Hydrogen alpha astrophotography.

[terryh]

Hi Guys,

This is my first post on Stargazers.

My first of many questions is:-.. I have a Canon 60Da and have just bought an Astronomix 12nm Ha clip filter for it. Will the pictures I take come out as though they are black and white or is the colour still in them and I have to process them somehow. I downloaded some trial Ha files from a facebook Astronomical site and they all looked to be black and white but when I looked at the colour channels the programme said they were colour Confused!!!. I also have LRGB filters at 1.25 and am wondering if I need to shoot pictures with these when im using the Ha filter. Also if anybody knows a good basic tutorial I could go and have a look at that would be great. I have a bit of experience shooting straight forward shots and stacking and processing in PixInsight and PSE 9.

Regards from

Terry

[ChrisLX200]

Welcome Terry. Yes, the narrow-band Ha will give a monochrome image, it is only a narrow light frequency and the other colours are blocked.

ChrisH

[sidelight]

Hi Terry,

HA is past red so with the filter on only the red channel will receive a signal.  So the images will look very red, the other channels should be blocked.  There is no need for the other filters as the light they would let through is being blocked by the HA filter.

The usual way to process just HA I guess is to remove the other channels as they would be just noise and convert the red to monochrome.  

I haven't ventured into HA myself so can't help with tutorials I'm afraid

Cheers

Ross

[ChrisLX200]

Ah yes, if the image properties (in PS) say it's a colour image then change the mode to grey-scale, then save it as such. I forgot you're using a DSLR.

ChrisH

[Macavity]

(Fairly Randomly) I found this link quite interesting.

http://starizona.com/acb/ccd/advimnarrow.aspx

Contemplating a little narrowband video someday...

Only basic Grey-Scale H-Alpha at first though!

[Uranium235]

Contemplating a little narrowband video someday...

You might be a little restricted in what you can go for, but M42 would be a good candidate for video in Ha - and perhaps some of the brighter PNs.

[sidelight]

Ah thanks Chris, not past red, firmly in the middle 

[terryh]

Thanks for the link and the info guys. I understand a little more now. So if im understanding right I should shoot a nebula say, in Ha, and then take the filter out and shoot normally with my dslr and then merge them.

[sidelight]

I would replace the red channel with the HA image.

[Uranium235]

Thanks for the link and the info guys. I understand a little more now. So if im understanding right I should shoot a nebula say, in Ha, and then take the filter out and shoot normally with my dslr and then merge them.

Yep, thats basically it.

Shoot your Ha, covert it to greyscale, then shoot your RGB and merge the two in Ps (merge the Ha with the red channel).

[terryh]

Wow, thanks, so im going to shoot in Ha, then in LGB and use the Ha as the red channel. Thatll work, I think my brain can cope with. One step at a time til I can run. Thanks all for your Input. Just bought some stuff off First light Optics and they enclose a brochure for this website.

[laser_jock99]

If you shoot through a Ha filter with a DSLR it looks like this:

You could just leave it 'au naturel' (my preferred rendition) or convert to mono (like pretending you have a mono CCD!!) or indeed use it as red channel/Ha data in another image.

[terryh]

Laser jock 99, if I could get a shot like the one you put on that would be brilliant. Certainly a lot of red which is what I want.

[Uranium235]

Wow, thanks, so im going to shoot in Ha, then in LGB and use the Ha as the red channel. Thatll work, I think my brain can cope with. One step at a time til I can run. Thanks all for your Input. Just bought some stuff off First light Optics and they enclose a brochure for this website.

Not quite, the red channel isnt completely replaced by Ha, its more like a 50/50 blend with red.

[ollypenrice]

The addition of Ha to an image can be done in a variety of ways. My favourite is to add the Ha to red in blend mode lighten. The blend mode chosen is very important. I sometimes add a vary low percentage of Ha as luminance at the end as well. Again using blend mode Lighten rather than Luminosity can be good. Not too much though, for me, or you get the 'pink with blue haloes' look. Since Ha traces the same gasses, pretty much, as H Beta (which is in the blue) you can legitimately blend a little Ha into blue as well, though personally I rarely do so.

Olly

[JohnC64]

Hi Terry,

In using a DLSR, I find that its best to extract the red channel only from the shot taken with Ha.  This is to remove the DLSR noise that is present in the green and blue channels(and the small bit of signal from brighter stars)  to create a "monochrome" image.

You then can merge this image with the RGB image as described by Olly above. There generally isn't much noise in the Green and blue but once stretching takes place it starts to show, so i find it best to remove it at the start.

Hope this helps

Cheers John