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First success adding Ha to an RGB galaxy - M31


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Our old friend M31.

Nothing remarkable about this image except that this is the first time I have successfully added Ha to an RGB galaxy and produced a result I like.

The breakthrough was friends explaining continuum subtraction and pointing me to this tutorial Advanced Narrowband Combination — Night Photons. The fog cleared and I now have some understanding of how to control Ha addition. I produced a whole range of images with different amount of Ha and different colour mappings, but this is the one I like best because it shows the Ha knots in the arms without whacking you between the eyes with it.

So just another boring M31, but one that has given me great pleasure.

Data from Pier 14 @Roboscopes in Spain (reduced Tak FSQ106 - FL 387mm, ASI 2600MM Pro with 3nm Antlia filters, unguided Paramount MX). 1.5 - 2 hrs each R, G & B, 5hrs Ha.


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Subtle addition of Ha to galaxies is the holy grail and I think you are right to be pleased with this one. We often see Ha features looking more like brakes lights in Las Vegas than anything else. Not in this one, though.


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