Daily Image
23-09-2014
North America and the Pelican
| Submitter: | Albert van Duin |
| Description: | At the end of summer, when the nights are getting longer and darker, the constellation of Cygnus, with all its beautiful emission nebulae, is visible high above our heads. An ideal target for testing a new astrographic telescope, designed and built by Rik ter Horst. It's a unique design, a corrected Schmidt-Newtonian with a 300mm mirror and a fully corrected field of almost 4 degrees. The photographical speed is F/2.5, so you can really make "snapshots" with the attached (H-alpha modified) Canon 5D MKII, a digital single-lens reflex camera with a full frame 24x36mm sensor. Adjusting such a fast optical system is not easy, the depth of field at focus is only 17 micron, so the tilt of the imaging sensor has to be precisely adjusted to get sharp star images across the entire field. The image above is a mosaic made from two completely different integrations. The left part was exposed for 15 x 60 seconds at 1600ISO, the right part 12 x 300seconds at 400ISO, as a result the latter has much less noise. A mosaic was made using PixInsight software, and it did a very good job equalizing both sides of the image and putting them together seamlessly. The result is a 34 Megapixel image that shows the North America nebula (NGC7000) and to its right the Pelican nebula (IC5070 and IC5067) Flat, dark and bias frames were used for image calibration. |
| Copyright: | astropix.nl |
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