presentation in pdf format 25/03/2006,07:47 3.37 Mb - EU-HOU

Logo: Armella Leung, www.armella.fr.to
mgr Monika Chudy
mgr inż. Łukasz Maślaniec
The Youth Astronomical Observatory at Niepołomice
translated by Robert M. Sadowski
This project has been funded with support from
the European Commission.
This publication reflects the views only of the author,
and the Commission cannot be held responsible for any use
which may be made of the information contained therein.
SAFETY FIRST !!!
IMPORTANT INFORMATION!
NEVER LOOK DIRECTLY AT THE SUN WITH
UNPROTECTED EYES - THIS MAY CAUSE TOTAL
BLINDNESS WITHIN SECONDS! ALWAYS BE SURE TO
USE PROPER OPTICAL FILTERS TO PROTECT YOUR
EYES. NEVER LOOK DIRECTLY THROUGH A
TELESCOPE TOWARDS THE SUN!
9 On a clear day we can see the Sun as a blazing disk of
some 0.5º in diameter.
9 The average distance The Earth – The Sun is equal to
149600000 km.
9 Knowing the both quantities one can calculate the true
diameter of the Sun (1 392 000 km).
9 In the 17th century it was observed that the Sun turns
around its axis every 28 days approximately, in the
same direction as the Earth – from the West to the East.
9 As the Sun is not a solid body, its different parts rotate
at different rate, depending on their distance from the
solar equator. The rotation period changes from 31
days near to the poles to 27 days in vicinity of the
equator.
Direct observation of the
Sun may cause
a permanent sight
damage,
so we have to apply the
proper protections against
its light.
The only safe method to
observe the solar disk is
projecting its image onto
the screen or using the
special filter.
The necessary equipment:
• A webcamera with the CCD matrix
• An adaption ring to connect the
camera with photolens
• A photolens or a telescope
• Photographic
tripod
or
an
astronomical paralactic mounting
• A Computer
+
The
photolens
+
Adaption ring to connect
the camera with
photolens (here with M42
thread)
The
webcamera
Telephotolens Pentacon f=500mm + webcamera Philips ToUcam Pro 840k
The focal length has to be chosen in accordance to your planned
observations, but remember - as longer f as smaller is the
available field of vision.
In the table beside the focal lengths of the most
popular photo lenses were put against the fields
of visions available with them.
Remember however that the given values refer
to the standard photo frame of size 36x24 mm,
while the size of the CCD element is much
smaller – for the webcamera Philips ToUcam
Pro 840k it is 4,6 x 3,97mm, for example.
Therefore for f = 500mm we could obtain field
of vision equal to 0.5 degree, and for f =
1000mm it still covered 16 minutes.
Focal length f
[mm]
Field of
vision
[°]
35
63
50
46
105
23
300
8
500
5
1000
2,5
The photographic tripod
with universal head
The tripod with
paralactic mount
Distance scale – for the sky observations this
usually should be set up to infinity
Aperture size – controls an amount of the incoming
light; in this lens, for example, the value 2 means the
diaphragm fully opened (maximal amount of light
comes into the camera), while the number 16 means
the smallest possible opening (minimal amount of the
incoming light).
A few examples of the aperture
sizes:
2
5,6
16
For the observations of the Sun the filter is
INDISPENSABLE
to protect your eyes as well as your equipment
As the special photographic filters are expensive, you can do it
yourself, using the Baader Planetarium foil
This filter is not intended for the visual
observations of the Sun!!!
Incorrect assembly may cause the serious
damage to your webcamera!!!
The Baader Planetarium foil is available at the photo and
astronomical shops.
Sold in big rolls or in retail quantities.
To make the Sun filter you may use any
demountable optical filter that fits to your
lens size. Of this you will use the rings
only.
Screw out the internal ring and remove
the original glass from it..
Cut out of the Baader foil the circle with diameter
just to fit the metal ring. A stiff cardboard ring will
help to fix it firmly in the mounting.
Replace the original
glass with assembled
element and screw in
both metal rings tightly
together.
The tripod with paralactic mounting and tracking system, the
telephoto lens MTO-1000/10, the webcamera Philips 840k ToUcam
II, the laptop computer
9A program to capture the video signal
from the webcamera (the application
K3CCDTools, for example)
9A program for the image digital
processing (the application RegiStax, for
example)
1. Choose the suitable place with visibility undiscriminated
by any trees or buildings.
2. Put up the tripod and mount the lens, but turn it off the
Sun.
3. Put the filter in place.
4. Mount the webcamera in place.
5. Connect the computer and plug in all the necessary
cables.
6. Check it all once again, in particular correct mounting of
the filter!
7. Start the webcamera software.
8. Turn the lens to the Sun.
To keep the records on:
Date of observation
Place of observation
Name of the observed object
Name of the observer
Method of observation
Specifications of your
equipment
9 Other important remarks
9
9
9
9
9
9
The K3CCDTools
Program
Okno główne
programu
On/Off button of the
webcamera image preview
The webcamera
image preview
window
I have my preview on, but still I
can’t see any image …..
Select the driver responsible for
video capture
In the „Video Source…” window select
the device, from which the image will
be captured.
(In this case it is the webcamera
Philips ToUcam Pro)
Still nothing…..
Maybe the image is just too dark?
On your toolbar there is a
shortcut opening the „video
source” window
Turn the auto mode off
Shutter speed
Gain
Manipulating with the above
parameters find the settings for the
best image.
Before starting ……
…let’s check the options.
Name the directory to save
the captured frames
Write in the name for the
saved files
Capturing images from the
webcamera
Select the number of
frames to be
captured per second
– the recommended
value is 5
frames/sec.
Save a series (300 for example) frames to the
avi file. The ESC key breaks this process.
Of course, each frame may be saved
individually as a bitmap, but keeping them
together in one file is more practical.
It is not all yet, because …
Apart from the series of frames with image of the observed object
(e.g. sunspots) you have to create :
•The dark frame – A frame taken with totally closed lens but at the same
settings as for the observations. It is to be subtracted during the digital
image processing to minimize noise due to the so-called dark current and
to remove the „hot pixels”.
•The flat field – A frame with image of the uniformly illuminated area (the
clear evening sky, for example). During the digital image processing the
images will be divided by it in order to remove noise, due to the unequal
pixel’s sensitivity.
In both cases you will need, as for the observations, to save a series (100,
for example) of frames.
You may process digitally the results of your
observations with help of any available
software – the application RegiStax, for
example.
Creating the darkframe and the
flatfield
Click the „select” button
Select a file with dark
frames
Choose „Create Darkframe” option from the
Flat/Dark menu
When the program is
finished with calculations
save the results as a
bitmap
Create the flatfield in analogous way,
selecting only from the menu the option
„Create Flatfield”
Digital processing of the observational
data
Load the
previously
created
„darkframe”
and „flatfield”
files.
Click on their usage at
the calculations
Load the file with images of the
observed object (the Sun, for
example).
With a help of slider you can
review all the frames, of
which select the best one.
Mark on that frame an object
with interesting details (a
sunspot, for example). Be
careful to mark the area big
enough to find the selected
object on this frame only.
Select size of the area to which
the frames are to be aligned.
Select the method
(gradient, for example)
of the frames aligning.
Push the
button „Align”,
and then „Limit”
Push the button
„Optimize&Stack”
Initially you may use the
recommended FFT settings. If
the results will prove
unsatisfactory however switch
on to the manual setting.
Put the sliders of the
particular layers into
postions to achieve
the best possible
result.
To improve your image you may
use the tools, known from the
other popular graphic
applications.
Finally push the „Do All”
button
The last bookmark
„Final” – here you
can do the last
corrections. The
processing should be
closed by pushing
the „Save image”
button.
9 There are different signs of solar activity such as the sunspots, the
protuberances, and the chromospheric flares.
9 The sunspots were known already in antiquity. They are mentioned in the
Chinese records as well as in the relations of the British sailors and the old
Russian chroniclers.
9 Actually the sunspots are just the darker areas in solar photosphere of size
from a few to 100.000 km and lifetime from tenths of days to a few months.
9 The central part (umbra) of the sunspot and its immediate vicinity
(penumbra) are some 1500oC cooler than the surrounding photosphere
(that’s why the sunspots seem to be so dark in spite of theit high
temperature).
9 The sunspots are related to the magnetic field, and their pairs have always
opposite polarities.
9 Groups of the sunspots emerge suddenly. Usually we can see two spots, in
whose vicinity the smaller spots appear gradually. Their number grows
steadily by 2-3 weeks, reaching a maximum, and then again falls down.
9 In the 1st half of the 19th century Samuel Heinrich Schwabe (1789 – 1875 )
has observed that the number of sunspots varies periodically, reaching its
maximum every 11 years.
9 The solution of this problem is due to Rudolf Wolf (1816 – 1893).
9
9
9
9
9
9
9
9
The sunspots are surrounded by the photospheric flares, brighter than the
undisturbed photosphere (what means that they are hotter than their
neighbourhood, in opposition to the sunspots).
The flares appear a few weeks before the accompanying sunspots, and
may outlive them even by a few months.
The scientists believe that many features of the Earth’s climate depend on
fluctuations of so called Wolf number.
What influences the changes of the solar activity – number of the sunspots
or rather their groups?
Influence of both of these phenomena had been united by Rudolf Wolf
(1816 – 1893)
On the basis of observations of the sunspots, documented since 1700, we
can state that the solar activity shows 11(or more precisely 11.3) years’
periodicity.
Its last minimum occurred in 1996.
The last maximum was in 2001, and overlapped part of the next year.
9 Swiss astronomer
9 He devoted all his life for
investigation the changes of the
solar activity and its relations to
the Earth’s magnetism.
9 Today the scientists believe that
many features of the Earth’s
climate depend on fluctuations of
so called Wolf number.
It is a measure of the solar activity, calculated as follows :
W = (10g + p)k
where:
g – number of groups
p – number of sunspots
k – a correction coefficient, enabling comparison of the results, obtained by the
different observers.
9 Groups of the sunspots emerge suddenly. Usually we can see two spots, in
whose vicinity the smaller spots appear gradually. Their number grows
steadily by 2-3 weeks, reaching a maximum, and then again falls down.
9 In the 1st half of the 19th century Samuel Heinrich Schwabe (1789 – 1875 )
has observed that the number of sunspots varies periodically, reaching its
maximum every 11 years.
9 The solution of this problem is due to Rudolf Wolf (1816 – 1893).
g=1
p=37
Number of
groups
g=1
Number of
sunspots
p = 37
g=2
p=2
g=1
p=1
g=2
p=2
Number of groups
g=7
Number of
sunspots
p=7
The Wolf number
W = 77
g=2
p=2
With help of the described above simple equipment
you can do many observations of the Sun, from the
films and photographs to more advanced forms, such
as an animation of the sunspot’s life story, for
example.
Doing such observations by yourself can bring about
considerable cognitive and didactic advantages for the
school children.
We invite everybody to experiment on your own.
Finally, let’s watch some photos made during our
observations.
f = 1000mm
f = 500 mm