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Binobooster (1 Viewer)

Some time ago I started, but not yet completed a systematic comparison of different means of "externally" modifying magnification of telescopes (including binoculars) by means of teleconverters (alias extenders, doubler,..).
I came to the conclusion, but cannot yet proof it, that optically relatively simple galilean (or, sorry to Jan and Gijs: Dutch) telescope concept teleconverters in front of the objective as discussed:
http://pages.mtu.edu/~shene/DigiCam/User-Guide/FZ-30/Converters/Lenses/Telephoto.html
tend to generally perform better than much more sophisticated devices put after the eyepiece. Brightness and field of view suffering obviously with a device put after the main telescope. But more interestingly I could never so far observe a clear gain in resolution with this set up.
Discussing this observation with experts inside and outside industry I was told, that most, even expensive binoculars, have only correction adapted to the performance of the human eye. A teleconverter put after such a binocular therefore cannot improve the performance of such an arrangement.
With better corrected telescopes, offering dedicated teleconverters put between prisms and eyepiece, the situation should be different.

HW
 
Hans, post 21,
Fortunately Hans, you were just in time to change "galilean"into "Dutch", otherwise we certainly would have asked the pope to ban you...
Gijs van Ginkel
 
Hi HW.
I don't think that is entirely true.
Some binoculars, if one is lucky can give much better resolution than the normal magnification.
My selected Japanese Celestron 20x80 gave much better resolution with a 7x binocular behind it.
I was able to read a hotel sign at 11 miles, when it was quite impossible at 20x.
Probably 80x would have been ideal, but I didn't have a 4x binocular to hand.

With the early 35mm rangefinder cameras one had the option of 35mmm, 50mm and 85mm focal lengths with front afocal components.
The inter lens shutter had the common rear component.

I have several 1.4x teleconverters that I use with good camera lenses, usually telephotos, which I use with Japanese monocular converters with 10mm erect image eyepieces.
I also use 2x or 2x to 3x teleconverters.
With the Vivitar Series 1 600mm f/8 solid Cat I could easily separate both components of epsilon Lyrae at 180x with clear space between the double stars about 2.5 arcsecond separation.
 
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Further to post 23.

Actually, in my experience, making good afocal components is more difficult than making good teleconverters.

The Zeiss Mutar 1.7x was the only Zeiss lens that I tested that used radioactive, probably thorium glass. I presume it was too difficult to make well using regular glass at that time. I suppose Zeiss may have occasionally used such glass elsewhere.

The only really useful point for me about afocal adapters is that it can make camera lenses faster.
For instance a 50mm f/1.2 lens can be changed to 30mm f/0.72 approx. with a wide angle afocal front component.

The very fast refractive Zeiss lens around f/0.3 I think uses this principal, maybe with an elliptical front element.

With binoculars I suppose large afocal front elements might be too large to use on roof prism binoculars.

The best solution is just to use high power regular binoculars designed for the job.

Incidentally, what year was the improved Swarovski colour neutral booster introduced? Did it have a different part number?
 
If I want to get a bit more magnification out of a binocular I just slap my smartphone over one eyepiece (with the relevant adapter of course). The results might not be brilliant but it keeps me happy. Sort of like phonescoping really but on a binocular.
 
mooreorless, post 26,
In the post you are referring to you mention about the extenders used, that they are phase coated. The extenders I know are lens-only types, so no phase coatings required. Did the extenders you used have roof prisms?
Gijs van Ginkel
 
Binastro said:
Further to post 23.

Actually, in my experience, making good afocal components is more difficult than making good teleconverters.

The Zeiss Mutar 1.7x was the only Zeiss lens that I tested that used radioactive, probably thorium glass. I presume it was too difficult to make well using regular glass at that time. I suppose Zeiss may have occasionally used such glass elsewhere.

The only really useful point for me about afocal adapters is that it can make camera lenses faster.
For instance a 50mm f/1.2 lens can be changed to 30mm f/0.72 approx. with a wide angle afocal front component.

The very fast refractive Zeiss lens around f/0.3 I think uses this principal, maybe with an elliptical front element.

With binoculars I suppose large afocal front elements might be too large to use on roof prism binoculars.

The best solution is just to use high power regular binoculars designed for the job.

Incidentally, what year was the improved Swarovski colour neutral booster introduced? Did it have a different part number?
Click to expand...




Binastro,

I have a Swarovski 2x Booster. The instructions for use that came with it are dated 2004. I purchased it in 2012. I use it occasionally on my 7x42 SLC B which was made in 2006. I never noticed any color difference while using it.

It came with adaptors for the 32mm ELs and the 10x42 SLC. You can also send in for free SLC twist in eye cups for older model SLCs.

I've looked for a part number on it and in the literature and on the Box for it but I can't find one.

Bob
 
Bob,
I have a Swarovski booster bought secondhand perhaps 3 years ago.
The instructions don't have a date?
It is almost as new, boxed.
The box has EAN and UPC numbered barcodes.

It says order the new SLC twist in eyecups free of charge.
Genuine Swarovski UK import.
It comes with adapter EL-32/Booster and Adapterring SLC 10x42.
But I have no Swarovski binoculars to go with it.

I got it to use with the Canon 18x50IS, and also an Opticron 2.5x bought secondhand.
Both were I think good prices.

However, I am not good at colour shades as birdwatchers seem to be, although good at textile shades.
So, I don't know how old the booster is.

I never seriously and firmly attached either booster to the Canon 18x50 IS, but with IS on I tried them and the Opticron booster was not really useful. A hand held small spotting scope jammed against the window frame is better.

I suppose the Swarovski booster firmly attached might work.
 
Gijs van Ginkel said:
mooreorless, post 26,
In the post you are referring to you mention about the extenders used, that they are phase coated. The extenders I know are lens-only types, so no phase coatings required. Did the extenders you used have roof prisms?
Gijs van Ginkel
Click to expand...

Hi Gijs, Yes I would say so with needing phase-coating. These are straight. I tried to look up under Vortex and there is not much info and could not find any under the Bushnell etc.
 
Binastro

Your post #29.

I have my doubts that the Swarovski 2x booster could be used on any other binoculars than the ones it is made for.

The Zeiss 3X12 Boosters might be a better choice but they are expensive. They have an eye piece that has some stretch to it.

They are special order through Camera Land.

Bob
 
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AP

Your post 32.

It probably can be used by some but I wouldn't have the patience for it I'm afraid. I have enough trouble using it on my 7x42 SLC B freehand now because the field is so narrow. I usually use it with the binocular on a tripod or on my small Polecat Monopod and when I can sit down because of my aching back.

Bob
 
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