M33 to SH2-126

On this page a 21°×40° wide-field view which covers most of the constellations Andromeda and Lacerta is presented. The center of the photographed region lies about 20° south of the galactic plane and is rich of high galactic latitude nebulae. Most famous objects are M33 (Triangulum galaxy), M31 (Andromeda Galaxy) and SH2-126, a large HII region in Lacerta.

The pictures below are downscaled versions. A full resolution image with more than 100 megapixels can be loaded with a Javascript viewer by clicking on the images in the first section. Selected details are shown in the second section. The third section presents some discoveries. Image and instrument data can be found at the end of this page.

Full views

Click on the images to load a full resolution version with more than 100 megapixels using a JavaScript viewer.

M33 to SH2-126 in H-alpha (red), blue continuum (green) and red continuum (blue)
The triangulum Galaxy M33 is depicted in the top right corner, the Andromeda galaxy M31 is in the center and SH2-126 is the red nebula at bottom.
This image is a false color composite in which H-alpha (including red continuum) is mapped to red, blue continuum (including [OIII] and H-beta emissions) is mapped to green, and red continuum (without H-alpha) is mapped to blue. Reflection nebulae appear green to blue, while HII regions are red. Stars in the continuum channels are partially subtracted to make the faint nebulae visible.

Selected details

Here are two details that also can be seen using the JavaScript viewer.
M31 with halo and including its companions M31 and M110
M31 accreting its companions M32 (the smaller one) and M110. The irregular shape of the halo is caused by remnants of of previously accreted galaxies.
SH2-1236 surrounded by high galactic latitude nebulae
SH2-126 (red) surrounded by high galactic latitude nebulae (mostly gray).


The views above show many nebulae that cannot be found in catalogs. (The JavaScript Viewer allows identifying objects using catalogs or SIMBAD and defining new objects.) Some (probably not all) of these unexplored nebulae have been collected in the list below. Click on the following link for a presentation.


Image data

Images where captured with a camera array which is described on the instruments page.

Image data are:

Projection type: Stereographic
Center position: RA: 0h04, DEC: 41°
Above: North is right
JavaScript viewer: North is up
Scale: 10 arcsec/pixel (in center at maximum resolution)
FOV: 40°×21° (RA×DEC, through center)
Exposure times: Sum of exposure times of all frames used to calculate the image.
H-alpha: 6.8 d
Continuum channels: 5.0 d

Image processing

All image processing steps are deterministic, i.e. there was no manual retouching or any other kind of non-reproducible adjustment. The software which was used can be downloaded here.

Image processing steps where:

  1. H-alpha only: bias correction, photon counting
  2. Dark current subtraction, flatfield correction, noise estimation
  3. Alignment and brightness calibration using stars from PPMXL catalog
  4. Stacking with masking unlikely values and background correction
  5. Extracting stars
  6. Denoising and deconvolution both components (stars and residual)
  7. RGB-composition
  8. Dynamic range compression using non-linear high-pass filter
  9. Tonal curve correction

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