For Photography, Please Note; Further Important Notes - Baader Planetarium HERSCHEL PRISM MARK II Instruction Manual

For photography, please note:

• Make sure that the filters are strong enough for focal solar photography – start with
the pre-mounted filters for visual observation and gradually replace the 2" ND filter
(1:1000, ND=3.0) which is pre-mounted in the prism housing with weaker filters, st-
arting with the ND1.8 (see also page 9). Photographically, we recommend to always
use the Solar Continuum filter to achieve a better contrast.
• Depending on the focal ratio of the telescope, the image may appear too bright in
the viewfinder of a DSLR. In this case, hold a suitable filter (e.g. a neutral density
filter # 2458245 / ND=1.8, 1:64) between the eye and the camera viewfinder, or use
the LiveView of the camera if possible.

Further important notes

1. Never install any filter directly in front of the Herschel prism. When observing the
sun with any Herschel prism, the unfiltered sunlight hits the prism with full energy.
For this reason, additional filters or polarisers must never be mounted between the
telescope objective and the Herschel prism – i.e. "in front of" the Herschel prism
– as the heat load would be so high that any lens or filter installed in front of the
Herschel prism would immediately shatter. In the exact unprotected focus of a 6"
refractor, f/6 to f/15, temperatures of up to 600 degrees Celsius prevail.
2. If the photographic version of the Herschel prism is to be used for visual observati-
on, make sure before each visual observation that the 1:1000 Neutral Density filter
(ND = 3.0 / # 2458332) has been reinserted on telescope-side in the rotatable filter
mount and that the sunlight is sufficiently attenuated for visual observation by ano-
ther filter (Solar Continuum, ND or polarising filter). Use the article number on the
filter cell (ND 3.0 =
is really in the beam of light.
3. Under no circumstances should welding glasses, black-exposed films or similar
aids be used as additional filters for visual observation, since in almost all cases
these allow the infrared radiation – which is harmful to the eye – to pass unnoticed.
4. Refractors with Petzval systems or other telescopes that have glass in the light
path near the focal point are also not suitable for the use of a Herschel prism.
In general, any Herschel prism may only be used on suitable refractors and only
without further filters/optics between the objective and the Herschel prism. Multi-
lens systems pose no problem as long as the optics are close to the front of the
telescope. As long as the light has not been focused (i.e. the energy is not yet con-
centrated close to the focal point), the heat input is not higher than the solar energy
on a white surface in summer. All refractor optics, whether oil-filled or with an air-
gap, which are sold by Baader Planetarium, are suitable for a Herschel prism. The
oils used are all UV-resistant. (However, we can only speak here for the products of
the brands we know – if necessary, check the manual of your telescope to see if it
is suitable for solar projection).
5. Reflecting telescopes without a special coating are not suitable for solar obser-
vation with a Herschel prism. With them, optical and mechanical components
(secondary mirrors, mirror mounts, etc.) are used close to the focal point and can
be destroyed by the high heat load. The only exception are the Baader Planetarium
Triband telescopes, which were specially designed for this purpose (see p. 19).
4
Manual: Cool-Ceramic Safety Herschel Prism Mark II
# 2458332) to check that the correct filter for visual observation