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ZEISS DTI thermal imaging cameras. For more discoveries at night, and during the day.

BTX Binoviewer for ATX scopes (1 Viewer)

I will finally get a chance to try it out and the extender tomorrow at Minsmere. Swarovski reps will be there if anyone has any particular questions they want me to put to them.

Apparently the BTX eyepieces are basically those of the 8x32 EL Swarovision.
 
No users of the BTX or the extender, or no one want to report their feelings about these?
I will take 1 or 2 months to get an extender myself but I'm curious about the judgement from present owners...
 
Meant to post this sooner but completely forgot (sorry). I had the chance to compare the BTX to my current 85mm ATX while at Minsmere at the start of the month.

Once correctly adjusted (e.g. IPD and head rest) the view felt more relaxing (even for someone like me whose vision in one eye is pretty useless). I could definitely see these having a place in the toolkit for those doing surveys or sea watches etc with long periods spent scanning with the scope. For the rest of us I think the zoom of the ATX/STX is likely to be more useful.

One important thing to keep in mind is that because you have to set the IPD as you would with a pair of bins, sharing a scope becomes rather less practical. Maybe it's just me but I enjoy being able to share views of a distant bird.

I also tried the extender on an 85 ATX, again comparing it with my own scope. The original idea was to fit it to my scope but since I use both the stay on case and balance rail that was going to be too much of a faff to fit. I was surprised at how bright the image was given the increased magnification, it was a rather overcast morning and even zoomed in the view while dimmer was still perfectly useable. Sharpness still seemed good too, though I didn't really test this. The extender was relatively light and compact so could easily be carried in the pocket of a scope pack and fitted when needed (at least for those not using the balance rail). I am also not sure how often atmospheric conditions would allow many of us to get the most out of the increase magnification - I regularly find heat haze prevents me for going much above 30/35x as it is.

Hope my far from scientific thoughts help.

James
 
Have only given the extender a brief test (in bright conditions) on my ATX95, but was pleasantly surprised by the quality of the image. It looks like it may be very useable at up to 100x at least. Look forward to using it during autumn wader passage.

Sean
 
Have only given the extender a brief test (in bright conditions) on my ATX95, but was pleasantly surprised by the quality of the image. It looks like it may be very useable at up to 100x at least. Look forward to using it during autumn wader passage.

Sean

Just posting to endorse comments above on the extender. I have found it much lighter in weight than expected and it has done the job for me on a distant c-ringed Brent last week- I don't think the ring would have been readable without it.

Also as commented above, I find I struggle with haze at higher magnifications with the ATX95. But I haven't really sought to work out if it is a feature of the model compared to others, or just because haze is haze.
 
Also as commented above, I find I struggle with haze at higher magnifications with the ATX95. But I haven't really sought to work out if it is a feature of the model compared to others, or just because haze is haze.

The latter. Haze is haze. However, the better a scope is corrected, the better it seems to do in haze. I think Kimmo mentioned that years ago, and I find it's true.

But no matter how good a scope is, haze will still be haze.

Hermann
 
Well I made an investment in the BTX while on holiday in Norfolk last week and am now able to say that from my perspective it's performance on my 95 is truly amazing! I miss the zoom, but this is more than made bearable by the pure viewing comfort and experience of using both eyes. Comparing directly with my 95 prior to purchasing I found that the resolution through the BTX was perhaps due to using two eyes, more comaparible with c40x on my scope eyepiece; this is far more succinctly expressed in an earlier comment by Kimmo on this thread.

On a more unhappy note, I'm probably the first that needs to send back to Swarovski, as on returning home to Kent and scanning for raptors, I noted a small piece of dust viewable against a light background! Now I know it's there, I of course find my eye drawn to it every time. I'm not overly concerned as of course Swarovski have an immense reputation for customer care, so I'll contact them tomorrow to find out how best to progress.
 
Gijs,

Many thanks for an excellent review and especially for the historical section. I will have to read it slowly with better time.

One small thing, though. In the photo of the BTX with another scope, the smaller scope is not an ATX 85 but an 80 mm Swarovski scope, either an ATM or an ATS 80 HD.

Kimmo
 
Kimmo, post 134,
Yes I think that you are right, I overlooked it as well as my proofreaders. I will change when I have time.

Vespobuteo, post 133,
I have not seen differences in color reproduction between left and right eyepiece.
Gijs van Ginkel
 
Hi Gijs.
I briefly read your review.
I hope to read it carefully later.

Horace Dall made binocular eyepiece devices for telescopes.
His design was copied my some professional makers.

I don't know when he made the first one.
It might be quite early.
I will see if I can find out the date he first made one.

He also made many eyepieces, microscope objectives with world record NA and solely kept Leitz microscopes going in the early 1940s in the U.K.

Many items were also aspherised by hand for improved performance.

He also specialised in high performance relay lenses for telescopes.

The trouble is if one breaks one of his optical items, nobody can reproduce it properly to its correct performance.

P.S.
We have gone back to 1931 papers by H.Dall, but haven't yet found details of his binoviewer.

I recall that it may have used a beamsplitter. I don't think he patented it and it was copied commercially later on.

He invented so many things and not all were recorded in print.

Just noted in today's news that carbon dating records the use of zero i.e. a dot leading to 0 in Indian mathematical texts 500 years earlier than previously noted.

I think this also means that Indians were more advanced than we thought, possibly also in making lenses.

P.P.S.
Just had a further reply.
H.Dall made a binoviewer for his 8 inch Maksutov supposedly to increase eye relief. Although I don't understand this.
I used his 8 inch Maksutov on Mars from his loft through the special window pane and the view was stunning, but we didn't use the binoviewer.

I still don't know when he originally made it.

There are fewer people to ask as we get older.
 
Last edited:
Binasttro, post 138,
I had not the intention to write a PhD thesis about the history of binoviewers, but using all historical data I had available I wrote a condensed review in the test report of the BTX with regard to the historical development of binoviewers/binocular eyepieces. Should be more than enough for most readers I hope, but perhaps not for specialists or professional historians.
Gijs van Ginkel
 
Thanks Gijs,
I agree with you.
Just thought I would mention some possible earlier versions.

The problem is now that the only people I can ask questions about optical matters and optical history are in their 70s and 80s.
It is very frustrating when I find that the only person I can ask is myself, and I don't have sufficient knowledge.

The most interesting knowledge is usually not on the internet, only in the minds of oldtimers, who are steadily getting older.
Inevitably quite a lot of knowledge will be lost.
 
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