January 11 2007 - First DSLR astrophotos (the sun)

These are the first astrophotos that I have taken through the telescope with my new canon Digital rebel XT DSLR camera. Here are three comparison shots of the sun all with the exact same processing and all with 20 stackked shots. The only difference here is the iso settings and exposures. Clearly you can see a difference between the three with the middle one probably being the best of the three. The one on the left was taken at ISO 100 with a 1/250 sec exposure. the middle one was taken at ISO 400 with a 1/1000 sec exposure and the right picture is taken at ISO 1600 with a 1/4000 second exposure. All shots taken with an 80mm celestron telescope. My theory was that If i increase the ISO, i would be able to decrease the exposures time (ie 1/4000 sec) which in theory would provide for sharper images. But when you increase the ISO you also increase the amount of noise and grainyness of the images thus decuting from the sharpness of the image. Results show that the best setting is probably ISO 200 - ISO 400 which provide a good balance between fast shutter speeds and litle grainyness. I think most of my future planetary images with the DSLR will be done either at ISO200 or ISO400.

PS I apologize for the large size. Blogger will not directly let me upload any images all the sudden so I am using photobucket for the time being. I will look for other alternatives so that i can upload a small image and then you will be able to click for the larger image if you want.