DayStar Filters SolaREDi Manual - Page 8

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A word about daytime seeing and limiting resolution:

During the daytime, radiant heating from the sun affects seeing significantly.

Characterized by turbulence or shimmering as seen over a hot street, seeing

can cause significant impact on quality of solar observations.

Bad seeing is caused by air of different temperatures mixing. This typically

happens within the lowest 10 feet of air. It occurs most often over pavement,

dark objects, rooftops and sometimes trees.

High cirrus clouds or "scuz" will cause scattering of sunlight in the high atmos-

phere which often makes for bad viewing conditions. A classic sign of high

cirrus clouds is the inability to achieve focus, or the need to "chase focus".

A jet-stream moving overhead can also hurt seeing conditions even on a

clear day.

While many of these conditions are beyond our control, observing in an area

with ideal conditions without pavement in the direction of viewing and on

days with no high cirrus will offer best results. Grass is the best environment for

daytime seeing stability.

The SolaREDi 60mm has a limiting resolution at 6562.8 of approximately 2.8

arc seconds. Over-magnification of the image will have resolution limitations

in which features can not be resolved. Also note that the sun's limb in hydro-

gen alpha is soft, with a fuzzy layer of chromosphere surrounding the surface.

Using eyepieces higher than 12mm in power, it is challenging to achieve

focus on the limb. For users who are interested in higher magnification, we

suggest one of our other models of T-Scanner or Quantum DayStar filters

which can mount to your existing telescope and be used up to 6.5" in clear

aperture.

Bandpass Expectations:

0.7Å users will find that prominences are easily

visible and very well-pronounced with a 0.7Å fil-

ter. Surface structure is not very contrasted, but

it is possible to see mottling on the surface and

large flares, plages and active regions.

0.5Å users will see prominences but not quite as

broad as with a 0.7Å due to wing shift in the

prominence. Surface detail will be much

stronger with a 0.5Å, revealing more detail in

active regions, filaments, spicule, and all other

features.

0.3Å users will see only very thin, hairline promi-

nences, but surface contrast will be very

defined and sharp. Soft chromosphere will

appear in highest detail with .3Å.

Features of the Sun in Hydrogen Alpha

By observing the sun with a narrow bandpass filter tuned to 6562.8Å, we can

observe the behavior of the Sun's Chromosphere. The chromosphere is like a

shell of gas around the Sun's

photosphere, always moving

and changing. The chromos-

phere's structure behaves differ-

ently in active regions than quiet

areas, where magnetic field

lines are stronger. Thought to be

tied to the photosphere, the chromosphere is governed by magnetic forces

and, yet it still has its own IntraNetwork (IN) of material oscillating every 5 min-

utes.

On the limb, even a rather wide

filter of 1Å or more will show

prominences, a detail of the

chromosphere

projected

against the dark black contrast

of space. To observe the details

of chromosphere on the face of

the sun, we need a narrower fil-

ter to eliminate more off-band light of the photosphere and continuum. We

need a filter less than 1.0Å. The narrower the filter's bandpass, the more con-

trast we will see - down to 0.4Å, where prominence structure is reduced due

to high velocity and subsequent wing shift.

Spicules

dominate the chromos-

phere in non-active regions and

have been studied exhaustively.

They are barely visible, last only

about 15 minutes, and resemble

a "burning prarie".

Some jets

can be seen shooting 10,000 km

up from the Sun's limb at velocities of about 30km/sec. Studied exhaustively,

they present a number of observing challenges, as they are too small to

resolve and move so quickly as to present wing-shift challenges.

Field Transition Arches (FTA's)

connect P and F spots - ele-

ments

opposite

polarity.

Inside an active region, where

sunspots are originally linked by

a FTA, a shear boundary forms.

Field Transition Arches are differ-

ent from filaments in that they

are thin and not very dark. The

FTA usually has plage or granular

structure underneath.