This is a Telescope Live dataset project, acquired by the SPA-1 CMOS (Takahashi 106FSQ refractor in Spain).  My mount is still in the 'shop' waiting on parts (electronics), so nothing from my own riig at this time.

My prior imaging of the California Nebula was with my 2600MC OSC camera and a short 2 hr exposure window, with the L-Extreme dual band filter.  It dual bands are Ha and Oiii, and there is almost no Oiii from this object with leaves you with a primarily red image (with an OSC palette) or the tedious and uninspiring work to create synthetic G and B channels from next to no data to blend with the Red (Ha).  So it is not a target I had much enthusiasm for after my first two acquisitions.

Being reliant on Telescope Live at the moment, I saw the HSO dataset from the SPA-1 OTA and decided to give it a try.  I did have to eliminate about 1/3rd of the frames due to clouds, but still had enough to work with, total integration time is approx 4.5 hrs (a little less).  It needs much more to get more of the faint Oiii component.  I was surprised at the strength of the Sii channel, and NOT surprised by the almost non-existent Oiii channel.  I did note that all three showed a slight halo around the object even after DBE (GraXpert) application.  The prominence of the halo was inverse to the signal strength of the channel, so don't know if this was an observing/atmospheric phenomenon or something else.  However the compiled SHO image did reveal dim nebula features within the 'halo', so not really definitive on a rationale for it.

I created a Lum mask from the Ha master to enhance some of the detail in the 'finished' image.  GraXpert, BXT, SXT, and NXT all contributed to both improved results and reduced workload, these tools should be in everyone's toolbox.

The end result is definitely NOT a monocular swath of boredom.  HDR helped bring out detail and slight 3D effect within the brighter nebula structure.  Color Mask + CRV helped to bring out a spectrum of color ranges not available in OSC imaging.  You may note that I don't mention GHS.  I've used it and I think PixInsight users should be familiar with it.  It is not a tool that is appropriate to every object, while I find Bill Blankenship's  Linked and Unlinked STF scripts provide a workable end result for everything.  That doesn't mean you won't need or want to tweak with CRVs or other tools, but you can be assured of starting from a solid base stretch.  IMO - YMMV.

The uploaded image is a jpeg.  The PNG version was still close to 73mb in size - one of the downfalls of working with data from full frame astronomy cameras is the size of the image files.

View, Like, and Comment below, let me know what you think!!!

From Wikipedia:

The California Nebula (NGC 1499/Sh2-220) is an emission nebula located in the constellation Perseus. Its name comes from its resemblance to the outline of the US State of California in long exposure photographs. It is almost 2.5° long on the sky and, because of its very low surface brightness, it is extremely difficult to observe visually. It can be observed with a Hα filter (isolates the Hα line at 656 nm) or Hβ filter (isolates the Hβ line at 486 nm) in a rich-field telescope under dark skies.=10.5px   It lies at a distance of about 1,000 light years from Earth. Its fluorescence is due to excitation of the Hβ line in the nebula by the nearby prodigiously energetic O7 star, Xi Persei (also known as Menkib).
The California Nebula was discovered by E. E. Barnard in 1884.By coincidence, the California Nebula transits in the zenith in central California as the latitude matches the declination of the object.