Quote:
Originally Posted by PRejto
Greg,
What is the definition of a bloated star? Yes, I know it looks bloated! But, is there a way to measure bloat? Is it reflected in FWHM? Or, is it just subjective? Also, is bloat just well overflow? or, is it caused by over sampling? You and I both would seem to be pushing it to the max. I would be a .55 arc-sec using the barlow. I managed OK at .63 using the same setup with my G2-8300 so it will be an interesting experiment! Maybe the "bloat" is seen more because of the camera sensitivity. Perhaps more of the image dancing around due to seeing is captured by the Sony chip and not so much by a slower Kodak??
Peter
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The SX Trius 694 is .74 arc seconds/pixel on the TEC180 which is about perfect sampling.
I get a fuzz halo around bright stars. It requires a lot of processing to correct it. I don't get this at all with my Proline 16803 with 95,000 well depth. The QE difference is there around 25% more QE but only from 60 to 77% in green and higher in Ha and O111. The effect is less with my CDK and usually only a few bright stars. I tried it last night (between being battered by winds which my TEC180 does not like!) and without the field flattener I see - on minimal testing - the same effect.
I have seen a similar effect from my ML8300 on a couple of bright stars in a galaxy image I did last year. That I put down to small well depth as well.
What baffles me is I don't see this effect on Mike Sidonios images. His stars look great despite being a fast telescope and 12 inches of aperture so if anything I would have expected it to be worse.
I wonder if SX changed something more than just add argon to the CCD chamber and usb ports on the Trius?
I think its a lack of anti reflection coatings on the CCD chamber window.
I'll take it up with Terry Platt. The camera is good apart from that.
Greg.