Baader’s VIP barlow lens sounds very important having the letters “VIP” as part of its title. The “VIP” stands for VIsual and Photographic so as its name suggests its a versatile barlow that can be used for both purposes.
Unlike typical barlow lenses which are housed inside a fixed length tube, the VIP barlow is modular in its configuration and it comes with a range of adaptors/spacers as standard. From top to bottom:
- 2″/1.25″ eyepiece clamp with 2 locking screws and non-marring insert (T-2 part #15; 2408190), You can use a 2″ mounted filter in the base of this part.
- T-2 female – M48 male expanding ring (T-2 part #29; 2458110)
- 2 x 15mm T-2 extension tube (T-2 part #25A; 1508154)
- 2x barlow lens in its own housing that is inserted into the 1.25″ nosepiece (T-2 part #14; 2458105)
Although the barlow has a 2x image amplification factor, the actual magnification depends on how far your eyepiece field stop (or camera sensor) is placed from the barlow element. This is the reason for its modular build. For example removing one of the 15mm spacers will bring the barlow close to an eyepiece (or sensor) and it results in a (lower) magnification of 1.76x. By adding additional extension tubes, such as the Baader 40mm extension, the barlow is at a greater distance from the lens and in this example the magnification increases to 2.6x. If you are interested in how to calculate the magnification(s) with different spacing options you can read more here. For those interested in imaging, this VIP-Barlow was designed for 35mm-film, so it also works fine with current full-frame DSLRs (24x36mm).
It should be pointed out that in the diagram above, the barlow lens element appears similar in apprearance to a GlasspathCorrector. This is a 2x barlow lens and it has nothing to do the 2.6x glass-path-corrector lens that Baader offer exclusively for binocular viewers.