Binoviewers - advice needed

[starlady]

I am thinking about buying a Williams Optics binoviewer but am confused by the advice that they may not work on some Newtonians - does anyone know which ones they mean?

I have an f4.8 Newtonian and an f10 refractor, can anyone advise me if a binoviewer will be usable at these focal ratios or not?

[kniclander]

I am not an expert but as no-one else has answered I will try based on my own experience. I have an F4.8 10" dob and my revelation binoviewers (basically, all the cheap ones are much the same in terms of what will/won't come to focus) would not quite come to focus becasue the extra length that the binoviewr adds means that there is not enough "in travel". the usual solution is to add in barlow which pushes out the focal point BUT (and this is quite a big but) the effect of the Barlow is increased by the distance between the Barlow and the e/ps (cos you stick the Barlow between the binoviewers and the scope. This effect can be mitigated by using a barlow where the lens screws off the barlow so that reduces the extra length (Antares do a cheap one like that). I found that a 1.6x Barlow did not make it work but a 2x Barlow did But it actually operated (and this is just my estimate) like a 5x barlow so my 20mm e/ps were actually giving me huge magnification.

Overall, i enjoyed it but I ended up sending the binovewers back becasue the pair I'd been supplied with (Scope n Skies, who else?) was actually battered about. I never replaced them cos I bought a guitar instead. Also, using cheap binoviewers in a big newt, for some reason some of the light path is blocked out - now I don't understand why that is at all but there is quite a lot of stuff on Cloudy Nights about it.

I would love to get into it again but if I were to do so i would wait until I could afford a little Mak (where there are no focus problems I understand) or a purpose built/adapted refractor. Not being able to binoview at lower powers was a real turn off for me.

just my 2ps worth. good luck.

[Peter Drew]

To reach focus using a binoviewer without a Barlow lens means using a binoviewer with an "optical correction system" (OCS) such as a Denkmeier unit, these allow reaching the focus on almost any telescope with minimum extra magnification than standard. Unfortunately, they are relatively expensive but high quality, there was one on the AstroBuyandSell site just recently.

[cdd2455]

I have a Denkmeier with 1.25 inch OCS, I use it in both my 12.5 inch f5 newtonian and in my f5.4 refractor, it works in both telescopes and, it's addictive to the point where I only rarely use a single eyepiece ( Nagler 20mm T2 ) any more.

Soon I'll be spending a few hundred euros on the Denkmeier 2 inch OCS to ensure I dont waste any light from the newtonian mirror, then another pair of eyepieces in the 24 to 26mm range, then perhaps a filter slide and perhaps a power switch. Then a bigger and slower dob to capture even more light and deliver it to the binoviewer.

The benefit of a binoviewer to my old eyes outweigh the cost.

Best Regards and Clear Skies

Carl

[starlady]

Thanks to all of you for the advice - I will need to save a few more pennies than i thought - the Denks sound good!

[brantuk]

Not so much technical but more commercial advice - the WO Binoviewers have been out of stock in the UK for around 6 mths now - you'll be lucky if you find a set brand new - latest forecast is mid May - a second hand set went on here a couple of weeks ago for around £100.

I saw a pair of "model 1" Denks sell at Kelling for £250 - I was just pipped at the post lol

[philming]

The problem some encounter with newtonians is a lack of back focus to be able to properly focus on the object you're aiming.

My advice, and I think you should REALLY follow : Go for a Baader Maxbright bino. You can order them with a "glasspath" that is some sort of a barlow, they exist at x1.25, x1,7 and x2.7. These just screw on the baader bino "nose", and act as a barlow as well. I've been using these successfully with a Mak 127.

So why Baader and not WO? First the prism are bigger on the baader so you'll lose less light on those. Second, for all the T2 adaptations Baader is providing for their Binos. I use a standard diagonal, and the problem can occure when the bino can just drop off the Diagonal. So Baader has released a T2 diagonal, and with this, your bino and EP are safe.

Third, I have read here and there that some people's vision just wont adapt with the WO. Dont know why but they just cant get the "stereoscopic" image.

So all that said, WO are making great products anyway (my Diag is a WO dielectric one) but well, as far as Binos go, prefer the Maxbright.

[kniclander]

The problem some encounter with newtonians is a lack of back focus to be able to properly focus on the object you're aiming.

My advice, and I think you should REALLY follow : Go for a Baader Maxbright bino. You can order them with a "glasspath" that is some sort of a barlow, they exist at x1.25, x1,7 and x2.7. These just screw on the baader bino "nose", and act as a barlow as well. I've been using these successfully with a Mak 127.

So why Baader and not WO? First the prism are bigger on the baader so you'll lose less light on those. Second, for all the T2 adaptations Baader is providing for their Binos. I use a standard diagonal, and the problem can occure when the bino can just drop off the Diagonal. So Baader has released a T2 diagonal, and with this, your bino and EP are safe.

Third, I have read here and there that some people's vision just wont adapt with the WO. Dont know why but they just cant get the "stereoscopic" image.

So all that said, WO are making great products anyway (my Diag is a WO dielectric one) but well, as far as Binos go, prefer the Maxbright.

hmmm - I'm not sure if this is entirely correct. The problem with binoviewers and newts is not lack of backfocus but lack of infocus because the binoviewer adds so much length to the optical train. As I understand it most maks will work well with most binoviewers because they have such long focus travel. so just because something works well with a mak, doesn't mean it will work well with a newt.

[philming]

Yes I dont have the slightest problem with binos. I dont even need the glassparh. And yes your're right, it's "infocus" problem on Newtons. Baader actualy sells a 2" adapter for those cases. And dont take me wrong, I'm not affiliated in any way to this company. I just see what's on paper (larger prisms i.e.) and the gear I personnaly use (T2 threading makes the whole system way safer) : I'm using a pair of AT Paradigm 18 mm on the bino, And well, with the weight of the bino itself, you'd better have a sturdy Diagonal. If not, and you have a little money on the side, definitly go for their T2 Dielectric miror diag. NO WAY the bino + eyepieces re going to end up on the floor this way.

So if WO isn't available in the UK for now anyway (rather strange, they're available in Germany and France for now afaik, well go for Baader ;-)

Small Edit : The model of Bino you should get depends on what you're going to look at as well. If you're goind planetary, Moon and such, a WO or Maxbrght is way good enough. As for deep sky objects, a Denk or MarkV makes sense. The prisms being even bigger, deep sky objects will definitly come through more easily on a high end Bino)