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20x60 ability

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#1 Chopin

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Posted 14 July 2005 - 07:39 AM

Anybody have an opinion on the capability of 20x60 sized binos for astronomy? I'm specifically refering to the Oberwerk 20x60 unit, as it seems to be a nice package based on specs. My only concern would be the 3mm exit pupil. My gut tells me that this would be too small for deep space fuzzies. Yes? No? :confused:

#2 EdZ

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Posted 14 July 2005 - 08:16 AM

My only concern would be the 3mm exit pupil. My gut tells me that this would be too small for deep space fuzzies. Yes? No?


Not true.

Image will not be extremely bright, but higher contrast and greater magnification (than average 10x to 15x binocular) will allow seeing many deep sky objects that might otherwise not be seen at all. The limitation here is on the light gathering power of a 60mm lens, but that will be offset somewhat by the additional benefit of 20x.

Some of my most enjoyable views using the BT100 with interchangable eyepieces are at magnifications that produce 2.5mm to 3mm exit pupils.

Broad area extended objects, such as the Rosette or North America nebulae, would probably benefit from a larger exit pupil. These types of objects need very dark skies and maximum brightness of image, therefore, large exit pupils. But many other objects can benefit from a little more magnification and hence a slightly smaller exit pupil.

edz

#3 Erik D

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Posted 14 July 2005 - 08:40 AM

Federic,

I like binos with ~4mm exit pupil for astronomy but 3mm would be fine too. I know several experienced bino astronomers who are quite happpy with the Canon 18X50 IS. Smaller exit pupil darkens the background sky and offer better contrast.

I have the Oberwerk 12X60. It's a very nice bino for the price. A few comments about your choice of a 20X60:

1. Given that you'll need a tripod mount with a 20X bino anyway why don't you spend a little more and get a 20X80 which collect 77% more light. Many 20X80s have ~3.5 deg FOV. The Oberwerk 20X60 is listed as having 3.0 deg FOV. You can cover 36% more area...

2. The Oberwerk 20X60 model is listed as having 10mm eye relief. That's pretty tight even if you don't need glasses to observe. A forum member just ordered the Oberwerk 20X80 LW a few weeks ago and is very happy with it. You should check his comments( Mike B)

Erik D

#4 Magellanico

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Posted 14 July 2005 - 10:28 AM

Hello!

Well, there is a review in S&T March 2001 of a Takahashi 22x60 binocular. The Oberwerk 20x60 should have similar views.

Clear Skies!

#5 Erik D

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Posted 14 July 2005 - 10:52 AM

The Takahashi 22X60 is essentially two Tak 60 mm APO refractors with flourite objectives joined together. Price is about $1,100 USD ~10 times the cost of Oberwerk 20X60 with superior optics. FOV is narrow at 2.2 deg....

Erik D

#6 Magellanico

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Posted 14 July 2005 - 12:44 PM

[quote name="Erik D"]The Takahashi 22X60 is essentially two Tak 60 mm APO refractors with flourite objectives joined together. Price is about $1,100 USD ~10 times the cost of Oberwerk 20X60 with superior optics. FOV is narrow at 2.2 deg....

Your are right. BTW, I am not saying about quality, price or FOV, but only that a 60mm has ability to do a good work. I have a Orion 8x56mm that works very well in many Messier object.

Clear Skies!

#7 Patrick

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Posted 14 July 2005 - 12:58 PM

My only concern would be the 3mm exit pupil.



When using a telescope to view DSO's it's not uncommon to get exit pupils 1mm and less. Viewing Jupiter at 230x with my 6" dob gives me an exit pupil of about 0.22mm. Of course, you might not want to go that small with binoculars, but as far as what the eye can see, it's pretty amazing.

Regards,

Patrick

#8 Chopin

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Posted 14 July 2005 - 01:44 PM

I will admit to a fair amount of ignorance on this subject, therefore I shouldn't be suprised by the replies. But I am. It's good to hear some positive feedback, and I appreciate the responses and suggestions.
Thanks for the "up-sell" Erik D.:grin: Your point is more than taken. In fact, the Obie 20x80 LW is the pair I initially leaned toward, but price will dictate my next purchase. If I can't swing the $200 for the 80's, I hoped that the 60's would be adequate at the least, being half the price (or about that), since they should be the same level of build quality.

Again, thanks guys for saving me from crossing these off of my list. :smirk:

#9 EdZ

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Posted 14 July 2005 - 01:45 PM

Viewing Jupiter at 230x with my 6" dob gives me an exit pupil of about 0.22mm.


?????
150mm aperture/230power = 0.65mm exit pupil

Generally, many telescope observers find that the exit pupils which provide optimum combination of brightness and resolution for DSO fall between 2mm and 3mm. Many DSO can't be seen unless high power is used, so we get down to 1mm exit pupils. Some find optimum resolution for small extended objects peaks at 30x per inch or at about 0.8mm exit pupils.

Short Focal length (fast) optics such as binoculars are generally not able to handle magnifications in the extreme. However a 3mm exit pupil is 8x per inch. That would not be considered extreme. You might find it difficult to hold the view with a 3mm exit pupil. Not the same as a scope where you only need to get one 3mm beam into one eye. here you need to get two of them set exactly to the roper IPD. With the narrow 3mm beam, being off by a little on the IPD will have a significant impact.

edz

#10 Chopin

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Posted 14 July 2005 - 01:55 PM

Short Focal length (fast) optics such as binoculars are generally not able to handle magnifications in the extreme. However a 3mm exit pupil is 8x per inch. That would not be considered extreme. You might find it difficult to hold the view with a 3mm exit pupil. Not the same as a scope where you only need to get one 3mm beam into one eye. here you need to get two of them set exactly to the roper IPD. With the narrow 3mm beam, being off by a little on the IPD will have a significant impact.

edz


I assume your reference is to allude that this magnification should be mounted, not only to stabilize fov, but also to get referential stability across the perpendicular plane of the eyes...

#11 EdZ

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Posted 14 July 2005 - 02:07 PM

No question about it, any binocular at 20x should be mounted. Not because you wouldn't be able to keep that 3mm exit pupil lined up with your eyes, but because at 20x you cannot possible get past the movement. Everything will be swimming in the view and motion sickness would be near at hand.

If you're intending to hand hold binoculars you need to be looking at 12x or 10x or Image Stabilized.

the Obie 20x80 LW is the pair I initially leaned toward, but price will dictate my next purchase. If I can't swing the $200 for the 80's, I hoped that the 60's would be adequate at the least, being half the price (or about that), since they should be the same level of build quality.



If you might consider 20x80s then you need to read the current discussion thread titled Oberwerk 20x80 Standards for info on several models of 20x80s and the mounts required to hold them.

edz

#12 brocknroller

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Posted 14 July 2005 - 03:39 PM

Is that urban, suburban, or rural CT? If urban or suburban, the 3mm exit pupil will enhance the contrast and allow you to see more rather than less, as Edz mentioned. Also consider the Pentax 20X60 PCF V (not the WP or WP II models, four samples of which were NOT as sharp as the PCF Vs). Hotbuys sells them for $180, other dealers probably still carry them too. There have been quality control problems with the Pentax PCF V line, but the views are unsurpassed for a 20X60 bin at this price point. I've used 20X80s that can't resolve as well (for example, I've tried to separate the rings of Saturn from the planet with Celestron, Swift, and Burgess 20X80s, but could not, however, I could easily w/ the Pentax 20X60s). That gives you an idea on how sharp it is.

Views of tight clusters like the Double Cluster are very impressive, as are other small DSOs. As mentioned, with faint extended nebulae, the 20X80 will probably work better.

You trade off ~ 1* FOV with the Pentax (2.2* vs. 3*). If you buy the Pentax, I'd recommend getting a "C" adapter (like an "L" but with another bar on top) and a 1X Mars dot finder for quicker location of DSOs.

I haven't seen the 20X60 Obies, the 15X70 had sharp optics; however, Kevin stands behind his products wheras at a camera store, particularly at a NYC dealer, you'd better check to see if they charge a restocking fee if you return them and how long you have to return them (by the time you get clear skies, it may be too late!).

My only beef with Obies is that they seem to go out of collimation easier than most bins, which is probably the trade-off for the low price. So you may need to tweak the collimation. Oberwerk has a site that shows how, failing that, Kevin will walk you through it.

Do you have astigmatism? If so, the 3mm exit pupil will help reduce it w/out glasses. The ER on the Pentax is twice that of the Obie, so if you do need glasses, Pentax is the way to go.

Has anyone compared the Pentax 20X60 PCF V to the Obie 20X60?

#13 Swedpat

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Posted 14 July 2005 - 04:02 PM

Also consider the Pentax 20X60 PCF V (not the WP or WP II models, four samples of which were NOT as sharp as the PCF Vs)....I've used 20X80s that can't resolve as well (for example, I've tried to separate the rings of Saturn from the planet with Celestron, Swift, and Burgess 20X80s, but could not, however, I could easily w/ the Pentax 20X60s). That gives you an idea on how sharp it is.


Brocknroller!

It's bad if the newer PCF WP and PCF WPII series are worse than the old one in the 20x60 version. I have only heard very positive opinions about the 10x50 PCF WP (II). Is it maybe difference in the optical quality between the models in the same serie? Is the 10x50 better than the 20x60?

I understand that one contributing factor to why you could separate the rings of Saturn from the planet with the 20x60 and not with the 20x80:s is that such bright objects as Saturn is best seen using high magnification and small exit pupil. Even better it would be with a 30x60. Or maybe a 20x30 would also work better than a 20x80?

Patric

#14 Patrick

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Posted 14 July 2005 - 04:33 PM

?????
150mm aperture/230power = 0.65mm exit pupil




Ed,

Your right, I read the wrong line in my eyepiece calculator spreadsheet. Good catch!

Patrick

#15 Chopin

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Posted 14 July 2005 - 05:39 PM

Thanks for the suggestion Bockenroller. I've nary heard a dicouraging thing about Pentax optics. Will keep in mind.

ps. Rural CT. (ave NELM 6.1-6.2)

#16 KennyJ

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Posted 14 July 2005 - 05:48 PM

< Even better it would be with a 30x60. Or maybe a 20x30 would also work better than a 20x80? >

Patric ,

You are correct to think this !

Three years ago ( after buying a Chinese 102mm refractor )
I finally threw out a 30 x 50 "home made" refractor which I'd put together using eyepieces from "give -away car -boot 10 x 50 binoculars mounted on a tripod seemingly constructed from matchsticks as a D.I.Y project long before I was born.

WHAT A TERRIBLE MISTAKE !

This contraption had been my " high - power scope " for years !

Yes -- 30 x 50 -- my HIGH power SCOPE !

I really miss the exquisite views of Saturn through that home -made instrument , to which I once jokingly attached a nameplate of " Taylor - Binks " -- just to confuse any passers -by who might have been interested in it.

I realise I am probably really stretching a "Swedish" ( not to mention INTERNATIONAL ) understanding of the English language here , but the reason I came -up with the name of " Taylor - Binks " was a kind of "local" send - up of another well -known British contraptionism which we Brits call " Heath Robinson ".

Edward Heath was at one time the British Prime Minister , and a guy in my neighbourhood was called Edward Taylor - Heath -- and a guy I once knew with the all - British - sounding surname of Binks insisted he was of Swiss decent.

" Swiss Family Robinson " -- ( a well -read book in the UK during my childhood half a century ago ) sprang to mind at the time :

-- hence the title " Taylor - Binks " !

If anyone ever happens to come across an odd looking telescope bearing the title " Taylor -Binks 30 x 50 " --

PLEASE LET ME KNOW !

( and tell it I'm missing it badly , and that my decision to part company with it was almost as rash and regretful as that of Steve Napier's to " leave " Cloudy Nights just because he didn't agree with a CN moderator's actions )

In summary , any optical instrument with specifications of anything approaching 30 x 50 -- is unlikely to be of much use in most , if not ANY situations ----

----- but for anyone suffering from the admittedly rare combination of acute astigmatism and bailiffs pounding on their doors , it can be of incomparable comfort to any such misfortunate soul with a penchant for observing that unique planet , Saturn.

Good evening Ladies and Gentlemen ,

Kind regards from that odd sod from Lancashire x

#17 Swedpat

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Posted 14 July 2005 - 07:03 PM

I realise I am probably really stretching a "Swedish" ( not to mention INTERNATIONAL ) understanding of the English language here , but the reason I came -up with the name of " Taylor - Binks " was a kind of "local" send - up of another well -known British contraptionism which we Brits call " Heath Robinson ".


Kenny!

Yes you do a bit, it demands some effort to understand particularly...but that is maybe comparable to your efforts to understand my sometimes clumsy english...:-)
Thank you for your commentary, I'm always glad to hear from you!

Patric

#18 DJB

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Posted 15 July 2005 - 01:02 AM

Hi Kenny,

I've always followed your posts, and I have no problem understanding what you intend. However, I do read your posts a bit slower, to make sure I understand.

Of couse, the English language was developed with all of it's insane "rules and regulations" from many older languages. I would just as soon well read the British rendition. How's the 7x50mm doin'?

Regards,

Dave.

#19 KennyJ

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Posted 15 July 2005 - 01:13 AM

Hi Dave ,

I'm still in the "honeymoon" stage with the 7 x 50s !

I've been using them more for watching aircraft soaring overhead than much else this past week.

I like these 7 x 50s !

Kenny

#20 DJB

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Posted 16 July 2005 - 01:32 AM

Hi Kenny,

Nice to hear of your continued interest in the 7x50s. Got my interest sparked, I must say that.

Great views and regards,

Dave. Oh, BTW, I also follow aircraft just for the fun of it, especially at night. I'm somewhat amazed at the time dilation before I realize that I can hear the sound waves going overhead!


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