New spotting scope from KOWA (1 Viewer)

[Tringa45]

The problem with longer f ratio's is you end up with a long small scope or a really long big scope.

Will,
Kowa's specs for the 66A include the TE11WZ 25-60x zoom. The length is 36,5 cm and weight is 1500 g.
For comparison, my ATM 65HD (also magnesium body) measures 36cm with the shortish 30x W.
I put the ATM on the scales without its eyepiece, but with the TE11WZ from my 883 and measured 1390 g.
The extra weight of the 66A can probably be attributed to the generously dimensioned prism also used on the 88 and 99.
Btw, I'm surprised that this new release has generated comparatively little interest so far. I regard the ATC/STC as something of an expensive gimmick but that thread has 411 replies and 61K clicks since September.
If I didn't already have two scopes the 66A would be my one and only choice; better than everything smaller and better than some larger.
It's even got two threads in the foot, just to please Bill Atwood.

Regards,
John

 

[MiddleRiver]

I'd love to see a pic of the 66 next to a 553 in order to get a sense of size/bulk...

 

[William Lewis]

Will,
Kowa's specs for the 66A include the TE11WZ 25-60x zoom. The length is 36,5 cm and weight is 1500 g.
For comparison, my ATM 65HD (also magnesium body) measures 36cm with the shortish 30x W.
I put the ATM on the scales without its eyepiece, but with the TE11WZ from my 883 and measured 1390 g.
The extra weight of the 66A can probably be attributed to the generously dimensioned prism also used on the 88 and 99.
Btw, I'm surprised that this new release has generated comparatively little interest so far. I regard the ATC/STC as something of an expensive gimmick but that thread has 411 replies and 61K clicks since September.
If I didn't already have two scopes the 66A would be my one and only choice; better than everything smaller and better than some larger.
It's even got two threads in the foot, just to please Bill Atwood.

Regards,
John

I agree, it does seem like an interesting option for those seeking a one and done if ultimate light gathering isn't high up the priority list - and some examples test well.

Will

 

[William Lewis]

I'd love to see a pic of the 66 next to a 553 in order to get a sense of size/bulk...

For what it's worth it did look similar form factor wise to the ATM 65 as John points out.

 

[jring]

Since the magnification range of the new 66 is identical to the 88 it must also have the same 500mm effective focal length. That would make the focal ratio a relatively high f/7.7, giving a good specimen the potential to have very well corrected aberrations. That is unless the designers decided that at f/7.7 they could get by with a doublet instead of a triplet up front.

Hi,

any well made f7.5 fluorite or better ED (FPL53 et al) doublet will be just fine up to 120mm aperture at least. Ask any owner of the plentiful chinese f7.5 FPL53 doublets up to 120mm or Takahashi FC or FS series doublets on the premium end of the spectrum which are around f7.5 to f8 for the most part (up to the FS 152).

And all these are used at slightly higher magnifications than any spotter... double aperture in mm is a conservative rule of thumb for useful magnification for general astro use. Planetary or double star observers will go quite a bit higher - but especially the latter tend to have quite relaxed rules for image quality... if you can see two airy discs on axis, it's good enough...

You only need a triplet with fluorite if you are going crazy fast like f5.5... and even then Kowa TSN-3/4 with a fluorite doublet at f5.5 was far from terrible...

Joachim, who likes his Skywatcher ED120 a lot...

 

[Tringa45]

Hi,

any well made f7.5 fluorite or better ED (FPL53 et al) doublet will be just fine up to 120mm aperture at least. Ask any owner of the plentiful chinese f7.5 FPL53 doublets up to 120mm or Takahashi FC or FS series doublets on the premium end of the spectrum which are around f7.5 to f8 for the most part (up to the FS 152).

And all these are used at slightly higher magnifications than any spotter... double aperture in mm is a conservative rule of thumb for useful maginfication for general astro use. Planetary or double star observers will go quite a bit higher - but especially the latter tend to have quite relaxed rules for image quality... if you can see two airy discs on axis, it's good enough...

You only need a triplet with fluorite if you are going crazy fast like f5.5... and even then Kowa TSN-3/4 with a fluorite doublet at f5.5 was far from terrible...

Joachim, who likes his Skywatcher ED120 a lot...

Hi Joachim,
Despite the availability now of hard coatings for fluorite, there does seem to be a reluctance by some manufacturers to put the fluorite edlement up front.
My 883 is a triplet with a central fluorite element, but then it's a very fast design with the -ve. focussing lens a long way back, a sort of telephoto construction, which keeps it short.
The vulnerability issue is the only explanation that occurs to me for Takahashi's use of Steinheil instead of Fraunhofer doublets on some designs.
A Steinheil construction seems to me a bit like starting a journey by driving the first few km in the opposite direction!

John

 

[jring]

Hi John,

yes, the old TSN single digit fluorite doublets from Kowa as well as the Tak FC series are Steinheil doublets. The optical disadvantage is small but measurable - that's why they went to Fraunhofer when they had the coating technology for the FS series.

The new FC series are once again Steinheil - they have enough triplets or quadruplets for high perfomance imaging...

Joachim