Barlow Lens Q-Barlow (1.3x / 2.25x)

 Baader Planetarium Q-Barlow 2,25x / 1,3x

Without the housing, the Barlow lens can be screwed either into the eyepiece revolver (for 2.25x magnification) or directly into an eyepiece (for 1.3x magnification)

The Q-Barlow lens can be unscrewed from the eyepiece adapter

This high-quality 2.25x Barlow made of exotic glasses provides the rare extension factor of 2.25x. So, there are no duplicate focal lengths when used with the eyepieces of the Q-Turret Set, and you can achieve higher magnification than with standard 2x barlow lenses if you do planetary photography with a web or video camera, and you can make better use of the camera's resolution. Read here the detailed report by Dipl.-Ing W. Paech: Hints + tricks for high-resolution lunar and planetary photography with a video module - a short "workflow" for SC telescopes with Baader accessories.

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: 1¼" Extension Tube – with 1¼" filter thread (#1905130 , € 19,- )

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.

The Baader Barlow lenses at a glance

With currently five different barlow lenses in Baader Planetarium's product range, it is not easy to keep track of which model fulfils which function best.

FFC – Fluorite Flatfield Converter (3x-8x Barlow Lens) (#2458200 , € 730,- )	90mm field of view also for medium format cameras - uncompromising quality even for extreme enlargements. Focus gain: depending on configuration about 1.5-2.6cm
Barlow Lens Carl Zeiss Abbe 1¼" (2x) (#1603321 , € 477,- )	Legendary Zeiss quality for the common magnification range between 2x and 3x (with additional T-2 extensions). With T-2 connection for cameras or eyepiece clamps. The qualitatively equivalent solution to the Fluorite FFC when smaller field size and smaller post-magnification are desired. Focus gain: About 3 cm
Barlow Lens VIP, modular , visual and photographic (2x) (#2406101 , € 228,- )	Versatile barlow lens for magnifications from 2x, for use with cameras (via T-2 thread) and eyepieces. Calculated for 35mm image diagonal (full format). With additional T-2 extensions it can also be used for slightly higher magnification factors. Focus gain at 2x: Approx. 3.3 cm
Barlow Lens Q-Barlow (1.3x / 2.25x) (#2956185 , € 55,- )	Inexpensive and amazingly high quality Barlow lens for the lower magnification range: In addition to being used as a normal Barlow lens with eyepiece clamp (with factor 2.25x), the Barlow element can also be used as a negative lens group when screwed directly into (almost) all eyepiece sleeves or directly in front of a camera with 1.25" filter thread and then provides a lower magnification of approximately 1.3x. Ideal for adapting a modern planetary camera to the resolution of an already long focal length telescope. Prerequisite: There must be no other elements in the nose piece that would prevent the approximeately 13 mm long Q-Barlow lens group from being screwed in. Focus gain at 2.25x: About 0.4 cm
Barlow Lens Hyperion® Zoom (2.25x ) (#2956180 , € 133,- )	Specially designed for the Hyperion Zoom eyepiece, also fits the filter thread of other eyepieces. With the included T-2 adapter, it can also be used directly on cameras; provides about 2.7x at 55mm working distance and about 2.3x at 25mm. Focus gain: About 1.1 cm

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