New Vixen BT81S-A doesn’t like low power!

[Chaz2b]

I recieved these binos in the post yesterday, unused. Set them up on my Manfrotto 190 as they are quite light. I took them out last night for their first viewing using ExtraFlat 19mm wide angle 65* eyepieces. I spent ages looking at Orion then over to the plaides, although the seeing wasn’t spectacular, you have to grab these moments! I was finding them quite enjoyable.

Now today! I set them up in my front room where I check out all my scopes and binos with varying equipment, and set sights on a farm on the quantock hills 6.8 miles away. 
I check for focus on the telegraph posts and tree branches as they are the thinnest.

I’m finding the focusers and pupillary movements very easy to use both at the same time! Neat.

I started off again with the ExtraFlats and was quite impressed with terrestrial viewing, so on went a pair of 15mm Televue plossls…hmmm not quite as good, then the 32mm tv plossls…wow! Now that’s what I wanted, very stable and crisp images. 
I then fitted the 40mm tv single plossl and it did not want to come to focus! Odd?, not enough infocus!

okay, tried my Baader mk3 zoom, again couldn’t get focus with that either for the same reason.

Finally I fitted a pair of delites, 18.2mm, hmmm again! These binos are very particular as to what eyepieces you use.

I’m not the most experienced Bino user here, even though I have quite a few pairs again, I’ve now tried all my eyepieces and found they don’t like high power as well.

The Televue 32mm plossls are favourite with daytime viewing, and the ExtraFlats for night viewing.

Now, will they benefit night time with fringe killer filters?

chaz

Edited November 11, 2023 by Chaz2b
Typo

[Franklin]

When I had a pair of those I tended to stick with lower power eyepieces, pairs of NPL30, LVW22 and SSW10 and they all came to focus ok. What I did find was that smooth nosepieces worked best so I ended up using SLV25 and SLV12. Vixen do say that 10mm and below is too much for the design but I tried a pair of SLV6 and they merged ok but at that power the CA began to show from the achromatic objectives. Superb for scanning star fields at low power.

[John]

The Tele Vue 40mm plossls are not par-focal with all the others in the series by some distance.

They don't show any more sky than the 32mm plossls though.

The Delite 18.2mm is par-focal with the 32mm TV plossl so should come to focus at the same point.

 

 

Edited November 11, 2023 by John

[Chaz2b]

Yes the delites did come to focus, just not nice viewing, as same with the 15mm plossls, but the 32mm plossls were very nice as I said, stable and crisp.

Going to try out the eyepieces I’ve collected from binos I’ve disassembled to make scope eyepieces with, don’t have many nose pieces though.

[Coco]

Hi

Some will not come into focus, my 23mm Axioms wont so I had to modify them, try not to push your bins to far, they are binoculars not telescopes. I'll bet a pair of 18mm Ultra Flats work fine. as will 10,15 & 24's

Cheers
Guy

 

[michael.h.f.wilkinson]

I wonder if the poorer viewing at higher magnifications is only to do with CA. I have found that my 2" Amici prism works nicely with the 31 mm and 22 mm Naglers, nd also with the 17mm ES 92 deg EP, but not at higher magnifications. The prism creates some odd, asymmetric diffraction spikes that really disturb the view. These bins have similar prisms that could cause similar problems. 

[SteveNickolls]

Hi, thanks for posting about your experiences with the new Vixen 81's. I've had my earlier version of the binoculars for around 10 years and use Vixen SLV eyepieces, notably pairs of the 10, 15 and 20 mm ones without issue. The binoculars do best with straight barrelled eyepieces. Hope you can get more clear sky soon to use yours under.

Cheers,

Steve