In afocal coupling the Nikon Coolpix 990 is aimed into the telescope eyepiece. Aiming the camera can be by hand holding the camera, mounting the camera on a tripod next to the telescope eyepiece, building or buying an adapter to hold the camera over the eyepiece or using an universal camera adapter to attach to the camera lens.

A benefit of the Nikon Coolpix 990 is that it has 28mm lens threads mounted on the camera body. Using a 28mm to T-mount adapter the Nikon Coolpix can be mounted to a standard universal camera adapter.

Seven Components of Afocal Coupling

• Nikon Coolpix 990.
• 28mm to T-mount Adapter from CKC Power.
• Orion Telescopes & Binoculars 20mm Sirius Plossel eyepiece.
• Orion Telescopes & Binoculars Universal Camera adapter - Prime Focus Adapter (first part of #5264).
• First Edmund Industrial Optics 48mm Barrel T-mount extension tube (K52-295 25mm) to reach focus and to hold the afocal camera assembly with a Edmund Industrial Optics 48mm Barrel T-mount Split ring mount.
• Second Edmund Industrial Optics 48mm Barrel T-mount extension tube (K53-231 20mm) to reach focus and to hold the afocal camera assembly with a Edmund Industrial Optics 48mm Barrel T-mount Split ring mount.
• Orion Telescopes & Binoculars Universal Camera adapter - 1.25" T-Adapter (second part of #5264) for the Orion ShortTube™ achromatic 80mm aperture rich-field refractor telescope or a 2" T-Adapter (#5269) for Orion Telescopes & Binoculars Argonaut™ 150mm Maksutov-Cassegrain telescope.

To reduce vignetting it is important to keep the eyepice as close as possible to the Nikon Coolpix 990 camera lens. The 20mm Sirius Plossel eyepiece is a perfect fit in the Universal Camera adapter in that it can be slid back against the 28mm to T-mount Adapter and the securing thumbscrew on the Universal Camera adapter still holds the eyepiece.

The longer 26mm Sirius Plossel requires a Edmund Industrial Optics short T-mount extension tube between the 28mm to T-mount Adapter and the Universal Camera adapter.

The shorter 10mm Sirius Plossel requires an Lumicon 1" thread-in extension tube (LAD110) mounted on the eyepice so that the securing thumbscrew on the Universal Camera adapter can hold the eyepiece.

The Coolpix 990 and Universal Camera adapter are held ridged with Edmund Industrial Optics 48mm Barrel T-mount Split ring mount (K52-304) and an Edmund Industrial Optics 2 inch Stainless Steel Mounting Post (K36-495). The Stainless Steel Mounting Post is held solid by a aluminum bar that is between the telescope and the mount. This configuration is still camera heavy and could use some rework to balance it better.