Pillars of Creation and a question

[Jon]

Here's an image of M16 I got last night - 16 x 5 min ISO 800 with the EOS 60Da and the Meade 10" SCT with 0.63 FR.

I was quite happy with some aspects of it - the stars are pretty round, as I seem to have sorted out some of my flexure issues by mounting the guidescope on a new Losmandy rail and rings that arrived from Bintel last week. It's certainly better than the improvised wooden job I had!

I think I can improve the noise as I only had 8 darks at anywhere near the temperature.

My question is regarding the vignetting you can see in the second image. This is after I have calibrated with flats, dark flats and darks in DSS. This is basically the output straight out of DSS - just a bit of stretching and saturation so you can see what's happening.

I'm getting this huge colour gradient when using the focal reducer - red in the centre, blue around the edges. This wasn't happening a couple of months ago, when the flats were eliminating the gradient pretty well. I don't think I'm doing anything different in the way I process or capture the flats, but something's going on.

Anyone had this themselves or got any ideas?

[Gem]

I have recently had red in one corner and green in the other... been wondering why myself. Only is apparent when I try to get the gain up when processing...

[Jon]

Grant, is that using the SCT or the refractor?

I also had one set of good data of the lagoon nebula ruined with one corner green and one corner blue ...

[Jon]

I've fixed the problem, seemingly by chance. I went into the RAW/FITS digital development settings menu in DSS. I'd tried everything in the RAW tab to no avail, but this time I went to the FITS tab (I never go near FITS - I take CR2 raw files, stack them in DSS and output as 32-bit TIFF) and checked the "Monochrome 16-bit FITS files are RAW files created by a DSLR" box and - hey presto! - the colour gradient vanished.

Grant, try this and restock the image with red and green corners and see ifet works for you.

[astronobob]

Cool Pic, Interesting & great you have soughted the colour gradient out, , !
Dig the scale on this Grant :thumbsup: Lots to ponder about with star birth etc !