Quote:
Originally Posted by Bassnut
Rob
There is pretty severe diagonal drift (eggy stars), and, it seems some really woofy extremes which maybe due to wind. The odd thing is, the error is opposite in the 2 images, did you rotate one?. .
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Hi Fred,
Aha, I get it! The two images are crops from the upper right corner of larger images, and haven't been rotated. I wanted to show the differences in star shape at the edge of the field with and without a flattener. So the eggy stars may not be guiding errors, they're probably coma in the case of prime focus and, I think, astigmatism with the P-FlatIII. No image rotation, it's just the stars in the corners are a different shape with and without the flattener.
So, maybe my guiding is OK, which would be a relief.
FL of the ED80 imager is 600mm, FL of the guidscope is 400mm. Pixel size of the webcam and 400d DSLR are the same from memory, 5.7um.
I wonder if other ED80/DSLR users crop the images to remove the distortion at the edge of field. Anyone?
Cheers,
Rob