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Baader 2" BBHS ® Prism Star Diagonal Prism with 2" ClickLock Clamp

Baader 2" BBHS ® Prism Star Diagonal Prism with 2" ClickLock Clamp

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Baader 2" BBHS ® Prism Star Diagonal Prism with 2" ClickLock Clamp

# 2456117

€ 450.00 Price excl. German VAT tax (19%): € 378.15

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2 Review(s) | Add Your Review

Manual and Recommended Use: Baader Star Diagonals(T-2 and 2")

2" BBHS prism star diagonal (BaK4 glass) with 2" ClickLock clamp and black case.
New included item since 01/2020: Baader 2" Safety Kerf nosepiece with 2" filter thread (#2408156, € 35,-) with additional grip and security from inadvertent slipping. This 2" nosepiece replace the former included 2" standard clamp with undercut
Provides greatest reflectance over most spectral range from 390 to 2000nm
BBHS = Broadband Hardsilver coating with dielectric protective overcoating
Much higher in brilliance than cheap dielectric coatings

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Product Questions

Tell me, please, what is the best diagonal to choose for observing objects of distant cosmos and planets:
Baader 2" BBHS ® Mirror Diagonal with 2" ClickLock Clamp
Baader 2" BBHS ® Prism Star Diagonal Prism with 2" ClickLock Clamp
And yet, the mass of them is indicated the same, is there any error here? The prism should be heavier? Thank you for your responses!

Question by: Evgeniy on Mar 28, 2017 8:13:00 PM | 1 Answer(s)

There was indeed an error in the specs, the mirror weighs 451g and the prisms weighs 513g. Regarding your question which to choose:
Usually prism diagonals are better suited for long focal length refractors and mirror diagonals for short focal length mirror telescopes.
This is because the total reflection with prisms is suboptimal when using short focal lengths due to nonlinear light reduction with high angle side light rays and chromatic prism effects. Also there are shifts in backfocus and it can influence the correction of high quality optics due to the glasspath (the speed of light is lower inside a dense medium like glass in comparison to air).
On the other side mirrors don't have the same maximum reflection values like a prism's lossless physical total reflection. Also a mirror is much more sensitive to transmission reduction when exposed to the air (sensitive silver layer getting weak very soon).
But with the Baader BBHS self protecting silver reflection layer on both diagonals (mirror and prism) the backsides of both principles are well compensated, this means the mirror diagonal will not loose any light due to aging anymore and the general light angle sensitivity of the prism diagonal due to reliance on total reflection alone is compensated by the additional BBHS layer below the total reflection hypotenuse area.
So the decision between diagonal mirror or prism is not as critical as it was until now.
But still a short focal length instrument favours a mirror diagonal.

Answer by: Baader Web Team (Admin) on Mar 29, 2017 10:49:00 AM

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PRISM-2Z 2456117 (2 inch diagonal with zeiss prism) I have a Celestron Evolution 9.25, with 2" visual back. Can I remove the nose piece and screw this diagonal directly onto my 2" visual back and use the lock ring LRING 2458270? Thank you. Jeff

Question by: Jeff Melcher on May 28, 2018 5:36:00 PM | 1 Answer(s)

Are the BBHS coatings easy to clean? Do the coatings have a life comparable to your dielectric coatings? Do the coatings degrade over time and at what rate? Is there a difference in performance between your dielectric diagonal and the BBHS one, what are the differences and are they significant or very slight? I own an early Televue APO 4 inch refractor.

Question by: John on Sep 9, 2016 1:29:00 AM | 1 Answer(s)

BBHS-mirror coatings require the same care during cleaning as you would give to the protected aluminum-coatings of a Newtonian telescope. Only dielectric coatings have the ultimate hardness to withstand any kind of mistreatment during a cleaning procedure - very similar to our Phantom-Group hard antireflection coatings applied onto our lens surfaces.

Any reflecting telescope with classic coatings can attain a lifetime of 20 or 30 years - correct handling provided. The same accounts for our protected silver-coatings, whereas the position of a stardiagonal within the optical train does provide much better protection against environmental influences, compared to the exposed surface of a primary telescope mirror.

We do regard the benefit of the BBHS hardsilver coating to be quite noticeable, compared to the reduced spectral range offered by a dielectric coating. Please check in the Internet for statements that would verify our position. Or look for the very extensive tests on star diagonals, performed by William Paolini (see tab "Downloads".

Please read more on the properties of our star diagonals and our design philosophy here: http://www.baader-planetarium.com/en/blog/baader-bbhs-reflective-properties/

Answer by: Baader Web Team (Admin) on Sep 15, 2016 8:22:00 AM

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What is the outside diameter of the nose piece? The precise inside diameter of the focusing tube on my refractor is 2.000 inches at 20 degrees Celsius +/- 0.001 inches. If it turns out that the nose piece is also exactly 2 inches, I could turn the nosepiece on a lathe. Your thoughts? What nose piece diameter would you suggest, if I had to turn it on a lathe?

Question by: John Aviste on Oct 12, 2016 9:30:00 PM | 1 Answer(s)

Is the prism in this diagonal (#2456117) a Carl Zeiss spec prism?

Question by: Brian on Jul 12, 2017 4:56:00 PM | 1 Answer(s)

Does the diagonal have an eyepiece stop?

Question by: Jan on May 25, 2018 5:17:00 PM | 1 Answer(s)

How can best I attach the Baader 2" Prism Star Diagonal (#2456117) to my C8 Edge HD? The native back focus of the C8 is 133m, and the diagonal has already 100mm which doesn't leave a lot for barlow or reducer attachments? Thank you

Question by: Christoph Mues on Mar 20, 2021 8:46:00 PM | 1 Answer(s)

How come the BBHS 2" Prism ClickLock diagonal has 100mm optical tube legnth, while the seemingly identical mirror BBHS diagonal has 112mm? Is that an error?

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Question by: Jan on May 25, 2018 4:19:00 PM | 1 Answer(s)

Do the Baader prism diagonals with BBHS coating work well with refractors faster than f/7 or f/8? I am wondering if chromatic aberration (or spherochromatism) would be a problem as the light propagates through the glass prism.

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Question by: Brian on Jul 13, 2017 4:00:00 PM | 1 Answer(s)

We do not recommend a prism for refracting telescopes unless the optical calculation of the objective lens calls for using a prism instead of a mirror.

For 100 years - all Carl Zeiss Refractor telescopes were designed to compensate for the added glaspath of a prism.

And throughout our 25 years of offering this prism we repeatedly found refractor telescopes - especially of very short focal length - where the airy disc went colorless only when adding a prism into the beam of light - as was the case with the "long gone" Astro Physics Traveler.

So please check carefully with your existing mirror star diagonal if the first ring of the airy disc appears reddish when observing a bright star - or better when observing an artificial star at high magnification. if this is found to be the case then a prism will bring a noticeable improvement.
If the first diffraction ring appears white already than a prism would not lead to an improvement but will induce a color error.

Answer by: Baader Web Team (Admin) on Jul 14, 2017 11:12:00 AM

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I already purchased this beautiful prism. Now I would like to attach the Giant Bino Mark V. How can this be done directly? With a 2"-Quick Changer ? If not yet, will you make them soon?
Or better: a Self Centering Adapter version ClickLock-QuickChanger. 2" and T2.

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Question by: Arthur on Dec 28, 2016 4:28:00 PM | 1 Answer(s)

Does the 2" nose-piece accept standard 2" filters such as Lumicon UHC? If not, what adaptor would i need?

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Question by: John on Nov 17, 2016 1:23:00 AM | 1 Answer(s)

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Optical tube lengths of 2" Clicklock and BBHS mirror diagonals

Recently we received the following questions on our 2" Clicklock Diagonal Mirror and wanted to answer including the below illustrations for other customers: Please note: all of the below information is also valid for our 2" BBHS mirror and prism diagonals (with slight differences in the specifiations such as optical tube lengths – please compare with specs on the product pages). According to image below is the optical path mentioned in technical data (112mm for #2956100 and 109mm for #2956100Z) measured along optical axis from point A to B or point A to C? what is the dimension from point B to C? Can 2” barrel (at point A) be removed from #2956100 and exchanged with another accessory (is it available?) to change the diagonal to #2956100Z (M68x1 thread)? Please note below our answer and adjusted graphic: The optical path of 112mm is measured A to C. The lightway from A to B would be ~71,5mm. Please note that the final endpoint of B is 3,5mm outside of the prism body (as illustrated in the below graphic), it looks just like point A in your drawing The Dimension from B to C (height of the SC-ClickLock) is 44mm. It is overlapping the...
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Specifications

Additional Information

Manufacturer	Baader Planetarium
SKU (#)	2456117
Net weight (kg)	0.51
Optical Design	Star Diagonal Prism
Inner Connection (lens sided)	Thread, M48, M55, 2" (50,8mm)
Outer Connection (lens sided)	Barrel, Dovetail ring, S58, 2" (50,8mm)
Inner Connection (eyepiece/-camera-sided)	Thread, Clamp, M55, 2" (50,8mm)
Reflection surface	BBHS coated, Dielectrically protected
Glas path	50 mm
AR-Coating	Phantom Coating® Group
Image Orientation	Erect image, Mirror inverted
Optical length (mm)	100
Clamping System	ClickLock
Deflection angle	90°
Inner Diameter / Clear Aperture (mm)	47.5

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