Hello,

This is my attempt at the very faint planetary nebula KK 26.

The nebula was imaged using narrow band filters, with the Edge HD11 and ASI2600MM Pro at an image scale of 0.26"/pixel.

STX was used to remove the stars from each channel. The 3 NB channels were processed individually before being combined to create a colourised, starless narrow band image. It took 4 attempts to get the processing of the NB images as I wanted them. This is a very faint object and even after 10 hours or more per channel, the signal in each channel was not very high. Initially I had tried BXT and NXT but came to the conclusion that there wasn’t enough signal to justify deconvolution and not enough for NXT to distinguish between real signal and noise. In the end I used the TVG noise reduction techniques described by @Jon Rista (see PixInsights Tips: Effective Noise Reduction (Part 2 of 3) | Nature Photography (jonrista.com)) . Each channel was stretched using Masked Stretch, exponential stretches of various degrees (depending on the channel) followed by some careful boosting of detail at different scales using MLT. Finally, the 3 channels were combined using the Narrowband colour script in PixInsight with the following settings:

• Red = Ha: hue 90, saturation 1
• Green = N2: hue 353, saturation 1
• Blue = O3: hue 203.1, saturation 1

For the stars I used a QHY5III715C and William Optics Zenithstar 61 II with field flattener, which is piggy backed on the Edge HD. The idea was to get RGB data using the Zenithstar 61, while the Edge HD 11 captures the NB data. This image is by way of an experiment with this approach and the equipment only really came together after I had already started collecting data for this project, hence just the 2 hours and 27.5 minutes of RGB data. Next time there will be much more.

The OSC star image was combined with the colour narrow band image using the “Align by Coordinates” script that referenced the Ha stars from the narrow band Ha image. On  my first attempt using the OSC star image, nasty halos appeared around the 3 very bright stars on the left hand side. The final RGB star image was created using the Ha stars as a luminance channel, combined with the a and b components extracted from the OSC star image. Although this worked, I think that it would be better for the focal lengths to be better matched, so on the next project I will try the Zenithstar with a x3 tele-extender and the QHY5III715C to get a much closer match to the Edge HD/ASI2600 image scale. This will require longer exposures, but in some ways that’s a good thing! I don’t think my computer could handle 10+ hours’ worth of 10s exposures! However, dark current may become more of an issue with the uncooled chip. What I really want is a cooled version of the QHY5III715C (or the equivalent from one of the other manufactures, I’m not fussy).

O3 dominates in the spectra of this object, hence the predominance of blue, but it does also contain Ha and N2 components as well. I deliberately left the N2 green as I felt this gave a more subtle shading between the Ha/N2 regions.

So, as to KK 26 itself. Unfortunately, there is not much to say about it, as it hasn’t been studied that much by the professionals. It was first miscatalogued as a dwarf galaxy in 1995 (see Visual search for galaxies near the northern crossing of the Supergalactic Plane by the Milky Way | Monthly Notices of the Royal Astronomical Society | Oxford Academic (oup.com)). But it was reclassified as a PNe by a later survey (see An Emission Line Survey of Nearby Dwarf Galaxy Candidates - NASA/ADS (harvard.edu)).

It hasn’t had much love from the amateur community either with very few images of it being around. That being said, there are a couple of fine images to be found on the internet: one by @Peter Goodhew with 87 hours of data (87 hours to reveal Karachentseva-Karachentsev 26 in Camelopardalis (Peter Goodhew) - AstroBin) and one from The Hole in the Trees Skybox observatory  (KK 26 photo - The Hole in the Trees Skybox photos at pbase.com).

This PNe does remind me somewhat of M76 without the lobes. During processing of the starless NB data I could just make out some wispy nebulosity on the northern (bottom) side of the nebula, but when mixing it with the RGB data I couldn’t really bring it out without ruining the rest of the image, so I have left it out in the final image shown here. KK 26’s shape suggests (warning: idle speculation follows) to me that the lobes have already dispersed back into the void, or the central star as become too weak to ionise them. So, I wonder if its faintness means it’s an old PNe who’s lobes have dissipated/faded away, leaving just the equatorial disk still visible. Unfortunately, the distance is unknown, so is it faint due to its distance (at 106” it’s not that small for a PNe, so unlikely) or is it due to its age?

Anyway, I hope you enjoy the picture and as always, comments and criticism are welcome.

Cheers,
Ian