--- In ccdimaging2@yahoogroups.com, "John A. Blackwell" <johnb@r...>
wrote:
> Hello,
>
> We had another nice clear (windy) night last night, so we avoided
> imaging Saturn (ohhh so tempting though!) and went for the Crab
> Nebula.
>
> http://www.regulusastro.com/regulus/photos/text/m1rgbcn212.html
>
> CN-212 ST-7 non-E non-ABG LRGB color composite. 15:10:10:24 minutes
> at -30C. This one ended up much better than last year's version
> which was too grainy (too short an integration time).
>
>


That's a nice crab John. Hey how do you like the CN212? Do you use it
mostly as a cassegrain or as a newt? How about collimation of it in
Newt mode, is it difficult?

Here is a Crab I shot last week in between storms. I used a C14 and
an FLI Dream Machine camera. I also used Custom Scientific 3nm FWHM
[SII], Ha, and [OIII] filters. I did a second and third version using
an [NII] filter with the others.

When you combine [SII], [NII] and Ha all of the data is in the "Red"
portion of the visible spectrum. Making a tricolor like I did gives
you some nice separation of those emission lines in a way that you
cannot see with an RGB image. Looks weird though....

[SII]=Red, Ha= Green, [OIII] = Blue

http://www.rdcrisp.darkhorizons.org/m1_crab_nebula_S2HaO3_page.htm

[SII] = Red, [NII] = Green, Ha = Red

http://www.rdcrisp.darkhorizons.org/m1_crab_nebula_S2_N2_ha_page.htm

finally here is an image made from [NII] and Ha only. These emission
lines are only separated by 2nm so it was interesting to me to see if
my filters could really differentiate between the species:

http://www.rdcrisp.darkhorizons.org/m1_crab_nebula_ha_n2_page.htm


Happy New Year!
Richard