Category

Visibility of the Stars 1

Introduction

Here we will show that changing the observing latitude alters both the appearance of constellations, and the constellations which can be seen

　To understand how the appearance of the night sky changes with latitude, we need to move on from the concept of observing the celestial sphere from the Earth's surface, and instead imagine looking down on an observer standing on the surface of the Earth from a point in space.
　However, understanding the concept will be the most difficult part of this experiment. With the aid of a model, and by acquiring images of the night sky, it will be possible to appreciate the way its appearance changes with location.
　In this classroom exercise, a webcam is installed in a globe of the Earth, and with it the figure of Orion is photographed. The webcam was installed in the model to represent the point of view of an observer, and since you can actually see this point of view as an image, it will be an aid to understanding.
　The target object to be observed was chosen to be Orion as pupils will be familiar with this at primary school level. Additionally, this constellation is visible from both the northern and southern hemisphere, but with a noticeably different appearance in each.

Experimental Method

Is the appearance of constellations the same from different locations?

　Are the same stars visible in Japan and Australia?
　As seen from Japan, stars which are visible in the southern part of the sky will also be visible in Australia.
(e.g. Scorpius in summer, and Orion in winter)

　So, when Orion is observed from Australia, how will it appear?
　Will it look the same as it does from Japan?

Things to Prepare

Webcam; computer; globe; figure of Orion; two small dolls; photograph of Orion as seen from Japan

←Creative Inc. WEBCAM5

Experimental Procedure

1. Acquire a photograph of Orion taken from Japan.
   
2. Attach the figure of Orion on the blackboard.
   
3. Mount a doll on the globe to represent an observer in Japan.
   
4. Mount a doll on the globe to represent an observer in Australia.
   -> With these dolls you will be able to see that from Japan, Orion will be visible in the southern part of the sky, while from Australia, Orion is visible in the north.
   
5. Orient the webcam to coincide with the view from the doll representing an observer in Japan, and take some photos.
   
6. Orient the webcam to coincide with give the view from the doll representing an observer in Australia, and take some photos.

Experimental Results

How did Orion appear through the Webcam?

　On the left is shown the figure of Orion as viewed from the observer in Japan (i.e. northern hemisphere) and on the right we see the view of the Orion figure obtained from the observer in Australia (i.e. southern hemisphere).
The view of Orion obtained from Japan is not dissimilar to the way we are used to seeing the constellation in the sky. However, we can see that as viewed from Australia, Orion is upside down relative to the view from Japan.

Photos & Figures

Diagram of Orion	Detailed figure of Orion (click for larger view)	Photo of Orion Taken on 2002 Dec 17 from the roof of MUE using a cooled CCD camera. Click on image for larger version. (Credit: Kazutaka Yoshida)