Skip to content

Baader OPFA Eyepiece Projection Adaptor (Versions I to VII)

SKU 2458142

Availability: Immediate Dispatch

  • Eyepiece projection adaptor system
  • Seven versions available
  • For imaging with digital and/or analogue (D)SLR cameras with removable lens

The Baader OPFA (Ocular Projection Foto Adaptor) is a complete accessory set for undertaking focal photography and eyepiece projection. The system has several telescope connections (see the Versions tab), camera side connections, and has a sliding focuser tube and two 40mm T-2 extension tubes.  A suitable T-2-ring for your camera must be ordered separately.

The OPFA projection system is light-tight and the fitments screw securely together to provide a sturdy "no-wobble" platform. With additional T-2 extension tubes, even extreme projection scales can be achieved – even with CCD cameras (see below for a diagram which shows how eyepiece projection works).

Eyepiece projection works in the same way, although there are some practical differences whether the camera is used WITH or WITHOUT lens. When working with a (digital) SLR camera, the lens is usually removed, and the camera body is attached directly to the projection unit. If the camera lens is integrated into the system, this is called afocal projection. This is the usual method when shooting with digital viewfinder cameras, where the lens can NOT be removed. For these cameras, we recommend the Baader ADPS, which can be set to a short distance between eyepiece and camera lens.

The following diagram shows the structure of the classic eyepiece projection with cameras, where the lens can be removed (e.g. DSLR). The focus plane or focal image of the telescope is projected onto the film/camera sensor via a projection eyepiece (similar to a slide projector, which projects the magnified slide onto a screen). The resulting focal length is called the equivalent focal length (fE).

Eyepiece projection diagram

The reproduction scale depends on the focal length of the eyepiece (fEP) and the projection distance (a). The equivalent focal length is calculated as follows (the longer it gets, the bigger the image on the film becomes):

f_E = fprimary × ((a ÷ fEP) - 1)

The effect of the different parameters can easily be seen from the formula. If the eyepiece focal length is reduced and / or the distance a (between focal point of the eyepiece and the camera sensor/film) is increased, the value of the equivalent focal length (and with it, the magnification) increases; the picture (image) gets bigger.

The image below shows the OPFA system with optional accessories.

Baader OPFA System

The parts marked in blue correspond to the OPFA-IV basic version, which has a male T-2-thread on the camera side and a female T-2 thread on the telescope side. Each OPFA (versions I-III and V-VII) has got another telescope adaptor included in the scope of delivery. In the example above, the adaptors of OPFA Version I and II are shown in green. The parts marked in red are not included in any OPFA system and are optional extras.

The unit starts on the telescope side, i.e. the sliding focuser (to the right; 2458010 (#24))). Shown in the picture are OPFA-I (1¼" nosepiece) and OPFA-II (2" nosepiece). If your focuser has a different connector, you have to choose between OPFA-III and OPFA-VII (e.g. OPFA-III for Celestron and Meade Schmidt-Cassegrain telescopes). This is followed by a sliding focuser with a T-2 locking ring. The 1¼" eyepiece (not supplied) is inserted into this sliding focuser and clamped in.

The sliding focuser and the locking ring allows fine adjustment of the projection distance possible by slightly pushing the eyepiece forward or backward. By loosening the locking ring, the complete unit can be rotated steplessly, until the attached camera is to set to a favourable orientation. For OPFA-I and OPFA-II the camera can also be rotated with the complete unit. Note that for OPFA-III to OPFA-VII, the connection from the OPFA to the focuser is a rigid screw connection. Here, the camera orientation can only be changed via the locking ring of the sliding focuser.

The two 40mm T-2 extension tubes are screwed onto the sliding focuser, the eyepiece (outer eyepiece body diameters of up to 38mm) will be inside of the T-2 extensions. The extensions are used to set the distance between eyepiece and camera (ie to establish the projection distance). By adding more T-2 extension tubes, the distance (and the image) can be enlarged. See the image below for parts for the OPFA:

OPFA T-2 Diagram

The OPFA is connected to the (digital) SLR camera through a camera-specific T-ring (not included).


In the table below, we present the 7 versions of the OPFA.

OPFA - Version I OPFA Version I
  • Consist of base version OPFA (single parts see OPFA IV)
  • Telescope side with 1¼" barrel (#2458155)
OPFA - Version II OPFA Version II
  • Consist of base version OPFA (single parts see OPFA IV)
  • Telescope side connection: to put into 2" nosepiece, with safety nut in the 2" barrel and Filterthread for 2" filters
  • Telescope side with 2" barrel (#2408150)
OPFA - Version III OPFA Version III
  • Consist of base version OPFA (single parts see OPFA IV)
  • Telescope side connection: to connect onto 2" SC threads of all Celestron (and Meade) Schmidt-Cassegrain telescopes
  • Telescope side with 16mm super short Celestron/Meade adapter with 2" inner thread (#2958500B)
OPFA - Version IV OPFA Version IV
  • Consist of focuser/eyepiece holder (T-2 part #24) and 2x T-2 extension tube 40mm (T-2 part #25B)
OPFA - Version V OPFA Version V
  • Consist of base version OPFA (single parts see OPFA IV)
  • Telescope side connection with outer thread M44 x 1, to connect on all Zeiss-telescopes with M44 inner thread
  • Telescope side with Zeiss-M44 Adapter (#1508005)
OPFA - Version VI OPFA Version VI
  • Consist of base version OPFA (single parts see OPFA IV)
  • Telescope side connection with  outer thread M43 x 1, to connect on all Vixen-telescopes with inner thread M43 x 1
  • Telescope side with Vixen-Adapter M43 (#1508037)
OPFA - Version VII OPFA Version VII
  • Consist of base version OPFA (single parts see OPFA IV)
  • Telescope side connection with M36.4mm (T-2 part #3) adaptor thread, eg. for Vixen, TAK
  • Telescope side with Vixen- /TAK Adaptor M36.4 (#1508039)


USAGE Ocular Projection Adaptor

For photography with digital and/or analogue SLR cameras with removable lens



TYPE OF ADAPTER Camera Adapter, Extension