It is a standard for us northern hemisphere photographers to grab this beautiful emission nebula in the constellation of Cassiopia, a good target for me in the UK from September through February. Click the image for the Original Full Size version on AstroBin with maps provided on the AstroBin site.
Something that is not obvious too many people is that many of these objects are actually large in terms of the amount of our sky they take up. The telescope used for this image only has a focal length of 360mm, many camera packages now come with a 200-300mm zoom lenses, so this is not that much different. As a reference this nebula has an apparent size around 2.5 times the size of the moon (150' compared to 0.5°), you don't see it hovering over you in the night sky because it's very faint, magnitude -12.7 for the moon, 18.3 for the Heart, yes weirdly negative magnitudes are brighter than positive ones. This difference in brightness is of course due to the distances involved 360,000-400,000 km away or it takes light 1.2 seconds to travel, Heart is 7,500 light years away, that is 197 billion times further away.
The centre of the image shows a group of bright stars, it is these stars that where formed inside the nebula that are now pushing the clouds away due to their radiation. They are estimated to be around 50 times the size of the sun. The radiation also excites the clouds that are made up (as much of the universe is) of mostly Hydrogen. When Hydrogen atoms are excited in this way they release a photo (particle of light) with a very specific frequency which is in our red portion of the spectrum.
At the bottom right of the image, part of the same nebula but it has its own common name, the 'Fish Head' nebula (NGC 896).
Acquisition Summary
This is a single nights work running from around 00:15 on 17th Sept through to 04:02.
54 4m exposures which were filtered down after removing some with cloud and outliers using the processing softwares analysis information for Full Width Half Maximum and Roundess of the stars in each frame. Final count of the images used for stacking was 47. Therefore this image is the equivalent of a 47*4m exposure 3h8m.
Flats - 20 and 1.5 second exposure using iPad Whitescreen full brightness and T-Shirt method
Darks - 15 exposure
ISO800, all frames exported in Raw format.
Canon 600D Modified by removal of the IR Cut filter
William Options Zenithstar II 61 with Field Flattener
Skywatch HEQ5 Pro Mount with Rowan Belt modification
ZWO 120mm mini for as guide camera using a 30mm focal length guide scope from SVBony
Nina, PHD2 and Green Swamp Server controlling the imaging session.
Majority of processing performed using Siril, finished with some Levels and Curve stretches in Adobe Photoshop.
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