Ha has luminance on galaxies?

[kirkster501]

Thinking of using Ha as a luminance for my current session on M33.  Will still blend red with Ha as well.

Whaddayareckon chaps?  Pro's and cons?

I can try it regardless.

[kirkster501]

Pardon spelling in title.  Ha as luminance I meant.

[Uranium235]

Nope sorry, that wont work. Galaxies are broadband objects, the only thing Ha will bring you on M33 is the "sparkly bits" of Ha.

[vlaiv]

In theory you could as galaxies are broad band objects, they also emit in Ha alpha, but signal strength is so weak (except for ha regions, and only nearby galaxies, close enough for ha regions to actually resolve) that it is just not worth it.

[Stub Mandrel]

@Rodd recently posted images of M33 with HA used to accentuate the red knots in it.

[ollypenrice]

Ha is deep red. Why would you illuminate an entire galaxy in the light of deep red when so much of its emission is in blue from the hot young stars in the spiral arms? It would simply subdue so much of this signal.

I would put the Ha where it naturally falls, which is in the red channel. It will then bring sparkle to the isolated HII regions scattered around the arms. It will also pick up some interesting ring-like structures. Ha is a real benefit in imaging M33 but not, for me, in the L channel.

Olly

[DaveS]

Won't work. Ha is narrow band to accentuate the the big HII regions. L needs to be as broad as possible consistent with your LP. Even here I've abandoned the idea of using a CLS-CCD as my L filter.

[kirkster501]

Thanks for your thoughts guys.  I'l abandon that idea then.

The reason i asked was the I know some folk use Ha as luminance on nebulae.   So i thought why not for galaxies as well.  I have been educated.