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

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

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

# 2454400

€ 245.00 Price excl. German VAT tax (19%): € 205.88

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1 Review(s) | Add Your Review

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.

Qty:

Product Questions

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)

Will it work on Meade ACF scts?

Question by: Bruno on Jan 24, 2019 6:04:00 AM | 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)

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)

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 see teleskop-express.com 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)

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)

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 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)

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)

The Alan Gee was designed for an ideal working distance of 121mm from the Alan Gee to the camera sensor/eyepiece at a classic Schmidt-Cassegrain. But you can also use it at different distances; 193mm e.g result in a focal ratio of f/3.5 - which of course compresses the usable image circle more, too.

The back-focus of an SC of about 146mm is the distance from the telescope's rear cell to the focal plane if there are no other lenses. If you use the Alan Gee, you place it in the desired distance from your camera (to achieve the desired compression ratio) and then focus with the telescope. Moving the main mirror changes the focal ratio of the SC, the data given in the manual refere to the resulting focal lengths when the Alan Gee is mounted as described in the manual.

But please note that the Alan Gee was designed years ago for Schmidt Cassegrains and not for the already flat field of an EdgeHD. For photographic use with an EdgeHD, we recommend the original Celestron reducers which were designed especially for the EdgeHD-optics.

The Alan Gee works fine with classic SCs, where it flattens the field and suppresses coma over a field of ca. 18mm - but with larger chips and smaller pixel sizes, this system is pushed to its limits. It is not recommended for pixel sizes smaller than 6-7my.

But for both EdgeHD and Schmidt-Cassegrains, the Alan Gee is a very interesting product for use with binocular viewers like the MaxBright II, because its working distance matches the back-focus of a binoviewer very good. Furthermore, the optical system of both Schmidt-Cassegrains and EdgeHD provides such a large back-focus, that the Alan Gee can almost double the field of view on most Celestron Schmidt-Cassegrains without visible vignetting. In the course of the development of the MaxBright II binoviewer, we have also developed a new T-2-cell for the Alan Gee. This new product - the AG Universal II - is designed for visual use with binoviewers and works even a little bit better with EdgeHDs, as they have a longer back-focus.

The AG II Universal as special reducer for binoviewing (but not for photography) will come to the market some months after the MaxBright II. If you are interested in binoviewing, we'd recommend not to buy the standard Alan Gee, because it deosn't offer the same connection options as the Alan Gee Universal. The Alan Gee Universal will be mounted directly between the binoviewer and the T-2-star-diagonal. We are looking forward to present this new product in 2020.

Answer by: Baader Web Team (Admin) on Sep 4, 2019 9:44:00 AM

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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)

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)

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)

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)

The main purpose of the UAG is to easily adapt a binoviewer, especially for telescopes upgraded to a 2" eyepiece holder like our 2" ClickLock..

A telecompressor can't really give you a wider field of view, it only gives you a wider field of view with the same camera sensor. It is usually better to use an eyepiece with a longer focal length and a larger field stop for visual use than to use a telecompressor.

With a Schmidt-Cassegrain, the inner baffle limits the usable field of view, as it has got a diameter of 37mm. Using a telecompressor behind the baffle (at the back of the telescope, which is the only place where you can put it), it can give you less magnification and a brighter image, but *not* a larger vield of view, as this is limited by the baffle. If you use a telecompressor or an eyepiece with a very large field of view and focal length, there will be vignetting at the edge.

So, you best option would be a 2" star diagonal combined with a long-focal eyepiece like the Hyperion 36; a telecompressoris only useful if you have a smaller camera sensor (like APS-C or smaller) or use 1.25" eyepieces (like in a binoviewer).

Please also take a look at this info from Celestron.com:
I want to use 2 in eyepieces with my SCT and/or Mak. Will there be vignetting from the OTA itself?
https://www.celestron.com/blogs/knowledgebase/i-want-to-use-2-in-eyepieces-with-my-sct-and-or-mak-will-there-be-vignetting-from-the-ota-itself

Answer by: Baader Web Team (Admin) on Mar 23, 2021 1:04:00 PM

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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)

There are several ways of adapting the Alan Gee to a telescope described in the manual at https://www.baader-planetarium.com/en/downloads/dl/file/id/213/product/1197/baader_alan_gee_ii_telecompresor_shapley_lens_f_5_9_manual_and_applications.pdf

You could e.g. use Baader T Adapter (BTA) for SC and MAK Telescopes (T-2 part #21) # 2408160 and Baader Expansion Ring 2"a/T-2i with 1mm optical path length (T-2 part #28) # 2958242.

But please remember two things: The compressing factor of the Alan Gee depends on the distance to camera or eyepiece, and it is designed to be used inside of the baffle of a Schmidt-Cassegrain, only then it will deliver the best results (which is mainly important for photography). If you want to use it with a 2" star diagonal, we recommnd that you use it as described in the manual between the nosepiece and the body of the star diagonal. If you want to proceed with T-2, we recommend the Universal Alan Gee II - Telecompressor (UAG II) # 2454405 which combines the Alan Gee optics with a 2" nose piece and a T-thread.

Answer by: Baader Web Team (Admin) on Jan 7, 2021 9:18:00 AM

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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)

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

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Question by: Mario Rossi on Oct 31, 2018 4:57:00 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.

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Question by: Michael Perata on Nov 23, 2020 10:02:00 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

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Question by: Tim McCollum on Sep 17, 2018 3:08:00 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?

Thanks!

-7

Question by: Carlos Labastida on Mar 19, 2018 6:15:00 PM | 1 Answer(s)

You have several options to use the Alan Gee for visual use; it shoud be mounted ca. 121mm in front of camera sensor or field stop. That's the ideal distance, but it doesn't have to be reached perfectly.

We have described them in the manual at https://www.baader-planetarium.com/en/downloads/dl/file/id/213/product/1197/baader_alan_gee_ii_telecompresor_shapley_lens_f_5_9_manual_and_applications.pdf

To use it with any of our 2" star diagonals, you need (as shown in Fig. 3 on page 2 of the manual) to remove the 2"-nosepiece from the mirror and replace it with
1) Baader Expansion Ring 2"a/T-2i with 1mm optical path length (T-2 part #28) # 2958242
2) the Alan Gee (you may have to remove the two extension tubes to achieve the best distance. The 2" Clicklock mirros has got an optical length of 112mm, so you probably have to remove both)
3) either
3a) Baader 2" / T-2 Nose Piece and Camera adapter (same as used by SBIG) (T-2 part #16) #2408150 if you want to insert the star diagonal into a 2" eyepiece holder or
3b) Baader T Adapter (BTA) for SC and MAK Telescopes (T-2 part #21) # 2408160 if you want to screw it directly onto your C9 1/4.

If you want to insert the Alan Gee into the telescope itself, you need the Centering ring for Alan Gee II Telecompressor # 2454410 (for C9 1/4), then you can lock it in its position with the standard visual back of your telescope.

I would not recommend combining the Alan Gee with a Barlow lens - you would use one optical element to shorten the focal length and then another one to extend it again. You'd be better of if you use instead one Barlow and adapt its magnification. The Q-Barlow 2.25x / 1.3x # 2956185 e.g. is designed for 1.3x or 2.25x, depending on where it is mounted, and the VIP 2x modular barlow lens, visual and photographic # 2406101 is designed for magnifications of 2x and more, depending on the distance. For calculating the different Magnifications with the VIP-Barlow, please check this PDF: https://www.baader-planetarium.com/en/downloads/dl/file/id/240/product/1062/calculating_different_magnifications_with_the_vip_barlow.pdf

Answer by: Baader Web Team (Admin) on Mar 21, 2018 12:22:00 PM

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Hi.
Will it work on a C6? How big is the corrected field at 0.35X? And at 0.59X? Thanks

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Question by: andrea on Apr 26, 2019 10:48:00 PM | 1 Answer(s)

Specifications

Additional Information

EAN Code	4047825011572
Manufacturer	Baader Planetarium
SKU (#)	2454400
Weight (NETTO)	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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