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Celestron Skymaster 25x100 FOV

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#1 EdZ


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Posted 16 April 2004 - 01:49 PM

Had a chance last night to check out the field of view on the Celestron Skymaster 25x100. It's advertised as 3.0°. It actually measures about 2.45°


#2 KennyJ


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Posted 16 April 2004 - 03:43 PM

This may not sound much less to some , but if these figures were "doubled" , we would be talking about a TFOV of 4.9 as opposed to one of a stated 6 degrees.

It continues to REALLY rile me that such important specifications as field of view and eye -relief are so commonly over - stated by manufacturers.

There ought to be a LAW against it , backed up by heavy financial penalties.

Regards , Kenny.

#3 BarrySimon615


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Posted 16 April 2004 - 04:48 PM

It almost seems like the methodology for measuring field may be based upon some other standard. Recently on this site, one of the other frequent responders narrated that a certain other 100 mm binocular, one favorably thought of, had a field that he could only document to be 2.8 degrees. I had the opportunity to view thru the same exact model binocular at the Kisatchie Star Party and I found that the extreme perimeter of the field could only barely "kiss" the two end belt stars of Orion at the same time. These two are 2.75 degrees apart, so let's call my measurement 2.8 degrees as well. A third regular contributor here also reported just 2.8 degrees in the same model. So what is going on, how are they measuring field? 2.45/3.0 is just under 82% of what is labeled and 2.8/3.3 is just under 85%. By area the smaller 2.45 degree field is just 66% of the labeled 3 degree field and the 2.8 degree field is just 72% of the labeled 3.3 degree field. This kind of disparity is striking and I feel strongly that manufacturers should both explain how the measurements are derived and if the explanation doesn't hold water, should relabel to reflect accurate measurements. I would bet that a fair number of binocular sales are based upon those binoculars having a specified field size. If they were mine, they would go back for a refund in a heartbeat.

Barry Simon

#4 nemo


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Posted 17 April 2004 - 01:21 PM

Ed and Barry,
Perhaps due to your efforts things may eventually evolve toward some sort of solution to the gross misinformation that seems to exist regarding manufacture's binocular specifications regarding FOV. Barry's idea about what criteria or methodology used to determine FOV could well bare fruit. One would think that there would be some sort of industrial standard for this. In the meanwhile Ed you may want to watch out for Chinese hit men.-smile-Keep up the good work guys!

#5 jmoore


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Posted 17 April 2004 - 02:06 PM

I'm with all of you on this one! This kind of misinformation is pervasive in eyepiece specs as well. I measured a "60-deg" Super Erfle at 52 degrees! No small error there.

Eye relief seems to vary a bit from spec...and my girlfriend's binos at 6.3 degs have a wider FOV than my 6.6 deg binos.

Give me a break!

So, what do we do about it?

#6 lighttrap



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Posted 18 April 2004 - 08:01 AM

About the only thing we can do about it is to continue to document it and post about it. And, of course, to return mislabeled and falsely advertised products with clear indications that it's the misleading advertising and labeling that is the cause of our complaint.

In the case of the Oberwerk 22x100s that I found had a 2.8* FOV, rather than the 3.3* FOV that was stamped on them, I returned them. The FOV was not the only issue with those. They were also optically inferior, and Kevin Buserow even confirmed that when I returned them. But, what also bothered me is that he told me after the fact, that he knew the FOV to be less than 3.3*. He said he's working with his supplier to have them re-labeled. But, in the meantime folks are still buying those with expectations that can't be met. In fact, he's still got those advertised on his website as having a "large wide-angle (3.3° FOV) eyepieces". He should modify that advertising, considering that he knows it to be false.
It does raise the interesting idea that perhaps the eyepieces are 3.3*, but the binoculars aren't. Either way, it doesn't matter, since the 3.3* claim is repeated in the spec chart for those binoculars. It's clearly misleading.

As for eyerelief, we could start a whole separate thread on the binoculars and eyepieces that don't live up to claims.

Mike Swaim

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