Additional Optical Accessories; Eyepieces; Maximizing The Field Of View; The Highest Magnification - Baader Planetarium SolarSpectrum RG18 Manual

Additional Optical Accessories

In principle, you can use any eyepiece that provides a sharp, high-contrast image.
Special H-alpha eyepieces are mainly corrected for the red part of the spectrum and
may not provide a similarly sharp image as in H-alpha when observing white light.
Long focal length eyepieces still provide a bright image even at the ideal focal ratio of
f/30 for an H-alpha filter and avoid over-magnification. Due to the telecentric system,
you reach high magnifications very quickly and end up in over-magnification very
soon with common eyepieces. The over-magnification would cause a sensitive loss of
sharpness.
Please note: Although the telecentrics have an ideal working distance, the systems
are very good-natured due to the parallel beam path, and you usually do not need an
additional extension tube in front of the eyepiece clamp for visual use – star diagonal
and H-alpha filter usually already provide sufficient distance. Even a bino-viewer can be
used without an additional glass path corrector.
We recommend eyecups with a foldable stray light shade, as they are also included in
the scope of delivery of our Hyperion and Morpheus eyepieces. An observation cloth
that is white on the outside and black on the inside or a sun shield (for T-2:
for 2": # 2959280, for M68:
suppress stray light and increase contrast.

Maximizing the Field of View

The maximum sizie of the field of view is determined by the clear apertures of both H-
alpha-filter and telecentric system. Especially at the smaller H-alpha filters, the entire
sun is therefore only visible to telescopes with a short focal length. Do not forget that
the focal length is increased by the respective factor due to the telecentrics. Per metre
of focal length, the Sun has a diameter of about one centimetre.
2" eyepieces allow lower magnifications and thus a brighter image, plus often a more
comfortable viewing behaviour and an even slightly larger field of view than 1¼" eye-
pieces can offer. The field stop diameter of 2" eyepieces is up to 47 mm, compared to
about 28 mm for 1¼" eyepieces.
Typical long focal length eyepieces provide the following exit pupils (EP) at f/30:
Classic Ortho 32mm
1¼" – # 2954132
EP at f/30

The Highest Magnification

The rule of thumb that the maximum magnification corresponds to twice the aperture
diameter in millimetres does not apply for H-alpha observations. At magnifications
beyond an exit pupil of 0.7-0.8 mm, the image quality suffers, which is due to both the
deep red wavelength used and the optimisation of most optics to the green wave-
length range in the middle of the spectrum.

Eyepieces

# 2959281, see application picture on page 3) also helps to
Hyperion 36mm
2" – # 2454636
1 mm 1,2 mm
Celestron Omni 40mm
1¼" – # 810246
1,3 mm
© 2023 Baader Planetarium GmbH
# 2959279,
Celestron Omni 56mm
2" – # 810248
1,9 mm
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