I've read conflicting opinions on the interweb and not all filters are made equal, so I put it out there to you...with broadband CCD imaging of an emission nebula like the Tarantula, what colours should we see?
Dunk my personal opinion is that broadband images of the Tarantula should be colour balanced as heavily turquoise. Certainly if you shoot it in narrowband the Oiii will result in a bias towards turquoise naturally based on the location of the spectral lines.
This is more broadband I'm interested in, i.e. RGB. I collected some data at the weekend with my ZWO filter set and when I blend the channels the Tarantula comes out a nice shade of green
Does anyone know of a reference point that should be strong OIII? I took a bunch of subs in G and B of the same exposure time, so it'd be interesting to compare.
I guess it's one of those things that could vary slightly due to the QE of different cameras and transmittance of the filters
Looking at the bandpass profile of the ZWO filters I'm using, OIII is squarely in the green filter, which explains why it's strongly green. Looking at my exposures, the green:blue is about 2:1.
Any suggestions on a nice set of RGB filters that would give me good ol' teal/turquoise/insert shade here* ? Oh, and inexpensive
Any suggestions on a nice set of RGB filters that would give me good ol' teal/turquoise/insert shade here* ? Oh, and inexpensive
Use the ColorMask script for free, Dunk
I'm only half joking. You'll never get perfectly accurate colour from any set of filters because of variations in sensor QE, atmospheric extinction, etc. You're better off honing your colour calibration technique.
Appreciate what you say about the filters, but...makes me wonder if a filter set where G and B overlapped for OIII would give richer signal, or conversely, overblow it.
The purple should be the areas where the OIII and Ha are mixing. I'd expect this to differ from an unmodded DSLR which wouldn't let as much Ha through.
Still need to work at it a little more I think, but it's a start...
looking at the G and B channels, the signal is WAY stronger in the G - but I'm not sure if that's because it has double the pixels in the bayer matrix... - either way its probably 5x plus richer in G (total guess)
not sure that helps at all. of course its rare to have o3 just by itself so a light pollution filter/osc will likely give a different hue.
Last edited by rustigsmed; 07-12-2016 at 02:17 PM.
Appreciate what you say about the filters, but...makes me wonder if a filter set where G and B overlapped for OIII would give richer signal, or conversely, overblow it.
The ZWO filters do look pretty crappy in that regard. The Astrodon filters have a much nicer overlap at 500nm. I'll withdraw my previous comment.
looking at the G and B channels, the signal is WAY stronger in the G - but I'm not sure if that's because it has double the pixels in the bayer matrix... - either way its probably 5x plus richer in G (total guess)
not sure that helps at all. of course its rare to have o3 just by itself so a light pollution filter/osc will likely give a different hue.
Thanks Russ! That's a pretty interesting result. Can't wait for Eta Carinae to get higher in the sky.
It hadn't occurred to me to stick the filter wheel in front of a DSLR...I'll have to give that a try
Quote:
Originally Posted by RickS
The ZWO filters do look pretty crappy in that regard. The Astrodon filters have a much nicer overlap at 500nm. I'll withdraw my previous comment.
From what I've found so far, the Baader CCD and Astronomik Deep Sky both overlap at 500nm. The Astrodons apparently are too tall to fit in the ZWO filter wheel.