© Baader Planetarium GmbH | 2023
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Safety Instructions
Observing the sun in white light (i.e. the photosphere in the continu-
um), including sunspots, granulation and solar flares, is exciting –
but it is not without danger if the following safety instructions are
not observed. If used improperly, eye damage - up to and including complete blindness
– cannot be ruled out. We therefore ask you to study our safety instructions carefully.
The Herschel safety prism was specially designed for solar observation as an acces-
sory for refractors. Even with an inexpensive refractor of about 80 mm aperture, you
can observe all solar phenomena in white light that are accessible to the amateur.
The Safety Herschel Prism is an accessory for the serious amateur. Its use on a tele-
scope requires responsible handling, so the following applies to visual observation:
• Never remove the 2" grey filter / ND filter 1:1000, density 3.0, already pre-mounted
in the prism housing for visual observation, and use at least one other filter, either
the Solar Continuum Filter included in the scope of delivery, a neutral density filter
or a single polarising filter.
• If you are using more than one telescope on your mount, make sure that the light
inlets of all other instruments (including finder scopes) are securely closed before
pointing the telescopes at the Sun.
• Always mount the Herschel prism on the focuser before pointing the telescope at
the Sun.
• Never leave the telescope unattended, especially when observing the sun with
children
• We have successfully used the Herschel prism on telescopes with apertures of
6 and 8 inch. However, because of the intense heat, we still recommend swinging
the telescope out of the sun or covering it when not observing – take a break every
hour or so to allow the equipment to cool down. The limit for the focal length is set
by the 2" nose piece. For every metre of focal length, the solar image is about 1 cm,
so the focal length should be no longer than 4.5 metres. If you can use your tele-
scope with a 2" focuser for solar projection, you can also use the Herschel prism.
• Do not use the Herschel prism on telescopes with an additional corrector, reducer
or flattener near the back of the OTA, as these components may otherwise heat up
too much.
• To avoid overheating, we recommend using the Herschel prism only on telescopes
with a focal ratio of f/6 or slower.
With this BAADER safety Herschel prism with light trap ("heat cage") and ceramic
end plate, no more dangerous light escapes from the housing. This makes the Her-
schel prism a safe instrument – also and especially for school astronomy. All necessa-
ry filters – including an optional polarising filter instead of the Solar Continuum Filter
– can remain permanently in the Herschel prism, so there is no danger when changing
eyepieces.
