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Sunday, April 21, 2013

A collection of images, Canon EF 200mm f1.8 optics

I have couple of high quality camera lenses for astronomical imaging, Tokina AT-X 300mm f2.8 and Canon EF 200mm f1.8.  Both lenses are wonderful instruments for an astronomical work, I always use them both full open. 

Focusing under a  fast f-number is very difficult task due to extremely narrow critical focus zone (At f1.8 the critical focus zone is around 7 microns, 7/1000mm) I have build an automatic focusing system for all camera lenses, images of it can be seen HERE and HEREThe system also compensates the temperature drift.

An other challenge is orthogonality between CCD-shell and optics. With slower optics this is not much a problem but with extremely fast optics a micron scale accuracy is needed. I have done hundreds of iterations with the CCDInspector  software to have my Canon EF 200mm f1.8 optics perpendicular with QHY9 camera. NOTE! There is nothing wrong with any mechanical part in a camera or the lens, the needed accuracy is just so high, that micron scale errors are seen, for example a protective glass over the CCD-array has a manufacturing  tolerance of 1/100mm and that's enough to course problems in orthogonality. (Well... I'm kind of perfectionist and most photographers doesn't see any problems with fast optics, I do.)

A collection of  my images with the Canon EF 200mm f1.8 optics
Images are shot between  2009-2012

Be sure to click the image larger! Note, a large file ~6MB

Canon EF 200mm f1.8

Canon EF lens Modification for the astronomical use

Since the Canon EF 200mm f1.8 lens is electronically focused and I'm using it without Canon camera body, I had to modified the lens to it to work. Be warned, the modification image series, behind the link HERE, is not for a weak minded persons!!!

Lens in use

Largest work with the Canon lens
A 18-panel mosaic of constellation Cygnus

More information and images of this project can be seen HERE.

Cygnus mosaic in frames

More info about the framed photo:

A collection of  my images with the Tokina AT-X 300mm f2.8 optics
Images are shot between  2008-2011

Be sure to click the image larger!
I have made a collection of Tokina AT-X 300mm f2.8 image as well. Images are partly over lapping with the canon collection, since I have used both instruments, Canon and Tokina, to collect the data.

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