WO Binoviewers - Getting the widest field of view

[wassit]

Hi,

I have Celestron C925 and a WO binoviewer and I have to say I love them!

I guess I am now going down the same route as so many before me looking to get a couple sets of eyepieces for the highest and least magnification.

I am presuming for the highest magnification the binoviewer does not add any limitation to the scope other than maybe some brightness loss, please correct me if I am wrong.

When it comes to the least magnification I keep reading about limitations caused by the clear aperture of the binoviewers themselves ( 20.2mm for WO I think ).

Does anyone know what it the highest focal length eyepiece I can use and whether there is any limitation to AFOV that goes with them? 

Thanks

[Avocette]

I understand that you will get vignetting and you won't benefit from the expected wider field of view. The 20mm WO EPs are pretty much optimum for your binoviewers. In the other direction, there is an argument for not going too short in EP focal length because it can make it more difficult to get the two images to converge properly. Hence the suggested solution for higher magnification is to use the Barlow nosepiece or higher magnification Barlow in front of the binoviewers. My personal experience is limited to the WO 20mm EPs, and a pair of SW 10mm Super Plossls which were supplied with my SW Newt and Dob and I prefer the 20mm EPs in conjunction with the 1.6x Barlow nosepiece or a 2x Barlow in my 1500mm focal length Dob.

[Northern Soul man]

Hi Ya Wassit and a very warm welcome to the SGL mate - a very nice choice of scope and the WO Binoviewer's, I think really do compliment the SCT - I have a set and use them mainly for Planetary/Luna - this is where they really do excel over cyclops mode - The times I have used them on Jupiter are probably THE best views I have had over all the years and different scopes used for Planetary, as Avocette correctly points out, the supplied WO 20mm and the 1.6 Barlow (also supplied) are probably just about right ( for my set up anyway), the views over mono mode just show a slight drop in brightness, but I think using both eyes makes up for the slightly dimmer views.

So the 20mm plus the 1.6 Barlow gives an effective mag of around x224 for my set up - just about ideal on Jupiter - but I think a lot has to do with the height of Jupiter above a lot of the light pollution and this height your moving into steadier seeing conditions - which I think have probably added about 70% better viewing conditions compared to - say the height of Saturn at the moment - so this with the added 2 eye mode over the last 2 apparitions of Jupiter have made for the best ever views for me.

I also have used a pair of Baader zooms with the eyecups removed (just unscrewed) and replaced with the much smaller eye cups which came with the zooms - so you can get the barrels of the zooms closer together - I've tried the different mags with the zooms - but still come out with the 12mm setting about the best - but the smaller type Plossl EP's are just about ideal - much lighter weight than the zooms added together with the ideal viewing position out the back end of an SCT make for an ideal night - just to align on Jupiter and have an hour or two just with the scope tracking.

So Planetary/Luna - really nice - just about ideal in combination with a long focal length SCT of any aperture I think - for just sheer comfort at the back end with a very comfortable seated eye position - I'm well sorted for a good few hours.

Now for DSO - here, for me - not so good, but it maybe just using the SCT with a much smaller field anyway - that you are going to struggle - just because your using an SCT - the small light loss will make a difference, yes, the objects are there - but this is where you need all the light gathering you can get to brighten and add that much sort after contrast needed for DSO work - I'm afraid its back to cyclops mode for DSo's - but with Jupiter so well placed over the last month or 2 the WO Binoviewer's have been well worth the cost, just for Planetary alone.

Paul.

[wassit]

Thanks for the responses and the welcome! 

You have both confirmed what I suspected, I have very much being enjoying Jupiter and the moon through them these last few months so maybe I will stick to the solar system for now. Saves me a few pennies too

[Merlin]

We shouldn't be put off too much by some observers saying that binoviewers are not very good for deep sky observing. I had a "pretty" view of the Orion nebula with the WO's attached to a modest SKYMAX 90.

Obviously, the bigger the 'scope the better.

[Northern Soul man]

NIce 1 Merlin - exactly right mate.  All the brighter Messier objects I've observed have been really nice  - a lot of it with me has to do with the light pollution more so than the dimming in the binoviewers - yes there is a dimming in the viewers when I have done a comparison on Jupiter - but its no so well pronounced as you might expect - it actually helps with my set up as it lowers the overall brightness of Jupiter's disk just enough as to make it much more comfortable and believe it or not, makes the lower contrast detail more visible as opposed to a brighter image that just washes out the fainter detail.

The brighter Messiers are well worth a look through Binoviewers - its just my skies that sort of limit the contrast far more than a drop in brightness which the Binoviewer's create, switching to mono mode under my skies really doesn't improve things by much - its the fault of light pollution and not the light being split in the Bino's.

Paul.

[neural]

Don't forget the Sun of course - with a bit of Baader film the BVs give superb views.

And, maybe this is weird, but don't knock it till you've tried it - doubles through BVs? Last night I was looking at Algieba, Cor Caroli, iota Leo (just) and especially Porrima, and could have added Mizar, Castor, maybe even xi UMa ... there must be a dozen or two that are bright enough.

[Mark in Macc]

I have exactly the same set up. I use 25 mm TV plossls for lower power, but as the others have mentioned, this doesn't give a wider field of view. I sometimes prefer this on the moon. I have opted for eyepiece pairs and also have a pair of 15 mm Vixen NLVs with modified eyecups for higher power. I have also borrowed a pair of 18 mm BGOs to try out, which are rather good. I concur with your assessment, the WO binos + C9.25 is superb.

[Tomofmoo]

Hi new to all this forum stuff I have got wo bino with sky watcher ed80 & ed100 and have enjoyed the views on both moon and planets so much so the rest of my toys are almost redundant now

[neural]

Don't forget the Sun of course - with a bit of Baader film the BVs give superb views.

And, maybe this is weird, but don't knock it till you've tried it - doubles through BVs? Last night I was looking at Algieba, Cor Caroli, iota Leo (just) and especially Porrima, and could have added Mizar, Castor, maybe even xi UMa ... there must be a dozen or two that are bright enough.

The suspense is over - I can now confirm that xi UMa is a good'un.