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Thursday, January 8, 2009

QHY9 & Canon EF 200mm f1.8 "Startest"

NOTE,
The JPG image is large, 2,7mb.
(You have to load the image from Picassa to see it in Full Resolution.)
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NOTE2,
The image looks litle soft. It's not doe the optics or focus but
very low altitude of the object up here North.
The maximum elevation was 29 degrees when Rosette was imaged.
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Here is a single five minute exposure about Rosette Nebula.
Stars are pinpoint from edge to edge. I haven't test the Chromatic aberration
yet, since I'm shooting narrowband at the moment.
There should be very litle of it doe the exotic class in the lens system.
You can read more about it from here:
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On the lower left corner stars are somehow stretched, thats not an optical flaw.
That happends when the camera is no absolute perpendicular to the lens.
The critical focus zone is only 7/1000mm and even slightest tilt can be seen in the image.
I'll correct thet later by rotating the camera in M42 0.75mm thread to an
other position.
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This is a single calibrated 5min. image.
Flat, Bias and One Dark frame for bad pixels is used.
Image is then stretched and converted to 8bit doe the JPG algorithm.
No other image processing is done.
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DETAILS:
Optics, Canon EF 200mm f1.8L @ f1.8
Camera, QHY9 astro camera
Guiding, QHY5 and PHD-Guiding on LX200 GPS 12"
Exposure, 1x300s
Filter, Baader 7nm H-alpha

2 comments:

alexander297 said...

Did u use the QHY9 with a filter wheel in this imaging session?
What the backfocus enough?

J-P Metsävainio said...

No, there isn't enough back focus, my QHY FW is about one mm too thick. I'm using a filter drawer system, neuman something, with this lens.