Telescope Reviews: Links to Resources and Information

Binoviewers and Clear Aperture
If selecting one of the 20mm CA binoviewers on the market, not only is there a light loss at the outer edges of the field stops, but also the Maximum True Field of View that you can get will be restricted to eyepieces with field stops about 22-23mm max.

Which binoviewers are actually the same?
Here's a series of measurements some that are the same

Which are the same? Which are different? Where are they made?
Keep in mind, these are actually the same binoviewer. The "BODY" of the Burgess C and the Stellervue BV3 are exactly the same. In fact both of these are exactly the same as the WO binoviewer and the Orion binoviewer and the older Moonfish BV. They appear to be the same as the Celestron and the Antares binoviewers. At various points in the past some of these older binoviewers had only 18mm clear aperture. The Stellervue, Orion, WO and BurgessC all have 20mm clear aperture. The only thing different about these binoviewers is the eyepiece holders. So, if one happens to have a brighter side than the other, that may be just luck of the draw.

Binoviewers that are not the same as those listed above include Baader Maxbright, BW-Optic, Lumicon, Televue, Seibert and Denkmeier.

edz

Here's the same binoviewer seen commercially available from a half dozen different dealers. It's shown here with options for every available configuration I've seen from any American dealer (1 screw, 3 screw and twist lock collets) .
United Optics - Kunming

Eyepiece FS Diameters for Binoviewers

Is there a scope that's best for binoviewing?
This post in the Binoviewer forum starts out " A few things you should know about binoviewers and scopes". This post explains not only how clear aperture affects the field of view, but also how the various attachments to the binoviewer nose change from the specified magnification factor when used in different scope/diagonal configurations. It is my experience, some people that are using binoviewers with an SCT scope have no clear idea what magnification they are using or what they are getting for true field of view. This post helps explain some of the above.

The Focal Length of an SCT scope
It is almost always NOT what is stated by the manufacturer. That is nominal focal length of an SCT. The calculations are complex, but the concept is relatively easy to understand. If you want to find the actual focal length of your SCT, read the next link about Drift Timing Eyepieces.

Drift Timing Eyepieces to Determine True Operating Magnification
You cannot trust the manufacturer stated power factors for binoviewers. There are just too many pieces in the light path that have an affect on the operating focal length. this is especially significant for SCT scopes, where many people are not even aware that the operating focal length is longer than the nominal stated, and that SCT focal length varies with every little turn of the focuser knob. You can determine YOUR operating power factors with your binoviewers. Here's how.

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Edited by EdZ (08/31/08 11:07 AM)