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Celestron SkyMaster Giant 15x70 VS Celestron 25 x 70 SkyMaster, Weather Resistant Porro Prism Binocular

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Showing 1-2 of 2 posts in this discussion
Initial post: Apr 7, 2010 8:04:49 PM PDT
socialdis says:
WHO can help me to compare these two Binocular? I am a beginner in this field. Much imformation is about Celestron SkyMaster Giant 15x70 ,but rare about Celestron 25 x 70 SkyMaster, Weather Resistant Porro Prism Binocular.
so I don't know which to buy. thanks!
1FCelestron 25 x 70 SkyMaster, Weather Resistant Porro Prism Binocular with 2.7 Degree Angle of View, U.S.A.
2FCelestron SkyMaster Giant 15x70 Binoculars with Tripod Adapter

Posted on Jan 21, 2013 7:27:13 PM PST
Hi! To decide between binoculars (binos), the first step is to determine if you will handhold them or put them on a tripod or similar thing. The higher the magnification (MAG) the harder to handhold. Magnifications higher than 8X are usually harder to handhold unless you have very strong steady hands. The reasons: if you can't hold them very steady, you will get a jumpy image and feel sick and, second, higher weights will fatigue your arms and also cause the jumpy image. You solve the weight problem with a tripod (heavy, cumbersome and costly but absolutely needed for binos 5 pounds or heavier), a monopod (lighter, easier, cheaper- 5 pound binos or less) or a chest pod (for binos 5 pounds or less it is unbeatable in portability, ease and cost:$35 total). It weighs 5 ounces and is very comfortable.

The second basic issue: the exit pupil (EP) in the binos being a close match to your own eye pupil when fully dilated. If there's not a close match, you will be missing some of the light and image coming through the binos and wasting your money. It would be like trying to drink from a fully open fireman's water hose. In the human eye pupil the GENERAL rule is: children and young people under 30 can dilate to the max of 7mm. Those 30 and older have more of a 4mm to 5mm pupil when fully dilated. In your binos, determine it by dividing their second number by the first: in a 10X50, 50 divided by 10= 5mm, adequate for all ages. In a 10X70, 70 divided by 10= 7mm, adequate for the younger than 30. Given that you will not stay young forever and will most probably use your binos in less than perfect, bright light at all times, the safest bet is to get a combination that gives you between about 4mm and 5mm exit pupil. In the two binos you want to choose from: a) in the Celestron Skymaster 15X70 you divide 70 by 15 and get an exit pupil of 4.7mm which is great. In the Celestron 25X70 you divide 70 by 25 and get an exit pupil of 2.8mm, which is too small and will get you that tunnel vison feeling, shown by that 2.7 angle of view that you quoted. Binoculars usually give you a wider, more 3D feeling than telescopes, so you should look for a wider angle of view, in the vicinity of 4 to 6, or more. Therefore, the 15X70 is the winner. In binos, the 15X70 runs in the bigger category and usually weighs around 3 pounds but is GREAT for both land and night sky. You solve the weight/stability problem with a tripod, monopod or the easy, cheap portability king: the chest pod mentioned previously. Make sure your 15X70 has a center focus (even if it has right diopter focusing too) so its easier to focus quickly for terrestrial observation. Then 15X70 can easily be your only binos. Enjoy!
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Discussion in:  Binoculars forum
Participants:  2
Total posts:  2
Initial post:  Apr 7, 2010
Latest post:  Jan 21, 2013

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