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View Full Version here: : WO Binoviewer questions??


skies2clear
23-11-2006, 01:38 PM
Firstly, since I'm new here, hello everyone and happy viewing :)

I recently purchased a William Optics Binoviewer package, complete with 2 X 22mm WA eyepieces and a 1.6X OCS. My scopes are all newtonians, mostly made by yours truly ranging from 5" f7 to 12.5" f6. Not surprising, I couldn't get enough in-travel on my focusers to get it working, even with the 1.6X OCS supplied. There's a lot of info around that suggests ways around this, like using an extension tube between the OCS and the BV, or a different OCS, like Seiberts multimag.....all of a sudden the cost of admission is spiralling upwards!

The idea was to spend as little as possible to see if I liked the idea of 2 eyes is better than one. Nevertheless, I managed to use an Ultima 2X barlow with success (this gives more like 4X though), and eventually did some mods to one scope to get it going with the 1.6X OCS, although this is temporary.

I'm curious to know if anyone has seen a similar thing to me, in that, when comparing the light throughput from the LHS to the RHS, the RHS is noticably brighter, as well as having a slightly, but noticable difference in colour hue/tint. I don't think the BV has alignment issues, as I don't have any problems merging the 2 images, even with higher powers (maybe I'm cross-eyed!!!). The image on faint objects is noticably dimmer using the BV, compared with mono viewing. It does give a pleasant view in other ways, described by many others before me.

With all the generic Chinese BV's around, I'm curious if anyone has noticed this. Maybe the beam splitter in mine is defective, or maybe cheap BV's are like this?

Otherwise, the finish is pretty good, and the supplied 20mm ep's are pretty good. If I could gauge the ep's in performance, I'd say for sharpness, contast and light throughput, they work better than GSO Superviews, but not as good as Pentax XW's or Tak LE's (surprise, surprise).

Any ideas or comments would be more than welcome,

Clear skies,
Nick

janoskiss
23-11-2006, 02:34 PM
With these cheaper Chinese units the brightness mismatch btw left & right is normal. Here is a telling comarison between the cheap and top Baader units:
http://www.pbase.com/mclemens1969/image/68856060

Based on what I've read only, and quantitative analysis of images in this review:
http://www.astromart.com/articles/article.asp?article_id=169
the best left-right matched of the budget priced binoviewers would seem to be the Denkmeier Standard. (In fact it seems to have better balance than the Denk II.)

skies2clear
23-11-2006, 04:17 PM
That's really good info thanks. Seems I put up with it unless I eventually upgrade to something better.

Mind you, like the Denk II's, when you view with both eyes, there is no noticable colour evident. I'm sure the Denk II's are excellent, but for me, if I was paying that much, I'd want my BV's to not have that problem at all....but then, we are all different in what we put up with.
I wonder if the best BV's improve a lot in resolution of very fine details over cheaper units. I notice the WO unit isn't as good as a mono setup in this regard, but the two-eye-brain thing makes up a fair bit anyway. Time will tell for me really....
If only XW's worked on my BV....maybe surgically removing my nose would help!

It's interesting to know, there are some really excellent BV deals apparantly going. A couple of BV manufacturers will accept your cheap BV's as trade-ins, so you have nothing to lose trying them, IF you decide to upgrade.

janoskiss
23-11-2006, 04:32 PM
You can remove the eyecups from XWs if you want to use them in BVs (the top bit unscrews and then the rest of it can be removed also). But there is little point with the budget unit IMO. The XWs are not going to magically fix the flaws in the BV's optics, which get worse ito aberrations the farther off axis you go. So widefields are of limited use (and can sometimes make things worse in fact). I found good plossls to be the best EPs for budget BVs.

skies2clear
23-11-2006, 04:53 PM
I never thought of that with the XW's, but a good comment about the value of trying it.....you gets what you pays for in the end.

Satchmo
24-11-2006, 09:03 AM
The net result of splitting the beam into two eyes and internal light losses , is about 0.5 magnitude on point sources : the brain doesn't reconstruct the image to the original brightness ( no free lunches in other words).

Mark

skies2clear
24-11-2006, 02:20 PM
Thanks Mark. Good explanation. BV'ing is not quite a substitute for true binos then, except for the price and size!