Observing Surface Features of the Sun for Amateur
Astronomers
Nikhil Anand

Mustafa Shahid

B.Tech Aerospace Engineering, IV Sem
Indian Institute of Space Science and Technology
Email: nikhil.myindia@gmail.com

B.Tech Avioncs, IV Sem
Indian Institute of Space Science and Technology
Email: mustafashahid4@googlemail.com

Abstract—Viewing the sun through a telescope is a very underrated astronomical practice. This paper will focus in detail on the relevance and significance of observing the sun. The various features on the sun are explained along with appropriate methodologies for safely viewing them. Three techniques are deployed to safely observe the sun. Further scope and interpretations of this experiment are also discussed.

I. I NTRODUCTION
Looking at the sun with naked eyes can be extremely dangerous, but with the right equipment, several interesting features of the sun can be revealed. Some of the notable features include sunspots, granulation and corona of the sun.

To view the surface, three techniques are used. each has its own advantage.
A. Surface features
1) Sun Spots : Sunspots are temporary phenomena on the photosphere of the Sun that appear visibly as dark spots on the surface. They correspond to concentrations of magnetic field that inhibit convection and result in reduced surface temperature compared to the surrounding photosphere.
Sunspots usually appear as pairs, with each spot having the opposite magnetic polarity of the other.

2) Granulation: The grainy appearance of the solar photosphere is produced by the tops of these convective cells and is called granulation.
The rising part of the granules is located in the center where the plasma is hotter. The outer edge of the granules is darker due to the cooler descending plasma. In addition to the visible appearance, which would be explained by convective motion.
3) Corona: A corona is an aura of plasma that surrounds the Sun. The Sun’s corona extends millions of kilometres into space and is most easily seen during a total solar eclipse.

B. Filters
The best way of looking at the sun safely is through a solar filter. There are two types of solar filters:
1) White light Filters
2) H-Alpha Filters
White light solar filters are simply very dark neutral density filters. These allow you to see sunspots on the surface of the sun and are ideal for viewing solar eclipses and transits of
Mercury or Venus.
Hydrogen-alpha filters are narrowband filters. Solar flares, prominences, and other associated activity can be viewed through them.

II. E QUIPMENTS
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Celestron Powerseeker 70AZ
Refracting Telescope
Focal Length : 700 mm;Eyepiece : 35 mm
Galileo Startracker 5.3 inch Newtonian Reflector
Focal Length : 900 mm Eyepiece : 25 mm
Solar Mylar Filters
X-Ray Sheets

III. M ETHODOLOGY
1) Using X-Ray sheets - Refracting Telescope
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Cut the X-ray sheet into a disc of area greater than the aperture of the primary lens of the telescope.
With the help of a cello tape attach it in front of the primary lens.
Using tinted sunglasses, carefully orient the telescope towards the sun.
Look through the eyepiece and try to bring the image into focus.
Once brought into focus, sunspots and granulation on the surface can easily be observed.

2) X-ray sheet filter obstructs only the visible light. IR rays can still pass through. However if the image is seen only for a short duration, the damage can be reduced. Tinted sunglasses were used to view through the eyepiece. The image formed was Similar to as through the solar filters , but the granulation was visible.
Sun spots were distinctly visible. Two as dots and one as a wavy flare. Observation was also tried without the tinted sunglasses, the image was too bright to be seen even for a few seconds, but the granulation in this case was evident. The atmospheric contour is visible in this method as well.

To focus the image on a screen, take a box and cover the inside of the base with white paper. Bring the box closer to the eyepiece and focus the image on the screen.
By moving the box closer or farther from the eyepiece, try to focus a sharp image on the screen.
2) Using Solar Filters - Reflecting Telescope
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Hold the solar filter in your hands and look at an incandescent bulb to check for any defects
The above step is extremely important as if any defects such as holes exist on the filter, looking at the sun through them can cause serious damage to the eye.
Once the absence of any kind of defect is ensured, mount the filter in front of the telescope.
Again using tinted sunglasses, carefully orient the telescope towards the sun.
Look through the eyepiece and try to bring the image into focus.
Once brought into focus, sunspots on the surface can easily be observed.
IV. O BSERVATIONS

1) Solar filters are the safest way to observe the sun, however they reduce the brightness of the image. Hence making it difficult to distinguish the granulation on the sun surface. A dark contour is visible , proving the sun has an atmosphere. The sunspots were clearly visible but were a bit dim as compared to the X-ray sheet method.

3) Projection of the image without enclosure generated a bright point when in focus which diffused into a circle when the screen was moved away. It was inconclusive whether the image quality diminished due to the background light or lack of focus. The next time projection was tried with enclosure. In this case the point was really bright and well formed. Upon moving the screen, the image was well defined till some point and then deteriorated. This is a good method but the main features like sunspots, granulation and the atmospheric contour are not visible at all. Eclipses can be observed and tracked with great accuracy using this method.

V. R ESULTS
1) Comparison between the three techniques

2) Verification of distance. 1 r2 dependence of image formation vs

VI. D ISCUSSION
1) Develop new techniques and materials for amateur astronomers to view the sun.
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Using appropriate welders glass

2) Determine differential rotational period of sun by monitoring position of sunspots.
Solar rotation is able to vary with latitude because the
Sun is composed of a gaseous plasma. The rate of rotation is observed to be fastest at the equator, and to decrease as latitude increases.
3) Observing solar flares/ coronal mass ejections
4) View solar eclipses
A solar eclipse occurs when the Moon, during its monthly revolution around Earth, happens to line up exactly between Earth and the Sun
5) View Mercury transit
A transit of Mercury across the Sun takes place when the planet Mercury comes between the Sun and the Earth, and Mercury is seen as a small black dot moving across the face of the Sun.
ACKNOWLEDGMENT
The authors would like to thank...
R EFERENCES
A
[1] H. Kopka and P. W. Daly, A Guide to LTEX, 3rd ed.
Addison-Wesley, 1999.

Harlow, England: