Processing:

This uses a modified Hubble Pallet to bring out the NB.  I also include the more natural NB Assistant version... but I like to enhance the O-III. Stars are from NB Assistant's RGB image added with Bill Blanshan's script. 

Various Collections for Comparison:

Have photographed this before as part of the Sharpless series.  Below was taken with my Takahashi 180Ed  with a CCD.... gives and idea of how small this is. 


Sh2 104 RGB H-Alpha


Sh2 104 H-alpha RGB Reprocessed in 2021

Basic Information From GalaxyMap:

A 2003 study concludes that about 450 solar masses of gas form a shell around an ionising O6V star at a distance of 4000 +/- 500 parsecs. The abstract also adds "We present millimetre-line imaging of the Galactic H II region Sh 104. We show that it is surrounded by a ring of molecular gas and dust. Four large molecular condensations are regularly spaced around the ring. These condensations are themselves fragmented and contain several massive dense cores. A deeply embedded cluster is observed in the near IR towards the largest condensation. It contains at least one massive star ionizing an ultra-compact H II region. The Sh 104 region is a good illustration of the ``collect and collapse' model for star formation triggered by the expansion of an H II region." [1]

Identifies two potential ionising stars: the O5 V [L85] S104 4 and the B0 V [L85] S104 3 and gives a distance estimate of 4800 parsecs for Sh 2-104.[2]

Notes:  1. ^ Deharveng, L., Lefloch, B., Zavagno, A., et al. (2003). "Triggered massive-star formation at the border of the H II Region Sh 104", Astronomy and Astrophysics, Vol. 408, L25-L28. [[url=http://adsabs.harvard.edu/abs/2003A%26A...408L..25D]2003A&A...408L..25D]

  2. ^ Lahulla, J. F. (1985). "UBVRI photometry of stars in several H II regions", Astronomy and Astrophysics Supplement Series, Vol. 61, 537-545. [[url=http://adsabs.harvard.edu/abs/1985A%26AS...61..537L]1985A&AS...61..537L]
Distance Estimates:

=item-distance-display4400 pc [[url=http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1982ApJS...49..183B]1982ApJS...49..183B]
=item-distance-display4800 pc [[url=http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1985A&AS...61..537L]1985A&AS...61..537L]
=item-distance-display4000 pc +/- 500 [[url=http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003A&A...408L..25D]2003A&A...408L..25D]
=item-distance-display3480 pc +/- 800 [[url=http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1984NInfo..56...59A]1984NInfo..56...59A]

GENERAL NOTE ON SHARPLESS2 OBJECTS>>>>>>>>>>>>>

There are 313 Sh2 objects.  All now imaged by yours truly.  These are basically the Hydrogen Alpha and other ionized nebulae around the edge of the Milky Way.

This is my collection:

Sharpless2

Wide-Angle Hydrogen Alpha Nikon Image Sh2 79-171

Please note there is also a Sharpless2 Group with now more than 3000 examples.

Sharpless2 Group

Other useful links include:

Gary Imm's Collection

GalaxyMap's Collection

The Sharpless Catalog

The MDW H-alpha Sky Survey

The Avedisova star formation regions and the Sharpless nebulae TABLE

Hope you enjoy these obscure but interesting objects...