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Garrett Gemini 20x80 UL Review

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#1 chgomonitor

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Posted 20 September 2008 - 06:40 AM

Gemini 20x80 Ultra Light Review

http://www.garrettop...uctCode=G2080UL

I’ve been an avid sky watcher for about 38 years, since I was a kid. Sadly, almost all that time from within the intensely light and air polluted skies of Chicago. I also do plane spotting, Lake Michigan watching, satellite observations and some nature work. About 12 years ago we moved out to the near northwest suburbs, where light pollution from suburban housing developments promptly followed. I’ve owned a couple of half-way decent 60mm refractors and several very cheap binoculars including 7x50’s, 10x50’s and 20x50’s.

For those lucky enough to live in dark regions, let me give me you some idea of how bad it is here. Today, on an average night in the center of downtown Chicago limiting magnitude isn’t a problem, because you can’t really see any stars. You are lucky to spot the bright planets. Out in the residential areas on the fringes of the city on a good night limiting magnitude is around 3 or less. My suburban back yard on a good night hovers around 4.0.

Actually, one of the most useful devices I ever found was a pair of very short (fast) non-prismatic binoculars with light weight glass lenses (independent focus) mounted on a sturdy black eye glasses frame. I think it was 2.8x28mm. That was 25 years ago and I can’t recall the manufacturer or find them on the web. Those usually got me down to around magnitude 5.0. You should also know that my vision is none too good. I’m very nearsighted and with age 50 fast approaching I’ve also now developed some fairly bad astigmatism.

My favorite objects are nebulae and galaxies, but local conditions are highly prohibitive for these activities. As a result most of my observations center around the moon, planets, a few good clusters and some double star work. I’ve always had aperture fever, but traditionally it has been very difficult to justify the cost because of the local seeing conditions. Early in my hobby I always kept an eye out for the then popular military surplus big binoculars, but whenever I found a set available cash was short. (I have also considered a bigger refractor).

Over the last few years my interest waned a bit, due to both time commitments and the rotten local conditions. But recently I’ve got back into casual and event based sky watching. I was very pleasantly surprised when I discovered how much the prices on larger binoculars had dropped. And so many choices…

I found the big binocular reviews in the cloudynight forums to be both a great starting place in choosing a pair and for whittling down my final selections. My thanks to the good people who operate this great astronomy resource.

I was originally interested in 25x100’s or even larger models, but I really wanted something I could also use hand held for short periods of time. (Having used 20x50’s I was familiar with the “shake” factor, too!). I ended up being quite concerned with the percentage of 20x80’s which were being returned due to collimation errors and shipping damage problems.

I know the tradition in astronomy binoculars is a 7mm exit pupil, but I seriously doubt that my pupils open up to even 5mm anymore, and you never really get fully dark adapted in skies this bright, anyway.

Something else which concerned me was that in the past few years I’d been shown a number of 10x50’s and 16x70’s, (both cheap and high end models) which exhibited what I personally judge to be “over coating”. These had dark green or dark orange coatings which were obviously thick enough to cause a visible color cast in their images - I didn’t care for that at all.

So after much web based research I finally settled on a pair of Gemini 20x80 Ultra Light Weights from Garrett Optical. Garret seemed to have a very, very low return rate on their 20x80’s and this model was amongst the lightest around. I also liked the very reasonable price and their freebies which included a great neck strap, decent looking case, lens pen cleaner and a very study looking (all metal) L tripod mounting bracket.

I ordered from the web and they arrived via Fedex in only 2.5 days, impressive. Very sturdy double box packing heavily padded with both peanuts and air cell plastic. Zero apparent shipping damage and a complete order.

I’m no coatings expert and I can’t judge to what extent this particular model may be fully multi-coated. But I do like the light blue-green coating which doesn’t appear to be overly applied. I can spot no sign of any light baffles near the objective lenses which would have the effect of reducing their appeture. The insides look reasonably black to me. The outsides have a thin but sturdy feeling rubber coating. This model lacks a center tripod mounting bar bracket in order to conserve weight. It uses a screw thread hole located at the front face of the center focuser assembly instead. (This point is well back from the center of gravity, however - rendering them quite front heavy when mounted).

The center focuser has a smooth action and seems very sturdy, almost a bit stiff. Its knob is deeply knurled and there is no back lash that I can detect. The right eye diopter adjustment has a wide range, a calibration dot and is also a bit stiff but also very smooth. When last checked my left eye was 20/400 and my right eye was 20/300 and there is ample focus adjustment room for even me. The eyepieces have fairly deep, stiff and sturdy fold-down rubber eye cups. I like the fact that when folded down they are still about one-eighth inch extended which gives protection to the surfaces of my eye glass lenses when I chose to observe glasses-on. I haven’t measured the IPD adjustment but it seems ample and again on the stiff side, which I like. Overall, the mechanical and optical assemblies seem very sturdy.

At just under four pounds handheld use for me is still practical in five minute sessions for an hour or two. I have tried mounting them on a very cheap monopod and that worked out quite well. Somewhere around here I have a cheap tripod, I have to find it. Garrett’s neck strap is very, very comfortable. The knob on the tripod L bracket adaptor is rubber coated but I don’t have enough finger strength to fully tighten it down. The large black nylon carry bag is of double box type construction and would appear to offer a good degree of protection. It does fit rather tightly and did not come with a shoulder strap. Garrett offers a hard case as an option.

Optically, these obviously aren’t Fujinons or Steiners but I’m suitably impressed. A long term user of cheaper optics I’m by no means a color aberration snob, but these seem pretty darn good CA-wise to me. I can see some well defined but very small CA with Vega in center of the field but very little if any on the moon’s edges. The field remains flat and decently sharp out to about the last fifteen percent or so where it quickly drops off. In terms of collimation they appear perfect to me. Close visual inspection revealed no visible defects in lens surfaces anywhere. Better performance would almost certainly mean at least one more objective lens element in each tube and unacceptable added weight.

While not a real test object I am able to fully split and resolve Alberio in Cygnus (34 arc seconds). Its beautiful blue and yellow colors are very well presented. Jupiter shows a clean little disk with just a suggestion of belt detail and it’s Gallilean moons are quite dramatic. I can quite easily spot the main central peak of the Copernicus crater on the Moon and there is a hint of at least 3 divisions at its apex. The Pleiades are very glorious and are fairly well framed within the field. Even with my rotten local conditions and a nearby bright moon out I am able to clearly see the real nebulosity present in the Orion nebula. I like the slightly high contrast view these binoculars offer as they help reduce my awful local sky glow. (They aren’t super-bright like many faster 7x50’s I’ve tried, but my estimate would probably differ in much darker skies).

These binoculars would profit from dew cap tubes, which they lack almost entirely. Not only for dew protection but this would also help reduce reflection artifacts from bright, nearby off-axis objects - which they aren’t fully free from. The eyepieces use a single, large rubber cap piece and the objectives have individual snap-in style soft rubber covers. I prefer the snap over design for both.

Overall I am extremely satisfied with these binoculars and would recommend them to anyone looking for inexpensive (?) 20x80’s. I had no problems ordering from Garrett and would do so again.

Tech Specs from the Garrett web page:

GEMINI 20x80 UL
20x80mm f/4.1; 2 Elements, 1 Group
Eyepieces: 4 Elements, 3 Groups
Eye Relief: 16mm useable (17mm total)
Exit Pupil: 4.0mm
True field of view: 3.0º (158 ft./1000 yds.)
Weight: 3 lbs., 15.75 oz.
Length: 12.5-in. (Case about 14 Inches tall)
Minimum focus: 25 meters
IPD: 57-72mm
Fully Broadband Multi-Coated
Transmission: 99.0%-99.7% per surface; >85% total
2-year limited warranty

Happy Sky Scanning! - Ted

#2 Alby

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Posted 20 September 2008 - 07:15 AM

Well done and welcome to CN.

#3 hallelujah

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Posted 20 September 2008 - 07:32 AM

My favorite objects are nebulae and galaxies, but local conditions are highly prohibitive for these activities.

Happy Sky Scanning! - Ted


Same here in the northern suburbs of Denver, although probably no where near as bad as yours.

Thanks for sharing and welcome aboard.

Stan

#4 EdZ

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Posted 20 September 2008 - 07:50 AM

Nice first impressions. thanks

I can spot no sign of any light baffles near the objective lenses which would have the effect of reducing their appeture.


Typically, there are no aperture reducing baffles anywhere near the aperture. Aperture reduction is generally caused by the deep baffle just before the prisms housing, or it is caused by the prism housing itself.

edz

#5 vincentdsnt

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Posted 21 September 2008 - 10:19 AM

chgomonitor, Thank you for your review.

I have a question about the two different Garret models,I can not decide between the UL and WL,in the case of the WL there is a aluminum center-bracket that also centers the weight front to back, and connects the front tubes solid together (is this a good thing?),all the the cost of weight and I guess other points unknown to me. Could I get some pros and cons on the two different mounting types on the UL / WL.
Thank you
Vincent

#6 chgomonitor

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Posted 21 September 2008 - 11:10 AM

Nice first impressions. thanks

I can spot no sign of any light baffles near the objective lenses which would have the effect of reducing their appeture.


Typically, there are no aperture reducing baffles anywhere near the aperture. Aperture reduction is generally caused by the deep baffle just before the prisms housing, or it is caused by the prism housing itself.

edz


Well yes, that is interesting. I can see one baffle down deep in the tube just in front of prism housing. It's hole is surprisingly large. Both of my 60mm refractors had similar baffles in their tubes as well. These play an important role in reducing stray (mostly off-axis) reflections. But I'm not quite sure I would agree with an assertion that these effectively reduce aperture. They are usually engineered so that the light cone's diameter is slightly smaller than their inside hole as it passes through at that point downstream, so to speak. I don't know how one would even measure the baffle's opening without extensive dis-assembly of the optical tube >AND< have an optical engineering diagram or otherwise be able to calculate the diameter of the light cone that deep in the tube. Am I missing something? Is there another way to test to see if the baffle is actually obstructing the light cone? Actually, I wish these had another baffle or two, as off-axis reflections is about the only (slight and common) optical fault I could find with these puppies. Your thoughts? very curious now...

#7 chgomonitor

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Posted 21 September 2008 - 11:27 AM

chgomonitor, Thank you for your review.

I have a question about the two different Garret models,I can not decide between the UL and WL,in the case of the WL there is a aluminum center-bracket that also centers the weight front to back, and connects the front tubes solid together (is this a good thing?),all the the cost of weight and I guess other points unknown to me. Could I get some pros and cons on the two different mounting types on the UL / WL.
Thank you
Vincent


That is a great question. I was concerned about rigidity of the design, and it seemed to me the center bracket would add considerable strength to the overall layout. But I can tell you, the UL's are very, very sturdy as they are and I don't plan on banging them around too much anyway, LOL.

Where I can see the center bracket being very useful is if you can slide the vertical tube which attaches to the tripod back and forth down the length of the horizontal center pipe in order to match center of gravity. That could give you a much, much smoother action on a tripod head or other mount. And I can tell you the UL's at least are very front heavy. On the UL the screw hole for attaching the the top of the "L" bracket is located right at the front end of the focuser assemble (behind a little pop-off cap - drove me nuts!). That point is far, far behind the center of gravity, leaving them very, very front heavy on the tripod. BUT - I don't know if the other model with the built in bracket lets you slide the vertical mounting tube down it's length or if it is fixed in position. Make sense?

Personally (and I'm a nut - I don't recommend this, actually) I wanted to be able to use 20x80's hand held for brief periods. I had considered the other model but the weight savings provided in the UL by their not having the center bracket was a big deciding factor for me in choosing this particular model. Choosing a model is a very personal decision, taking in many different factors. For me, weight is/was a biggie.

Actually, you should probably give Garrett Optical a call and discuss the differences and inherent features with them. They will know more about the details than I do. I've heard they are very helpful.

And yes, they are BIG. Everyone who sees them always says; "Whoa, those are HUGE!" Too funny...

Happy Sky Scanning! - Ted

#8 CESDewar

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Posted 22 September 2008 - 10:41 PM

Thanks Ted - a very nice "first impression" review that helps us gauge what our reaction would be if we were to have a pair of these binoculars ourselves.

I agree that these can be usefully handheld (as long as one reminds readers that image stability is definitely compromised at this magnification). Resolution may be questionable handheld at this mag, but the fact remains that for catching faint objects, it indeed does work!






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