The Herschel Prism For Advanced Users; Solar Photography In Calcium Light; 1¼" Filters - Baader Planetarium HERSCHEL PRISM MARK II Instruction Manual

The Herschel prism for Advanced Users

Solar photography in calcium light

In the dark blue spectral range, around
400 nanometres, photospheric flares in
the vicinity of sunspots, which can only
be observed visually in white light near
the edge of the sun, can also be made
visible further towards the centre of the
sun. To do this, the contrast of flare are-
as near the edge is dramatically increa-
sed with the Baader calcium filter Gen II
# 2961590. This filter, with a half-width of
about five nanometres, only lets through
the emission lines of calcium.
To use this very narrow band filter, you
should replace the ND3 filter with a wea-
ker filter to achieve a sufficiently bright
image. Try the ND1.8 first before trying even weaker filters if necessary. The Solar
Continuum filter and any polarising filters must also be removed.
Please note: Since the human eye is virtually blind in the spectral range below
420 nm, visual observation is not possible. Only cameras can be used as sensors –
preferably astronomical cameras or video modules.
It is a mystery to us why competitors offer "CaK" telescopes for visual use, while
every tanning salon is legally obliged to warn against looking directly into UV-A radi-
ation – and that is exactly what happens when you visually observe the calcium line
below 400 nm.
To take advantage of the high quality of the Baader calcium filter in combination with
a Herschel prism, the refractor objective should also be of high quality (apochromatic).
Simple double-lens achromatic objectives are usually very poorly colour-corrected in
the blue spectral range, so that no sharp images can be obtained in this spectral range
with them.
1¼" filters
1¼" filters can be screwed directly into 1¼" eyepieces or cameras and used e.g. with
the Baader 2" to 1¼" ClickLock
ever, they cannot be inserted directly into the 2" filter holder of the
Herschel wedge.
Alternatively, you can screw 1¼" filters directly into a 2" filter
thread using the 1¼" filter holder for T-2 and 2" filter
thread # 1508031.
For cameras with 2" nose piece and T-2 adapter
thread, you can replace the nose piece with Baa-
der 1¼" T-2 nosepiece
18
Manual: Cool-Ceramic Safety Herschel Prism Mark II
reducer # 2956214
®
# 2458106.
Calcium-line-image of the sun. Monochrome camera at
Celestron ED80/600 with Herschel prism, ND1,8-filter und
Baader Calcium-filter Gen II
on the Herschel wedge. How-
# 2961590
# 1508031