In a Galaxy Far, Far Away… Welcome to South Mountain Astronomy Club

By Alex Nachman

Welcome to the first South Mountain Astronomy Club blog post!

Nestled in the valley of South Mountain Park in Phoenix, AZ, our South Mountain Environmental Education Center is home to ODSI. Installed in September of 2018, ODSI stands for Optical Deep Space Imaging and is a telescope that can see deep into outer space.

This is a Celestron telescope that uses an equatorial mount in order to explore the cosmos. Mounted in a valley between two ridgelines, the mountains keep the city light pollution at bay and allow for some beautiful night sky imaging!

The telescope that ODSI uses is a compound, or catadioptric, telescope that uses two mirrors and a lens, rather than just one or the other. This allows for a relatively short tube but a large diameter viewing distance which makes the telescope very easy to transport. Due to its unique properties, this telescope can not only image planets and stars, but deep space objects like galaxies and nebulas that can be tens of millions of light years away.

The focal length on this telescope can even change to give perfect viewing conditions for a close object or an object very far away. The focal length tells how large of an area can be captured and the magnification of objects in that area. When both mirrors and the lens are used in ODSI, the telescope has a focal length of 10, meaning it can image close objects like the planets. With one mirror removed, the secondary mirror, ODSI has a focal length of 2 and can image far away galaxies!

The larger the focal length number, the field of view becomes narrower and thus images will have a higher magnification. The lower the focal length number, the field of view becomes larger and thus the images have a lower magnification but can be seen much further away. So when the telescope has a focal length of 10 it has a narrower field of view and can, thus, image closer objects. When the focal length is shorter, at 2, it has a much larger field of view and can image objects further away, like galaxies.

One recent feat that ODSI accomplished was an image of the Orion nebula. Using the native focal length of 10, ODSI acted as huge lens for the camera. The Orion nebula is a diffuse nebula only 1,344 light years away. This makes it one of the closest nebulas to Earth and makes for easy viewing through ODSI. The Orion nebula is huge gaseous cloud where star formation is occurring. Using a DSLR camera and a 30 second exposure, ODSI was able to get a beautiful shot of the nebula, pictured below.

Come learn how to take photos with ODSI and learn all about space science with our club. We hold monthly meetings as well as telescope play time! If you are interested in learning more about astrophotography, topics about space, how to master ODSI, or joining our club, please visit our website!

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