13.4 Practical 9: Exploring the Physics of the Sun
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13.4.1 Aims
In this practical, you will be observing the Sun over a number of days to determine the
evolution of photospheric and chromospheric features, understand limb darkening,
and determine the Sun’s differential rotation rate. In addition, you will learn how to
observe the Sun in a safe manner.
13.4.2 Planning
You will need to observe the Sun over a period of approximately 14 days in order
to determine the Sun’s rotational period. You may have to overcome inherent safety
features that prevent the telescope from pointing at the Sun. Before observing, you
should ensure that the correct filters are fitted and that you understand the procedures
for solar observing at the facility you will be using. It will be beneficial if you can
observe in both hydrogen-alpha and white light if at all possible. The author suggests
that you use a webcam as your image device and that you undertake lucky imaging
in order to improve resolution.
13.4.3 Observing
Ensure that the solar telescope is correctly set up and the required filters are in
place and are undamaged. If the solar telescope is coaxially mounted with another
telescope, ensure that it has its lens cap firmly attached.
Open the dome and point the telescope at the Sun. Many telescope control programs will not let you perform this action. Consequently, you may have to drive the
telescope to position manually; please check with your observatory staff whether you
need to do this, and if so, how it is done. Start your webcam, and using the shadow
of the telescope, nudge the telescope until you see the disk of the Sun. At this point,
you may need to focus the solar telescope and adjust the webcam’s exposure time
(or frame rate), brightness, and gain in order to get a clear image.
Once you are happy with the image, capture approximately 15 s of video. Lucky
image this video file using Registax, for example, to produce a high-resolution image.
Save this image for processing later and then shut down the observatory.
13.4.4 Analysis
Using the images obtained, measure the movement rates of sunspots over the face of
the Sun over the course of 14 days.
191
13.4.1 Aims
In this practical, you will be observing the Sun over a number of days to determine the
evolution of photospheric and chromospheric features, understand limb darkening,
and determine the Sun’s differential rotation rate. In addition, you will learn how to
observe the Sun in a safe manner.
13.4.2 Planning
You will need to observe the Sun over a period of approximately 14 days in order
to determine the Sun’s rotational period. You may have to overcome inherent safety
features that prevent the telescope from pointing at the Sun. Before observing, you
should ensure that the correct filters are fitted and that you understand the procedures
for solar observing at the facility you will be using. It will be beneficial if you can
observe in both hydrogen-alpha and white light if at all possible. The author suggests
that you use a webcam as your image device and that you undertake lucky imaging
in order to improve resolution.
13.4.3 Observing
Ensure that the solar telescope is correctly set up and the required filters are in
place and are undamaged. If the solar telescope is coaxially mounted with another
telescope, ensure that it has its lens cap firmly attached.
Open the dome and point the telescope at the Sun. Many telescope control programs will not let you perform this action. Consequently, you may have to drive the
telescope to position manually; please check with your observatory staff whether you
need to do this, and if so, how it is done. Start your webcam, and using the shadow
of the telescope, nudge the telescope until you see the disk of the Sun. At this point,
you may need to focus the solar telescope and adjust the webcam’s exposure time
(or frame rate), brightness, and gain in order to get a clear image.
Once you are happy with the image, capture approximately 15 s of video. Lucky
image this video file using Registax, for example, to produce a high-resolution image.
Save this image for processing later and then shut down the observatory.
13.4.4 Analysis
Using the images obtained, measure the movement rates of sunspots over the face of
the Sun over the course of 14 days.