But usually, it's much easier to use a lens at a slower f/ratio than it it was desingned for, than to use it at a faster f/ratio.
For the adaptation to SC-threads or 2"-focusers, please take a look into the manual which you can find in the download section of the website.
For purchase in/delivery to the United States, please contact our distributor www.alpineastro.com.
We do not sell these spacer rings alone, but maybe TS has them or even includes them with their Special Edition.
Thanks a lot
Also, If I want to use the Alan Gee telecompressor for Prime photography using Barlows / Eyepiece Projection, do I need to get additional adapters?
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)
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
Manufacturer Baader Planetarium SKU (#) 2454400 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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