Baader Cool-Ceramic Safety Herschel Prism (Visual/Photographic)

A 2" Herschel Wedge Prism

The prism is a 2" wedge prism according to Herschel. It works by first-surface reflection, in white (integral) light, and gives an erect, mirror-inverted image, like a star diagonal. The prism carries Baader's Phantom Coating Group anti-reflective coating on one side.

A Herschel prism is designed for use with refractors. Use the prism only as described in the instructions Baader supplies with it.

Included Filters

Both versions include the Solar Continuum 7.5 nm 2" filter (540nm, #2961581) and the Neutral Density filter 2", ND 3.0 (T=0.1%, #2458332). The Photographic version adds three more Neutral Density filters:

• ND 1.8 (T=1.5%, #2458331)
• ND 0.9 (T=12.5%, #2458322)
• ND 0.6 (T=25%, #2458321)

The optical length with two filters of 2 mm glass thickness (ND 3 and Solar Continuum) is 112.4 mm, against 115 mm without filters.

Brightness Adjustment with Polarising Filters

Baader builds in a rotation mechanism for polarising filters, which it calls the best method for brightness adjustment in visual solar observation and solar photography in white light. Stepless brightness adjustment is possible in combination with the optional Polarizing Single Filter 2" (#2408342) and the included Neutral Density filter. The polarizing filters are not included.

Ceramic Solar Finder, S58 Dovetail and 3-Point Adjustment

Baader fits the prism with a ceramic solar finder for pointing the telescope at the Sun. The 2" nosepiece has an S58 dovetail and Safety-Kerfs, and the prism has a new 3-point adjustment system preset in the factory.

Baader's Safety-Kerf groove system gives the focuser's clamp excellent grip, just like a classic safety groove, and in addition the prism cannot tilt if the telescope's clamping mechanism is in an unfortunate position; with a simple safety groove the clamping screws may just miss the groove or sit on its edge.

Connections and the 2" ClickLock Eyepiece Holder

The connections are:

• Telescope side: 2" nosepiece and S58 dovetail outside; M48, 2"/SCT thread and M55 inside.
• Eyepiece side: 2" bore with the ClickLock holder; 2"/SCT thread, M55 and S58 outside.
• Optical length: 115 mm without filter; 112.4 mm with two 2 mm filters.

Baader's 2" ClickLock clamp has no clamping screws: a 20° turn of the rotary lever with light pressure holds 2" accessories securely. Like a quick-action chuck, it holds the inserted item on three sides, and leverage multiplies the torque; a ratchet lets you hear and feel whether it is open or closed, and the massive tension ring holds accessories without scratches. Every eyepiece is aligned parallel to the axis automatically, even with diameter deviations.

Visual and Photographic Versions

The prism body is the same in both versions. The Visual version (1.60 kg) includes the prism, the Solar Continuum 7.5 nm filter and the ND 3.0 filter. The Photographic version (1.74 kg) includes the Visual set plus the ND 1.8, ND 0.9 and ND 0.6 filters.

Care of the Filters

Baader's cleaning guide says filters can be cleaned like eyepieces, especially hard-coated ones such as all Baader filters: apply the cleaning fluid to the cloth, never onto the item itself. Clean optical surfaces as seldom as possible, avoid fingerprints, which contain fats and acids that harm coatings, and remove dust with a clean, fat-free brush before using any fluid. Keep the dust caps on when the prism is not in use.