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A few Questions on Oberwerk 20x80 Standard

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#1 Guest_**DONOTDELETE**_*

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Posted 26 February 2004 - 03:26 AM

I recently received my Oberwerk 20x80 standards from Kevin at Big Binoculars.com. What I've noticed during daytime viewing is that the images are a little dark and slightly fuzzy compared to my Obie 15x70 which are nothing short of phenomenal. I know the extra 5x will darken the image somewhat, but what I find strange is that while I view the night sky with the 20x80s, the views are better than during daytime terrestial viewing. The images are bright and clear. Everything snaps into focus. There is no false color on the cresent moon. In fact, the view of the moon is better than with my 8" SCT. I can only pull out 3 stars in the Trapezium of M42 but I think that's still pretty good considering the light polluted skies of Las Vegas. Jupiter was bright and showed slight banding. And while viewing the Stratosphere Hotel tower at night from 5.9 miles away, I can actually make out people riding the "big shot" ride on the top of the 1,500 ft. tower and also just barely see people in the restaurant on the 107th floor. Of course, the tower is extremely well lit at night but it's all artificial light. Also, in terms of magnification I notice there seems to be little difference in the 15x70s and 20x80. I thought the extra 5x would make more of a difference. Kind of a bummer because most of my observing is daytime terrestial.
So I guess my questions are:
1. Is it normal for the views to be better at night with less light than during the day with more light?
2. Does the 80mm aperture absorb neon light or star light better than sunlight?
3. Should the extra 5x between the 15x70 and 20x80s make more of a difference?
Thanks in advance for your comments.

#2 Diego

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Posted 26 February 2004 - 06:00 AM

Hey, I was in Vegas 3 weeks ago! Lost all my money of course.
While driving there, I saw some pretty clear skies some miles away from the city. Maybe you should try them there if you havn't already.
I would guess that the fuzzyness in coming from scattered light inside the binos. The darkness probably from the smaller exit pupil as compared to spotting scopes or birding binoculars.
These giant binos are best for night use. Remember that they are short f-ratio refractors, so unless they are "apo" or "ed", you will get false color in day light and bright objects. Even the 25x150 Fujinon MT has false color in day light (not that I've used one, just read about it).

Diego

#3 Guest_**DONOTDELETE**_*

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Posted 26 February 2004 - 12:37 PM

Diego,
Thanks for the input (sorry you lost all your money!).
The best dark skies around here are about 50 south of Las Vegas in southern Ca. When the weather clears up I'll make a trip down there with the local astro club and see how they perform.
Thanks,
Eric

#4 EdZ

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Posted 26 February 2004 - 01:12 PM

Where you should really begin to see the difference in magnification is on targets like dense clusters where in the 15x stars are just a little too close together to be resolved and in the 20x the apparent separation, now 33% larger, will allow you to resolve quite a bit more.

Set up both your 15x70s and your 20x80s and observe M36 and M37. See any difference?

edz

#5 KennyJ

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Posted 26 February 2004 - 01:33 PM

< 1.Is it normal for the views to be better at night with less light than during the day with more light? >

I find this can be the case with some binoculars, which seem to me , either by design or otherwise ,to be "optimised" for celestial rather than terrestrial use.

As has been mentioned before , there are many differences between a good astro bino and a good birding bino , and one that is very good for one activity can sometimes be very poor for the other --and vice -versa.

<2.Does the 80mm aperture absorb neon light or star light better than sunlight? >

There is really no comparison between the amount of light provided by sunlight and that provided by either neon or distance star -light.

< 3.Should the extra 5x between the 15x70 and 20x80s make more of a difference ? >

This depends what you mean by "more of a difference".

I too have spent hours comparing views through 15 x 70 binos and 20 x 102mm scope ( admittedly not quite the same comparison ) and must admit that there have been times when I've questioned whether or not there REALLY is a 33% increase at 20x over 15x.

This is a psychological effect.

Even a slightly larger exit -pupil and wider TFOV can combine to give the impression of a brighter image , and a brighter image , especially for terrestrial use , i almost always a desireable attribute.

Also if you are hand -holding both binos ,the steadier image at 15x will help resolve more.

Also the 33% increase in magnification also equates to a 33% increase in the effects of mirage.

These are only my opinions of course , but I hope it helps.

Regards --Kenny.

#6 Guest_**DONOTDELETE**_*

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Posted 27 February 2004 - 01:12 AM

EdZ and KennyJ-Thanks for the advice.
KennyJ-I think you're right about the psychological effect. The more I look through both pairs, the more I can see. They both have their own attributes in their own way. I'm trying to learn as much as I can and am going through previous posts which has also been helpful.
Edz-Thx again for your advice in your e-mail a few weeks ago. The bogen legs and head are a good match for them. The p-gram won't be here for another two weeks because of being back ordered. When it arrives I'll be able to compare both pairs of binos on mounts and I'm sure I'll see the difference.
Regards,
Eric


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