Celestron Skymaster 25x100


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Subject: good optics, great for the price
By: Anonymous (xxx.xxx.105.67)
Date: 07/02/2004 06:52:28 am PDT
I have in good seeing seen Airy disks of stars. Great optics, maybe not as good color correction as $1,000+ apochromatic scope, but you don't notice it except on bright objects like moon and Venus.
Wonderful value. They are heavy, not really usable handheld. As with any set of binoculars of this size, you will need to invest in a heavy duty binocular holder. Be aware though you may need to add extra weights for most commercial holders, as they are normally made for binocs a few pounds lighter than this baby.
I did have to send back the first pair I bought, due to a variation in the lens coating, but both sets I have looked through had the same optical performance (very good).
To appreciate these binoculars, you must see the Milky Way in a dark sky site. The wide field of view compared to a scope and the light gathering of these big lenses just knocks your socks off. I was looking at the several nebula in the Sagittarius region a few days ago and I had the impression someone had turned on headlights aimed right for me.


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Subject: Skymaster 25x100
By: edz
Date: 11/28/2004 03:53:56 pm PDT
Field of view is stated as 3.0°. It actually measures 2.45°
Oberwerk 22x100 has a measured 2.7° fov.

Objectives are multi-coated. Prisms and eyepieces are coated with what appears to be simgle MgF. Oberwerk is FMC.

Arrived with collimation only 1 arcminute out from perfect. probably would not be noticed by most people. It is noticed by my eyes.

Weight about 10#. This requires a heavy duty tripod head asembly on the order of Bogen 3246 with Bogen 501 head. About $400 for a stand up tripod.

Interpupilary distance has a very narrow to very wide adjustment, better than Oberwerk.

Eye Relief stated as 15mm and exit pupil distance actually does measure 15mm. BUT the lens is recessed 6mm. So usable eyerelief is only 9mm. With glasses on, my usual viewing mode, about 15% of the field of view is cut off. Not recommended for those who must eyeglasses. Oberwerk 22x100 has 11mm eyerelief and shows entire field of view.

A 14" double star can be cleanly split at 50% out from center, is still good at 60%, but is poor at 70% out. Even doubles of 21" and 22" can be seen at 70% to 75% out. Image sharpness drops off very quickly beyond 70% out. By 80% it is rather poor. Net usable field of view is 80% of 2.45° = 2.0°, much less than Oberwerk 22x100.

On-axis resolution is very good. I cleanly split doubles of 7.8" (Mesartim), 7.4" and 7.1"(Struve 953).

Limiting magnitude was mag 12.0 in Naked Eye mag 5.8 skies.
Looses about a half magnitude in the outer 50% of the field.

Sees more faint objects than 22x100 several 80mm binocs and Fujinon 16x70. But images are not as fine a pinpoint as the renouned Fujinon.

No CA seen on-axis, but considerable CA seen when bright objects moved to outer areas of field of view.

Center mounting post was too short. On my heavy duty tripod, I could not adjust the binoculars any closer than about 60mm IPD because the barrels hit the tripod head.

Go choice for deep sky views, but with a lot of little deficiencies that should not be present in a $300-$400 binocular.

edz


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