Sorry to dig up this thread 1.5 years later, but I am now in position to try this and make it work with the Kowa TSN-PA7 photo adapter.
I have the Kowa TSN-883, TSN-11WZ, TSN-PA7 (with window) and a Nikon D3300 (CF body so it is light). Shooting with an ISO of 800 or 1600 and 1/800 shutter speed in daylight it works really well. I can slap the TSN-PA7/Nikon on in just a few seconds to take the photo.
The problem is that I have too much magnification at 25x zoom. According to Kowa, with the 2/3 CCD format of the D3300 I have the equivalent of a 1750 mm (37.5x) F/12 lens. Slow and very long. I never use the 60x setting because the f stop drop to F/28 and who needs a 90x equivalent lens.
So I figured I would try to use as long of focal length wide angle eyepiece as possible. I came up with the Baader Hyperion 31mm 82 degree eyepiece that has 1.25 and 2" barrel mounts.
I attached the 1.25 barrel mount and put it in the eyepiece socket on my 883. So far so good. I have about 50% more viewing angle than I had with the 25-60x wide angle lens. The is a slight vignetting on the edges but only a couple percent of the image diameter. You get worse if the eyecup is too far out. The focus setting is very close to the 25-60x setting only about 1/2 turn of the fine focus knob. Still can focus to infinity.
Doing a quick calculation, using the 465 mm focal length of the 883 (correct me if I am wrong, but that is the number Kowa gave me), I now have a 15x magnification optically and a 22.5x equivalent telephoto. I also gain in F stop to a much better F/5.6. Again correct me if I am wrong but I have been working with a Kowa digiscoping tech on this.
The Baader Hyperion eyepiece extends out 4mm (with eyecup) shorter than the Kowa 25x-60 wide eyepiece. It is a tad smaller diameter so I can used the TSN-PA7 adapter with a small light blocking spacer mounter in the TSN-PA7. I have to mount the Baader Hyperion eyepiece first before I test the focus shift from eye to camera. It is close with the Kowa 25x-60 wide.
Now the hard part. Mounting the 1.25 eyepiece. Luckily Kowa now had a 50% of the problem solved now. The TSN-EC2 adapter. It screws into the 883 eyepiece socket just above the bayonet mount. There are three mount flanges for an TSN-820 series (I think) eyepiece. I can machine off the bayonet mount and have a minimum 35 mm ID opening, stepping up to larger diameters. Since 1.25 is 32.7mm, I can machine a collar to fit into the TSN-EC3 adapter so the 1.25 eyepiece will just slide in. I can drill set screws into the adapter to hold the eyepeice.
I am currently waiting to get an adapter that screwed onto the TSN-1,2,3,5 series scopes. It is suppose to have the same threads so that I can screw the TSN-EC2 adapter into it so I can turn the adapter on the lathe with damage to cut of the adapter tabs. I will probably just buy a cheap aluminum 2" to 1.25" adapter and turn it down to fit into the TSN-EC2.
Any suggestions?
David
