Konica Minolta ACT 100 Teleconverter 1.5x (1 Viewer)

Seemed too good to miss at a tenner.

Just arrived via DPD.
Driver went to wrong building first, but luckily did ring my bell rather than scarpering off like some DPD drivers.

Gave him a small tip, as I think they are paid very little.

Made mistake of opening while cold, but this time optics did not mist over.

Seems to be 4 multicoated elements.
Big piece of glass 75mm, maybe 76mm front element.

Field, no glasses, about 45 degrees?
With computer screen glasses beautifully in focus, and sharp. Even at the edge almost sharp. Field maybe 40 degrees.
Will try to refine field size when the 50mph wind gusts subside and if the night sky is clear.

In light polluted places the gain with 2x similar optics is about 2 magnitudes, because the sky background is darkened.
Hoping to get one magnitude gain with this.
Should double the stars I can see, with even large constellations in the field.

Monocular obviously as outside diameter is about 89mm.

Couldn't see any stars in deep twilight, so the first observation was of a close pair of crows near the end of a swaying branch of the large oak tree. I wonder what maximum wind speed they can stay put. The gusts today were 50mph, 80kph.

Just now looked at Orion in a clear sky. Very light polluted. The stars are brighter and the magnification helps. Possibly 1 magnitude gain.

With the computer screen glasses the field is 37 or 38 degrees, although only 30 degrees is sharp. Near the edge even bright stars are blurred and difficult to see.

Without glasses the field is about 43 or 44 degrees, but for me out of focus. I am long sighted and have little accommodation.

The outside front is 90mm diameter with a good front cap.
The front filter thread may be 86mm?
The rear 49mm? filter thread cap is missing. There is good clearance till the curved rear element, so glasses don't scratch it.

The device seems mint except for the price sticker of £30 secondhand, which was reduced to £10. I wish they wouldn't damage perfect items with very sticky labels. I got most off with water, but don't have sticky remover.

I have seen this teleconverter mounted on a Leica digital compact.

Visually this is useful for seeing whole constellations with ease, except maybe Hydra?

Specs say 5 elements in 3 groups.
This seems to be correct. There are 6 bright multicoating reflections and 2 fainter reflections probably from cemented surfaces.

Price $230 ~2004.

This seems to be high quality optics.

Weight given as 500g.

There is slight pincushion distortion nearing the edge.

This device gives me super eyes, or at least a super eye.

Over 32 degrees the field is sharp and I can see no obvious aberrations.
The Moon is just as free from artifacts as with sharp vision with my distance glasses.

Things are just larger and at night the stars are 2.5 times brighter.
I makes me wonder what it would be like to have the eyes of an eagle or hawk with maybe 5 times better resolution or at least the ability to detect small moving objects at two miles.

There is a ring of vignetting from 32 degrees to 38 degrees maximum field using my computer screen glasses.
This affects the moon and stars but is not so obvious terrestrially.

Without glasses the field is 44 degrees but not sharp for me, so I cannot use the full field.

It seems that high class afocal adaptors like this have 5 elements in 3 groups.
The Nikon version is heavier and contains 2 ED elements.
The old Zeiss Mutar was 1.7x and used radioactive glass, such is the difficulty of making good similar teleconverters.

This ACT-100 weighs 513g. The front cap an additional 20g.

It needs to be big to achieve the wide field, so two are too large to make a binocular.

This for me is a very useful aid.

Have you seen this thread on CN?

https://www.cloudynights.com/topic/536652-home-built-nikon-2x54-widefield-binos/

Thanks Jerry.

Yes, I have seen that and I bought two mint Nikon TC-E2 2x teleconverters for £15 each.

I can use them with Minolta eyepiece correction filters for the manual focus film cameras, which fit perfectly, or less well with slightly larger ones for the Minolta AF film cameras.

However, I have little accommodation and am far sighted.

The Nikon 2x are O.K. but don't have the enormous flat field of the ACT-100, at least for me.
I can just see the main Orion stars with the Nikons, but have trouble keeping the stars all sharp.

I might one day get the Vixen 2.3x focussing binocular which would be better for me.

But the quality with the Konica Minolta ACT-100 is extraordinary, as I can se no optical errors when easily seeing all of the main stars in Orion.
I also hope to try it on Ursa Major, which covers about 25.7 degrees for the main stars.

The Konica Minolta ACT-100 is much larger than the Nikon 2x mentioned. This may be why the performance is so good.
There may be even larger afocal teleconverters. I remember seeing some giant ones listed.

Younger people will probably find the Nikon 2x teleconverters suitable, but I am not happy using them.

P.S.
The ACT-100 1.5x (513g) weighs 3.3x as much as the TC-E2 2x (153g).

The ACT-100 is a much larger optic.

The ACT-100 is a 1.5x75 optic compared to the TC-E2 2x54 optic.

For me I have swapped a smaller field and higher magnification for a lower magnification much wider flat field.
The ACT-100 suits my eyes better than the TC-E2.

So I have the excellent Dowling and Rowe independent eye focus 4x22 16.5 degree field binocular.
The Bushnell Xtrawide 4x21 (actually 3.5x21) fixed focus 18.5 degree field binocular, which is only sharp for me near the edges, but still useful.

And now the ACT-100 1.5x75 monocular with 38 degree field, of which 32 degrees is sharp.

This is a great optical device for me.

Early this morning I looked at Leo. With my distance glasses few stars were seen in the awful pollution.
Switching to my computer screen glasses and the ACT-100, all the brighter stars were seen and they were bright. I noticed the strong orangish colour of Gamma Leonis, which surprised me.

All the stars were pin sharp over the 32 degree extent of Leo's main stars.
Up to 35 degrees the stars were good, but at the edge of the 38 degree field even the bright stars became dim.

The magnification for me with my computer screen glasses is probably about 1.65x and the stars are about 1.2 magnitude brighter, about 3.0x rather than my initial 2.5x estimate.

Basically this device turns the clock back more than 20 years for me with the ever increasing light pollution and my eyes aging.

I have two of the TC-E2s and one TC-3, they are fun for stargazing on those clear cold nights.

A.W.