Optolyth Osiris 10x40 (1 Viewer)

Good condition.
Very lightweight.
Coatings fair only. Uncoated and single and multicoating.
1980s ??
Internally clean.

118m. Crow on chimney pot. Feathers scraggy?, not normal sleek crow.
Crows stay put for 5 minutes, so much better subjects than magpies.

Centrally little or no CA. Bright overcast day 24C.
Quite a lot of CA moving to edge.
Curved field also near edge, can be partly refocused.
Pincushion. Will check.

Seems to be about 4mm exit pupil. Will check.

Although central resolution is good, I cannot hold it very steady because it is too lightweight. 12x45 Russian much steadier.

Very strange and rather nice bright thin blue ring all around field stop. Most odd. Why is this seen?

For a birdwatcher probably good as minimal weight, but needs a tree or something to brace it.

Weight with strap. 474g.

Weight without strap ~462g.

Eye relief is small. In fact previous owner cut off the eye cups.
Central resolution is very good, when I can hold it more steadily.

Ghosting, flare and glare from a streetlight in or just outside field. Poor.
Right side (5/10) is worse than left side (5.5/10).
Overall I would say 5/10, although I will clean surfaces to see if it improves a bit.
This is a poor performance as the field is not large. Partly due to insufficient coatings.

Incidentally, with the Russian 6x24 I can see ghosting in the daytime in bright overcast conditions. Seems to be of or from prisms. How others don't notice this I don't understand.

BINASTRO,
I HAVE DESCRIBED AND INVESTIGATED THE OPTOLYTH OSIRIS 8X40 RECENTLY. THIS IS POSTED ON THE WEB-SITE OF HOUSE OF OUTDOOR, LOOK UNDER "VERREKIJKERS TESTEN EN VERGELIJKEN'AND SCROLL TO THE PARTICULAR TEST. REMARKABLE GOOD COLOR REPRODUCTION BUT NOT VERY BRIGHT. PRODUCED AROUND 1960 PROBABLY.
Sorry for the capitals, was too lazy to change it.
Gijs van Ginkel

Thanks Gijs.
I'll have a look.

I note the lack of baffles in the 10x40. This may explain the glare problems partly.
There is matt black inside, but real black special light absorbing material would be better.

Gijs.
I read your review of the 8x40 and understood about half. Sufficient anyway.

Most interesting was your review of Dutch and Belgium optics.
I visited Belgium often on business.

Particularly interesting are the mirror systems of Bouwers at Old Delft.
I have never seen such a binocular. A Russian one was mentioned, but I don't know if made or not.


Kipp scope looks more like Dollond than Ross.

Distance meter = rangefinder. I had a British one about 2m baseline.

I see no mention of Lichtenknecker.

P.S.
I have/had a high quality Philips lens about 100mm f/1.1 from memory. I though that perhaps Zeiss made this for Philips, but maybe it was made by Den Oude Delft or even in house by Philips?

Eventually clouds cleared. Transparent sky.
00.22 BST this morning.
Jupiter close to the Moon. About 1.6 deg lower left.
Brightish star about 1.2 deg lower right. Gamma in Virgo? which had been occulted about 3 hours earlier.

View in 10x40 Osiris looked good centrally, but a lot of false colour and blur near edge.

02.01 BST. Jupiter 1.1 deg left. Star about 2.0 deg right. All very low, about 4 to 5 deg elevation. Very murky.

Also viewed both times Kowa 20x50.
From this a Rough estimate of field of 10x40 Osiris is about 5.3 deg, but not a proper measurement.

I don't find the Osiris view relaxed. Not sure why yet.

It has ribbed green armour.

I find Japanese and selected Russian Porro prism binoculars nicer.

P.S.
Yes, it was Porrima magnitude 2.7.
A double star 2.6 arcsecond separation, I think.
Both magnitude 3.5.

Jupiter, the Moon and Porrima were nice in the 10x40 Osiris.
Just a little too far apart for Kowa 20x50, perhaps 2.9 degrees, say 3 degree field needed.
Would have all been seen in Canon 18x50 field nicely. Jupiter moons may have been visible also in 18x50.

Just measured the objective apertures as 40.0mm using vernier calipers.

Also the exit pupils seem to be 4.0mm but judged by eye and ruler.

Surprised that they seem to be as marked.