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Old 11-01-2014, 12:49 PM
avandonk's Avatar

avandonk is offline
Join Date: Aug 2005
Location: Melbourne
Posts: 4,786
I will state the evidence again. My Astrodon R,G,B and HA filters are parfocal. The HA is 8 micron different to the RGB which are identical.

I took four sequential images of a non descript area with no bright stars or nebulosity. NOTHING changed apart from the four filters. Here are the four unstretched fit images only corrected for flats and darks.


This data should give you the same numbers in CCDI.

It is a shock to the unprepared mind that the best filters on the planet also need to be very accurately orthogonal (better than one second of arc!) to the optic axis of a high quality fast astrograph such as the RH200 with the large chip on the PL16803 camera to get the 'best' stars in the corners.

Below is a small image of the test field.

I was hoping I was wrong! I just needed confirmation from others to see if I had made any logical errors. It is very difficult to change one's erroneous thinking when it is set like concrete.

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