Nikon 13x-30x (21mm-9mm)zoom adaptation

[YKSE]

Finally got around to do the 1.25" adaptation of my pair of Nikon zooms, 3D printed plastic after some measurement, here's some pictures of this adaptation.

1. original size compared with 18mm BCO and 25mm Tak ortho.

 

2. Stripped down zoom for adaptation compared with the original one

The lower thinner ring has a tiny recessed screw holding it on place, once removed, both rings screws off easily. The thicker upper ring rotates freely too, so it's better to remove it for adaptation.

3. The 3-D printed adapter is added to the picture, some filing was needed to fit perfectly. be noted, the lower thread on left picture is to be forced-threaded in the adapter, so that the adapter should sit secured.

 

4. The adapted zoom compared with original one.

5. the adapted zooms (about 1mm higher than the original ones) compared with BCO 18 and Tak ortho 25.

[YKSE]

Now some observations and measurement done with the zoom, here's what I've got:

1. Field stops (after drift timed Altair) and AFOV(flash light measurement)

FL                FS             AFOV

21mm      14.5mm       40.6°

15mm      10.7mm       46.4°

9mm        8.4mm        54.9°

100g weighs the zoom with the adapter, it's about par focal(less than 1mm focus travel) with Baader Mark III zoom with 1.25" nosepiece.

2. Geometrical distortion and Latteral color:

Just perceivable pincushion, calculations shows 4-7% across the zoom range, very mild vignetting in 9mm, vignetting disappear when close to and lower than 11mm. just perceivable blue ring in the field stop when looking at bright sky.

3. FC, astigmatism and scatter control on Vega with 120ED

Very flat field, Vega is focused in the edge as in the center, some astigmatism seen in outer 10% edge, very good scatter controll, in level as Leica zoom across the zoom range.

4. Solar observing with PST:

Excellent, as described in here: https://stargazerslounge.com/topic/301472-sol-in-ha-2017-10-08/?do=findComment&comment=3298335

Mark III zoom could only go to 12mm, while Nikon went to 9mm with no loss of detail(faint threads of proms).

5. Binoviewing on the Moon with 120ED(1.7x GPC in front of 2" prism diagonal for about 2x):

Barely perceivable color in Luna limb, no problem in merging images even in 9mm (about 200x with the GPC), seeing were about average though, best view were about 11mm settings with my simple "feel-stops" adaptation, no merging difficulty despite the pairs may not have the exact focal length.

21mm:

13mm

 

[Piero]

Nice review Yong!  

I've found that my Nikon MC zoom offers a very marginal optical improvement to the Vixen SLVs I had. Used in combination with the Zeiss Abbe Barlow or Baader VIP, the planetary views through Nikon zoom (and the Vixen SLVs) improve to something in between the Zeiss zoom / Docter and the native Nikon Zoom / Vixen SLV. 

Last evening, I realised that the cheap 1.25"-to-0.96" reducer I sometimes use with the Nikon zoom can be quite useful when used with the Zeiss barlow because this adapter also works as an additional 20mm spacer! Therefore, the ZB + 40mm spacer + that reducer operates at 2.93x, making the zoom work from 103x to 240x (~7mm-3mm) with the Tak-100. 

It's a nice little eyepiece in my opinion.

 

How do you compare it against your Leica ASPH? 

[YKSE]

Piero,

The weather has been terrible this year, so I've only got a couple of nights out so far

The comparison I've done with Leica and Docter were scatter controll, which I rate as one the most important factor for lunar, Solar and planetery, my impression is that the Nikon zoom has a tad better scatter controll than excellent Leica, in level with Docter.

The ability to zoom and small footprint is a huge advantage in binoviewing compare to Leica and Docter.

[Piero]

Also to me, scatter control in the Nikon zoom is very good, I'd say close to the Docter. In my opinion, on planets/Sun/Moon contrast and sharpness are not at the level of the Docter though. Again, these are very good particularly with the Zeiss barlow, I'd say between a Vixen SLV and the Docter, but not on par with the latter. I feel that the colour tone in the Nikon zoom is very very close to the Vixen SLV, a bit warmer than the Docter and warmer than the Zeiss zoom. Vixen SLVs cooler than TV Delos.

I agree that represents a nice ep choice for binoviewing. It seems very comfortable for that use. Last summer, the Nikon zoom + Zeiss barlow gave me a very neat view of Saturn with the Tak-100. In particular, the (complete) Cassini division and a couple of belts were well distinct. It's a nice little weapon.