Baader ADPS Afocal Digital Projection System, female T2 Thread (Base Version)

The basic thought:

Digital cameras with a fixed lens nevertheless allow the use of a telescope to extend the focal length. Here, not only the magnifying effect of the eyepiece is used, but also its collimating effect.

The ADPS (= Afocal Digital Projection System) holds the eyepiece on a defined place and additionally provides the connection to the telescope and the T2 ring of the camera. However, the characteristics of the afocal projection must be taken into account:

The projection system is very similar to the Baader OPFA system for DSLR cameras - but the distance between the projection eyepiece and the lens of a digital camera can be set to a much shorter value!

Eyepiece projection (so-called afocal projection) in combination with compact cameras requires a much more precise setting of all mechanical distances than in the classic eyepiece projection with a DSLR, where the lens can be removed from the camera body.

Baader´s ADPS projection system is made of a very finely stepped series of extension rings (and a T2 locking ring) to adapt it to any 1.25" "eyepiece (with a diameter of up to 38 mm), so that the eyepiece can be positioned as close as possible to the first lens of the camera lens! Only this close distance makes a sharp image without vignetting possible.

Practical work:

Advantage of the ADPS system compared with standard adaptations:

offers a variable distance for fine-adjusting the magnification

very variable because different T2 extension rings can be used for more magnification

parts screwed together, thus very stable and rigid

consists of T2 parts that can also be used otherwise

Components of the ADPS-IV T2:

T2 push-focuser with T2 thread on both sides

T2 locking ring

two T2 extension tubes, 15 mm each

one T2 extension tube, 7.5 mm

Which eyepieces are suitable for projection?

The ADPS accepts 1.25" eyepieces up to a diameter of 38 mm. Especially orthoscopic (Abbe) and Plössl eyepieces of 6-15 mm focal length are recommended.

Calculating effective focal length if using camera lens:

f_e = f_cam × f_scope/f_ep = f_cam × M

f_e is the effective focal length

f_cam is the focal length of the camera lens

f_scope is the focal length of the telescope

f_ep is the eyepiece´s focal length

M is the magnification of the telescope

The camera has to be focused to infinity for a correct result. This will also optimize image quality, as the lens is designed for this.

Information to the set-up (from right to left):

The parts marked blue correspond the basic version ADPS-4 with T2-threads on both sides. "Schiebefokussierung" means push focuser, a "T2-Verlängerungshülse" is a T2 extension tube.

The parts marked green are included with ADPS 1-3 and ADPS 5-7 (shown here: ADPS-1 and ADPS-2). They are the telescope side connectors.

The parts marked red are not included with any ADPS!

A central component of all ADPS systems is a sliding focuser (marked in blue) with a T2 locking ring. The 1.25" projection eyepiece (not included in the ADPS) is inserted into this sliding focuser, and the sliding focus allows precise adjustment between eyepiece and camera lens.The locking ring allows the camera to be rotated continuously relative to the focuser in order to optimally position the camera for an image.

Then, three T2 extension tubes (2x 15 mm, 1x 7.5 mm, also marked blue) are screwed onto the sliding focus, the eyepiece (with a maximum outer diameter of 38 mm) is now inside of the tubes. These tubes are used to achieve the correct projection distance. In addition, you need both the DT adapter (BA2458040) and a suitable DT ring to connect the camera to the ADPS.

Please note: The manufacturers of digital cameras without interchangeable lens want to prevent the zoom lens on your camera from damage, when is retracting or extending! That´s why many cameras either don´t have a filter thread or some strange thread not commonly used on the camera. Then, you must buy some adapter for front filters from your camera dealer! This is usually a large-sized adapter with a certain length which makes sure that even a fully extended zoom lens can not touch a filter.

Please always read the operating instructions of your camera and check which thread size is offered on your camera body as adapter thread on the camera side. That´s usually really easy! If none of Baader´s digital DT-rings fits directly onto the filter thread of the camera lens or the camera body itself, then the necessary spacer ring must be ordered from your photo retailer. These items are usually called filter adapter. Only if such a thread is available, a camera can be attached to the ADPS via the DT adapter and one of the DT-rings.