Lumicon DigiCam Adapter

Lumicon DigiCam Adapter

I wanted to try some afocal photography using my Canon S400 with various telescopes. For this type of photography, the principal issue is mounting the camera so that its optical axis is aligned with that of the eyepiece, and setting the camera at the correct distance from the eyepiece to best match the exit pupil of the eyepiece to the entrance pupil of the camera. There are various mounting schemes out there but one of the most common and arguably the most versatile is the type that clamps to the eyepiece. I chose the Lumicon Universal Digi-Cam Adapter which accommodates eyepieces up to 2.6" in diameter and retails around $50.



As seen in the photo, this device has a yoke that surrounds and clamps to the eyepiece via a moving jaw. Extending below the yoke is a screw-driven "XY" stage that facilitates translating the camera perpendicular to the optical axis to align the camera lens to the eyepiece. There is a clamp knob at the junction of the X and Y axes that serves to lock the position once set. The camera mounts to a platform with the typical 1ž4-20 screw which, residing in a slot, allows moving the camera in and out along the optical axis.

The main yoke and jaw are die-cast, probably from zinc as it feels heavier than aluminum. The camera platform is hard plastic. Also included are a reducing block for small outside diameter eyepieces and a 1ž4-20 male/female spacer which I assume is used to replace the camera mounting screw and permit mounting the whole assembly on a tripod.

The first thing to do is clamp the yoke to the eyepiece using some care to ensure it's sitting square. Next is to mount the camera. The first thing you notice is that for any reasonable camera, the stage must be near the uppermost limit of its travel. There is about 3" of downward travel which will accommodate an unusually tall camera. With the XY clamp knob loose, there is a lot of slop in the XY stage. Keeping the knob slightly tightened helps reduce this slop. To align the camera, turn it on, fasten it to the mount and turn the translation screws to center the camera's lens on the scopes eyepiece. Zoom to wide angle, and look at the image on the camera's LCD screen. You'll see an illuminated spot on the screen. This is because the field of views of the camera is wider than the apparent field of view of the telescope. Translate the camera left and right and up and down to center this spot. Twist the camera slightly left and right on the platform to get even illumination across the spot. Move the camera in and out to get the spot as evenly illuminated as possible. Getting all this right takes a bit of fiddling and iteration. Zoom the lens until the camera's LCD is filled. Keep in mind the lens of your camera probably moves in and out as you focus or zoom so keep enough clearance between it and the eyepiece to allow for this.

There are a number of focusing methodologies but the simplest is to remove the adapter and camera, focus the scope (using your glasses if you wear any), reattach the adapter and camera, and let the camera autofocus. Another I method I use is to set the camera on infinity and focus the telescope by observing the image on the camera's LCD. To take the shot, I can either leave the camera on infinity or let it autofocus. It should be obvious that you don't want the flash going off. Also, to prevent image blur due to shaking, use the camera's self timer or a remote shutter release. You can drape a dark piece of fabric over the camera's lens and the eyepiece to help prevent reflections of surround light off the lenses. Experiment with various camera settings to see what gives you the best reslts.

In the example adapter I received, the camera platform was not perpendicular to the yoke so that it was not possible to align the camera properly with the eyepiece. There is no adjustment for this so I machined the edge of the camera platform that contacted the yoke to rectify the problem. Other options would include shimming or filing.



One advantage of the Lumicon adapter is that it will accommodate large diameter eyepieces such as the Zeiss zoom eyepiece and a 35mm Panoptic. In the case of the Panoptic, I had to remove the thin plastic strip in the bottom of the yoke to get it to fit.

In all, I find this mount to be serviceable and reasonably priced, particularly if you have the means to correct the perpendicularity of the camera platform.






Louis Hlousek