Universal Alan Gee II - Telecompressor (UAG II)

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Universal Alan Gee II - Telecompressor (UAG II)

# 2454405

€ 196.00 Price excl. German VAT tax (19%): € 164.71

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I would be interested in using the UAG II with my conventional C9.25 for monocular observations. I would use it as suggested, i.e., replacing a 2" mirror diagonal's nosepiece with the UAG II, and inserting it into a 2" Clicklock visual back. In this way, the 1.25" eyepiece would be at the nominal distance of ~121 +/- 1 mm from the reducer.
However, some users claim that the UAG II causes aperture loss in this configuration, i.e., the light cone hitting the secondary would be too wide and thus cropped, due to the primary being pushed forward too much in order for the telescope to reach focus with the reducer.
My question is: is this true, and if yes, what would be the amount of the aperture loss? Also, do the UAG II and the original Alan Gee Mark II differ in this respect (the latter being inserted further up into the baffle tube)?
Question by: Istvan on Mar 29, 2021 4:03:00 PM | 1 Answer(s)

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I have a C8 EdgeHD with a UFC in front of the flip mirror. I’d like to use the UAG II along with the Maxbright II binoviewers. Is this possible? How much if any does the UAG II add backfocus?
Question by: Kelly Thorstad on Sep 30, 2020 8:38:00 AM | 1 Answer(s)

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I have a C8SE with 2" TV Everbrite Dielectric and I use the original maxbright with 2 x 17.5 Morpheus. Can you please tell me how the the UAG-II would improve my setup. What difference would I see, if any?
I also read about the ideal distance of "121mm", by using the bino + 2" TV diagonal, what is my distance?
Also can the UAG-II be used in conjunction with the GPC 1.7?
Thanks for your help, I am trying to learn!
Question by: Emilio on Jan 14, 2021 5:17:00 PM | 1 Answer(s)

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Can it be used in the Takahashi Mewlon 180c? With Baader T Adapter (BTA) for SC and MAK Telescopes (T-2 part # 21). The Mewlon to S / C converter would also be used in the telescope of course.
Question by: VICTOR on Apr 21, 2020 1:32:00 AM | 1 Answer(s)

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I am interested in purchasing the Universal Alan Gee and the MaxBright II Binoviewer for my Celestron 9.25 evolution, which has a 1.25" star diagonal. Are there any other components I would need to make this setup work?
Question by: Nathan on Aug 2, 2020 10:49:00 PM | 1 Answer(s)

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I have a 127 Mak, please would your UAG II be suitable to use on this?
Question by: Christopher Edwards on Sep 7, 2022 10:19:00 AM | 1 Answer(s)

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I’d be interested in using the universal Alan Gee with my Maxbright binoviewer (old version) and for visual mono with my meade acf 12”. I already own a click lock diagonal. I’m not interested in photography
I’d appreciate your input about field of view with the acf and if it can be used with my old binoviewer.
Question by: Rafael barragan on Jun 25, 2020 4:50:00 PM | 1 Answer(s)

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Universal Alan Gee II - Telecompressor (UAG II)

The Universal Alan Gee II is the only telecompressor/reducer on the market which works fine with a binoviewer.

The standard Alan Gee Telecompressor Mark II was designed by Roland Christen (the producer of AstroPhysics apochromatic telescopes) as a reducer for Schmidt-Cassegrains which also delivers a flat field. The Universal Alan Gee II (UAG II) puts the optical elements of the Alan Gee in a regular 2" nose piece with an additional T-2-thread on the telescope side. The UAG II can be used for visual observations with Celestron EdgeHD telescopes. too.

The combination: Mark V Giant Bino / Baader 35mm ED-eyepieces / Universal Alan Gee II (UAG II) / Baader T2 Prism delivers a field of view of ca. 1,2° when used with a C8 – that's 72 minutes of arc, as much as a 2" 40mm eyepiece will show you! So, instead of waiting for an (unaffordable) 2" binoviewer, you can achieve the same effect on most SC-telescopes with the UAG II – be it monocular with a star diagonal or binocular with a binoviewer!

Please note that the reducing factor of the UAG II only depends on the distance between UAG II and eyepiece. It is designed for a working distance of 121mm then you get a reduction factor of 0.59. But if you focus to a focus plane farther away than the designed back focus of a Schmidt-Cassegrains or EdgeHD telescope, the focal length of the telescope itself becomes longer, and you get a different reducing factor than that which is calculated only from the distance between reducer ad eyepiece. The result depends on the individual adaptation and the telescope, we can't give a universal value for the reducing factor – but you will clearly notice the much larger field of view.

Use with a binoviewer

The UAG II can be attached directly to all Baader T-2 star diagonals with the included  Baader T-2 / 7.5 mm Extension Tube (T-2 part #25C) (#1508155 , € 22,-) . Although a binoviewer could mechanically also be attached to a 2" star diagonal, we recommend for a Schmidt-Cassegrain the short adaptation with a T-2-prism and the Baader T Adapter (BTA) for SC and MAK Telescopes (T-2 part #21) (#2408160 , € 63,-) , so that the ideal focus point (and the focal length of the telescope in front of the UAG II) don't change too much from the original design. A binoviewer with T-2 thread like the MaxBright® II or the Mark V Großfeld (Giant)-Binocular (#2456410 , € 1425,-) can be attached directly to the UAG II. The distance to the eyepieces is then about 120 mm.

Monocular use with a star diagonal

The UAG II can also be installed in front of a T-2 star diagonal. In addition, you need a T-2 eyepiece clamp and – depending on the desired distance/reduction factor – a T-2-extension. The UAG should be as close to the telescope as possible, so we recommend the optional Baader T Adapter (BTA) for SC and MAK Telescopes (T-2 part #21) (#2408160 , € 63,-) to attach it to the telescope's SC-thread. If your telescope is equipped with a 2" ClickLock eyepiece clamp (#2956220 for C8/C925 or #2956233 for C11 and C14), you can also use this with the 2" nose piece of the UAG.

Baader 2" star diagonals with removable 2" nosepiece, you can also use the  Baader Expansion Ring 2"a/T-2i with 1mm optical path length (T-2 part #28) (#2958242 , € 25,-)  to install the UAG in front of the star diagonal. It replaces the 2" nose piece. The distance between eyepiece and reducer is then equal to the optical length of the star diagonal. To place the UAG closer to the telescope, you can use the optional Baader T Adapter (BTA) for SC and MAK Telescopes (T-2 part #21) (#2408160 , € 63,-) genutzt werden.

Photographic Use

The UAG II may also be used with a camera (up to APS-C sensor size); the distance between UAG II and camera should be 121mm. The Alan Gee II was originally designed to be placed inside of the baffle of a Schmidt-Cassegrain, so for photography we still recommend the classic  Alan Gee Telecompressor Mark II (T-2 part #20) (#2454400 , € 275,-) in a configuration as described in its manual.

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Additional Information

EAN Code 4047825044303
Manufacturer Baader Planetarium
SKU (#) 2454405
Optical length (mm) < 50
AR-Coating Multi-Coated (MC)
Usage MaxBright II Binocular
Optical Design Field Flattener, Telecompressor
compatible telescopes Schmidt-Cassegrain

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Martin Herbst 74/03/2024 15/03/202417:58
  • Rating:
Dieser Telekompressor ist die perfekte Ergänzung für das Bino auf einem SC. Beobachte mit einem Celestron C9,25 mit Großfeldbino.Bis zum Rand Scharf und Kontrastreich.Ich bin Sehr begeistert von der Qualität dieses Telekompressors.Reduziert sogar den Glasweg. Kann man auch vor dem Zenitspiegel einsetzen für noch mehr Brennweitenreduktion mit kleinen Einbußen bei der Randschärfe aber Die Vorteile überwiegen klar. Man Spart sich ein Zweites Teleskop mit Weniger Brennweite. Vielen Dank für dieses geniale Zubehör.
  • Sehr universell einsetzbar
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Mirom 319/11/2022 16/11/202209:43
  • more than 2 year(s)
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UAG II and visual observation with EdgeHD 8''
My experience with UAG II is positive. I am a visual observer owning a Celestron EdgeHD 8'' and with its 2000mm focal length and f10 aperture, it is very difficult to observe large emission nebula objects. With the UAG II, however, the focal length is cut in half and the improved aperture is immediately visible in the eyepiece. One can enjoy observing nebulae like North America or the beauty of the Andromeda galaxy in a wide field. Yes, the optical quality of the image will deteriorate, stars especially near the edge of the field of view suffer from coma, but that is to be expected. But in visual observation, the positives of a wider field of view outweigh the negatives.
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