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© Baader Planetarium GmbH | 2021
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Manual: SunDancer II
Using a Telecompressor
Especially on long focal length telescopes, very high mini-
mum magnifications are achieved through the 3x telecentric.
With a telecompressor, the focal length can be significantly
reduced again. The SolarSpectrum Research Grade H-alpha
0.4x Telecompressor 2"
(# 2459260)
has proven itself. It has
SC threads on both sides and can be used both photogra-
phically and visually. Its ideal working distance is 74 mm
with a corrected field of view of 16 mm diameter.
To screw it onto the T-2 connection thread of the SunDan-
cer II, you need:
1) Reducing-Ring 2"i / T-2a, with 1.5mm optical length
# 2958244
.
2) SolarSpectrum Research Grade H-alpha 0.4x telecom-
pressor 2"
# 2459260
3) Reducing-Ring 2"i / T-2a, with 1.5mm optical length
# 2958244
4) T-2 Conversion Ring
# 2958110
You will need additional adapters to place an eyepiece or a camera in the desired di-
stance. The included focusable 1¼" eyepiece clamp
(# 2458125)
has an optical length
of 29-35.5 mm. For the ideal working distance of 74 mm you still need a
5) T-2 / 40 mm Extension Tube
# 1508153
On the other hand, for a camera, the necessary adapters depend on the backfocus
of the camera.
The ideal distance will give you a reducing factor of 0.4x. However, the telecompres-
sor can also be used with a shorter distance, in which case the compression factor
changes. Instead of the 1¼" eyepiece clamp, the Baader 2" ClickLock T-2 (M42i x
0.75) clamp
(# 2956242)
with 36.6 mm optical length can also be used.
Note:
On obstructed systems, the "secondary mirror shadow" becomes visible when
the exit pupil of the telescope becomes larger than the aperture of your own eye pupil.
This is more noticeable during the day than at night, as the pupil then opens less wide.
Using a dark observation hood during daytime observations helps your pupil to open
wider.
Using a Bino-Viewer
The sun is particularly impressive in a bino-viewer; the relaxed binocular vision allows
details to be seen even better.
Compared to the standard 1¼" eyepiece clamp, a bino-viewer only needs about one
centimetre more back focus thanks to the use of a telecentric system, and a glass
path corrector is superfluous. To use a bino-viewer with T-2 connection, simply screw
the T-2 coupling nut onto the T-2 thread of the SunDancer II instead of the 1¼" eyepi-
ece socket. If you are using the binocular attachment with Zeiss micro bayonet, screw
the Baader TQC Heavy Duty T-2 Quick Coupler
(# 2456313A)
or the T-2 Standard
Quick Coupler with Zeiss Micro Bayonet
(# 2456313)
onto the SunDancer II.
In this configuration, only the glass path correctors for Zeiss
ring dovetail can be used, which are screwed directly
into the binocular
(# 2456314Z and # 2456316Z)
.
Due to the parallel beam path of the telecentric,
however, their effect changes so that the 1.25x
glass path corrector only saves about 3 mm
back focus; the 1.7x saves about 5 mm.
The change in magnification is corre-
spondingly small – in practice, the
glass path corrector behind the
telecentric should be omitted.
Please note that the combi-
nation of the SunDancer II
with telecompressor and
glass path corrector
in front of a binocular
attachment does not
work – and would be
useless as you reduce
the focal length only
to increase it right
away again.
The T-2 thread also allows
bino-viewers to be used with the
SunDancer II, here the MaxBright
II with a pair of 36 mm Hyperion
Aspheric eyepieces in 1.25"
configuration.
SunDancer II with
Telecompressor
2
3
1
2
3
4
4
Above are the necessary parts to connect the telecompressor to the SunDan-
cer II, on the right they are fully assembled.
1
Note:
The maximum field of view is limited by the 19 mm aperture behind the etalon;
the telecompressor can only reduce this image circle. As a rule of thumb for the size of
the solar disk, it appears about 10 mm in diameter per metre of telescope focal length.
Therefore with the built-in 3x telecentric, the whole sun disc (with prominences) can be
viewed in telescopes with a native focal length of up to about 600 mm.
