Category Archives: Broadband RGB

The Pinwheel Galaxy (M101)

The Pinwheel Galaxy (also known as Messier 101, M101) is one of the largest disk galaxies known with a visible diameter of 170,000 light years. This grand-design face-on spiral galaxy is located at a distance of 27 million light-years from us in the constellation Ursa Major

A unique feature of M101 is the high population of extremely bright star-forming regions (called H II regions) scattered across its spiral arms. Observational evidence indicates that close gravitational interaction with companion galaxies created waves of high mass and condensed gas which continue to orbit the galaxy centre. These tidal forces compress interstellar hydrogen gas, which then triggers strong star formation activity. The lopsided asymmetric structure of M101 is also due to the tidal forces from these local gravitational interactions.

Right ascension: 14h 03m 11.88s | Declination: +54° 21′ 00″ | Distance: 27 Million Light Years | Field of view: 37.4 x 24.9 arcmin

Camera: SBIG STL-6303E
Telescope: PlaneWave Instruments CDK 12.5 F/7.9
Guiding: External 80mm F/4 guidescope with an Atik 314L+ for guiding
Mount: Paramount PME
Filters: Astrodon Series E LRGB
Exposures: Luminance (34 x 5min), Red (12 x 5min), Green (14 x 5min), Blue (13 x 5min)
Binning: Luminance 1×1, RGB 2×2
Total exposure: 6 hours
Image composition: LRGB
Scale: 0.73 arcsec/pixel
Image acquired: Over 8 nights during May & June 2013

Image capture with MaxIm DL, FocusMax, ACP; Image processed with MaxIm DL, PixInsight, Photoshop CS4

The Whirlpool Galaxy (M51) from Nerpio, Spain


A classic spiral galaxy in the constellation Canes Venatici – it is 30 million light years distant and 60 thousand light years across with an estimated mass of 160 billion solar masses.  One arm of the galaxy is interacting with a smaller galaxy (M51b or NGC 5195).  The very pronounced spiral structure of the Whirlpool Galaxy is believed to be the result of the gravitational interaction between it and its companion galaxy.

This image represents something of a departure for me as my emphasis to date has been on narrowband imaging.  The dark clean skies at AstroCamp in Spain now open up the possibility of capturing high quality broadband colour data.  Image reduction and luminance deconvolution was carried out using MaxIm DL.  PixInsight was used for further pre-processing and colour calibration, LRGB composition, noise reduction and sharpening.  Final processing and jpeg creation for publishing on the web was carried out in PhotoShop CS4.

Right ascension: 13h 29m 53.88s | Declination: +47° 12′ 00″ | Distance: 30 Million Light Years
Field of view: 37.4 x 24.9 arcmin

Camera: SBIG STL-6303E
Telescope: PlaneWave Instruments CDK 12.5 F/7.9
Guiding: External 80mm F/4 guidescope with an Atik 314L+ for guiding
Mount: Paramount PME
Filters: Astrodon Series E LRGB
Exposures: Luminance (30 x 5min), Red (21 x 5min), Green (21 x 5min), Blue (21 x 5min)
Binning: All filters 1×1
Total exposure: 7.7 hours
Image composition: LRGB
Scale: 0.73 arcsec/pixel
Image acquired: Over 9 nights during April & May 2013

Image capture with MaxIm DL, FocusMax, ACP; Image processed with MaxIm DL, PixInsight, Photoshop CS4

Leo triplet of galaxies

The Leo Triplet is a small group of galaxies about 35 million light-years away in the constellation of Leo.  This galaxy group consists of the spiral galaxies M65, M66, and NGC 3628 (‘The Hamburger’).  Image acquired and processed with help of Olly Penrice at Les Granges Astronomy Holidays, SE France.

Right ascension: 11h 19m 44s | Declination: +13° 19′ 10″ | Distance: 35m Light Years
Field of view: 53 x 53 arcmin

Camera: Atik 4000 Mono (Kodak KAI 04022)
Telescope: TEC APO140ED F/7
Filters: Baader LRGB
Exposures: Lum 30 x 15 min; Red 11 x 10 min; Green 8 x 10min; Blue 15 x 10min
Total exposure: 13 hours
Image composition: LRGB
Scale: 1.56 arcsec/pixel
Image acquired: March 2012 from Les Granges, SE France.

Image capture with Artemis Capture; Image processed with Registar, AstroArt 5.0 and Photoshop CS3