This image is the result of a spontaneous decision to pick up my camera and tracker once I saw that the night might be clear.

I’ve never given up on trying to see how much nebulosity I can pull out from the sky using my stock DSLR, especially the famous Hydrogen alpha line. Of course, a modified camera will collect more Ha signal within the same time but it’s a myth that stock DSLRs are blind in Ha.
When you browse through the image, you can clearly see the North America and Pelican nebula, the Gamma Cygni nebula, the Crescent nebula, the Veil nebulae and the Tulip nebula to name a few well known ones.

From the present result, I’m personally satisfied with what is possible with the Canon EOS250D. To keep unwanted signal out, I’ve given the IDAS LPS-D3 filter a try (link to manufacturer’s website). It has some interesting properties. Besides filtering out the classical yellowish sodium light, it’s also optimised to subpress the blue peak of nowadays “white” LEDs in addition to the greenish sky glow.

Although I’m living at a (fortunate) Bortle 4 place, I think that the data and result benefited from the use of the filter.

Since the filter gives a cyan colour cast, I was asking myself how I might get the white balance done (more or less correctly). As it turned out, I wasn’t as difficult as I though. After integrating the data in PixInsight, I’ve selected a small patch of sky which I believed represented the sky background very accurately, i.e., which is free of signal but only sky background. I applied a background neutralization on this patch to have the intensity levels scaled as, like always, the green channel of the OSC was dominant. With this, the background was roughly scaled. I then applied the simple ColorCalibration process from PI which I tuned to select all data above the background as signal and the rest as background. With that a white balance was done which gave a quite well known and natural look. The Ha came out in a nice red while most stars were white.

From this on, I turned the linear image over to Affinity Photo where I performed the final steps of processing. A little denoise plus a histogram transformation (as it’s done in PI). Since Affinity works in a non-destructive way, I used its function to remove background gradients on the linear image while seeing it stretched through HT. It’s remarkably well implemented. As far as I can tell, it doesn’t seem to apply a certain function order for the whole background gradient but it’s an interpolation with varying degree (I suppose it’s a Bezier curve) from measurement point to measurement point. That helped me to remove some colour cast from the sky’s background. Finally, some selective colour saturation, which I hope I didn’t exaggerate and voila, image done!

For calibration, I’m only using bias frames and flats. Notice, that I’m using a modest ISO of 400 to maximise dynamic range and keep read noise to minimum. ISO400 is a decent balance for this camera. Checkout the website photonstophotos.net for information on your camera. It will help you finding the sweet spot for imaging.

To keep the stars in a fairly good condition, I reduced the aperture to f/3.5. Still on a 50mm lens, this is a 14mm aperture.

Long story short, I think it’s an image which is worth to be presented, so I hope you find it interesting and let me know your opinion.

Clear skies,
Björn