Capturing Large Objects with CCD Camera

by Jan Wisniewski

Extended objects are not commonly imaged with CCD cameras because CCD chips are relatively small (unless very expensive) and will cover only small objects at optimal resolution (~2 arcsec./pixel).

To get around this "CCD size problem", shorter focal length can be used to achieve larger field of view while sacrificing resolution:

Mosaic allows an assembly of even larger images using multiple tiles

Step-by step protocol:

The final mosaic assembled as above is to some extend distorted. Each tile is affected by optical distortions of you imaging system. In the above case I used "skewing and translation" to aliogn individual tiles but "rotation and translation" works even better. Due of the large angular size of the resulting mosaic, it will always be somehow distorted on the screen (even if fitted to conform to any of the standard cartographic projections.

Note: Assembly of small mosaics with Photoshop was described article by Robert Gendler & Joel Gelber published in Sky & Telescope (June 1999)

See more examples of large CCD mosaics

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Jan Wisniewski