Nestled between the gorgeous Flame Nebula and the intimidating Horsehead, is the home planet of the Kerbals. They are a peace loving people, and having just become a space-faring civilization, little do they know that roughly 1200 light years from their beautiful planet Kerbin, lies the home planet of the war mongering species of Man, called Earth. At such a relatively close distance, it’s only a matter of time until the two civilizations come into contact with each other. Can the peace loving Kerbals hold their own when the corporate might of Mankind come knocking with their galactic-class mining ships? The Kerbals have, at least, 1200 years to prepare for that eventuality. For now however, they are happy to look up at the night sky and wonder, “Where the kell did Jebediah hide the Horse’s body?"

DOWNLOAD

You MUST download TextureReplacer Replaced, if you haven’t already.
Download the skybox.
Unpack the ZIP archive and place the GameData folder into your KSP install directory, replacing the original.

TECHNICAL INFO

The skybox was captured using SpaceEngine 0.9.8. Later, I used 'real' images of the individual objects, from various sources (see full list below), to add more detail.
How did I choose which objects to make visible and which ones to ignore? I increased SpaceEngine’s magnitude limit to the 8th (from the default of 7th) and exported the skybox at 4096px resolution. I kept the objects which were visible in the exported images. For example, even though the Eagle nebula is ~3300 ly away, it wasn’t showing inside SpaceEngine, whereas the Lagoon nebula which is farther away at ~5200 ly was visible; probably because the Lagoon is nearly 4 times larger than the Eagle.
How ‘realistic’ IS this skybox? The locations of the stars, nebulae and galaxies in the sky are precisely where they should be, at least according to SpaceEngine, but I have taken some artistic liberty with their sizes. For example, the Flame nebula should appear a lot larger, and the Great Carina nebula, a lot smaller, in the sky. My priority was to create something dynamic and intriguing without making it too overwhelming or too unrealistic. As such, I wouldn’t claim the skybox to be a very ‘realistic’ depiction of the sky from that location in space. Not to mention, many of the nebulae and galaxies shouldn’t even be visible. However, I have reduced the brightness of such objects to make them hard to spot.

Click here to view a labeled screenshot of all the nebulae and galaxies in the skybox.

CREDITS and SOURCES
There are lots! Please expand the 'spolier' section below to see the full list of credits and sources. All other objects, except the ones exclusively mentioned below, are sourced directly from Space Engine v0.9.8.

Galaxy ESO 97-G13, Circinus
Credit:   NASA/Andrew S. Wilson (University of Maryland); Patrick L. Shopbell (Caltech); Chris Simpson (Subaru Telescope); Thaisa Storchi-Bergmann and F. K. B. Barbosa (UFRGS, Brazil); and Martin J. Ward (University of Leicester, U.K.)
Source:   https://www.nasa.gov/mission_pages/hubble/multimedia/Circinus.html
License:   Public Domain / Attribution

Galaxy NGC 5128, Centaurus A
Credit:   ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray)
Source:   http://www.eso.org/public/images/eso0903a/
License:   Creative Commons Attribution 4.0 International (CC BY 4.0)

Galaxy M83, Southern Pinwheel
Credit:   ESO
Source:   https://www.eso.org/public/images/eso0825a/
License:   Creative Commons Attribution 4.0 International (CC BY 4.0)

Galaxy M31, Andromeda
Credit:   Torben Bjørn Hansen
Source:   https://www.flickr.com/photos/torbenh/6105409913
License:   Creative Commons Attribution 2.0 Generic (CC BY 2.0)

Galaxy M33, Triangulam
Credit:   Alexander Meleg
Source:   https://commons.wikimedia.org/wiki/File:M33_-_Triangulum_Galaxy.jpg
License:   Creative Commons Attribution-ShareAlike 3.0 Unported (CC BY-SA 3.0)

Galaxy UGCA 39, Maffei 2
Credit:   Atlas Image courtesy of 2MASS/UMass/IPAC-Caltech/NASA/NSF; Image mosaic by R. Cutri (IPAC)
Source:   https://www.ipac.caltech.edu/2mass/gallery/maf2atlas.jpg
License:   Public Domain / Attribution

Nebula M78
Credit:   ESO/Igor Chekalin
Source:   https://www.eso.org/public/images/eso1105a/
License:   Creative Commons Attribution 4.0 International (CC BY 4.0)

Nebula NGC 2023
Credit:   ESO/J. Emerson/VISTA. Acknowledgment: Cambridge Astronomical Survey Unit
Source:   https://www.eso.org/public/images/eso0949e/
License:   Creative Commons Attribution 4.0 International (CC BY 4.0)

Nebula Barnard 33, Horsehead
Credit:   Ken Crawford
Source:   https://commons.wikimedia.org/wiki/File:Barnard_33.jpg
License:   Creative Commons Attribution-ShareAlike 3.0 Unported (CC BY-SA 3.0)

Nebula M42, Orion
Credit:   Bryan Goff
Source:   https://commons.wikimedia.org/wiki/File:Backyard_photo_of_the_Orion_Nebula.jpg
License:   Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)

Nebula NGC 2818
Credit:   NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
Source:   http://hubblesite.org/image/2464/news_release/2009-05
License:   Public Domain / Attribution

Nebula Puppis A
Credit:   NASA/CXC/IAFE/G.Dubner et al & ESA/XMM-Newton
Source:   https://www.nasa.gov/chandra/multimedia/puppisA-2014.html
License:   Public Domain / Attribution

Nebula NGC 3372, Eta Carinae
Credit:   Harel Boren
Source:   http://www.pbase.com/boren/image/151851961
License:   Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)

Nebula NGC 3324
Credit:   ESO
Source:   http://www.eso.org/public/images/eso1207a/
License:   Creative Commons Attribution 4.0 International (CC BY 4.0)

Nebula ESO 170-6, Fleming 1
Credit:   ESO/H. Boffin
Source:   http://www.eso.org/public/images/eso1244a/
License:   Creative Commons Attribution 4.0 International (CC BY 4.0)

Nebula HD 44179, Red Rectangle
Credit:   H. Van Winckel (KU Leuven), M. Cohen (UC Berkeley), H. Bond (STScI), T. Gull (GSFC), ESA, NASA
Source:   https://apod.nasa.gov/apod/ap040513.html
License:   Public Domain / Attribution

Nebula M8, Lagoon
Credit:   ESO
Source:   http://www.eso.org/public/images/eso0936a/
License:   Creative Commons Attribution 4.0 International (CC BY 4.0)

Nebula IC 2118, Witch Head
Credit:   NASA/STScI Digitized Sky Survey/Noel Carboni
Source:   https://www.nasa.gov/multimedia/imagegallery/image_feature_1209.html
License:   Public Domain / Attribution

Nebula NGC 2024, Flame
Credit:   ESO and Digitized Sky Survey 2. Acknowledgment: Davide De Martin
Source:   https://www.eso.org/public/images/eso0949k/
License:   Creative Commons Attribution 4.0 International (CC BY 4.0)

Nebula M45, Pleiades
Credit:   Zdeněk Bardon/ESO
Source:   https://www.eso.org/public/images/pleiades-ch17-bardon-cc/
License:   Creative Commons Attribution 4.0 International (CC BY 4.0)

Nebula NGC 7000, North America
Credit:   Oliver Stein
Source:   https://commons.wikimedia.org/wiki/File:North-America-nebula.jpeg
License:   Creative Commons Attribution-ShareAlike 3.0 Unported (CC BY-SA 3.0)

Nebula NGC 1499, California
Credit:   Zdeněk Bardon/ESO
Source:   https://www.eso.org/public/images/pleiades-ch17-bardon-cc/
License:   Creative Commons Attribution 4.0 International (CC BY 4.0)

Nebula NGC 7380, Wizard
Credit:   Chuck Ayoub
Source:   https://commons.wikimedia.org/wiki/File:Wizard_Nebula.jpg
License:   Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)

Nebula Sh2-190 and Sh2-199, Heart and Soul
Credit:   NASA/JPL-Caltech/UCLA
Source:   https://www.nasa.gov/mission_pages/WISE/multimedia/wiseimage20100524.html
License:   Public Domain / Attribution

Nebula M1, Crab
Credit:   ESO
Source:   https://www.eso.org/public/images/eso9948f/
License:   Creative Commons Attribution 4.0 International (CC BY 4.0)

Nebula Sh2-274, Medusa
Credit:   ESO/Digitized Sky Survey 2
Source:   https://www.eso.org/public/images/eso1520c/
License:   Creative Commons Attribution 4.0 International (CC BY 4.0)

LICENSE
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) license. Expand 'spoiler' section below, for the details.

You are free to:
• Share — copy and redistribute the material in any medium or format
• Adapt — remix, transform, and build upon the material for any purpose, even commercially.

Under the following terms:
•   Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
•   ShareAlike — If you remix, transform, or build upon the material, you must distribute your contributions under the same license as the original.
•   No additional restrictions — You may not apply legal terms or technological measures that legally restrict others from doing anything the license permits.

Notices:
• You do not have to comply with the license for elements of the material in the public domain or where your use is permitted by an applicable exception or limitation.
• No warranties are given. The license may not give you all of the permissions necessary for your intended use. For example, other rights such as publicity, privacy, or moral rights may limit how you use the material.

For the full legal code, visit https://creativecommons.org/licenses/by-sa/4.0/legalcode

Closing Notes - Since this is my first attempt at a 'mod' I would love to receive your feedback, even if you hated it! I have more such skyboxes planned for KSP and will update this thread when I am ready to release each of them. Thanks!

SinfulD's Skybox Collection - The Horsehead Nebula