Old 23-03-2017, 09:57 AM
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Probably a silly question


Why do people use filters with mono cameras?

For example if you shot a DSO with a mono camera (eg atik 383 L+ Mono) you would get the full spectrum, Ha, O2, S2 and luminance all in one go. Then if you mixed in the same scene with a colour camera (eg atik 383 L+ Colour) you would have an image in a lot less time?

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Old 23-03-2017, 10:11 AM
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Peter Ward
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What your are suggesting is what mono imagers have being doing for some time. LRGB, and the method does give better SNR's with colour images.

However as the luminance data contains not just Ha Oiii etc, but the full visible spectrum, you will not get the data you can only obtain by isolating these wavelengths by using an appropriate filter.
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Old 23-03-2017, 10:21 AM
clive milne
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Paul, to use an analogy; imagine you are listening to music at home with the vacuum cleaner, coffee grinder and lawn mower also going at the same time.

RGB filters are like turning two of these noise sources off.
Narrow band is like turning all three off, leaving only the music.

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Old 23-03-2017, 10:34 AM

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Sorry for the slight diversion, but it occurred to me during this discussion that it would be really cool for each pixel to be able to record the full amplitude versus frequency (/wavelength) data (i.e: spectrum) at that pixel. Then you could capture to your heart's desire (with heaps of data storage) and easily deconstruct the signal later with appropriate software and without requiring any external filters during capture.

Maybe it's one of those big NASA or military thingies that's under wraps.

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Old 24-03-2017, 07:38 AM
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Thanks for all the replies.

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Old 24-03-2017, 08:45 AM
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What you're suggesting is already being done.....
A spectrograph - which disperses the visible wavelengths allowing each wavelength to be recorded is used. All the, say, emission wavelengths of the target, Hb, OIII, Ha SII etc. etc. are independently recorded and can be recombined as required.
(use google translate if your French is poor ;-) )
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Old 27-03-2017, 11:42 AM
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One other comment that has not been mentioned is that one-shot colour cameras are less sensitive and offer lower resolution than a mono camera with RGB or NB filters. Another problem is that inbuilt Bayer filters on colour cameras are not tuned or of the same quality as high quality filters designed specifically for asto imaging.

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