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Blue Fireball 2" Eyepiece Extension Tube with 80mm (3.15") Extension # X-05

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New, improved design - Now with two large thumbscrews!

This high-quality Blue Fireball extension tube can be inserted into any 2" telescope focuser to gain an additional 80mm (3.15") of back-focus travel. With this, eyepieces and accessories that you may not have been able to use because your telescope tube was too short are usable again!

Lack of sufficient back-focus travel is a common problem with many of today's fast f-ratio telescopes, especially if you have a low profile focuser or a short telescope tube that is optimized for binoviewer viewing. The 80mm extension tube alleviates this problem. This tube can also be used with 1.25" accessories with the use of commonly available 1.25"-2" adapters (sold separately).

This practical and superb quality adapter is made from precision machined aluminum and is black anodized. It includes a brass compression ring that clamps around the inserted eyepiece or accessory. Because the set-screw does not come in direct contact with your eyepiece or diagonal, their barrel will not be scratched or dented. The inside surface of this tube is black-matted to enhance contrast by reducing stray light reflections and is threaded to accept standard 2" telescope filters. 2" barrel is smooth sided.


  • Total length = 115mm (4.53")
  • Extension provided = 80mm (3.15")
  • Insertion depth = 66mm (2.60")
  • Maximum outside diameter (excluding thumbscrews) = 62mm (2.44")
  • Weight = 6.4 oz.


Note: Occasionally, the product you receive might have a slightly different cosmetic appearance or labeling than what is shown. This can often change from batch to batch according to the whims of the manufacturer. However, you will always receive a brand new, original product as described above.

Description copyright: Agena AstroProducts - Reproduction without permission prohibited.

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Filed under: Eyepieces & Accessories