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Altair 2 Inch Positive Lock 90 Degree Prism Diagonal

Altair 2 Inch Positive Lock 90 Degree Prism Diagonal

Quality prism diagonals give far light less scatter than coated mirrors and therefore better contrast than any diagonals using reflective mirror surfaces, including dielectric ones. Prism diagonals are therefore especially good for high power planetary and lunar observing where sharpness and contrast are critical, especially with high quality refractors with an F7 or longer focal ratio. Perfect for serious planetary observers wanting a low scatter premium prism with superb mechanics to match.

Regardless of the coating methods used, all reflecting mirrors produced consist of tiny particles evaporated or deposited onto glass which, no matter how carefully deposited, will produce scatter and reduce contrast as the light "scatters". Another distinct adavantage of a quality coated prism is cleaning, durability is excellent with no long term loss of reflectivity like a mirror, cleaning can be performed in the same way as with any lens or eyepiece.

The Altair prism diagonal has a BK7/K9 prism with excellent clarity and smoothness, as well as special anti reflective coatings.

The prism surface cannot even be seen with the naked eye when looking into the diagonal, unless there is dust on the surface.

The special "Positive Lock" compression ring will never mar your accessories and is completely secure.
Ideal for refractors and large eyepieces or binoviewers.
Top quality prism with special broadband multi-coatings.
Clear aperture of 43mm, with an optical path distance of 125mm.
Essentially maintenance free.
Includes a 2" to 1.25" adapter with brass compression ring for smaller 1.25" eyepieces or GPCAM/Hypercam.
Threaded for use with standard 2" astro filters (M48x0.75mm thread).
Blackened interior for high contrast (especially recommended for the moon, sun and planets!).
Includes dust caps both ends.

Customer Reviews

  A solid high quality item  This is my first 2" diagonal and I was influenced by the previous reviewer who is obviously more experienced. This is a solid high quality product and despite the weight Harrison's delivery charges are still about a third of that charged by other well known dealers and it still arrived the next day.  (21/06/2019) Graham Shimmin - Herefordshire


    I was looking for two reasonably priced star diagonals that I could use as work horses. I currently owned at the time, and still do, the handmade Vernonscope mirror star diagonal ( consider the finest diagonal in the world.and the price really does reflect this quality.) After a lengthy chat with Ed, he convinced me he had a diagonal that would give any other star diagonal a run for its money. he really was not kidding! He had some Quality prism diagonals in stock, made by a UK company called Altair, at a price I considered insanely reasonable. I took a leap of faith and bought one, and tried it out. within 24 hours I was back for a second one. Folks, The build quality are fantastic! The performance of the Altair prism diagonal, combined with my orthoscopic eyepieces, and used on my apo-refractor telescopes do not disappoint. These diagonals are brilliant!   (15/11/2018) James Howes - london


Our standard delivery charge for most of the UK is £2.95. All orders are shipped promptly, lower value items are sent Royal Mail 1st class and higher value or larger goods are shipped via reputable courier. All goods are shipped fully insured with FEDEX, UPS, DPD and Royal Mail, we do not use budget courier services, please note we can only ship to UK mainland addresses. We are not able to ship to forwarding agents or PO boxes.

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We hold stock, dozens of telescopes and literally thousands of accessories that we ship out each business day, normally orders received before lunch are shipped that business day. We also direct ship from our UK suppliers, this means we have access to thousands of products that can ship fast to our customers.

Deliveries to UK mainland addresses are all shipped with fully insured premium services for £2.95, *some exceptions apply including many AB, FK, HS, IV, KA, KW, PA, PH, ZE postcodes. We will quote delivery charges to these areas where applicable prior to shipping (this does not normally affect lower value items shipped by Royal Mail).

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Altair 2 Inch Positive Lock 90 Degree Prism Diagonal

MPN: DIAG2-PRISM





Price: 125.00


Quality prism diagonals give far light less scatter than coated mirrors and therefore better contrast than any diagonals using reflective mirror surfaces, including dielectric ones. Prism diagonals are therefore especially good for high power planetary and lunar observing where sharpness and contrast are critical, especially with high quality refractors with an F7 or longer focal ratio. Perfect for serious planetary observers wanting a low scatter premium prism with superb mechanics to match.

Regardless of the coating method used, all reflecting mirrors consist of tiny particles evaporated onto glass which, no matter how carefully deposited, will produce light scatter and reduce contrast.

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