Thursday 28 June 2012

2012-06-24: Andromeda Galaxy (M31)

Last Saturday I captured this image of the Andromeda Galaxy (M31) from Boada, Salamanca, Spain. The equipment used was a Canon 550D, a 200mm SIGMA APO teleobjective with an exposure of 60 secs at ISO 12500. The Celestron CG5 mount was used to perform the tracking.

The used teleobjective is apochromatic and it is quite convenient for astrophotography.  However, I have discovered that the field is not flat enough. Although I cropped the image the distortion is clear. As Miguel commented,  it is an empirical assessment about something that astronomers knew long time ago: you must use a telescope, i.e. a large optical length to achieve a flat field close to the axis.... It has been sacrificed in standard photography... so, forget to use all the photographic stuff for astro!!!!!