Filaments
appear as large, dark eye-
brows across the surface of the Sun.
With a brightness of about 10% of the
disk due to scattering, they appear
dark on the surface, but on the limb,
show as a prominence. Active Region
Filaments (ARF) differ from Quiescent Region Filaments (QRF). ARF are darker, small-
er and have more coherent fibril structure along their axis. A sheared magnetic field
runs parallel to this axis, permitting a sizeable flare. QRF may produce a big Coronal
Mass Ejection (CME). An ARF may erupt and reform several times.
Plages:
Most of the active region area is occupied by plage. Considerable atmos-
pheric heating takes place in the
plage. It is bright in everything from
Halpha to the Calcium H and K lines.
This heating is thought to account for
an absence of spicule. While absent
over plage, spicule are prominent
around its edges.
Elerman Bomb:
A remarkable feature
of Emerging Flux Regions is the
Ellerman bomb. Bright points with very
broad H-alpha wings (±5Å) that are
low in the atmosphere so they are not
visible on H alpha centerline. Called 'moustaches' for their appearance on spectro-
graph, they appear spectroscopically like wide moustaches with a gap in the mid-
dle. This strange and tiny feature typically occurs at the center of the EFR or in the
edges of spots - where the field is breaking the surface.
Solar Flares
are intense, abrupt releases of energy which occur in areas where the
magnetic field is changing by flux
emergence or sunspot motion.
Stresses in lines of force build up slow-
ly and are released in flares. They
occur most frequently at neutral lines
where a filament is supported by hor-
izontal sheared field lines. This event
can only take place along a magnetic inversion line. When many lines of force are
involved, two ribbons of emission appear, brightening simultaneously.
Emerging Flux Regions:
An area on the Sun where a magnetic dipole, or "flux tube"
is surfacing on the disk, eventually producing a bipolar sunspot group. Each pole of
an EFR is often marked by pores or
small developing sunspots. Surges or
even small solar flares can sometimes
occur in EFRs. An EFR emerges with
small bright H region with little surges,
then weak arch filaments (AFS) over
bright plage connect small spots on each dipole. Growth is rapid, forming in just a
few hours.
Operating temperature:
The SolaREDi is operable on-band in a tempera-
ture range of approximately 40°F. In climate conditions below the minimum
operating temperature of the SolaREDi, the filter will not operate on-band.
A heating strip can be applied at the barrel section containing the black
screw. This will allow users to increase the operative temperature range of
the instrument. DayStar filters recommends the Kendrick Astro Systems
product line, in particular, the Kendrick Firelite heater is a compact, inex-
pensive and effective accessory.
The SolaREDi telescope assembly may also change temperature and
require settling time when first removed from its storage and placed into
use.
Also, during the day, as the temperature of your SolaREDi telescope
increases, you may need to adjust the tuning action in order to stay at
6562.8Å.
Tuning / Tilting action:
The optical filter assembly stack is located in the
eyepiece barrel before the eye-
piece. It is mounted on pivot
points which allow the assembly
to tilt. The red headed thumb-
screw on the side of this barrel
will cause the optical assembly
to tilt, and change the wave-
length of light exiting the filter.
Your optical image will not
move or need re-focusing with
this tilt.
Filtration and safety:
The optical solar filter stack is mounted at the rear, eye-
piece end of the SolaREDi alpha telescope. Alone, it provides off-band
rejection density greater than 6.0 from X-ray to beyond 2 microns. This means
that it is safe to look directly into the rear of a properly assembled SolaREDi
alpha telescope without an eyepiece. The SolaREDi alpha telescope
requires no additional blocking filters or special diagonals or eyepieces and
unless it is disassembled with tools, the telescope cannot be rendered unsafe.
Should any element of the filter age or degrade, that degradation would
cause a darkening of the image and not an unsafe filtration.
