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Thursday, January 23, 2020

A deep view to the California Nebula, NGC 1499

I have been shooting few nights with my "new" wide field instrument. Undersampling is a great thing if you want to capture very dim and diffused gas structures with a minimal exposure time. The Tokina AT-x 300mm f2.8 optics combined to CCD with 9 micron pixels (Apogee Alta U16 4096x4096 9 micron pixels) gives me a spatial resolution of 6 arcseconds/pixel. The problem with one pixel stars is actually not a problem. I'm using dither when imaging and when lights are stacked, it delivers
beautifully rounded stars..

California Nebula, NGC 1499
Please, click for a full size image

Image is in natural colors combined from the narrowband channels. H-alpha = Red, O-III = Green and O-III + 20% H-alpha = Blue. This is a very deep image, I haven't seen those extended shapes at upper right and  around the brighter nebula.


The California Nebula is an emission area located in constellation Perseus. It appears to resemble outlines of State of California on long exposure photographs, like this one. It has a very low surface brightness and it's very difficult to observe visually. Distance from my hometown Oulu, Finland, is about 1000 light years.
this image spans around five degrees horizontally. The Wikipedia article states, that the angular size is about 2,5 degrees (Five full Moons side by side) but as can be seen in this image, the actual size, with a dim outer parts, is much large.

H-alpha exposure alone
Please, click for a full size image

H-alpha  image contains seven 20 min sub exposures stacked together. Exposure time is 2h 20 min..

Technical details
Processing workflow
Image acquisition, MaxiDL v5.07.
Stacked and calibrated in CCDStack2.
Deconvolution with a CCDStack2 Positive Constraint, 33 iterations, added at 50% weight
Color combine in PS CS3
Levels and curves in PS CS3.

Imaging optics
Tokina AT-x 300mm f2.8 camera lens

10-micron 1000

Cameras, filters and guiding
Imaging camera Apogee Alta U16 and Apogee seven slot filter wheel
Guider camera, Lodestar x 2 and an old spotting scope of Meade LX200
Astrodon filters,
5nm H-alpha 3nm S-II and 3nm O-III

Total exposure time
H-alpha, 7 x 1200 s, binned 1x1 = 2 h 20 min.
O-III, 2x 1200 s, binned 2x2 = 40 min.

On older image of California nebula in mapped colors
The apparent scale in a sky
Please, click for a full size image

This is a large object, note, the size of the Moon is marked, as a scale, in all of the images above.

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