"The Sharpless catalog is a list of 313 Ha-band emission nebulae located generally north of the -27 ° declination, although it also includes some nebulae south of this declination. The first edition was published in 1953 with 142 objects (Sh1) and the second and the final version was published by US astronomer Stewart Sharpless in 1959 with 312 objects. Sharpless also contains some planetary nebulae and supernova remnants, in addition to Ha regions. " - this is the official and probably well-known description.
When photographing objects from this catalog over the years, however, I came across a few of them theoretically of a completely different type. Theoretically - because delving into the available descriptions - I found that despite the extremely low emission, Ha Sharpless had every right to call them emission nebulae.
What objects am I writing about?
The first is the dust area I photographed in 2013 designated as Sh-73 in the Hercules constellation. It shows poor Ha emission, unfortunately not recordable with amateur equipment.
The second object is my most recent work from July 2022, labeled Sh2-63 (also LBN 86) just below the Eagle constellation at a declination of -14 degrees. A very clear and bright nebula is also not available in Ha for amateur equipment.
You can read a little more and see an interesting description here:
https://jthommes.com/Astro/Sh2-63.htmThe other two objects with similar characteristics are Sh2-33 and Sh2-36.
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