Luminance v Ha

[telecasterguru (Frank)]

I don't know if this has been asked before but what is the difference between a Luminance filter and a Hydrogen Alpha filter?

Is it just the bandwidth that the filter lets through or is it moer than that?

Thanks

Frank

[multiweb (Marc)]

Originally Posted by telecasterguru

I don't know if this has been asked before but what is the difference between a Luminance filter and a Hydrogen Alpha filter?

Is it just the bandwidth that the filter lets through or is it moer than that?

Thanks

Frank

A Ha Luminance is only red. A normal Lum lets in Red, Blue and Green.
That's why it's harder to process colors using a Ha blend. If you don't do it right you'll mute the blues and greens and will get those salmon pink pictures. Also Ha will bring more faint details and tighter stars (also less of them) than a normal Lum.

[Bolts_Tweed (Mark)]

Yep to Marcs comments - my method is to take RGB and if the image looks ok I will spend the time on ha nd Lum. To evaluate quality I usually synthesise a lum by converting the RGB to a Grayscale and process that as a prelim lum.

On keepers (In Darryl Kerrigans words - ones destined for the poolromm) I usually spend a lot of time gathering Ha as well as Lum but combine them into a final Lum - if you blend correctly you can end up with all the faint Ha data from that filter as well as covering the tonal map with the lum filter - still requires more processing than straight lum but yields a far better result IMO.

So yep - it's bandwidth but use of both of them both can be advatageous. eg the red filaments in the Crab or the streamer curtain above the horsehead can be captured by the narrowband Ha but it wont be as obvious in the lum - but as Marc points out you need the lum data to avoid the salmon nebula - I remember when salmon was a food type not a colour.

Makr bolton

[dugnsuz (Doug)]

Originally Posted by multiweb

A Ha Luminance is only red. A normal Lum lets in Red, Blue and Green.
That's why it's harder to process colors using a Ha blend. If you don't do it right you'll mute the blues and greens and will get those salmon pink pictures. Also Ha will bring more faint details and tighter stars (also less of them) than a normal Lum.

Originally Posted by Bolts_Tweed

Yep to Marcs comments - my method is to take RGB and if the image looks ok I will spend the time on ha nd Lum. To evaluate quality I usually synthesise a lum by converting the RGB to a Grayscale and process that as a prelim lum.

On keepers (In Darryl Kerrigans words - ones destined for the poolromm) I usually spend a lot of time gathering Ha as well as Lum but combine them into a final Lum - if you blend correctly you can end up with all the faint Ha data from that filter as well as covering the tonal map with the lum filter - still requires more processing than straight lum but yields a far better result IMO.

So yep - it's bandwidth but use of both of them both can be advatageous. eg the red filaments in the Crab or the streamer curtain above the horsehead can be captured by the narrowband Ha but it wont be as obvious in the lum - but as Marc points out you need the lum data to avoid the salmon nebula - I remember when salmon was a food type not a colour.

Makr bolton

Great answers.
Mark - I'm going to try out the PS actions on your section of the leyburn astro site...Cheers
Doug

[Bolts_Tweed (Mark)]

gday Doug

They are a bit primitive compared to Carbonis just automating some processes I use - some I have got from this forum. If you have problems let me know.

I will also check if they are the latest version - I've added some pinching routines, star colour enhancement and star minimisation that is really handy with bloated blue starts in RGB

PM me if you have problems - or suggestions for somehting else is also welcome

Mark