Vixen BT81-S Binocular Telescope Unboxing/Review

[Chris]

Firstly thanks to FLO for a great service as always These ex- display Vixen BT81-S binos arrived today so here are some unboxing pics initially but I'll also be doing a bit of a review on them

[Chris]

Time to mount them and see how they sit on my AZ4?

Size, weight, and balance wise the AZ4 looks to be a good match. oh and those deep blue objective coatings look delicious. Good start so far!

The BT81-S has both a vixen dovetail and 2x 1/4" witworth threads on the under side of the dovetail. I mounted these pair by reversing the L-bracket which came with my AZ4 and using the 1/4" threaded hole furthest back on the dovetail for the best balance.

[Dude_with_the_tube]

looks awesome.let us know your first light and thoughts of these.

Clear skies! 

[Chris]

Now the Vixen BT81-S Binocular telescope doesn't come shipped with eyepieces, however, I do have a pair of WO 20mm 66 degree EP's that came with my Binoviewer so lets give them a whirl!

These are friction fit which was a slight worry as the WO EP's have a taper on the barrel. I found that the left eyepiece sat slightly loose in the holder but the right side is a good fit. I think both sides will be fine with straight barrel eypieces but I will see if the left side can be tightened a nats whisker? The helical focuser for the right eyepiece is silky smooth and the left side was initially slightly gritty before freeing up. The barrels adjust smoothly for interpupilary adjustment, if anything they could do with a touch more friction to give me the confidence that they will stay put? I will see if this is an issue in use when I get them out under the stars a couple of times. My guess is that it won't be an issue

[Chris]

Being very careful not to blind myself I pointed the Vixens at a distant chimney in the opposite direction to the Sun. Both eyepieces snapped into sharp focus. Really at this point I should have started to evaluate the views for such things as chromatic aberration (CA) and edge performance but I simply just enjoyed the views! I didn't notice any significant CA in hindsight, just a bit of yellow fringing near the edge but I will do a proper evaluation under the stars. All I can say at this stage is the distant chimney looks very close and sharp, fine detail could be seen even though it must have been around 150m away.

The Vixen bino telescope has a focal length of 480mm so my WO 20mm eyepieces gave 24x. The objectives are 81mm so the focal ratio is f/5.93, so F/6 will do

I had a go at pointing my Canon 1100D down one of the lenses to give a vague idea of the views but I didn't get the sharpest focus with the camera so take it with a pinch of salt.

There does seem to be vignetting towards the edge on the pics but I can't say I noticed this with my eyes so I will have to double check.

[Grotemobile]

I can see a couple of 5mm EPs on

order soon.96x should be good on these.

Have fun

Steve

[Chris]

Finder and eyepiece pair suggestions welcome as I will be in the market for these soon. I already have an ES 16mm Maxvision so its tempting to buy another to make a pair at 30x, I'll have to look at the barrel on the maxvions to see if they are suitable also. with a bit of saving I could spash out on a pair of Vixen SLV's around 12-15mm but that could end up really denting the wallet

[Chris]

I can see a couple of 5mm EPs on

order soon.96x should be good on these.

Have fun

Steve

Hi Steve, thanks I would love to think they would cope with 96x but the engineering and tuning would need to be incredibly precise to allign both optics for that mag so realistically we are talking about 40x maybe 50x times max. The site for these says not to go above 10mm eyepieces so I will try 12mm at the top end and see how it goes

Chris

[Chris]

looks awesome.let us know your first light and thoughts of these.

Clear skies! 

I definately will do Might just be on the back burner for a week or two as my wife is having twins by C-section tomorrow morning! I'm sure I'll get the odd 20 minutes between nappies for a bit of astro though

Chris

[Dude_with_the_tube]

I definately will do Might just be on the back burner for a week or two as my wife is having twins by C-section tomorrow morning! I'm sure I'll get the odd 20 minutes between nappies for a bit of astro though

Chris

wow,thats something!grats on new family addition mate!  

[NGC 1502]

I definately will do Might just be on the back burner for a week or two as my wife is having twins by C-section tomorrow morning! I'm sure I'll get the odd 20 minutes between nappies for a bit of astro though

Chris

Couldn't the missus hang on for a few days to give you a chance for first light ?   Gotta get her priorities right you know 

Looking forward to your observing report, whenever it comes, and all the very best to yourself and family, Ed.

[Chris]

wow,thats something!grats on new family addition mate!  

Thanks Dude

[Chris]

Couldn't the missus hang on for a few days to give you a chance for first light ?   Gotta get her priorities right you know 

Looking forward to your observing report, whenever it comes, and all the very best to yourself and family, Ed.

thats not the half of it, its also my wifes birthday tomorrow which means I'll have three birthdays to fund at the same time each year!

Thanks Ed

[F15Rules]

Hi Chris,

Firstly, I hope everything is going/goes well with your new arrivals and that all 3 birthday people are healthy and safe :-).

I love those binos, and the white paintwork just looks the business. Can you mount a mini finder on these? Do you even need to? (Would look cool though!).

Am loving my new BA8 10.5x70s and will be interested to hear how much of a step up the Vixens are. How about getting a pair of nice quality 32mm eps to give 15x81's??  

All the best to you and yours Chris.

[nightfisher]

Really nice, im not a bino person but these Vixens just look the part and should perform superb, how about a couple of sets of Revelation plossl`s maybe a pair of 11mm and a pair of 15mm

[Chris]

Hi Chris,

Firstly, I hope everything is going/goes well with your new arrivals and that all 3 birthday people are healthy and safe :-).

I love those binos, and the white paintwork just looks the business. Can you mount a mini finder on these? Do you even need to? (Would look cool though!).

Am loving my new BA8 10.5x70s and will be interested to hear how much of a step up the Vixens are. How about getting a pair of nice quality 32mm eps to give 15x81's??  

All the best to you and yours Chris.

Thanks buddy and I'm glad your getting on well with the BA8's I knew you would like then

All three are doing well My wife will be in hospital for a few days after the C-section this morning and our lovely twin girls Freya Olivia and Seren Elsa Lock are on the special care baby unit as they are prem twins. I'm hoping my wifes upto visiting them in the morning but I've took some pics for her in the meantime

After just a quick daytime go with the Vixens so far I can say two things: 1) They look great, 2) they are very very comfy to use on my AZ4 mount. I've reached the chapter in Steve's book about evaluating binoculars so I will be using the steps depicted by Steve when it comes to a proper review And yes there is a finder shoe on the left optic for either a finder or red dot which is great, I don't know for sure but I'm thinking an RDF will work great with these

15x81 will suck in a lot of light when it comes to a star count, and also give a good FOV if vignetting isn't an issue?

I'll keep you posted on the Vixens

Chris

[Stu]

Many congratulations to you and your wife Chris. Hope all continues to go well and that the twins are out of special care very soon.

Enjoy your time with them, the binos will wait :-)

Stu

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[Chris]

Really nice, im not a bino person but these Vixens just look the part and should perform superb, how about a couple of sets of Revelation plossl`s maybe a pair of 11mm and a pair of 15mm

ah you see if you're not a bino person these Vixen's might just change that I'm liking the sound of those mags and Plossls will be very economically viable! I'm going to have to give EP's some serious thought as I've read that these Vixens really shine with quality EP's like the ortho like Vixen SLV's. But then again for the price of a pair of these (220 quid) I could get a full range of Plossl pairs! Its just knowing how much worse the views would be with the plossls? Guess it depends partly on the quality of the plossl?

Chris

[Chris]

Many congratulations to you and your wife Chris. Hope all continues to go well and that the twins are out of special care very soon.

Enjoy your time with them, the binos will wait :-)

Stu

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Many thanks Stu I can only describe it as magical cuddling them on specal care earlier this evening, I can't wait until my wife can do the same tomorrow Yep the binos can indeed wait, just getting my astro fix before bed, its been quite a full on day

Chris

[Stu]

It's a wonderful feeling, I have a 4 month old little girl so know something of what you are experiencing. Magical is definitely the word :-)

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[Chris]

I don't think my 2 year old has quite grasped whats about to happen to his world!

p.s. Congrats on your recent addition Stu!

[Stu]

I don't think my 2 year old has quite grasped whats about to happen to his world!

p.s. Congrats on your recent addition Stu!

:-). Funny :-)

I know someone who brought their new baby home and their sibling asked at the end of the first day 'when is the baby going home'!

Some adjustment to be made :-)

Have fun.

Edit: just thinking, when they are older you can hang one off each eyepiece of the binos and let them observe together ;-)

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[F15Rules]

Many congratulations Chris, you must feel on top of the world..

Of course, 3 means juggling is a new skill for you to master, I had to do the same (not twins, a boy and two girls) what seems many years ago (the youngest is 20 and at uni now)..but I well remember the feeling of holding a person that you had a hand in creating -special!

Keep us posted!

best,

Dave

[Chris]

As the babies will be on special care for a while I did make use of the first clear sky for ages last night. I got a good 40 minutes before the clouds appeared!

I viewed M31, M81 & 82, M27 plus lots of stars! They worked very well on the AZ4 with the tripod low which allowed me to sit comfortably on a garden chair and view with no neck strain. Its very relaxing using two eyes and you do see alot more due to the summation of two detectors. Whilst looking at M81/82 I tried closing one eye at a time, the galaxies were a lot less apparent with just the one. I did the same thing with M27 with the same effect, with both eyes plus a pair of Baader UHC filters I could see a very clear dumbell shape using direct vision, whilst using just one eye I had to employ averted vision to see any shape to the dumbell. 

Very pleased with the above they are pure joy to use in terms of viewing comfort and they show a lot for there size!

Now for the worrying bit Bright stars do show a deep red single spike extending from them which I think must be lateral chromatic aberration, I've not seen this before despite owning a number of optical systems so I need to look into it a bit more. I'm hoping its to do with my eye pieces rather than the objectives which were a pair of WO 66 degree 20mm. Next time out I will try my BGO 12.5mm ortho in each optic and see what happens. The effect seems exagorated with my UHC filters which show a clear seperated broken ring of red around bright stars. I was expecting the usual purple fringe which is fine for an f/6 achro but the single red spike from bright stars might look like a scene from the film Tron with objects such as the Pleiades so I need to get to the bottom of things really. I'll investigate this more next time out (which will be the next time its clear as I don't want to sit on this issue). If I can sort it with better eyepieces then I will be very pleased with these Vixens, fainter stars are lovely and sharp and aberration free so for DSO's they work well. Bit worried about using them on brighter objects such as the Moon, planets, clusters etc.

P.s. I also have a second 25mm super plossl heading my way from Emad so I can try those and see what happens. I also need to try and loosen the left focuser a tad as its very stiff. Hopefully all niggles that can be ironed out

Now back to special care for us

Chris   

[Chris]

Second time out with them tonight, burning the candle at both ends at the moment trying to figure these binos out.

I think I've so far concluded that the red star spike on bright stars last night was infact miscollimation! i.e an out of focus star from the right side gets incorrectly super imposed onto an infocus star on the left side. I really struggled to merge the image of bright stars tonight. if I adjusted the interpupilary adjustment to where I wanted it there was actually quite a severe double image i.e the same star was doubled approximately 1 apparant cm apart! last night I had almost corrected this by having the right hand side interpupilary adjuster swung down very low compared to the left side so the eyepieces were at a jaunty angle but obviously not quite enough to solve things.

Also collimation seems slighlty better if I have the left eyepiece slightly sagging down which is easy to achieve as the left friction fit is looser than the right. Conversely, the left focus adjustment is much stiffer than the right so there is a bit of mechanical assymetry before you get to the collimation. These are not quite the grab and go binos I had hoped for so far, I was only at 24x mag so its not like I was trying to push things too far