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Equipment Discussions >> Binoculars

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contrailmaker
Pooh-Bah


Reged: 01/02/09

GBT 100/90 arrived
      #3694329 - 03/20/10 07:35 PM

Well, I know everybody has been waiting to hear about these.

Just received mine earlier today. Mounted them on the Orion versa-go and went on to look them up thoroughly. The main thing everybody wants to know first.

Looking from the eypiece side, three sides of the prism edges are clearly seen. Looking through my 25mm EPs they are also visible. The exit pupil shows only one cut-out at the very top that seems to cover perhaps less than 10% of the disk. Not bad.

I measured the objective lens diameter using the flashlight method and more directly using the measuring tape near the objectives, being carefull not to touch the lenses. Both came to 95mm. Rough measurement here, but definitely smaller than 100mm. So far, so good.

The left eyepiece holder was very hard to open to where the EPs would fit. I did not want to force anything so I just turned it to the stop and the eyepieces fit although very tightly. The problems came when I tried to focus the left side. All eyepieces would come more or less close to focus but the image was very distorted. I have never seen anything like this before on a scope. Same result with all EPs tried including the shipped EPs. Don't know if this is the result of the prisms shaken out of position during transport. Nothing seemed loose and no rattling sounds.

The right side worked flawlessly. Easily coming to sharp focus and no issues with the EP holder. The interpupilary distance adjustment seemed smooth and precise but the images were so disparate that I was only able to do a very rough collimation check. At 24x I could merge one sharp image with the other very blury image. No sense to continue from there.

Looking with a flashlight into the objectives, the inside of the tubes were nice and clean, but the objectives were not. Both had small but clearly visible coating blemishes and both had fingerprints on them.

What a drag. These are going back for replacement. I will give GO the chance to make it right. Stay tuned.

cm


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elwaine
Pooh-Bah


Reged: 06/18/06

Loc: Jupiter
Re: GBT 100/90 arrived new [Re: contrailmaker]
      #3694434 - 03/20/10 08:32 PM

CM, did they come with a certificate saying they had passed the 14 point inspection?

Larry

Edited by elwaine (03/20/10 08:33 PM)


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pcad
Carpal Tunnel
*****

Reged: 01/17/05

Loc: Connecticut
Re: GBT 100/90 arrived new [Re: elwaine]
      #3694494 - 03/20/10 09:09 PM

I had a similar experience with the first Apogee RA88SA I received. The second one wasn't perfect either, but was usable. Sorry to hear that you're having a similar experience.

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GlennLeDrew
Postmaster
*****

Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: GBT 100/90 arrived new [Re: pcad]
      #3694552 - 03/20/10 09:33 PM

I'd like to be a fly on the wall in the factory. Just how many corners are the assemblers required to cut in order to move product out the door in the minimal time?

I'm becoming increasingly convinced that while cheap scopes can be had with a reasonable degree of confidence, the chances of a satisfactory outcome scale as the inverse of the square of the number of objectives. (For the mathematically-challenged, two objectives result in a confidence factor 1/4 that for a cyclopean instrument.)


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Wes James
Postmaster
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Reged: 04/12/06

Re: GBT 100/90 arrived new [Re: GlennLeDrew]
      #3694742 - 03/20/10 11:07 PM

Very disappointing report. I'd be very unhappy. Really makes me distrust their 14 point inspection. And I'm very sorry to have to say that. It's just not getting any better, it seems. I will say that I had my 20x110's out tonight, and find them very enjoyable... and everyone who views through them are impressed. It's too bad the same can't be said for their 100mm 45/90* bino's.

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beachchairbill
Pooh-Bah


Reged: 11/06/08

Re: GBT 100/90 arrived new [Re: Wes James]
      #3694786 - 03/20/10 11:32 PM

Anyone have a list of the 14 points.

I have number 15 and it's the flashlight test and that's the one that shakes up the purchaser.

Kenny - have you started your inner list yet - eh.

Beachchairbill


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Photoner
professor emeritus


Reged: 12/06/06

Re: GBT 100/90 arrived new [Re: Wes James]
      #3694789 - 03/20/10 11:33 PM

The 14 points are not listed. My big GO's arrived with a total factory defect [mounting threads so fouled could not mount the unit to a tripod] and had to bounce back for repair (direct replacement was not offered) and then there was the recent post (above) on internal casting defect on another unit so we're up to 16 points needed at least.

Quote the raven

Edited by Photoner (03/20/10 11:45 PM)


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KennyJ
The British Flash
*****

Reged: 04/27/03

Loc: Lancashire UK
Re: GBT 100/90 arrived new [Re: Photoner]
      #3695033 - 03/21/10 04:50 AM

Sandycoastreclinerwill ,

Rest assured I am keeping tabs and remaining inert .

I am a wiser man this morning after breakfasting on these two threads -- and also a wider man -- following my belated birthday meal out last night !

Kenny


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Mr. Bill
Postmaster
*****

Reged: 02/09/05

Loc: Northeastern Cal
Re: GBT 100/90 arrived new [Re: KennyJ]
      #3695898 - 03/21/10 03:21 PM

Interesting the difference in the two reports of the effective aperture measurement using flashlight method. on the GTB100 90s...

This report of 95mm and a previous report of 80mm, certainly well beyond differences in measurement error.

The raytrace analysis that Glen and I discussed on the other thread "Anyone purchase the GTB 100/45 past six months" (and EdZ mentioned prior to that on the same thread) shows severe vignetting that would make the actual number closer to 80mm than 95mm.....



Edited by Mr. Bill (03/21/10 03:39 PM)


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Mr. Bill
Postmaster
*****

Reged: 02/09/05

Loc: Northeastern Cal
Re: GBT 100/90 arrived new [Re: GlennLeDrew]
      #3695906 - 03/21/10 03:25 PM

Quote:

I'd like to be a fly on the wall in the factory. Just how many corners are the assemblers required to cut in order to move product out the door in the minimal time?

I'm becoming increasingly convinced that while cheap scopes can be had with a reasonable degree of confidence, the chances of a satisfactory outcome scale as the inverse of the square of the number of objectives. (For the mathematically-challenged, two objectives result in a confidence factor 1/4 that for a cyclopean instrument.)




Don't forget that binoculars also have many reflective surfaces in the prism group and interbarrel collimation issues....I'd say that increases the chances of problems many fold beyond your estimate.



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GlenM
Vendor - Lyra Optic


Reged: 05/20/07

Loc: Lancashire England
Re: GBT 100/90 arrived new [Re: contrailmaker]
      #3696041 - 03/21/10 04:30 PM

I am really disappointed for you. I hope everything can be sorted out to your satisfaction.

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Mr. Bill
Postmaster
*****

Reged: 02/09/05

Loc: Northeastern Cal
Re: GBT 100/90 arrived new [Re: GlenM]
      #3696076 - 03/21/10 04:39 PM

It would seem to me that all these returns on Garrett's dime for defects would really eat into the profit margin...would'nt it be cheaper and easier to REALLY do the 14 point inspection? The gross defects discussed on this thread and the recent others would easily be detected with the most casual visual inspection.

Makes one wonder whether the collimation check was done.



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GlenM
Vendor - Lyra Optic


Reged: 05/20/07

Loc: Lancashire England
Re: GBT 100/90 arrived new [Re: Mr. Bill]
      #3696086 - 03/21/10 04:43 PM

I must say that these problems certainly need looking into for sure.

I feel so disappointed for people who have problems.


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beachchairbill
Pooh-Bah


Reged: 11/06/08

Re: GBT 100/90 arrived new [Re: GlenM]
      #3696568 - 03/21/10 08:51 PM

What are the 14 points of inspection? I'm sure we can come up with the points that were not checked.

Beachchairbill


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mtb54703
professor emeritus
*****

Reged: 11/12/08

Loc: Eau Claire, WI
Re: GBT 100/90 arrived new [Re: contrailmaker]
      #3696795 - 03/21/10 10:47 PM

I too currently have a pair of the Garrett Optical 90 Binocular Telescope, at least until tomorrow. I would like to note that they also appear to be the same model sold by Orion Telescopes.

There's a bit of a story itself behind this... the short version is that these 90s were a replacement for a pair of the 45 degree version that I sent back for a collimation check ( I was only successful getting images to merge at low power) and some debris visible in the prism turret. It turns out the debris was actually a chip. I was offered a significant discount or a replacement when the next shipment arrived. Since I opted for the replacement I asked if I could upgrade for the $100 retail price difference - which they allowed me to do.

After months of delay - all of which was totally out of Garrett Optical's control and with which I really didn't mind since it was cold and snowy here in Wisconsin, the 90s arrived 3/17 via FedEx Ground. I have to wonder sometimes what happens behind the scenes when a box is plastered with white on red labels stating "Delicate Instruments - Handle With Care" on the outside. Can't help but think its kind of like walking around with "Kick Me" sign stuck on your back!? But the box appeared in good shape, no better or worse than the average box I typically get delivered from them.

The binos themselves were inside their own storage case, which was supported inside the shipping box by a couple inches of foam all the way around.

Out of the box the binos appeared to cosmetically perfect - no scratches on the paint, lenses were clean. The tubes appeared clean with no debris or casting flaws. For some reason they weren't quite as sexy looking as the 45 degree version - I guess the lines were just not as curvy?!

Of course when you get a replacement something the first thing one does is check to see if its any better than the something being replaced. So I took particular attention to the view down the focusers. There it was, bigger even than last time - a chip in one of the prisms in the right side turret. It was out on the edge and I did need to look quite a bit off axis to see it so it really wasn't in the optical path - but still, it shouldn't be there. One other item to note, when looking down the focusers of the 45's there was some pretty apparent cutoff caused by the edges of the prisms - the 90s appeared to be better in that respect (appearances aren't everything).

That evening after work I mounted them on the tripod - I figured even though I'd already decided this pair was going back, I might as well take them for a test drive while I had them.

The self centering focusers are a vast improvement over the o-rings of the 45s (the new 45s apparently now have a similar focuser). The self centering focusers are still going to present problems with any EPs with the safety/security undercuts. My non-OEM EPs are a pair of Smart Astronomy Extra Flat 19mm EPs - fortunately the barrels can be unscrewed and reversed and they worked find in the new style focusers. I placed the OEM EPs into the binos and pointed them down the street about a 1000 feet to a for sale sign on the neighbors yard. The focuser on the left tube was quite stiff to turn compared to the right. What was really nice was the IPD adjustment, much nicer than grabbing the turrets on the 45s and moving them by hand. This screw adjustment feature for the IPD was one of the reasons I opted to replace the 45s with the 90s since I had liked using the 45s during our clubs public viewing sessions last summer, but constantly moved the binos every time I went to adjust the IPD for the different viewers.

After focusing each EP I opened both eyes and.... hmm.... this can't be... double images - one on top of the other, just slighty. At this point I tried all the tricks I did with the 45's such as reseating each EP, rotating one EP, different EPs. All the results were the same - these binos were not collimated! I ended up loosening the right EP holder, making it just loose enough that I could push on the top edge of the EP and tip its position in the focuser. Pushing the right EP slightly forward did the trick - one single image when looking through both eyes.

Again I was starting to wonder if the collimation issue was really just me. I had emphasized and re-emphasized in emails with Garrett Optical during the wait that I was in no big hurry and wouldn't even mind a further delay if the binos could be check for collimation up to 70x. I brought in a couple other people to look through them. They both thought the view was nice and didn't mention anything about a double image. Then I loosed the EP holder had them push the right EP slightly forward while looking through again - then they said "Wow" that's a lot better! Neither had realized how bad it was on their first look.

I sent an email to Garrett Optical that night calling out the chipped prism and the collimation issue. TOS prevents me from including the reply I received the next day so all I can say is that I was shocked. I sent a reply after thinking about it for a day and telling them them that given issues with collimation and chipped prisms I would just prefer to have a refund. A few hours later I received an email with a pre-paid shipping label. The final out come is TBD.

I didn't get them to FedEx before they closed on Friday so I will have drop them off on Monday. In the meantime I took the opportunity to re-do the flashlight aperture test. I had initially done this on the second night and conferred the results with a few other members on the binoculars forum - they were so.. well.. shocking.

This afternoon I set up my test environment again. I mounted the binos on my large Bogen tripod. I took another tripod and secured a newly purchased Coleman MAX 110 lumen LED flashlight. I printed off (and verified) a paper cm ruler and taped it across the the front the left tube. In front of that I placed a digital camera to record the image of the light cone projected onto the paper. I found that the largest diameter cone projected was with the focuser screwed all the way in/down - so I went with that. I took 2 second exposures with the flashlight at distances of 2cm, 10cm, 20cm, 30 cm and 55cm (the highest I could go) above the EP. The 2cm distance gave the widest diameter cone. The cone dropped off considerably at 10cm and was consistent at all the other distances. I believe the 2cm distance is too close because if you look closely you can see several light cones being projected on the the paper - the smallest cone is consistent with the cones projected with the light source at the 20/30/55cm distances.

Rather than stating the obvious, I'll post the pictures and leave the assessment as an exercise for my fellow forum readers...

It would probably be a really good idea if someone else could validate my testing method as well test a different pair of 90s.

Edited by mtb54703 (03/21/10 11:48 PM)


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mtb54703
professor emeritus
*****

Reged: 11/12/08

Loc: Eau Claire, WI
Re: GBT 100/90 arrived new [Re: mtb54703]
      #3696797 - 03/21/10 10:48 PM Attachment (148 downloads)

The binos themselves.

The distance from the front of the tubes (dew shields retracted) to the gold ring just in front of the lower prism housing is 12.125". I measured the outside of the edge of the objective to 1.625" from the front edge of the tube (again with the dew shields retracted).

Edited by mtb54703 (03/21/10 11:02 PM)


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mtb54703
professor emeritus
*****

Reged: 11/12/08

Loc: Eau Claire, WI
Re: GBT 100/90 arrived new [Re: mtb54703]
      #3696800 - 03/21/10 10:49 PM Attachment (130 downloads)

Down the focusers...

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mtb54703
professor emeritus
*****

Reged: 11/12/08

Loc: Eau Claire, WI
Re: GBT 100/90 arrived new [Re: mtb54703]
      #3696802 - 03/21/10 10:50 PM Attachment (117 downloads)

Almost straight down the right focuser...

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mtb54703
professor emeritus
*****

Reged: 11/12/08

Loc: Eau Claire, WI
Re: GBT 100/90 arrived new [Re: mtb54703]
      #3696803 - 03/21/10 10:51 PM Attachment (104 downloads)

Down one tube...

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mtb54703
professor emeritus
*****

Reged: 11/12/08

Loc: Eau Claire, WI
Re: GBT 100/90 arrived new [Re: mtb54703]
      #3696805 - 03/21/10 10:52 PM Attachment (114 downloads)

From the front...

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mtb54703
professor emeritus
*****

Reged: 11/12/08

Loc: Eau Claire, WI
Re: GBT 100/90 arrived new [Re: mtb54703]
      #3696807 - 03/21/10 10:53 PM Attachment (93 downloads)

Dew shields extended...

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mtb54703
professor emeritus
*****

Reged: 11/12/08

Loc: Eau Claire, WI
Re: GBT 100/90 arrived new [Re: mtb54703]
      #3696812 - 03/21/10 10:55 PM Attachment (98 downloads)

Test setup for the aperture test...

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mtb54703
professor emeritus
*****

Reged: 11/12/08

Loc: Eau Claire, WI
Re: GBT 100/90 arrived new [Re: mtb54703]
      #3696813 - 03/21/10 10:56 PM Attachment (91 downloads)

Ruler validation...

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mtb54703
professor emeritus
*****

Reged: 11/12/08

Loc: Eau Claire, WI
Re: GBT 100/90 arrived new [Re: mtb54703]
      #3696814 - 03/21/10 10:56 PM Attachment (111 downloads)

Light cone with light source 2cm above EP...

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mtb54703
professor emeritus
*****

Reged: 11/12/08

Loc: Eau Claire, WI
Re: GBT 100/90 arrived new [Re: mtb54703]
      #3696816 - 03/21/10 10:57 PM Attachment (90 downloads)

Light cone with light source 10cm above EP...

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mtb54703
professor emeritus
*****

Reged: 11/12/08

Loc: Eau Claire, WI
Re: GBT 100/90 arrived new [Re: mtb54703]
      #3696820 - 03/21/10 10:58 PM Attachment (133 downloads)

Light cone with light source 20cm above EP...

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mtb54703
professor emeritus
*****

Reged: 11/12/08

Loc: Eau Claire, WI
Re: GBT 100/90 arrived new [Re: mtb54703]
      #3696822 - 03/21/10 10:58 PM Attachment (79 downloads)

Light cone with light source 30cm above EP...

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mtb54703
professor emeritus
*****

Reged: 11/12/08

Loc: Eau Claire, WI
Re: GBT 100/90 arrived new [Re: mtb54703]
      #3696824 - 03/21/10 10:59 PM Attachment (88 downloads)

Light cone with light source 55cm above EP...

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Rich V.
Post Laureate
*****

Reged: 01/02/05

Loc: Lake Tahoe area, Nevada, USA
Re: GBT 100/90 arrived new [Re: mtb54703]
      #3696830 - 03/21/10 11:05 PM

Thanks, Mike, this is just what everyone has been wanting to know! I'm seeing 80mm minus a large cutoff at the top! It alone looks like it could be approaching 10%.

This looks to be a pretty compromised "100mm" binocular.

Sorry this didn't turn out like you had hoped.

Good luck and thanks for going to the trouble to document this. Much appreciated!

Rich V


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Joad
Wordsmith
*****

Reged: 03/22/05

Re: GBT 100/90 arrived new [Re: Rich V.]
      #3696841 - 03/21/10 11:09 PM

That is what I see too. Is this a repeat of the Apogee problem?

And it is such a pretty looking binocular too. The eyepiece holders look especially nice. But . . .


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Mr. Bill
Postmaster
*****

Reged: 02/09/05

Loc: Northeastern Cal
Re: GBT 100/90 arrived new [Re: Rich V.]
      #3696845 - 03/21/10 11:13 PM

Looks to me like it confirms our (EdZ, Glen LeDrew, myself) suspicions based on raytrace analysis about the vignetting problem....

I'm real sorry that we are right as I wanted a pair of 100mm 90s.



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Rich V.
Post Laureate
*****

Reged: 01/02/05

Loc: Lake Tahoe area, Nevada, USA
Re: GBT 100/90 arrived new [Re: Joad]
      #3696847 - 03/21/10 11:13 PM

I'm also wondering about the descrepancy between Mike's aperture results vs. Contrailmaker's measure of 95mm.

Rich V


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Mr. Bill
Postmaster
*****

Reged: 02/09/05

Loc: Northeastern Cal
Re: GBT 100/90 arrived new [Re: Rich V.]
      #3696882 - 03/21/10 11:30 PM

Quote:

I'm also wondering about the descrepancy between Mike's aperture results vs. Contrailmaker's measure of 95mm.

Rich V




Look at Mike's first measurement...if you count the "penumbra" about 95mm.


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beachchairbill
Pooh-Bah


Reged: 11/06/08

Re: GBT 100/90 arrived new [Re: Rich V.]
      #3696890 - 03/21/10 11:34 PM

Mike,

A nice solid report. When are they going to learn or will they.

Beachchairbill


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contrailmaker
Pooh-Bah


Reged: 01/02/09

Re: GBT 100/90 arrived new [Re: Mr. Bill]
      #3696893 - 03/21/10 11:36 PM

Agree with the above. My measurement had the flashlight too close to the EP.

cm


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Mr. Bill
Postmaster
*****

Reged: 02/09/05

Loc: Northeastern Cal
Re: GBT 100/90 arrived new [Re: contrailmaker]
      #3696898 - 03/21/10 11:39 PM

Damn...they sure are pretty.



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mtb54703
professor emeritus
*****

Reged: 11/12/08

Loc: Eau Claire, WI
Re: GBT 100/90 arrived new [Re: contrailmaker]
      #3696900 - 03/21/10 11:40 PM

Quote:

Agree with the above. My measurement had the flashlight too close to the EP.

cm




Did you re-test? It would be nice to have a definite second opinion (actually a third and fourth would be better). Pictures would even be best.



Edited by mtb54703 (03/21/10 11:44 PM)


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Rich V.
Post Laureate
*****

Reged: 01/02/05

Loc: Lake Tahoe area, Nevada, USA
Re: GBT 100/90 arrived new [Re: Mr. Bill]
      #3696909 - 03/21/10 11:45 PM

Yeah, I raced down to the later pics and didn't look very well at the first. Very suspicious!

When you do the "LeDrew flashlight projection test" the flashlight does have to be held at a distance.

Rich V

Edited by Rich V. (03/21/10 11:46 PM)


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Mr. Bill
Postmaster
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Reged: 02/09/05

Loc: Northeastern Cal
Re: GBT 100/90 arrived new [Re: Rich V.]
      #3696977 - 03/22/10 12:24 AM

The up side....CA correction better than expected.



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Mr. Bill
Postmaster
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Reged: 02/09/05

Loc: Northeastern Cal
Re: GBT 100/90 arrived new [Re: Mr. Bill]
      #3697104 - 03/22/10 01:54 AM

Some final thoughts....

20 years ago, before common use of the internet and sites such as CN, we would never be able to do what we have done here, communicate with others with common interests and form a real time de facto consumer interest group.

Each one of us would remain ignorant of the experiences and objective evaluations of others that would allow us to make informed decisions on substantial purchases such as these binoculars. We would have to "roll the dice" and find out for ourselves without the benefit of others.

I'm sure that the vendors do not share such an enthusiastic view of this as I do....

I'm proud to be a member of this forum and CN.



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lightyear44
Pooh-Bah
*****

Reged: 12/29/09

Loc: Ontario
Re: GBT 100/90 arrived new [Re: Mr. Bill]
      #3697282 - 03/22/10 07:01 AM

Perfectly said, Mr. Bill -David.

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mtb54703
professor emeritus
*****

Reged: 11/12/08

Loc: Eau Claire, WI
Re: GBT 100/90 arrived new [Re: mtb54703]
      #3697430 - 03/22/10 09:06 AM Attachment (53 downloads)

Quote:


The distance from the front of the tubes (dew shields retracted) to the gold ring just in front of the lower prism housing is 12.125". I measured the outside of the edge of the objective to 1.625" from the front edge of the tube (again with the dew shields retracted).




Quoting myself...

Doing the math using the front of the objective as the starting point, its 266.7mm (10.5") to the back of the tube or start of the prism housing. With the stated specifications of 100mm f/6.1 I calculate the diameter of the light cone to be about 56mm (2.2") when it reaches the back of the tube.


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EdZ
Professor EdZ
*****

Reged: 02/15/02

Loc: Cumberland, R I , USA42N71.4W
Re: GBT 100/90 arrived new [Re: mtb54703]
      #3697731 - 03/22/10 12:02 PM

Quote:

Quote:


The distance from the front of the tubes (dew shields retracted) to the gold ring just in front of the lower prism housing is 12.125". I measured the outside of the edge of the objective to 1.625" from the front edge of the tube (again with the dew shields retracted).




Quoting myself...

Doing the math using the front of the objective as the starting point, its 266.7mm (10.5") to the back of the tube or start of the prism housing. With the stated specifications of 100mm f/6.1 I calculate the diameter of the light cone to be about 56mm (2.2") when it reaches the back of the tube.




Which makes me question that it seems very unlikely that this is f/6.1. If it were f/6.1 and the prism aperture is as stated 21-22mm, (assuming there is some small estimation errors in these positioning assumptions) the effective aperture would be showing up as about 40-50mm. As I said earlier in this thread, there's too many assumptions to know the answer. But, one thing is for sure, there are not 50+mm prisms inside these binoculars.

edz


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elwaine
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Re: GBT 100/90 arrived new [Re: Mr. Bill]
      #3697756 - 03/22/10 12:10 PM

Quote:

Some final thoughts....

20 years ago, before common use of the internet and sites such as CN, we would never be able to do what we have done here, communicate with others with common interests and form a real time de facto consumer interest group.

Each one of us would remain ignorant of the experiences and objective evaluations of others that would allow us to make informed decisions on substantial purchases such as these binoculars. We would have to "roll the dice" and find out for ourselves without the benefit of others.

I'm sure that the vendors do not share such an enthusiastic view of this as I do....

I'm proud to be a member of this forum and CN.






Thank you Mr. Bill. That was well said.. and worthy of re-posting.

Larry


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Joad
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Re: GBT 100/90 arrived new [Re: elwaine]
      #3697800 - 03/22/10 12:29 PM

Just to add: it was Mr. Bill's Cloudy Nights review article on the early 2000's Oberwerk 25X100 45° BT that helped me buy my first big Obie.

Subsequently, I traded my 40X100 for the newer, fully multi-coated 100mm BT with interchangeable eps.

And Mr. Bill subsequently went from a Fuji 150 to the fully multi-coated 100mm BT with interchangeable eps.

By the way, Mr. Bill has a place in the California mountains. So do I.

And we both have grey beards.

I'm wondering if we are the same person.











Naaaah, he's got better gear and writes a better review.


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Mr. Bill
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Re: GBT 100/90 arrived new [Re: Joad]
      #3697815 - 03/22/10 12:34 PM

Quote:



...I'm wondering if we are the same person.






Naaa....I'm certifiably nuts and you're merely eccentric.



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Re: GBT 100/90 arrived new [Re: EdZ]
      #3697848 - 03/22/10 12:50 PM

Quote:

Which makes me question that it seems very unlikely that this is f/6.1. If it were f/6.1 and the prism aperture is as stated 21-22mm, (assuming there is some small estimation errors in these positioning assumptions) the effective aperture would be showing up as about 40-50mm. As I said earlier in this thread, there's too many assumptions to know the answer. But, one thing is for sure, there are not 50+mm prisms inside these binoculars.

edz




Ed, I'm confused here; I don't recall anyone measuring a 21-22mm front prism aperture. The REAR prism aperture (just in front of the eyepiece) of the GBT100 45° model has been measured to be in the 21-22mm range and perhaps this applies to the 90° model as well, but there has been no accurate figure for front prism aperture by anyone that I recall regarding either model. This I assume would require disassembly of the binocular to accurately measure.

I'm just double checking which aperture we're talking about here; I'm assuming it's the front that's in question.

Rich V


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GamesForOne
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Re: GBT 100/90 arrived new [Re: Rich V.]
      #3697872 - 03/22/10 01:00 PM

Quote:


Ed, I'm confused here; I don't recall anyone measuring a 21-22mm front prism aperture. The REAR prism aperture (just in front of the eyepiece) of the GBT100 45° model has been measured to be in the 21-22mm range and perhaps this applies to the 90° model as well...




That is the way I would interpret the 21-22mm figure as well. It probably is the clear aperture diameter of the eyepiece turret assembly -- similar to the clear optical seals you find on binoviewers on the eyepiece end.

---
Michael McCulloch


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Mr. Bill
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Re: GBT 100/90 arrived new [Re: GamesForOne]
      #3697890 - 03/22/10 01:06 PM

I think I started that in an earlier post on the other thread....

I emailed Zack about the aperture available to the ep fieldstop and he responded....

"Rough measurement of the clear aperture near where the eyepiece barrel seats by the prism - looks like between 21-22mm. I hope this is helpful to you."


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mtb54703
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Re: GBT 100/90 arrived new [Re: Mr. Bill]
      #3697948 - 03/22/10 01:27 PM

I printed off my picture looking down the right focuser of the 90s. On the picture I measured the ID at the bottom of the focuser and the ID of the visible ring - 50mm and 34mm respectively. Obviously the picture is not 1:1, but the values can be scaled knowing that the ID at the bottom of the focuser is 31.75mm.



Code:

34 x
-- = -----
50 31.75

x = (34 x 31.75) / 50

x = 21.59mm




Again, this is the rear prism aperture. As RichV says - we can't know the front prism aperture without disassembly and we also don't know the distance of the light path through the prisms.


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Re: GBT 100/90 arrived new [Re: mtb54703]
      #3697972 - 03/22/10 01:38 PM

We can't positively know the front prism aperture. We do know in some cases the front prism shelf opening can be larger than the rear. However, that is not the norm, that is the exception. Glenn documented one such case, and others have mentioned a few cases. In every case that I have ever seen, the front and rear openings are the same diameter. But as has been stated numerous times in this thread, there are several things we just don't know.

edz


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Re: GBT 100/90 arrived new [Re: EdZ]
      #3698010 - 03/22/10 01:53 PM

I'm developing the sneaky suspicion that the f/6.1 figure could well have been taken from the *actual* working aperture of 80mm (c.f. exit pupil diameter and magnification). If so, the objectives' real f/ratio would be 6.1 * (80/100) = f/4.88. The overal aspect of the instrument would seem to verify this....

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KennyJ
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Re: GBT 100/90 arrived new [Re: GlennLeDrew]
      #3698062 - 03/22/10 02:20 PM

Glenn's suggestion seems the most plausible explanation for this little quandary .

" Sneaky " would seem a most apt description , given the instrument is advertised as a 100mm unit !

Kenny


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Mr. Bill
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Re: GBT 100/90 arrived new [Re: KennyJ]
      #3698157 - 03/22/10 03:04 PM

I downloaded Mike's picture, put it up against a picture of my BT100s, adjusted the images so that the bottom focuser diameters were the same using a mm ruler and measured the clear aperture disks...

I got a rough diameter ratio of 3 to 5.


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contrailmaker
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Re: GBT 100/90 arrived new [Re: Mr. Bill]
      #3698178 - 03/22/10 03:15 PM

I read the BT100s have a baffle that restrics the aperture to less than 100mm. Has anybody measured it?

cm


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Re: GBT 100/90 arrived new [Re: contrailmaker]
      #3698187 - 03/22/10 03:19 PM

Quote:

I read the BT100s have a baffle that restrics the aperture to less than 100mm. Has anybody measured it?

cm




The clear aperture has been variously measured from 93mm to 96mm....I've measured it at 95mm.


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Re: GBT 100/90 arrived new [Re: contrailmaker]
      #3698191 - 03/22/10 03:20 PM

yes, that is well-documented. Various measures indicate 94-96mm.

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contrailmaker
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Re: GBT 100/90 arrived new [Re: Mr. Bill]
      #3698199 - 03/22/10 03:23 PM

Thanks Mr Bill and EdZ. I am considering the BT80/45s, Bigbinocs.com says they are effectively 75mm. Would prefer the 100s but portability dictates otherwise. I figure that with binocular summation they would get close to what I see with my 100mm refractor.

cm

Edited by contrailmaker (03/22/10 03:26 PM)


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Mr. Bill
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Re: GBT 100/90 arrived new [Re: contrailmaker]
      #3699802 - 03/23/10 11:18 AM Attachment (81 downloads)

Thought a "side by side" comparison would be instructive.

First the GBT100 90....


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Mr. Bill
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Re: GBT 100/90 arrived new [Re: Mr. Bill]
      #3699803 - 03/23/10 11:19 AM Attachment (81 downloads)

Then the BT100 45....

As they say, a picture's worth a thousand posts.


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Re: GBT 100/90 arrived new [Re: EdZ]
      #3700167 - 03/23/10 02:42 PM

Quote:

Which makes me question that it seems very unlikely that this is f/6.1. If it were f/6.1 and the prism aperture is as stated 21-22mm, (assuming there is some small estimation errors in these positioning assumptions) the effective aperture would be showing up as about 40-50mm. As I said earlier in this thread, there's too many assumptions to know the answer. But, one thing is for sure, there are not 50+mm prisms inside these binoculars.

edz




Now that we know the effective aperture is 80mm, then it should be relatively easy to check the focal length.

Get 2 or three well known standard eyepieces. I've never seen brand name eyepieces vary much from the stated focal length. Put them in and measure the exit pupil (focused on infinity). There will be some error within the measures, but you should get close. If these are 610mm, then
a 30mm eyepiece should give 610/30 = 20.3x and that would give 80/20.3 = 3.94mm exit pupil
a 20mm eyepiece should give 610/20 = 30.5x and that would give 80/30.5 = 2.62mm exit pupil

Anybody bother to check that yet?

edz


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Mr. Bill
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Re: GBT 100/90 arrived new [Re: EdZ]
      #3700211 - 03/23/10 03:08 PM

Quote:



Anybody bother to check that yet?

edz




Does anyone still have them to check?



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mtb54703
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Re: GBT 100/90 arrived new [Re: Mr. Bill]
      #3700229 - 03/23/10 03:18 PM

Quote:

Quote:



Anybody bother to check that yet?

edz




Does anyone still have them to check?







No - mine are on FedEx truck somewhere between St Paul and Tulsa. I don't own a loupe so I'm not sure how accurate I would have been on that measurement.

A 50mm difference in focal length at 30x would be 4.28mm instead of 3.92mm - I guess I would have been able to tell which of the 4mm line it was on at least.

Maybe CM still has his?

Edited by mtb54703 (03/23/10 03:18 PM)


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EdZ
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Re: GBT 100/90 arrived new [Re: mtb54703]
      #3700240 - 03/23/10 03:24 PM

Quote:

A 50mm difference in focal length at 30x would be 4.28mm instead of 3.92mm - I guess I would have been able to tell which of the 4mm line it was on at least.




Actually based on what we know now, I'd expect to see more than a 100mm difference in focal length.

edz


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KennyJ
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Re: GBT 100/90 arrived new [Re: mtb54703]
      #3700242 - 03/23/10 03:24 PM

Could any of the FedEx employees at Tulsa not be contacted as a matter of urgency to carry out the tests ? -- providing they all carry loupes , of course ! :-)

Kenny


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Mr. Bill
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Re: GBT 100/90 arrived new [Re: KennyJ]
      #3700257 - 03/23/10 03:31 PM

I sent an email to Zach Garrett with the above pictures of the rear apertures of the BT100 45 and his GBT100 90 (just in case he's not lurking this thread.)

Also mentioned the measured effective aperture for both.

See if I get a reply.

Edited by Mr. Bill (03/23/10 04:50 PM)


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Mr. Bill
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Re: GBT 100/90 arrived new [Re: Mr. Bill]
      #3700278 - 03/23/10 03:40 PM

All this sorta begs the question on how the real (not clone) Miyauchi 100mm 90 would fare, both on available aperture at the fieldstop and effective aperture.



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GamesForOne
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Re: GBT 100/90 arrived new [Re: Mr. Bill]
      #3700300 - 03/23/10 03:51 PM

Quote:

I sent an email to Zake Garrett with the above pictures of the rear apertures of the BT100 45 and his GBT100 90 (just in case he's not lurking this thread.)





I'm not sure what such photo comparisons prove. My APM picture makes your BT100-45 clear aperture look positively tiny.

---
Michael McCulloch


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KennyJ
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Re: GBT 100/90 arrived new [Re: Mr. Bill]
      #3700304 - 03/23/10 03:52 PM

Mr. Bill ,

Is Zake a relation / business partner of Zach Garrett ?

Kenny


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Mr. Bill
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Re: GBT 100/90 arrived new [Re: KennyJ]
      #3700319 - 03/23/10 03:55 PM

Quote:

Mr. Bill ,

Is Zake a relation / business partner of Zach Garrett ?

Kenny




It's his brother, Kenny



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Re: GBT 100/90 arrived new [Re: GamesForOne]
      #3700337 - 03/23/10 04:00 PM

Quote:

Quote:

I sent an email to Zake Garrett with the above pictures of the rear apertures of the BT100 45 and his GBT100 90 (just in case he's not lurking this thread.)





I'm not sure what such photo comparisons prove. My APM picture makes your BT100-45 clear aperture look positively tiny.

---
Michael McCulloch




I agree. Without a scale in the photo it's very difficult to tell anything. IF all photos were sized at the exact same scale, perhaps we could tell gross differences easily, but how can we be sure photos are sized exactly the same?

edz


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Re: GBT 100/90 arrived new [Re: EdZ]
      #3700432 - 03/23/10 04:45 PM

That's pretty dramatic....Mike's method of assuming the focuser barrel ID is about 32mm (1 1/4 inch) and then scaling the clear aperture against the bottom of the focuser barrel seems logical to me.

Could a difference in focal length and the vignetting of the BT100 aperture account for this?



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Re: GBT 100/90 arrived new [Re: Mr. Bill]
      #3700438 - 03/23/10 04:48 PM

Quote:

That's pretty dramatic....Mike's method of assuming the focuser barrel ID is about 32mm (1 1/4 inch) and then scaling the clear aperture against the bottom of the focuser barrel seems logical to me.






I thought of that. In the BT100 photo, I could not tell what was the focuser barrel.

edz


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Mr. Bill
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Re: GBT 100/90 arrived new [Re: EdZ]
      #3700601 - 03/23/10 06:15 PM Attachment (69 downloads)

OK...

Removed the top of the turrent can (containing the helical focuser) off my BT100 45s.....

Drumroll please....the rear prism face is 32mm across, the rear aperture measures 26mm. Notice left edge measurement is the sliver....camera slightly off dead center. It was tough getting this good a shot offhand.


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Mr. Bill
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Re: GBT 100/90 arrived new [Re: Mr. Bill]
      #3700608 - 03/23/10 06:19 PM Attachment (65 downloads)

Another....

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GlennLeDrew
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Re: GBT 100/90 arrived new [Re: Mr. Bill]
      #3700643 - 03/23/10 06:38 PM

Excellent, shots, Mr. Bill! At 32mm, those are generously large prisms for a Porro II. In the RA88 I collimated for a friend, the prism face widths were ~24mm, with the clear aperture being closer to 21-22mm.

When taking photos into prism essemblies, the farther back you can place the camera the better. From up close, perspective effects cause a rapid change of scale with distance from the lens. The result is that an aperture lying farther inside the instrument can appear rather smaller than it really is, when compared to other apertures, etc. closer to the lens.

If necessary, one could move so far back so that the image scale is hardly better than 1mm/pixel (0.5mm/pixel is certainly quite adequate). If the idea is to assess comparative apertures most accurately, better to sacrifice some resolution in order to get closer to an isometric image from which to take measurements.


@EdZ,
I was going to suggest the exit pupil measurement, too, but you beat me to it!


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Mateyhv
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Re: GBT 100/90 arrived new [Re: Mr. Bill]
      #3700660 - 03/23/10 06:47 PM

Quote:

It would seem to me that all these returns on Garrett's dime for defects would really eat into the profit margin...would'nt it be cheaper and easier to REALLY do the 14 point inspection? The gross defects discussed on this thread and the recent others would easily be detected with the most casual visual inspection.

Makes one wonder whether the collimation check was done.






The sentence I put in italics is absolutely true, after some time its clear for me that there is no such a thing called 14 points inspection. The only inspection seems to be if the binos are in the box and the address to be shipped to... very dissappointing..

Matey


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Mr. Bill
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Re: GBT 100/90 arrived new [Re: GlennLeDrew]
      #3700671 - 03/23/10 06:50 PM

Thanks for the tip...next time I won't be so lazy and will mount the camera on a tripod. I took about 30 shots to get those.



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mtb54703
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Re: GBT 100/90 arrived new [Re: mtb54703]
      #3703455 - 03/24/10 10:13 PM

A bit of follow up on my post...

My 90s arrived back in Tulsa today.

Was offered a full refund but also asked to carefully consider other binocular options they have to offer - specifically the 110 Signature Series.

Obviously another pair of 90s are out - not going there again. 45s? Need to get a feel for the quality in this last batch. Maybe the 110s...




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Re: GBT 100/90 arrived new [Re: mtb54703]
      #3703501 - 03/24/10 10:33 PM

Mike...
Go for the 20x110s....want a report.



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mtb54703
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Re: GBT 100/90 arrived new [Re: Mr. Bill]
      #3703954 - 03/25/10 08:50 AM

Quote:

Mike...
Go for the 20x110s....want a report.






I've seen many recommendations for the 110 Signature Series. I'm on the fence between those and another pair of 45s - don't know if I want to roll the dice or not on another pair of 45s.



On my original pair of 45s I really enjoyed using a pair of Smart Astronomy Extra Flat 19mm EPs (65 APOV) for about 28x. So in the Signature series I leaning towards the 28x pair until I saw the usable eye relief was 11mm.

My initial choice in the purchase of the 45s was due to two factors:

- the ability to use different EPs
- the 45 degree design.

After using them I pretty much settled down on a single pair of EPs so I don't think that interchangeable EPs is that big of a factor any more.

I could really go for a 45 degree 100mm or so bino with a fixed magnification of around 25x - that would be sweet.


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Pat G.
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Re: GBT 100/90 arrived new [Re: mtb54703]
      #3704362 - 03/25/10 12:51 PM

"I could really go for a 45 degree 100mm or so bino with a fixed magnification of around 25x - that would be sweet."

It seems a shame to limit a large instrument to a single power. Different items look better at different powers.

On another note, I really love my 45° binos for astronomy.


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Mr. Bill
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Re: GBT 100/90 arrived new [Re: Pat G.]
      #3704463 - 03/25/10 01:41 PM

Since we're wishing....

How about a fixed magnification 45 degree ocular 25x120 binocular the same build quality as as the Signature 110s apparently are? I would like a 5mm exit pupil with a 65 degree afov for dark site MW scanning. I find 5mm to be optimal under really dark skies.

A weight of 25 pounds would seem reasonable if you figure the 110s are 16 pounds and scale them up.

That's a whole lot better weight wise than the Oberwerk 120s which are about 45 pounds.

Oh, and around $1500 since the 110s are $700 this seems doable..OK I'll go $2K



Edited by Mr. Bill (03/25/10 03:24 PM)


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Erik D
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Re: GBT 100/90 arrived new [Re: Mr. Bill]
      #3704527 - 03/25/10 02:12 PM

Quote:

Since we're wishing....

How about a fixed magnification 45 degree ocular 120x25 binocular the same build quality as as the Signature 110s apparently are?





Clarification please. Do you mean 25X125 mm?

I usually prefer 4 mm exit pupil for binoculars 60 mm or bigger. My skies are not very dark, usually mag 4 to 4.5 so higher magnification with 4 mm exit pupil do better for me.


ERik D


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Mr. Bill
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Re: GBT 100/90 arrived new [Re: Erik D]
      #3704674 - 03/25/10 03:32 PM

Quote:

Quote:

Since we're wishing....

How about a fixed magnification 45 degree ocular 120x25 binocular the same build quality as as the Signature 110s apparently are?





Clarification please. Do you mean 25X125 mm?

I usually prefer 4 mm exit pupil for binoculars 60 mm or bigger. My skies are not very dark, usually mag 4 to 4.5 so higher magnification with 4 mm exit pupil do better for me.


ERik D




Dyslexia in my fingertips.. also, rounding off to 5mm; should have said 4.8mm

I have the skies to take advantage of 5mm (4.8mm) exit pupils so for me that would be optimal. My eyes can dilate to around 5.2mm, so that's about all I can effectively use.


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mtb54703
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Re: GBT 100/90 arrived new [Re: mtb54703]
      #3706040 - 03/26/10 09:16 AM

Quote:

I too currently have a pair of the Garrett Optical 90 Binocular Telescope, at least until tomorrow. I would like to note that they also appear to be the same model sold by Orion Telescopes.





Just as a follow up I sent an email to Orion asking about clear aperture on their new 100/90 models. Their reply was.... well... email them and ask them yourself.

As for thoughts on look-a-likes...

We know these 100/45s and 100/90s offered by Garrett, Orion, APM, Baraska are all from BA6 series offered by United Optics.

While I do believe importers can customize their selection, I doubt that to be anything more than glass selection, coatings, focal length within constraints of the physical enclosure, EP selection, color, and embossing.

Given that United Optics offers one model of a 100mm 90 degree binoculars (22x/33x/40x100
#BA6-203037100) I suspect that offerings by Garrett and Orion are identical in the physical respect. We've estimated what size opening is required at the front of the prism housing given the objective diameter, focal length and length of the main tube - and having had a pair of those 90s in my possession I can say its physically not possible, so I don't see how the Orion offering could have a different clear aperture than the Garretts.

Edited by mtb54703 (03/26/10 09:41 AM)


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GamesForOne
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Re: GBT 100/90 arrived new [Re: mtb54703]
      #3706228 - 03/26/10 11:07 AM

Quote:


Just as a follow up I sent an email to Orion asking about clear aperture on their new 100/90 models. Their reply was.... well... email them and ask them yourself.





What a teaser! Ah, c'mon what was the reply?


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Rich V.
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Re: GBT 100/90 arrived new [Re: GamesForOne]
      #3706313 - 03/26/10 11:44 AM

I'm betting they had no idea!

Rich V


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F.Meiresonne
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Re: GBT 100/90 arrived new [Re: Erik D]
      #3706324 - 03/26/10 11:51 AM

Quote:

I usually prefer 4 mm exit pupil for binoculars 60 mm or bigger




Me too, and that also because my skies are not that dark.
That also the reason i tend to opt for higher magnification model like a 15x70 or 22x85 instead 10.5x and 15x respectively.


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mtb54703
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Re: GBT 100/90 arrived new [Re: GamesForOne]
      #3706333 - 03/26/10 11:54 AM

Quote:

Quote:


Just as a follow up I sent an email to Orion asking about clear aperture on their new 100/90 models. Their reply was.... well... email them and ask them yourself.





What a teaser! Ah, c'mon what was the reply?




Ignorance is bliss I guess....


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mtb54703
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Re: GBT 100/90 arrived new [Re: mtb54703]
      #3706499 - 03/26/10 01:14 PM

Quote:

Quote:

Quote:


Just as a follow up I sent an email to Orion asking about clear aperture on their new 100/90 models. Their reply was.... well... email them and ask them yourself.





What a teaser! Ah, c'mon what was the reply?




Ignorance is bliss I guess....




I ended up not being to contain myself and I replied to the support dude at Orion with and explanation on how to check clear aperture and some photos from the GO model.


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Rich V.
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Re: GBT 100/90 arrived new [Re: mtb54703]
      #3706701 - 03/26/10 02:53 PM

Well done, Mike!

Rich V


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Mr. Bill
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Re: GBT 100/90 arrived new [Re: Rich V.]
      #3706753 - 03/26/10 03:26 PM

I talked to Cory Suddarth about his collimation class coming up (hopefully) this fall and he mentioned he did the week long class for the Orion service dept. so I would think that there are competent people there....although I've apparently never had the opportunity to talk to any when I called with technical questions.



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daniel_h
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Re: GBT 100/90 arrived new [Re: Mr. Bill]
      #3707110 - 03/26/10 06:22 PM

mr Bill..i have also talked with Cory more later

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AndR1
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Re: GBT 100/90 arrived new [Re: mtb54703]
      #5464135 - 10/10/12 04:58 PM

Quote:



The distance from the front of the tubes (dew shields retracted) to the gold ring just in front of the lower prism housing is 12.125". I measured the outside of the edge of the objective to 1.625" from the front edge of the tube (again with the dew shields retracted).



I've bought the same (different color... and no logo like here) directly from Kunyang Zhicheng Optical Co. It arrived some days ago. Same sizes, same design (see no real difference... but there is no ruler at photo here to compair all sizes). I've made the same test and ... there is NO sector cutting, it has round circle 96-97 mm aperture (96,0 -96,5 for left and near 97,0 mm for right)...
Maybe I've missed some new theme about the issue... but if not, could you, please, give me any idea how they managed to make it much better?

Andrew

Edited by AndR1 (10/10/12 05:02 PM)


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GamesForOne
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Re: GBT 100/90 arrived new [Re: AndR1]
      #5464759 - 10/11/12 01:34 AM

Quote:


I've bought the same (different color... and no logo like here) directly from Kunyang Zhicheng Optical Co. It arrived some days ago. Same sizes, same design (see no real difference... but there is no ruler at photo here to compair all sizes). I've made the same test and ... there is NO sector cutting, it has round circle 96-97 mm aperture (96,0 -96,5 for left and near 97,0 mm for right)...
Maybe I've missed some new theme about the issue... but if not, could you, please, give me any idea how they managed to make it much better?





Is your bino a 45 degree or 90 degree? I don't think we've had a report of a 90 degree model with 96mm clear aperture. The 45 degree models, yes.

---
Michael Mc


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AndR1
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Re: GBT 100/90 arrived new [Re: GamesForOne]
      #5465078 - 10/11/12 10:01 AM

Quote:

Is your bino a 45 degree or 90 degree? I don't think we've had a report of a 90 degree model with 96mm clear aperture. The 45 degree models, yes.

---
Michael Mc




90 degree! Mine looks like just the same as shown at the photo from the post #3696797 - 05:48 22/03/2010 - just different color ! (Tried to insert this photo again but failed to make it for some reason... ...Well, it doesn't matter as mine is REALLY identical - just black instead of white colour - to mentioned one and adding image gives nothing new at all.)

Edited by AndR1 (10/11/12 03:10 PM)


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Mark9473
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Re: GBT 100/90 arrived new [Re: AndR1]
      #5465399 - 10/11/12 01:36 PM

Check that your image is below 200 kB.

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GamesForOne
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Re: GBT 100/90 arrived new [Re: AndR1]
      #5465630 - 10/11/12 04:24 PM

Quote:

Quote:

Is your bino a 45 degree or 90 degree? I don't think we've had a report of a 90 degree model with 96mm clear aperture. The 45 degree models, yes.





90 degree! Mine looks like just the same as shown at the photo from the post #3696797 - 05:48 22/03/2010 - just different color ! (Tried to insert this photo again but failed to make it for some reason... ...Well, it doesn't matter as mine is REALLY identical - just black instead of white colour - to mentioned one and adding image gives nothing new at all.)




How about posting photos of the projected image circle for your measurement with a ruler visible, and a picture of your measurement setup showing the bino and light source placement?

From whom did you actually order the binos? Was it from here?

---
Michael Mc


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AndR1
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Re: GBT 100/90 arrived new [Re: GamesForOne]
      #5465679 - 10/11/12 05:00 PM

Quote:

How about posting photos of the projected image circle for your measurement with a ruler visible, and a picture of your measurement setup showing the bino and light source placement?



Well... now I've disassembled all staff and actually I've got no photo for measurment procedure (just some photos of bino) as my camera is in need of repirement just now... But I did all just as it was recommended by Glann LeDrew...
I'm going to place photo as soon as my camera would work.

Quote:

From whom did you actually order the binos? Was it from here?




Yes! It's right place and right product (but different color)...


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AndR1
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Re: GBT 100/90 arrived new [Re: GamesForOne]
      #5471679 - 10/15/12 02:28 PM Attachment (40 downloads)

Quote:


How about posting photos of the projected image circle for your measurement with a ruler visible, and a picture of your measurement setup showing the bino and light source placement?



Hi!
As my camera is out of order and now it’s in long repair process into authorized shop, I’ve borrowed a camera from my neighbor just for one evening to make photos. As I’ve got no options for hanging flashlight above binoculars eyepiece I’ve made modernization and used placed rather long paper tube (near 400 mm) of proper diameter at the eyepiece barrel and placed my flashlight here. Well, photos made by this camera turned out not so good as expected… I’ve got rather acceptable photos of my measurement but very bad one of my equipment. Additionally, after short period my flashlight runs out of buttery charge and only charged pair of accumulators was into the camera! So, I replaced paper tube with black PVC tube of bigger diameter and with the length near 250 mm and placed LED lamp (“corn” type lamp) here and repeated the measurements – with the same result. I’ve got photo of my new "measurement arrangement" - well, it has too poor quality to put it here – and some photos of the result. Sorry for rather strange angle of view – I was in the big hurry!
As you could see, all lines go with 5 mm distance, so we’ve got the same result – near 96 mm aperture…
Well, is it something wrong with my measurement or something wrong with my binoculars?


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AndR1
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Re: GBT 100/90 arrived new [Re: AndR1]
      #5471682 - 10/15/12 02:29 PM Attachment (27 downloads)

Nearly the same with the ruler (sorry for the poor quality...)...

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AndR1
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Re: GBT 100/90 arrived new [Re: AndR1]
      #5471689 - 10/15/12 02:31 PM Attachment (30 downloads)

And the picture that I got with the lamp.

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GamesForOne
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Re: GBT 100/90 arrived new [Re: AndR1]
      #5472917 - 10/16/12 09:15 AM

Quote:


As you could see, all lines go with 5 mm distance, so we’ve got the same result – near 96 mm aperture…
Well, is it something wrong with my measurement or something wrong with my binoculars?




One more question: Did you have a low-power eyepiece inserted and focused approximately for infinity?

If so, it appears your binos do have more than 95% clear aperture which would be a first for the 100mm Miya-clone 90 degree bino telescopes as far as I have seen reported here!

How would you judge the color correction and edge sharpness? Do the eyepiece barrels have compression-ringed SCDs? Which 3rd party eyepieces do you know reach focus?

---
Michael Mc


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AndR1
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Re: GBT 100/90 arrived new [Re: GamesForOne]
      #5473209 - 10/16/12 12:16 PM

Quote:


One more question: Did you have a low-power eyepiece inserted and focused approximately for infinity?



Yes, near infinity...
And I've used for the second round of measurements 22x (27 mm as it could be concluded from 610 mm focal length of bino) eyepieces that go with bino.
Quote:

How would you judge the color correction and edge sharpness? Do the eyepiece barrels have compression-ringed SCDs? Which 3rd party eyepieces do you know reach focus?




I've bought bino without tripode and U-fork as:
1) Their tripode and U-fork are rather heavy and the delivery from China means bunch of money - much more as from USA for the same weight or volume for example!
2) I've got very good wooden tripode (USSR style)ShR-160, so it means no need of any compromissed China tripod.
So, just now I've got nothing to support the bino and with 6 kg of weight no hand-held observation is possible, you know! I've ordered DIY-style of U-mount for this bino to one of our masters, but it takes some time for making it... So, I'll report my impressions later - as U-mount arrives and weather would be good... I've just made a quick glance through it for day-time and could say that I see some minor chromatic abberation (with 22x eyepiece, too... and with 40x - more), but much less as I see with my Zhummel 25x100 (not a big surprise - 1:4 or near objective VS. 1:6) for the same conditions. Well, it's not very serious comparision or estimation for such a glance...
About 3rd pair of eyepieces - actually, I've got no 3d pair of eyepieces (26 mm plossl pair is not a big difference to 22x = 27.7 mm)... and now I'm looking for buying some good pair of wide-angle 1.25" eyepieces both for bino (and for my Dob-12" as well).

Quote:

Do the eyepiece barrels have compression-ringed SCDs?



I'm sorry - what is SCDs?
The eyepiece barrels seem to have teflone (?) ring ...


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GlennLeDrew
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Re: GBT 100/90 arrived new [Re: AndR1]
      #5473389 - 10/16/12 02:27 PM

I'd like to see a photo looking into one objective, with the little circle of light produced by the eyepiece located very near the edge of the objective. This will be another useful way to assess how much of the objective contributes to image formation.

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AndR1
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Re: GBT 100/90 arrived new [Re: GlennLeDrew]
      #5473465 - 10/16/12 03:30 PM

Quote:

I'd like to see a photo looking into one objective, with the little circle of light produced by the eyepiece located very near the edge of the objective.



Glenn, I'm not sure I've understood what should I do in the right way... Any additional description or/and link or/and scheme would be help...
Anyway, no new photo untill my camera will be repired ... or replaced by new one!


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GlennLeDrew
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Re: GBT 100/90 arrived new [Re: AndR1]
      #5474141 - 10/16/12 10:38 PM

You take a photo looking into the objective from roughly 50cm distant. But instead of having the camera exactly centered, move it toward one side until the little circular image produced by the eyepiece appears right at the edge of the objective.

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AndR1
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Re: GBT 100/90 arrived new [Re: GamesForOne]
      #5553832 - 12/04/12 11:53 AM Attachment (28 downloads)

Quote:


How would you judge the color correction and edge sharpness? Do the eyepiece barrels have compression-ringed SCDs? Which 3rd party eyepieces do you know reach focus?



Well, finally, I've got some days ago my hand-made U-mount and two third-part eyepieces (Meade 5000 SWA 20 mm) to try my bino... just for day observation, as now weather here is much to be desired. Those eyepieces reach focus, but there is one problem - the compressing ring is at the grove of eyepiece and it's not tight enough. So, two rings were purchased from local turner and it solved the problem (I could place a photo here if somebody likes to see it).
About colour correction. I compared bino side-by0side with my achro refractor Apogee 90/600 with the same eyepieces and it looks like there is not a big difference for CA correction ... well, maybe bino is a bit better, but I'm not sure. Anyway, it looks not so close to any ED or APO, as there is no big difference with a good (as my Apogee - I've compared it with some other achros) achro refractor.

See photos from objective side... although I'm not sure if it's the same thing as Glenn wanted to see...

Edited by AndR1 (12/05/12 01:31 AM)


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AndR1
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Re: GBT 100/90 arrived new [Re: AndR1]
      #5553833 - 12/04/12 11:54 AM Attachment (26 downloads)

Another one...

Edited by AndR1 (12/04/12 11:54 AM)


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AndR1
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Re: GBT 100/90 arrived new [Re: AndR1]
      #5553839 - 12/04/12 11:55 AM Attachment (28 downloads)

And here the photo of the bino, mounted on hand-made U-mount.

Edited by AndR1 (12/04/12 11:58 AM)


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GlennLeDrew
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Re: GBT 100/90 arrived new [Re: AndR1]
      #5553885 - 12/04/12 12:28 PM

Those photos looking through the objective's edge would suggest that the bino likely works at or near full aperture. Having an eyepiece installed would provide a clearer idea of vignetting, for then one would have a field stop located at the focal surface. Things often appear a bit better with this 'test' when no eyepiece is installed...

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AndR1
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Re: GBT 100/90 arrived new [Re: GlennLeDrew]
      #5554977 - 12/05/12 01:30 AM

Glenn, eyepices WERE installed for those photos! You could see contour of Meade 5000 SWA 20 mm at post #5553832 (not in focus of my camera).

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