astromomy magazine about the trips of four well-off Israelis to a well-equipped astronomy resort in Namibia?
A neighbor just returned from South Africa, in whose army he has served, confirms the quality of Namibian night skies.
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Mr. Bill
Postmaster
Reged: 02/09/05
Loc: Northeastern Cal
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Re: MrBill's review of Gemini 25x100 IF MkII binos
[Re: Gordon Rayner]
#5222391 - 05/14/12 05:37 PM
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Gordon
Sounds interesting, but the wife has her heart set on other stuff besides astronomy, and I've always wanted to see the Outback being an ol' desert rat.
Also, I'm looking forward to some world class fly fishing in New Zealand.
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DarkDisplay
super member
Reged: 12/21/10
Loc: Texas
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Re: MrBill's review of Gemini 25x100 IF MkII binos
[Re: Gordon Rayner]
#5222420 - 05/14/12 05:56 PM
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Odd. I've got these very same 25x100's (Garrett MKII) and the views of the moon, star clusters, etc. are very nice. No problems. Of course, any bino might have a defect.
- Frank
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Mr. Bill
Postmaster
Reged: 02/09/05
Loc: Northeastern Cal
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Re: MrBill's review of Gemini 25x100 IF MkII binos
[Re: DarkDisplay]
#5222439 - 05/14/12 06:00 PM
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Just my opinion...YMMV, etc.
This is not an individual sample defect...I hold optics to a high standard, as the folks in this forum know.
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GlennLeDrew
Postmaster
Reged: 06/18/08
Loc: Ottawa, Ontario, Canada
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Re: MrBill's review of Gemini 25x100 IF MkII binos
[Re: DarkDisplay]
#5222445 - 05/14/12 06:03 PM
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Bill,
Is what you describe as coma really eyepiece-induced astigmatism?
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Mr. Bill
Postmaster
Reged: 02/09/05
Loc: Northeastern Cal
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Re: MrBill's review of Gemini 25x100 IF MkII binos
[Re: GlennLeDrew]
#5222470 - 05/14/12 06:24 PM
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Could be....comet head pointed toward center, tail radially toward fieldstop.
Whatever it is, it's nasty!
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daniel_h
Carpal Tunnel
Reged: 03/08/08
Loc: VIC, Australia
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Re: MrBill's review of Gemini 25x100 IF MkII binos
[Re: Mr. Bill]
#5222836 - 05/14/12 11:16 PM
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Bill i don't have a copy but the astro society library does - if you get to Melb ill show you the tarantula thru the Club's 20"
i will test my pair for dbl separation if the sky clears - who can do the sums what the resolvable separation should be? i was thinking 10 arc sec
Edited by daniel_h (05/14/12 11:19 PM)
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RichD
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Reged: 11/08/07
Loc: Derbyshire, UK
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Re: MrBill's review of Gemini 25x100 IF MkII binos
[Re: daniel_h]
#5223085 - 05/15/12 06:04 AM
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Shame, looks like the chinese have a way to go yet. I don't use my Garrett 30x100s anything like as much as I used to due to so so optical quality (especially after several years of using fujinons). However I thought maybe they had improved the design by now.
Good things cost money and I suspect that $400 for two 4" refractors plus prisms, plus mechanical connection etc is just not enough outlay to do it right.
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Mr. Bill
Postmaster
Reged: 02/09/05
Loc: Northeastern Cal
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Re: MrBill's review of Gemini 25x100 IF MkII binos
[Re: GlennLeDrew]
#5223345 - 05/15/12 11:03 AM
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Quote:
Bill,
Is what you describe as coma really eyepiece-induced astigmatism?
IMO, eyepiece design and quality is the main thing still lacking in Chinese binos. They seem to have their act together in coatings and fit and finish.
Wonder what they could do to improve this with an increase of $50-100 in pricepoint?
Garrett and BigBinocular, are you listening? I wonder how much they can change the basic BA10 design parameters....whether there are choices in eyepieces for these by vendors.
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GlennLeDrew
Postmaster
Reged: 06/18/08
Loc: Ottawa, Ontario, Canada
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Re: MrBill's review of Gemini 25x100 IF MkII binos
[Re: Mr. Bill]
#5223604 - 05/15/12 02:03 PM
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Indeed, the eyepiece is as important a part of the system as the objective. At about f/4, and for larger than around 45-50 degrees apparent, a minimum of five elements should be employed, and the design optimized for the specific objective's field curvature and aberrations.
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Mr. Bill
Postmaster
Reged: 02/09/05
Loc: Northeastern Cal
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Re: MrBill's review of Gemini 25x100 IF MkII binos
[Re: GlennLeDrew]
#5223661 - 05/15/12 02:30 PM
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Well, the Garrett website makes a big deal out of 5 element eps and f/4.65 objectives that give better center sharpness and edge correction than previous model.
One of the reasons I bought them....gotcha! I still fall for marketing hype, but OTOH who knows until you try product.
I agree the on axis image is sharp, but I would hate to see what the previous model's off axis images look like if these are significently better.
Edited by Mr. Bill (05/15/12 02:33 PM)
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GlennLeDrew
Postmaster
Reged: 06/18/08
Loc: Ottawa, Ontario, Canada
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Re: MrBill's review of Gemini 25x100 IF MkII binos
[Re: Mr. Bill]
#5223742 - 05/15/12 03:11 PM
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As an example of serendipity. Years ago a friend had me modify a Japanese-made 15X80. It had the usual Kellner-like eyepiece with about 50 degree AFoV. Good on-axis, softening a fair bit toward the field edge. I adapted a pair of Meade 20mm 'Research Grade' Erfles, resulting in 14X. At the edge of the 65 degree apparent field stars were quite better than at the edge of the original eyepiece. The field curvature was largely accommodated for, which was probably the greatest benefit. That bino was NICE to view through!
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Mr. Bill
Postmaster
Reged: 02/09/05
Loc: Northeastern Cal
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Re: MrBill's review of Gemini 25x100 IF MkII binos
[Re: GlennLeDrew]
#5223765 - 05/15/12 03:26 PM
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Quote:
As an example of serendipity. Years ago a friend had me modify a Japanese-made 15X80. It had the usual Kellner-like eyepiece with about 50 degree AFoV. Good on-axis, softening a fair bit toward the field edge. I adapted a pair of Meade 20mm 'Research Grade' Erfles, resulting in 14X. At the edge of the 65 degree apparent field stars were quite better than at the edge of the original eyepiece. The field curvature was largely accommodated for, which was probably the greatest benefit. That bino was NICE to view through!
That dates you.. 
I had (still have) a Meade 20mm Research Grade Erfle....
I nicknamed it the "Awful Erfle."
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DarkDisplay
super member
Reged: 12/21/10
Loc: Texas
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Re: MrBill's review of Gemini 25x100 IF MkII binos
[Re: Mr. Bill]
#5224363 - 05/15/12 11:15 PM
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There are several reviews of the "previous model" 25x100 on the Garrett website. Also, you should find a lengthly one here on Cloudy Nights by Art Fritzson. I knew you'd be interested.
- Frank
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Mr. Bill
Postmaster
Reged: 02/09/05
Loc: Northeastern Cal
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Re: MrBill's review of Gemini 25x100 IF MkII binos
[Re: DarkDisplay]
#5224515 - 05/16/12 01:25 AM
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Just read the reviews on Garrett's website....guess I should have bought the "previous model."
Seriously, when is the last time you read a critical product review on a vendor's website?
I wrote Garrett of my findings....let's see if they show up.
That's why we have forums like this.
Edited by Mr. Bill (05/16/12 02:07 AM)
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Mr. Bill
Postmaster
Reged: 02/09/05
Loc: Northeastern Cal
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Re: MrBill's review of Gemini 25x100 IF MkII binos
[Re: Mr. Bill]
#5224948 - 05/16/12 11:32 AM
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Expanding on the question of objectivity in evaluation of binocular optics...
Given modern manufacturing practices with heavy emphasis in CNC machining, automated assembly and inspection techniques, etc. the variability between samples has been really tightened up and QC issues are much less than even 5 years ago.
When it comes to evaluation we now have several tools at hand to take subjectivity largely out of the equation.
Effective aperture flashlight test reveals vignetting issues quickly and reliably.
Field illumination profiles can be measured quantitativly using edz's laser technique.
Collimation can be quickly checked by using my one barrel focused/ other barrel defocused startest.
Actually when it comes to checking optics, you have a sample of two....each barrel can be seperately evaluated and compared to the other. If you see the same thing in both barrels, you can be reasonably assured that it is a true representation of the strengths and weakness of the optical design.
What is left to opinion is whether its satisfactory or not, is a good value, pleasant to use, ergonomics, etc.
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