Infrared Pass Filter; Triband And Other Telescopes - Baader Planetarium HERSCHEL PRISM MARK II Instruction Manual

Infrared pass filter
While focal photography of the whole sun has few problems with
air turbulence (seeing) due to short exposure times and low mag-
nification, things change when you use pro-
jection photography. The larger the equivalent
focal length, the longer the exposure time. This
greatly increases the susceptibility to seeing
effects.
Seeing effects are wavelength-dependent
– stronger in the short-wave spectral range
(blue), less in the long-wave spect-
ral range (red). Therefore, it can be
worthwhile – especially when shooting
with video modules and long focal
lengths – to use a very dark red filter to
completely block the short-wave part
of the spectrum. Ideally suited is the
Baader IR pass filter (1¼":
# 2458386), which is also popular in
2":
planetary photography and significantly
reduces seeing effects there as well. To
use an IR pass filter, the Solar Continu-
um Filter must be removed. This filter can only be used photographically.

TriBand and other telescopes

Even though we wrote in this manual that the Herschel prism is only meant for re-
fractors, there are two exceptions: The
Baader TriBand Schmidt-Cassegrain tele-
scopes and Schiefspiegler telescopes.
The Baader TriBand SCT are modified
Schmidt-Cassegrain telescopes with
8", 9¼" and 11" apertures that have an
energy protection filter integrated into
the Schmidt corrector plate. Originally
designed for high-resolution H-alpha ob-
servation with SolarSpectrum or Baader
SunDancer filters, the special coating also allows both deep-sky narrowband photo-
graphy and solar observation with a Herschel prism. Since the TriBand coating is not
transparent at 540 nm, the SolarContinuum must be removed and replaced with an ND
or polarising filter.
Schiefspiegler telescopes are somewhat out of fashion and are not currently in series
production. However, they are the only reflecting telescopes that are obstruction-free
and can provide sufficient backfocus for a Herschel prism. Please refer to the opera-
ting instructions of your telescope to find out whether your model is suitable for solar
projection or a Herschel prism, or whether, for example, correction lenses close to the
focus prevent this use.
# 2458386;
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