The projection adapter option should be considered if your digicam lens has filter threads (or if you can get an adapter for your digicam that will hold a threaded filter in front of the lens), but the scope eyepiece
you want to use cannot accept one of the direct Digicam-to-Eyepiece Adapters. In this case you may be able to use an “Eyepiece Projection Camera Adapter”. This is a barrel inside of which an eyepiece
fits; the top of the barrel is threaded and you screw your digicam to it. Televue sells such an adapter that is designed to hold Radian eyepieces (shown here on the right).
ScopeTronix sells an “Eyepiece Projection Camera Adapter” for 1.25” eyepieces (shown here on the left - click on the image for a larger view). Like
the Televue adapter described above, it is also a barrel into which an eyepiece fits - the photo shows a Meade Series 4000 15mm Super Plössl inserted. The ring on the right in
the photo is the “Digital Camera Lens Adapter”. It screws onto the Eyepiece adapter after an eyepiece is inserted, and your digicam screws onto it. The whole
assembly then replaces your scope’s eyepiece. You will need to radically move your scope’s focus knob to bring this into focus, because the eyepiece is now a lot farther away from the mirror.
For most Eyepiece Projection Camera Adapters there is a limited range of eyepieces (diameter plus length) that will fit into the adapter. For example, with the Scopetronix adapter the eyepiece can’t be
more than 1.5” in diameter nor longer than 1 3/8” (excluding the 1.25” part that slides into an eyepiece holder). Actually, the maximum length depends a little on which Lens Adapter you need - the 41mm
adapter may let an eyepiece stick out past the lens adapter a little, but the 37mm and the 26mm adapters won’t. So the only eyepiece I found to work is the Meade 15mm mentioned above, although I
didn’t do an exhaustive search.
However, Scopetronix has recently introduced an Eyepiece Projection Camera Adapter
that has a barrel whose length can be varied (shown here on the right), and this is likely to help you adapt a specific 1.25” eyepiece to your digicam. Note also that CKC Power sells similar adapters.
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