Teapot Asterism In Sagittarius


Teapot Asterism

This wide angle photo of the Teapot Asterism was produced by stacking 4 photos taken on
August 21, 2017 at about
10 pm EDT with a Canon Power Shot 8 megapixel camera.  The exposures were 10 seconds long and taken at ISO 400.  A tripod was used and a two second exposure delay was set after shutter release to eliminate camera motion.  The focus was fixed at infinity and flash was suppressed.

Sky Safari Screenshot of Teapot Asterism


Ten seconds is about as long an exposure that is possible with a fixed camera before rotation causes the star images to streak.  ISO settings above 400 introduce a lot of noise.

Stacking was done with Nebulosity 4 using the command sequence: Open File-Batch-Align and Combine Images-Translation, Rotation and Scale.  Images were translated so epsilon Sagittarius in the lower right were aligned, and rotated and scaled so sigma Sagittarius matched.  In stacking images at low altitude it is best to choose two alignment stars near stars you are interested in rather than stars near the corners of the image.  Saving as a FITS file was cancelled in favor of saving as a JPEG file.  The Display Auto box was unchecked and a Black level of 25000 and a White level of 26000 set to eliminate remaining noise and brighten the intensity of the stars.  The images were then cropped using Paint to show only the Teapot.

— Bernie Young