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Has anyone heard of this? Binocs modification.

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#1 Glassthrower

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Posted 13 May 2005 - 08:07 PM

After I submitted my review of the Celestron 25x100 Skymaster binocs, I received this via email :

I liked your review. I also have a pair sold by ACME OPTICAL. When I
was talking to MR. ACME about them he stated that the retainer ring for
the lens were installed very tightly and could warp the lens and cause
problems with the star images at the edge of field. My pair was slightly
out of alignment which I easily fixed myslef so when I was doing that I
also loosen the rings. Boy were they tight ! Both sides come to a clean
focus and the star images are pretty tight to the edge. I was using them
last night and noticed that I could easily see the belts on Jupiter with
them. Maybe this is the problem with yours ?


I have changed the name of the optical store and the person in question - just to be courteous, since I didn't ask permission to post this.

Does this sound reasonable? I'm very reluctant to tinker with things I do not understand, so I would like some more opinions. I do have a problem (shortcoming?) with the clarity of my FOV, but from what I have heard, this is not that unusual for cheaper Chinese-made binocs like mine.

Is this worth a try? Or do I run the risk of making things much much worse?


Then, I read this in one of the reviews here on CN regarding an improvement to a pair 25x100mm Apogee binocs :

(by Eugene Artemyeff) http://www.cloudynig...=183&pr=2x48x60

I made a couple of cardboard 60mm aperture masks to see if the chromatic abberation could be lessened. I am pleased to report that the masks almost completely eliminated the yellow/purple at the edge of the moon. Lunar viewing is now superb. The craters and other features remain tack sharp and the absence of color is very satisfying. Likewise with Saturn. Where without the masks I could not even tell if there were rings or not, with them I can now make out the rings crisply on either side of the planet. The gap between the planet and the rings is clean and symmetrical. On Jupiter, using the aperture masks, I was able to eliminate all yellow hazing at the edges and was even able to see banding on the planet. This is definitely the way to go with these binoculars on bright objects.


What is an "aperture mask"?????

In the same review, I also noticed what looked like a red-dot scope or similar finder-type thing mounted on the binocs. What is this and what does it do?


Ok folks, I'm sorry, I keep editing this post and asking more questions, but I MUST know.... :question:


Mike

#2 Erik D

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Posted 13 May 2005 - 09:34 PM

Masking down a 100mm to 60 mm objective increases the effective F ratio. Let's assume your 25X100 is a F4. Masking it to 60mm increase it to F 6.67. This will reduce visible false color on bright objects but also reduce brightness and resolution. Your 100mm bino is now a pair of 25X60s. You'd reduce the light collect area by ~2/3...Prof Ed can give you the equation for reduction in resolution in arc seconds.....

Personally I prefer to leave precison optical "tune up" to the pros. I know of one gentleman who had the Binofixer perform a tune up on his Burgess Optical 25X100 a while back and he was quite happy with the outcome. PM me for details.....

Erik D

#3 Claudio

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Posted 14 May 2005 - 03:04 AM

he stated that the retainer ring for
the lens were installed very tightly and could warp the lens


To much pressure on lenses, prisms, mirrors can easily produce glass strain, thus aberrations will be observed.
Regards
Claudio

#4 Guest_**DONOTDELETE**_*

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Posted 14 May 2005 - 07:35 AM

Erik, does stopping down the aperture really reduce CA?

#5 Joe Ogiba

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Posted 14 May 2005 - 08:49 AM

Stopping my 120mm F5 refractor down to 50mm (F12 effective FL) cuts out about 90% of the CA but it's still not even close to my 80mm F6 fluorite triplet APO. My new Canon 10x42L IS WP's have no noticable CA thanks to high quality L series optics, featuring 2 Ultra-low Dispersion (UD) lens elements (on each side).

Joe

#6 Steve Napier

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Posted 14 May 2005 - 09:18 AM

There is a very interesting thread on www.birdforum.net about a lad who has stopped his 10x42 FL down to 39mm {a very small stop down that} and he says its improved the view no end.
Futher contributors to the post claim he should send his binoculars back to Zeiss as they maybe badly made.

I once stopped my 10x50 Dekarems {I gave these away yesterday} to only 25mm to see how the brightness altered and found that during the day there was no appreciative difference what so ever.

When seeing conditions are bad I regulaly stop my 3" refractor down,both Edz and myself experimented with this on a star in Bootis last year we managed to split this double {E bootis} with only 60mm and most books claim at least a 75mm aperture is needed.
Steve.
P.S. Ive just been informed that there is to be a school marching band at Manchester Bucaneer"s home games next season. :usa:

#7 Guest_**DONOTDELETE**_*

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Posted 14 May 2005 - 11:01 AM

Stopping down one's bins can only clean up longitudinal CA, which is the form of CA we are most familiar with. However lateral CA is uneffected.

#8 Glassthrower

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Posted 14 May 2005 - 12:09 PM

Thankfully, I do not have a big CA problem. Or if I do, then I don't recognize it, so it makes no difference to me.

What about the telrad-finder looking thing on the binocs? Is that a telrad, or a red-dot finder or what?

Personally I prefer to leave precison optical "tune up" to the pros.


Where does one take a pair of binos for a "professional tune up"?

Mike

#9 Erik D

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Posted 14 May 2005 - 02:02 PM

The gadget on top of Eugene's 25X100 is a red(?) dot finder. A Telrad is the same concept(unity finder) but bulkier. I don't use a finder with my 20X80 or 25X100 binos but would recommend getting a small red dot finder instead of a Telrad if you want one. Oberwerk, Stellarvue and many other dealers have them. I've seen Larry P at UA showing a finder with a velcro mount around his Tak 22X60 bino....

Professional Bino Tune Up? EdZ posted <binofixer@aol.com> a few days back....I've heard he did a very good job for someone with a BO 25X100.

Erik D


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