Collecting Photons

M33 – Pinwheel galaxy

M33 is part of our small local group of galaxies and it is the second largest as seen from home. This and the favourable orientation of the galaxy plane allow the detection of a tremendous amount of details in its spiral arms. Here processing has been directed at the optimal display of the arms and dust clouds. North is right.

Celestron 8, f6.3; Canon 350D Hutech modified type I filter. 53x8’ at iso 800. I have used a antipollution filter not only to reduce background, but to increase the contrast of the HII regions with the continuous sorces. Indeed, in this way the image looses some depth but has a better rendering of the emission nebulae.

Processing: calibration (offset, dark, flat) in Iris. Hyperbolic asin stretch. Gradient elimination in PixInsight. Curves with luminance masks in PixInsight. Ten iterations of Richardson-Lucy deconvolution brought the best star images down to about 2.2”. Final touches in Photoshop CS2.

The galaxy is so full of prominent features that several have received separate catalogue numbers as seen in this map: the labels are immediately north (right) of the object.

Some of these objects are among the largest H II regions known. Especially prominent is NGC 604 seen here at half resolution:

Interestingly, some of the emission nebulae appear quite blue rather than red. See for example the nebula IC 132:

A search with SIMBAD revealed that in this area are present some very dense clusters of hot stars. Possibly, in this image the continuous spectra is prevailing over the Hα emission returning a white-blue appearance.

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Send anything that comes to mind to Gimmi Ratto gimmi@in.cnr.it