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Asteroid Hunting

June 30, 2012  •  Leave a Comment

Conjunctions near Dawn [APOD]

I usually don't photograph asteroids and I've never hunted for asteroids before. In Nightscape photography it's quite difficult to find a way to show an asteroid in a beautiful context. They are just too dim. I missed a chance when Vesta was really bright and easy to see with the naked eye a few years ago due to weather and I thought that was all between me an asteroids.

But while photographing the cojunction between Jupiter, Venus and Aldebaran I found, with surprise, that asteroids Ceres and Vesta were both in the same field of view as the conjunction. At magnitudes 7.85 (Vesta) and 8.6 (Ceres) they were not visible to the naked eye but should be easy to capture them with the camera. I know I can get up to magnitude 11 or even more with a long exposure and my cameras so the hunting begun.

In my first try it was easy to capture Ceres as it was near Jupiter but my field of view was not large enough for Vesta. I used stellarium to see where Vesta was supossed to be and determine which bright stars should be included in the frame to capture both asteroids. I found the star f-Tau a magnitude 4 star was just above Vesta so including f-Tau should also include Vesta. Another early wake up and another try.

After taking the photos I used stellarium again to recognize the star-field and find the Asteroids. Vesta was a very easy find located below f-tau as expected. Ceres was dimmer but appeared clear in the photo too. Now it was 2 out of 2. I got Jupiter, Venus, Ceres and Vesta in the same photo along with the Pleaiades, Hyades and Aldebaran. If you like conjunctions as I do you will realize this was fun.

I kept shooting until sunrise and I was very surprised to find that the asteroids were still visible in the photos in the glae of dawn. The horizon was very bright and they sky turned a definitive blue but yet the brightest stars were visible to the naked eye and the two dim asteroids were also visible in the photo. This is the first time I've seen asteroids in a scene that is not taken at night time. 

If you want to get Ceres and Vesta use Stellarium to find references near them to help you frame the shot. Use a 50mm or higher focal lens as the longer the focal length the more light you will be able to capture shoot as long as you can avoiding trails at the widest aperture you can use to avoid comma in the borders. Pump the ISO as needed, usually up to 1600.

I'll keep shooting this conjunction waiting for the Moon to join the show on July 14th and 15th. Both Ceres and Vesta will still be in the field of view, now that will be quite a grouping!


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