Alan Gee Telecompressor Mark II (T-2 part #20)

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Alan Gee Telecompressor Mark II (T-2 part #20)

# 2454400

€ 275.00 Price excl. German VAT tax (19%): € 231.09

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  • unique and extremely versatile telecompressor system that delivers the finest wide flat fields your SCT is capable of
  • The result is a sharp, wide, flat field, at a fast focal ratio of f/5.9, optical length <50mm
  • Please Note: The close coupling required for the telecompressor to reach focus with binoviewers limits it's use to only the Baader/Zeiss and Celestron binoviewers.

Product Questions

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Does the Alan Gee come with the spacer tubes described in the manual or are those purchased separately?

Thank you.
Question by: Mike on May 4, 2018 11:04:00 PM | 1 Answer(s)
I've very interested in this product but want to make certain I'm clear on what I would need to use it with my old model C9.25, ZWO ASI1600MM Pro (6.5mm back focus distance), ZWO EFW (20mm thick) and ZWO OAG (16.5mm thick).

In addition to the Alan Gee & the provided 19mm spacer tubes, I would need:
BTA T-adapter
Baader Varilock 29 (at 20mm position)
Baader Centering ring

Is that correct?
Thank you.
Question by: Mike on Dec 12, 2019 7:41:00 PM | 1 Answer(s)
Will this work with a Celestron C11 with the Baader 2” click lock visual back?
Question by: David on Jan 5, 2021 3:55:00 PM | 1 Answer(s)
Is it possible to use the telecompressor with a C11 ?
In that that case is there any adaptator to be used ?
What if a crayford is used ?
Question by: Frederic on Jan 28, 2020 11:25:00 AM | 1 Answer(s)
I recently acquired the Alan Gee Telecompressor to replace the stock Celestron x0.63 reducer. I'm using it only for photographic purposes on my C9.25, with an ASI294. It's a really well-built piece of kit.
I religiously followed the instructions from the manual, page 12: I bought the #2454410 centering ring, the short BTA #2408160, kept the two supplied 19mm spacers with the Telecompressor, and used 45.5mm T2 spacers to achieve a 121mm working distance. Surprisingly, that yielded an effective focal ratio of f/D = 5.2, which was way too low (stars in the corner were distorted). I then removed the 45.5mm T2 spacers completely, and got around f/5.6 (still a bit of star distortion but quite less so).
Do you see why the Telecompressor yields so much unexpected reduction? Is the 121mm distance really computed from the Sharpley lens that is on the camera-side, or the one farther in the baffle of the telescope?
Question by: Clouzot on Mar 16, 2021 10:09:00 AM | 1 Answer(s)
Will it work on Meade ACF scts?
Question by: Bruno on Jan 24, 2019 6:04:00 AM | 1 Answer(s)
I Wish to attach your Alan Gee Telecompressor to an older Meade 16” LX200, F/10, so I can attach a spectrograph that operates at F/5. What additional adapters do I also need to purchase?

Thank you,
Ron DiIulio, Director
Astronomy Program
University of North Texas, USA
Question by: Ron Diiulio on Dec 24, 2020 8:13:00 AM | 1 Answer(s)
what year of production?
Question by: Alexandr Martynov on Jun 23, 2021 4:04:00 PM | 1 Answer(s)
I have an older Meade LX200 7" Maksutov telescope. Can I use the Alan Gee telecompressor with it, both visually and photographically? What additional tubes or accessories would I need?
Question by: Steve Schaffer on Jun 1, 2018 6:45:00 PM | 1 Answer(s)
The telecompressor slides into the baffle of my Celestron 8SE SCT but is not secure and slides out. I use a 2" Baader Click-Lock and a 2" nose piece that attaches to my OAG. There is nothing securing the telecompressor inside the baffle. How can I make sure it does not slide out?
Question by: George on Jul 11, 2020 11:55:00 PM | 1 Answer(s)
I see has a special edition Alan Gee Tele for SCT focuser. So can i make one with a regular Alan Gee and a regular 2"-T2 adapter.It seems the SE AG tele has a short threaded tube over AG tele compressor then the 2"-T2 over those tubes...Also if i buy SE AG from Teleskopexpress are the 2 rubber rings and metal ring sold alone if I wanted to use inside my Celestron C5 it would seem there is a middle tube missing from SE AG?Any one else sell SE AG?I just got a Baader 31mm,,very nice glass.Thanks for your time
Question by: frank oneill on Jun 7, 2017 8:51:00 PM | 1 Answer(s)
I want to use the Telecompressor for visual and i want to know how it need to be use with :

Celestron C11 (no edge)
2956233 Baader 2" ClickLock SCL (3.3")
2956100 Baader 2" ClickLock Diagonal Mirror
2956214 Baader 2" to 1¼" ClickLock Reducer (T-2 part #15B) with 31.5 Eyepieces

In the manual it seem need :

2408150 Baader 2" nosepiece to T-2 / M48 (T-2 part #16)
2958242 Baader Expansion Ring 2"a/T-2i with 1mm optical path length (T-2 part #28)

But it's not clear. Can you explain ?
Question by: Romain on Sep 11, 2020 5:18:00 PM | 1 Answer(s)
Tell me, what is the diameter of the pipe?
Question by: Alexandr Martynov on Jun 15, 2021 9:27:00 PM | 1 Answer(s)
I’m looking for the widest fov out of C8 for visual use. I see you recommend having the UAG for visual use, but concerning using the stock sct-1.25” visual back and 1.25” diagonal wouldn’t the 2” size of the UAG be too big to fit? And the t-2 thread is also useless in this configuration?
Wouldn’t the original Alan gee be much better fit for such configuration? Considering it sits inside the baffle and the stock visual back is used as the locking screw of it.
Also, using your 31/36 aspheric, wouldn’t using the original Alan gee allows to screw the eyepiece to the sct thread with the Alan gee In it’s place? And In general , which is more suitable for C8 with/without focal reducer, the 31 or the 36?
Thanks in advance
Question by: Lior on Mar 23, 2021 10:41:00 AM | 1 Answer(s)
Hello! Does he correct coma?
If you screw it to a diagonal mirror, will it cover the entire APS-C matrix?
I have a Meade 8 "lx90 telescope. Thank you.
Question by: Alexandr Mart on Jun 9, 2021 2:33:00 PM | 1 Answer(s)
I would like to use the Alan Gee Telecompressor Mark II with my Celestron 9.25" SCT regular XLT Coatings version (not Edge version). I also have a Baader Planetarium 2 inch Clicklock Mirror Diagonal. Can I use this configuration for visual use? What kind of adapters do I need?

Also, If I want to use the Alan Gee telecompressor for Prime photography using Barlows / Eyepiece Projection, do I need to get additional adapters?

Question by: Carlos Labastida on Mar 19, 2018 6:15:00 PM | 1 Answer(s)
It is usefull on a Meade LX200 classic 10" f/10? Does it works also as field flattener?
Question by: Alex on Oct 24, 2019 8:02:00 PM | 1 Answer(s)
I'm considering getting a Alan Gee Telecompressor for visual & photographic use with a non-Edge Celestron C9.25. What adapters would I need to connect a CCD camera with a 1.25" filter wheel (and possibly an OAG)? For visual use, I have an Astro-Physics Maxbright 2" diagonal.

Thank you.
Question by: Mike on Nov 8, 2018 11:37:00 PM | 1 Answer(s)
I am a bit confused about the difference between the back-focus of a non-Edge CF C11 (reputedly about 146mm, the same as the Edge version) and the "ideal working distance" for the AG of 121mm.

Specifically, I have an AG I want to use again after a pause of a few years. It is currently in a 2" push-fitting without spacers which attaches the telescope to a Starlight AO unit, OAG, filterwheel and 694 CCD. The total from the back glass of the AG to the chip is about 129mm with the most compact connections I've found, or 8mm more than ideal.

I think for this reason, someone once told me to place the AG behind the AO and in front of the OAG/Filterwheel/CCD. However, this seems to me to be less than idea too. At the time, I ended up not using this set-up much in favour of the Hyperstar because the OTA was on a Fork-Wedge combination and quite wobbly. I have now deforked the OTA and put it on a decent EQ mount - so want to try this set-up again.

So my questions are: what is the best configuration? In the back of the optical tube inside the push-fitting with the 129mm to the chip or placed behind the AO and then at the "ideal" 121mm from that point? And what is the relation between the 146mm and 121mm?
Question by: Lynn on Sep 2, 2019 6:01:00 PM | 1 Answer(s)
I am thinking of buying an Alan Gee MkII, I am mostly confused as its visual use and which diagonals to use with it. I have a 9.25 SCT (non-HD). Is is only recommended to use with 2" diagonals or can I use it with the smaller T2 diagonals such as the T2 BBHS Zeiss prism? I was thinking of using that with the #16 T2 2" nose piece holding the Alan Gee and the T2 1.25 with diopter adjustment #8. I would be using the Baader Hyperion aspheric with 1.25 nose piece as well as other Hyperion eyepieces with 1.25 nose pieces. Would the combination of the aforementioned be best? I only have been thinking about using the prism because I want to get the widest and brightest view possible visually, and I also want to use the diagonal for the future purchase of binoviewers. I also don't want to by another 2" diagonal especially the click lock as I already have a Celestron twist-lock 2" diagonal.
Question by: Aaron on Jul 11, 2020 12:04:00 AM | 1 Answer(s)
Can I use the Alan Gee on a C14 (non EdgeHD, it's an old C14 Fastar) for visual use (not CCD)? How much will the focal reduction be (C14 is a f/11 telescope, not f/10)?

Thanks a lot
Question by: Mario Rossi on Oct 31, 2018 4:57:00 PM | 1 Answer(s)
I have purchased the Alan Gee MkII and need to adapt it to my 2” Moonlite focuser which is mounted to my GSO RC8. It looks like I will need items 16 and 26 to do this. Where is the best place to order these from to be shipped to the states? I have various spacer rings to use with my Altair Astro 183C PROTEC camera that had 17.5 mm flange distance. The AG was purchased from Agena AstroProducts. Thanks, Tim
Question by: Tim McCollum on Sep 17, 2018 3:08:00 PM | 1 Answer(s)
I have a new C11 EdgeHD with a Celestron OAG. Will this work with what I have for imaging and if so what adapters do I need.
Question by: Michael Perata on Nov 23, 2020 10:02:00 PM | 1 Answer(s)
Will it work on a C6? How big is the corrected field at 0.35X? And at 0.59X? Thanks
Question by: andrea on Apr 26, 2019 10:48:00 PM | 1 Answer(s)

Additional Information

EAN Code 4047825011572
Manufacturer Baader Planetarium
SKU (#) 2454400
Net weight (kg) 0.09
Optical length (mm) < 50
AR-Coating Multi-Coated (MC)
Usage 8" Schmidt-Cassegrains
Optical Design Field Flattener, Telecompressor
compatible telescopes Schmidt-Cassegrain

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M. Kohl 267/09/2006 25/09/200604:57
  • Rating:
.... zum Alan Gee II
...ich besitze schon seit einiger Zeit ein Celestron 11. Mein Interesse gilt hauptsächlich der Astrofotografie und ich habe schon verschiedene Telekompressoren ausprobiert, war aber mit der Abbildungsleistung nicht ganz so zufrieden. Der eine Kompressor war in der Abbildungsqualität gut, leuchtete aber nur ca. 24 mm des Kleinbildformats aus. Der andere Kompressor leuchtete zwar das Kleinbildformat gut aus, dafür war die Abbildungsqualität nicht so gut. Der Alan-Gee II Telekompressor leuchtet sowohl das KB-Format gut aus und liefert auch perfekte Sternabbildungen bis zum Rand des Dias bzw. des Negativs.

Ein Beispielfoto, aufgenommen auf Kleinbildfilm zusammen mit einem Celestron 11
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