Kowa TSN eyepiece questions... (1 Viewer)

Ok, so I finally received my new to me Kowa TSN 823M from AU today....

Scope looks very nice, and only came with the 20-60x z7 EP...

Zooms just were never my thing so I ordered the Kowa adapter that fits the 660 style Eyepieces. (I have a handful).

So, The question I'm asking is about the adapted eyepieces...
The TSN 660 series EPs are virtually identical to the late 820x series eyepieces with what appear to be only differences in that bayonet lugs and the lower/bottom lens appears smaller on the 660 series EP's...

I had a TSN 82SV (660 series EP) and the TSN 821M side by side once, both with 27xLER and I could not distinguish any difference in performance, clarity, resolution or field of view. Actually, the 82SV appeared very slightly brighter.

If I use the 660 series eyepieces on my TSN 823M, am I at any disadvantage as opposed to using the late model 820x eyepieces? Why did the 820 series use such a large lens on the bottom of the eyepiece?

Maybe it's a non question, but I am very curious if anyone knows.

Hi,

usually a larger field lens means a larger field stop and this is used to get a wider true field. Since the 820 series used a wider bayonet, I would expect it to have EPs with wider true fields - although I don't really see those in the specs...

The 14mm EPs (30x for small bodies, 32x for the 820 series) both have around 70 deg afov and the true field is correspondingly even a bit wider in the small bodies. Maybe they planned to bring out something like a 20x wide EP but didn't...

Anyways, you will just notice a slightly higher than spec magnification - or maybe not without a side by side comparision to the same EP in a small body. The 820 series bodies have a focal length of roughly 450mm as opposed to the 420 of the small bodies - probably to keep the focal ratio around f5.5 as it was with the original single digit 77mm series. With 82mm aperture and 420mm focal length we would get a focal ratio of f5.1 and that is crazy fast for a fluorite doublet.

Joachim

Thanks for the thoughts Joachim

I have seen modern 21x wide eyepiece for the 820 series and a 20xwide for the smaller scopes on the used market, they seem to be very rare. I tried to bid on a 20xWide EP and the seller refused. (Didn't want to mail it out of the UK).

Not a big deal there, Not something I was dying for anyway I guess.

Must be a hassle to ship an item out of the UK/EU? English and Germans seem to be the most uptight about international shipping...(?) I sell items regularly and usually don't blink when I have an international buyer...

Here's a photo of the ep I was mentioning.

Hi,

cannot comment about UK, but over here a package to the US is like 35€ with DHL - plus you probably will have fill in a customs form and the recipicient might get hit with duties and/or tax - although I'm not sure how this is handled stateside...

Joachim

I had an eyepiece come a little over a year ago from Germany to the US. I don't remember what shipping method was used but it did not cost 35 euros.

I don't think it's the cost..(Especially if the buyer pays shipping).

jkingrph said:

I had an eyepiece come a little over a year ago from Germany to the US. I don't remember what shipping method was used but it did not cost 35 euros.

Click to expand...

I also thought it was cheaper, but that's what I found on DHL site - and others were not different. Maybe due to the lack of air cargo capacity in the current situation...

Joachim

jring said:

I also thought it was cheaper, but that's what I found on DHL site - and others were not different. Maybe due to the lack of air cargo capacity in the current situation...

Joachim

Click to expand...

One has to be careful when choosing which shipping carrier to use. When shipping from the USA to international destinations I was told by the US Postal Service any parcel leaving the USA shipped internationally and insured by the USA Postal System would not be covered for loss or damage once it left the USA and handled by a second delivery carrier. If the item is lost for example once it leaves the US Postal officials hands your out of luck. One has to use one of the major international shippers to make sure your item being shipped is totally insured if being shipped from the USA. I have found using such a carrier the insurance cost covering that loss or damage is extremely expense. I am sure our international forum members have to consider the same decisions when shipping to the USA.

I saw that you said that you don't like zooms, but modern zooms are miles ahead of units like the kowa Zoom that you have just received. A wide angle zoom, with good eye relief and top image quality might change that view on the subject.. For the 823M I would recommend trying The Baader Hyperion mk IV Zoom,.. Side by side with the ts21 there is no difference in field of view, brightness, eye relief or sharpness. The Ts21 is a great eyepiece, but truly don't see the point when you can have a. Zoom that performs as. Well, and then some.. The adapter for the 660 series eyepieces is not a bad idea if you have already eyepieces, although it's expensive and not easy to find (seems that you already sorted one anyway). I am not familiar with kowa 600 series eyepieces but small bayonet older eyepieces are not in par with modern eyepieces in regards of the optical coatings. For Me the lack of contrast and excess on internal reflections are evident, even in the older 823 32X, and all of the older vintage eyepieces.
The mark IV baader zoom fits directly the threads of the 823, is not expensive and truly gets the performance of the scope well up there...It might change the way you feel about zooms....

HI Mayoayo,

thanks for the reply.

On zooms it's just a personal preference...I just don't have use for an eyepiece over 40x. I guess that's part of it.

The eyepieces I have on hand are TE14WD, TSE-17HD and the newer z9 20-60x I received as an extra.
I also have a fujinon 25xler EP That fits right just like the others and has a real sharp (although a bit flat color) view.

20x ep I pictured was something I wanted for a smaller 60mm scope, not quite related.

I would like to try the bader zoom you mentioned, I've read about them here and there. Maybe someday if one comes up reasonably priced I might try it out.

The adapter was pretty expensive for what a small part it is...I gave $80 for it, but I felt it was a good way to use my eyepieces w/0 further investment.