Baader Planetarium Q-Barlow 1.3x/2.25x Barlow lens

The Barlow can either be screwed into the Q-Turret eyepiece turret or combined via the special, included adapter with all 1.25 "eyepieces. In this case, it acts as a 2.25x Barlow. With the Q-turret revolver and the Classic Eyepieces, this results in the following focal lengths: 2.7 mm, 4.5 mm, 8 mm and 14 mm

Alternatively, it can also be screwed directly into an eyepiece and then increases the telescope focal length by a factor of 1.3. The Barlow element has an M28.5 male thread (corresponding to the filter thread of 1¼ "eyepieces), the housing has got a M28.5 female thread. The factor 1.3x is achieved when the Q-Barlow is completely screwed into the 24mm long push-in sleeve of an eyepiece whose field diaphragm lies 2mm inside the push-in sleeve. This corresponds to the design of our Classic Plössl/Ortho eyepieces; with other eyepiece designs, the magnification factor may vary slightly.

Attention: When fully screwed in, the Barlow element protrudes 13mm into the 1.25" plug-in sleeve. On eyepieces where lens elements in the 1.25" sleeve do not allow the Q-Barlow element to be screwed in, it can only be used in the 1.25" adapter with factor 2.25x. If necessary, you can use it on these eyepieces with the 18.5mm long 1¼" extension sleeve with 1¼" filter thread on both sides.

Use on a planetary camera

The bare lens mount of the 2.25x Q-Barlow lens (without the 1.25" eyepiece holder) can be screwed into every 1.25" filter thread. To do so, remove the lenses with their threaded mount from the rest of the housing. Without the eyepiece clamp, the Barlow has no longer an extension factor of 2.25x, but only of 1.3x (when it is screwed completely into the filter thread). The reason for this is the shorter distance between the lenses and the image plane.

It may be that you can't insert the lens mount completely into the filter thread, then the magnification factor is closer to 1.5x.

But if the 1.25" nose piece of a camera provides a M28.5 filter thread, you can usually insert the Barlow completely, and because of the shorter distance the provided factor is ca. 1.3x. This is intentional and was one of the aims of the design. At 2.25x, an image circle of 25 mm is provided free of vignetting, while the fully lit image circle at 1.3x is 13mm.