| Using a Nikon 600mm f/5.6 Manual Focus Camera Lens as a Telescope |
Attaching a telescope eyepiece to a camera lens creates a telescope. In an effort to increase the light gathering ability for digiscoping, I
acquired a Nikon f/5.6 600mm manual focus lens. For the eyepiece I selected the Pentax 30mm XW with a 70 degree AFOV to
maximize the zooming ability of my Nikon Coolpix 8400 camera. The Pentax 30mm eyepiece has a two inch diameter barrel, which I
selected for two reasons:
1) It appeared that a 1.25 inch eyepiece might not capture the entire light path exiting the lens resulting in uneven lighting.
2) The two inch barrel is threaded on the inside for 48mm filters, and I wanted this for mounting the eyepiece to the camera lens.
To attach everything to the lens I use Nikon part K-3:
To the K-3 bayonet mount is attached via screws with nuts the following:
A 55mm female to 52mm male step ring fully screws into a 52mm female to 48mm male step ring. With my electric drill I drilled 4
holes into the step ring combination to align with the four holes in the K-3, directed slightly at an angle outward. For screws I went to
the hardware store and bought 4 miniature screws the same diameter as the four that come with the K-3, only longer, and with nuts.
There is very little extra room on the top of the step ring combination where both the nuts and the eyepiece have to fit. I had to use the
electric drill to widen the holes and set the screws out at a slight angle so the eyepiece would screw on the full length of the step ring
threads. I used nuts because I wanted to make sure that the entire combination would not seperate in the field. A better home
machinist could probably add some material to the inside if the step ring combination and use the machine screws that come with the
K-3. Once I had this combination made and I made sure the eyepiece would screw on completely, I tightened the nuts and secured
them in position with several layers of plastic cement, and also applied some to the screw threads above the nut. Without this or a
similar step the nuts will loosen quickly.
This combination gives both infinity focus and a minimum focus of 14 feet. In experimented with other combinations and putting the
eyepiece back a short distance drastically limits the infinity focus.
