Zeiss Victory Diascope 85 t* fl star test pictures (1 Viewer)

[BoldenEagle]

Hi,

here are star test diffraction patterns for Diascope 85 fl inside and outside focus. Zoomed to 75x and light source was silver flagpole knob about 40 meters away.

I think there is not anything else wrong with it but some spherical aberration is involved.

In direct comparison with my Kowa Prominar 883, Diascope usually feels the sharper one. Haven't done any precise resolution comparison but this Diascope sample likely is better than my Kowa.

I have earlier posted star test pictures of my Prominar sample to the Kowa section. Obvious differences are Kowa's prism defect and maybe some amount more of spherical aberration and a little bit of coma and astigmatism.

Juhani

 

[binomania]

Hi,

here are star test diffraction patterns for Diascope 85 fl inside and outside focus. Zoomed to 75x and light source was silver flagpole knob about 40 meters away.

I think there is not anything else wrong with it but some spherical aberration is involved.

In direct comparison with my Kowa Prominar 883, Diascope usually feels the sharper one. Haven't done any precise resolution comparison but this Diascope sample likely is better than my Kowa.

I have earlier posted star test pictures of my Prominar sample to the Kowa section. Obvious differences are Kowa's prism defect and maybe some amount more of spherical aberration and a little bit of coma and astigmatism.

Juhani

Hi, thanks for your experience!
I come from the astronomy sector and I love doing star tests , however
the objectives of the spotting scopes are mounted under pressure in a cell protected by O-Rings or another sealing system. This allows excellent protection from infiltration, but can generate a "warping" of the elements and deviations on the optical axis due to the uneven compression of the sealant. For this reason I don't like doing this kind of test in sports optics...but i thank your for your report.

 

[BoldenEagle]

Here are again the star test result for this sample of Zeiss Victory Diascope 85FL. This time taken indoors at about 8 meters of distance and using APM HDC XWA 3.5mm eyepiece (with Baader adapter, I can also confirm that this combination can be focused to infinity without problems).

These pictures don't tell the whole story because I was not able take pictures when unfocused to just two rings (+ central point) but that showed nearly identical patterns both sides, except for the colours. When unfocused as far as in these pictures, in the outside pattern the bright central point turned dark and if unfocused even further, there seemed to be some sort of darkish central zone.

As there is no any other aberrations (maybe just very slight astigmatism) to speak of, than this weird SA, this sample has excellent sharpness. The contrast is not as good as is for example in my Kowa 883 but still this Diascope sample is the sharper of these samples.

Regards, Juhani

 

[Troubador]

But what do birds and animals look like through the Diascope? Surely the purpose of a spotting scope is to look at nature?

Lee

 

[BoldenEagle]

But what do birds and animals look like through the Diascope? Surely the purpose of a spotting scope is to look at nature?

Lee

As said, this sample has excellent sharpness, so the views are great, regardless of what you are looking at. This sample is slightly better (in terms of sharpness and resolution) than my Kowa 883, and it can be seen also in the field when looking at birds, at least in some circumstances. Kowa 883 has better contrast, which may help in some conditions but usually this Diascope sample can resolve smaller details.

Other than optical quality, I don't like this Diascope because of it's narrow fov (with 20-75x zoom) and poor eye relief (I wear glasses). Also the focus mechanism with single two speed knob is not good, in my opinion Zeiss "fixed" something that was already excellent (dual focus system of the former Diascope model) and made it worse.

So in a summary; I would say that there is a strong correlation between how good the star test looks and how "sparkling" the birds appear when you look through the scope. After all, I think the most important function of a spotting scope, at least for me, is to show the tiniest details of the (most distant) targets and a poor sample fails to deliver that. One can avoid the poor samples by doing a star test, very simple.

Regards, Juhani

PS. This Diascope is not my scope, my family member owns it and is very happy with it.

 

[Troubador]

Thank you Juhani

I have an older model Diascope 65 with two separate focusing wheels and I too prefer this solution.

Lee