Narrowband imaging with a color camera...

[Alveprinsen]

So, considering the fact that the sky is mostly cloudy whenever its a new moon, and clear as crystal when there is a full moon, I've considered getting a narrowband filter so that I dont have to NOT image whenever the moon is up.

Could I do narrowband imaging with a modified DSLR camera? I know that I'd need four times the exposure time, but still... Imaging four times slower is better than not imaging at all IMO.

As I understand, the narrowband image can be used as luminance in a color image?

Anyone have any experience with this?

Sincerely, Alveprinsen.

EDIT: some questions:

1. What kind of narrowband would I want to get? I am using an astro modified and cooled Canon EOS 600D with a Skywatcher Explorer 200PDS scope.

2. For the filter, would I need a filter-wheel, or should I be able to just screw that directly into the coma correcter? Its a Baader-something, bought from FLO.

[Alveprinsen]

Ok, so FLO just confirmed to me that their Baader 2" H-Alpha 7nm will fit my coma corrector, and from extensive googling I've come to learn that 7nm is the way to go.

Still... when focusing the camera.. Will I even be able to see the star which I am trying to focus on? How is visibility through these filters? I am using a bahtinov mask and stuff to focus. Will I have to focus without the filter, before screwing it in or what?

Alveprinsen.

[laser_jock99]

Narrowband with a colour CCD is possible- you just won't be using all your pixels so resolution might suffer. 7nm is the way to go for modified colour cameras.

Regarding focusing- aim the scope at a bright star (Betelgeuse is good for Ha) and try focusing roughly in zoomed live view mode. If that doesn't work then use your Bahtinov mask and say 5 second exposures to get to optimum focus. Then you can use GOTO to aquire your target or your finder scope.

This is the Pelican Nebula through 7nm Baader Ha and colour DSLR

[riklaunim]

You can also thing about using a UHC filter (like the Baader one) to catch H-alpha with red and O III / H-beta with green (+/- blue). It won't be as narrow as narrowband, but still good for a color camera.

If your DSLR has a clear filter mod, not the Baader one that cuts IR then you could also thing abouth photographing not in narrowband but in broad IR band like with Baader IR-Pass, Astronomik ProPlanet 742 or cheap dark red visual filter. The shorter the wavelength the bigger the atmosphere diffraction effect so: O III will be poor, H-alpha much better while longer IR wavelenght even better. CMOS sensors have some random color sensitivity to IR so you could get a false color image of some star clusters, galaxies.