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Thursday, November 6, 2008

The California Nebula, NGC1499

S-II, H-a and O-III composition, Hubble palette
H-a+35%S-II, O-III and O-III+30%H-a, "Natural color" composition

Same image, than top but with supressed stars
to better show actual nebulosity

This image looks very different, than images of California Nebula usually do.
There is two reasons.
First is, that this is a three color narrowband image, there is not
too many of them, least I haven't seen one.
Second reason is,
that image is "upside down" compared to usual precentation format.
I did this for a reason, narrowband composition reveals new structures in nebula,
they are very three dimensional and this position shows them best.
Imaging data: Camera, QHY8
- Filters, Baader 7nm H-alpha, Baader 8,5nm O-III and Baader 8nm S-II
- Optics, Tokina AT-X 300mm @ f2.8 - Exposures, 5X 1200s H-alpha, 2 X 1200 O-III and 2X1200s S-II + flats and bias
- Guiding, LX200 GPS 12" + PHD-guiding and Lodestar

This is how Claifornia Nebula is usually shown.


dick said...

Hi, why do you make a switch to the monochrome Qhy9 if you make this wonderfull!! narrow pictures with a colour camera Qhy8? What improvement do you expect to make?

regard Dick

J-P Metsävainio said...

Hi Dick!

QHY8 is a color camera.
The Bayermatrix in the ccd is not a good match with narrowband filters.
Exampl. H-alpha is using only Red pixels, so only 1/4 of resolution of the ccd is used.
In B&W camera, all the pixels are used, hence the reolution is four times higher.
The sensitivity of B&W ccd is higher too.
I still have the QHY8, and I'll use it this winter to shoot broad band color images in a dark place, outside of city lights.

As you can see, both cameras are very suitable and versatile for astroimaging.