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"new" 70mm 45s

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#1 Mr. Bill

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Posted 04 January 2013 - 06:23 PM

Just found these on Big Binocular website.

http://www.bigbinocu....com/70bt45.htm

Anybody with first hand knowledge?

Didn't 90 degree versions have effective aperture and edge of field illumination issues?

:question:

#2 Rich V.

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Posted 04 January 2013 - 08:01 PM

Didn't 90 degree versions have effective aperture and edge of field illumination issues?

:question:


It was the 100mm 90° that had effective aperture problems and considerable vignette. The MKII version of the Garrett 70mm measured full aperture, IIRC. Don't know about the illumination of field, though.

There was a long thread a while ago about these:

Garrett BT70-90 MK II's arrived!

Still looking for the reference to the flashlight aperture test; maybe it was another thread...Searching CN can be a pain sometimes!

Rich

#3 daniel_h

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Posted 04 January 2013 - 09:42 PM

i think i remember 68mm being quoted, it was close (i agree searching CN is a pain-the lists can be huge)

#4 GamesForOne

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Posted 05 January 2013 - 10:19 AM

Didn't 90 degree versions have effective aperture and edge of field illumination issues?

:question:


It was the 100mm 90° that had effective aperture problems and considerable vignette.


Not meaning to get off-topic, but we do have one poster who recently purchased a 100mm 90° model direct from the Chinese factory and it tests at very near full aperture with the appearance of good field illumination to the edges.

I don't know if/when this model will propagate to dealers such as Garrett and Orion, but it appears the shortcomings have been addressed at least in the one sample that has been reported.

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#5 peter k

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Posted 06 January 2013 - 01:59 PM

Yes. approximately 68mm effective aperture on the 90s (link to my original post).

I believe the 45-degree version has been on the United Optics web site for years--just no US distributors until now.

#6 STEEL

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Posted 07 January 2013 - 10:33 AM

Beautiful optics.. attention to the inter-pupil distance 68 mm max (my eyes are almost 70 mm),hope that as soon as possible this small problem is modified.

#7 Rich V.

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Posted 07 January 2013 - 11:02 AM

Good point, Steel, I hadn't noticed the 68mm max. IPD spec for these...

Rich

#8 OBERWERK

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Posted 07 January 2013 - 12:01 PM

Good point, Steel, I hadn't noticed the 68mm max. IPD spec for these...

Rich


True, and we'll soon change that. In the mean time, there is an IPD linkage stop that can be easily removed to gain additional width. The binocular's handle then acts as the new stop, and it will then go to 78mm.

#9 kray1

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Posted 07 January 2013 - 03:05 PM

I have the 25 x 100 Garrett and the 15 x 70 Oberwerk; would the 70mm/45 binocular telescope really add that much to my viewing experience?
If so, what addtional magnifications be most beneficial for this bino?

#10 OBERWERK

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Posted 07 January 2013 - 03:39 PM

I have the 25 x 100 Garrett and the 15 x 70 Oberwerk; would the 70mm/45 binocular telescope really add that much to my viewing experience?
If so, what additional magnifications be most beneficial for this bino?

The image quality is exceptional, very sharp at 47x (8mm eyepieces). The combination of versatility and high quality, in a small relatively-lightweight (8.5 lb.) package is quite unique.

#11 Mr. Bill

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Posted 07 January 2013 - 04:09 PM

Not to mention 45 degree oculars which are very desirable for those of us that spend most of our binocular time looking up....

Kevin...meant to ask, what is the prism clear aperture?

Am I going to vignette my 24 Pans with a 27mm fieldstop?

I think I remember 22mm being mentioned for the 90s.

:question:

#12 Rich V.

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Posted 07 January 2013 - 04:21 PM

Kray, you're pretty well set for wide field views. A 70mm BT would give you a range from 16x to maybe 50x. Your current large binos at 25x@ 2.5° and 15x@ 4° already cover the lower mags a 70mm BT would provide. The only gain would be in the 25-50x range but I think for the sake of avoiding redundancy, a 100mm BT would be more appropriate with its 25x-75x mag. range. If you only want to travel with one multi-purpose instrument, though, a 70mm BT might just be the ticket.

BTs have a big advantage over straight-through bino designs in their viewing comfort. You can sit comfortably and look through the angled eyepieces all the way to zenith; try that without some kind of p-gram or chair mount with your 25x100s.

A binocular telescope gives you the ability to reach low to medium telescopic magnifications but still retain the advantage of binocular vision. You reach a point at higher mags where a telescope is superior to a BT due to its simpler optical design and higher resolution, though.

It comes down to different optics for different purposes. I personally use fixed mag. binoculars up to 22x for WF use, a 100mm BT for 33x-71x midpower views and telescopes up to 300x or so. One or another optic I have will frame an area of the sky or object the way I want to see it!

Rich

#13 OBERWERK

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Posted 07 January 2013 - 04:34 PM

Not to mention 45 degree oculars which are very desirable for those of us that spend most of our binocular time looking up....

Kevin...meant to ask, what is the prism clear aperture?

Am I going to vignette my 24 Pans with a 27mm fieldstop?

I think I remember 22mm being mentioned for the 90s.

:question:

Prisms are 24mm, but there is a 23mm stop at the base of the focuser.

#14 Rich V.

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Posted 07 January 2013 - 04:43 PM

Bill, you still get 20x @ 3.3° with your 19 Pans; 4°+ @ 16x with the 24s. I can't imagine the vignette with the 24s would be so bad as to be a deal breaker. :D

To add to any vignette, though, there might be quite a bit of field curvature with such a short focal length objective!

Rich

#15 Mr. Bill

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Posted 07 January 2013 - 05:18 PM

Not to mention 45 degree oculars which are very desirable for those of us that spend most of our binocular time looking up....

Kevin...meant to ask, what is the prism clear aperture?

Am I going to vignette my 24 Pans with a 27mm fieldstop?

I think I remember 22mm being mentioned for the 90s.

:question:

Prisms are 24mm, but there is a 23mm stop at the base of the focuser.


Looks like 19 Pan with 21.3mm fieldstop would be ideal...

:cool:

#16 OBERWERK

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Posted 07 January 2013 - 05:27 PM

Looks like 19 Pan with 21.3mm fieldstop would be ideal...

:cool:

Yes, that would be 20x (375mm f/l).

#17 Mr. Bill

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Posted 07 January 2013 - 05:31 PM

Guess another issue is the robustness of the collimation...looks like you would have to pull the top of the "can" to make adjustments.

:question:

#18 OBERWERK

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Posted 07 January 2013 - 05:54 PM

Guess another issue is the robustness of the collimation...looks like you would have to pull the top of the "can" to make adjustments.

:question:

Yes, a pain to adjust, but it is a robust 3-point push-pull system. Once set, maintaining alignment will not be an issue with this model.

#19 planetmalc

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Posted 08 January 2013 - 12:42 PM

The studs on the sides of the tubes suggest that the instrument could be supplied with a proprietary fork mount (like Miyauchis were) - is this going to be the case?

#20 kray1

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Posted 09 January 2013 - 07:58 PM

Thanks for the suggestions. The 100s certainly would give higher mags but I think that I will be happier with the 70s at 47X. That should offer a nice increase over the 25 x 100 and less light to tame the views of Jupiter and Saturn.

#21 GlennLeDrew

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Posted 10 January 2013 - 01:45 AM

"...and less light to tame the views of Jupiter and Saturn."

First, such an instrument is not at all ideal, nor intended, for planetary observation. To *want* less aperture so as to deliver a dimmer image is tantamount to sacrilege. Filters will do this, and they will not come close to harming the image as much as the optics themselves likely will at the required magnification. And if the optics could stand up to it, increasing the magnification to the point of a 1.5mm or smaller exit pupil will suffice to make the image surface brightness low enough for 'comfort.'

If you want to observe the planets, there are far better instruments available at rather lower cost.

#22 Mr. Bill

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Posted 10 January 2013 - 11:10 AM

Kevin B recommends a max magnification of 47x with these binos. Glenn's comments above are right on target IMO.

:cool:

#23 kray1

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Posted 11 January 2013 - 12:44 PM

I suppose that I really should be using a telescope however,my experinces with monocular, upside down and reversed images leaves me totally unsatisfied. As a casual observer, i need something quick and easy to take outside and view. Also, the expense of a binoviewer setup for infrequent use seems a waste.

#24 Joad

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Posted 11 January 2013 - 01:12 PM

Alas, one of the most important lessons I've learned both from experience and from discussions here on Cloudy Nights is that when it comes to amateur astronomy, everything is a compromise. I, too, once hoped that a binocular telescope (like my Oberwerk 45° BT100) would be an all purpose instrument. It isn't, even with interchangeable eps giving me a view up to 85X with the eps I have. The fact is, as has already been noted in this thread, that binoculars aren't quite the thing for planetary viewing, both because you cannot reach the high magnifications that planets require and because getting a tightly merged image at high binocular power is very difficult.

Binoculars aren't useless for planetary viewing, by any means, but you need a telescope to get the best out of planets.

#25 SMark

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Posted 11 January 2013 - 01:32 PM

I will admit that I am quite happy about how well the Moon, Jupiter, and Saturn can look in my 30x80. Back in high school my first binocular was a 30x70 and I much enjoyed the Moon and planets then as well. I'm satisfied "settling" with that when I don't have the desire to get my telescope out and set-up... which lately is most of the time.

But I think much of it also is expectations. I don't expect any binocular to do that well on the planets, so my perception with the 30x binoculars is positive. If I had a BT, I'm sure that I would be expecting much more along those lines. Which is why I'm not convinced yet that I should even consider getting one. Another big issue with me is weight, though this 70mm should be quite manageable. But anything bigger takes me well over 10 lbs. and so becomes more difficult to move around with.






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