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 a second section Image and instrument data can be found at the end of this page.

There are short descriptions below each image.

Full views

Click on the images to load a full resolution version with up to more than 100 megapixels using a JavaScript viewer. If browser cannot handle this or in case of low bandwidth connections you can try the half resolution version. The links can be found below the images.

Some browsers (namely Gecko based ones like Firefox) cannot downscale properly with Javascript, they just downsample. This results in noisy images and randomly appearing and disappearing stars while zooming. If such artifacts appear you can try the direct download version and use the browsers built-in viewer. Download links can be found below the images.

Direct download is also recommended for mobile devices (and devices with touchscreen) because browsers for these devises usually have a integrated viewer which is faster than the Javascript viewer and can handle larger data.

M33 to SH2-126 in H-alpha (red), blue continuum (green) and red continuum (blue)
Full resolution (39 MB): Javascript Viewer Direct download
Half resolution (10 MB): Javascript Viewer Direct download
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 visualization is a false color image where H-alpha (including red continuum) is mapped to red, blue continuum is mapped to green and red continuum (without H-alpha) is mapped to blue. White calibration was derived from star average which is why galaxies look white. H-alpha emission nebulae appear red in this image.
Stars are partially subtracted. Further image processing steps are dynamic range compression using a nonlinear hi-pass filter and tonal curve correction.

Selected details

Here are two details that also can be seen using the Javascript viewer (if browser works correctly).
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
SH2-1236 (red) surrounded by high galactic latitude nebulae (mostly gray).

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°
Orientation: North is left (exactly)
Scale: 10 arcsec/pixel (in center at maximum resolution)
FOV: 21°×40° (through center)
Exposure times: H-alpha: 6.3d, continuum channels: 4.6d (sum of exposure times of all frames used to calculate the image)

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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