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Single filter adapters

Single filter adapter for ZWO ASI and Celestron RASA 8

Here’s another solution for those ZWO ASI cameras with the distinctive black sensor tilt plate:

  • ZWO ASI 2400 MC Pro,
  • ZWO ASI 2600 MM/MC Pro,
  • ZWO ASI 6200 MM/MC Pro.

For those who don’t need the complex functionality of filter drawers, I designed an adapter that allows you to place a single filter and work with the Celstron RASA 8 telescope. The device provides the required backfocus of 28.70 mm.

The adapter will be especially useful for those photographing with a single filter and a color camera. Also, those who decide to take long photography sessions and do not need to bother with frequent filter changes, may find that instead of a drawer it is enough to use the adapter. Although structurally less complex, it is nevertheless a very clever solution, cleverly addressing the exacting demands of shooting with RASA and large-sensor cameras.

As you can guess, it is not a just a connector, but a carefully thought-out device. It carries quite unique features. They all come from the fact that the adapter is not simply screwed into the center thread of the camera, but screwed with screws to the outer plane of the tilt plate. Such a procedure allows four advantages:

  1. The central threaded connector must have a certain wall thickness. When it is screwed into the M42 hole, the light of this hole is significantly reduced, obscuring the corners of the sensor, especially when the cone of light enters the camera at very sharp angles as is the case with the RASA 8. However, the solution proposed by Astrodevice is free of this drawback and the opening through which the light enters is as wide as possible.
  1. The widely spaced 6 screws allow the adapter to be screwed on solidly, thus achieving a uniform distribution of gravity and pressure. Not only do we get a perfect differential of the connection, but also resistance to the deformation of the geometry under the influence of the camera dropping under its weight.

  2.  Such a solution makes it possible to introduce additional screws for tilt adjustment, mounted directly in the adapter. Thanks to them you can make sensor tilt adjustment without removing the adapter and the camera and without disturbing the settings of the original tilt plate. So if you use the camera for several telescopes, you can set the tilt on the original plate, put the adapter on and modify the correction specifically for RASA.

    This feature is called Front Tilting Mechanism.

  3. This mounting method makes it easy to put on a possible additional spacer. If you are struggling to get a non-standard backfocus on your telescope, all you need to do is insert a thin shim between the adapter and the tilt plate. This way you can easily offset the sensor additionally by a few tenths of a millimeter.

The adapter allows you to screw in a standard 2″ astronomical filter. To use it, of course, you need to unscrew the original glass window from your telescope.

To screw in the adapter you will use the standard M87 nut supplied by the manufacturer together with the telescope.

Astrodevice single filter adapter front view
Single filter adapter mounted on a camera
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