NGC7293 - The Helix Nebula
The Helix Nebula (also known as NGC 7293) is a planetary nebula located in the constellation Aquarius. This object is one of the closest of all the bright planetary nebulae to Earth. Measured by the Gaia mission, the nebula is roughly 650 light-years away. It is similar in appearance to the Cat’s Eye Nebula and the Ring Nebula. The Helix Nebula has sometimes been referred to as the “Eye of God” as well as the “Eye of Sauron”
The Helix Nebula was formed by an intermediate to low-mass star shedding it’s outer layers near the end of it’s evolution. Gases from the star in the surrounding space appear, from our vantage point, as if we are looking down a helix structure. The remnant central stellar core is destined to become a white dwarf star. The glow of the central star is so energetic that it causes the previously expelled gases to glow brightly.
Now that we’re past the science bit, where do I start with this?
After my last astro outing to capture M20, I spent a lot of time taking my mount apart to remove as much of the friction, backlash and general “not working well” as I could. I ended up re-greasing the worm drives, the taper bearings in both axes and getting the mount working as smoothly as I could. I think the RA axis is still a bit “sticky” in one area and I’m hoping that further usage will get rid of that. The worm drive was also slightly “tight” compared to the DEC axis and I’ve since loosened the locking ring that holds it in place. Hopefully this won’t introduce any backlash.
I also spent time rebuilding the dark library for the guide camera. The number of “hot” pixels it has now is just staggering. How many? So many that the guiding algorithm started trying to use them as guide stars. The fact that the guide scope was slightly out of focus did not help matters at all.
I am also suspecting that the latest iterations of KStars/Ekos has a few bugs in it. My guiding used to be perfect - quick calibration, accurate guiding and the ability to “dither”. Since the last update, my guiding has been crap - unable to calibrate, and always losing track of guide stars after a “dither” operation.
Where ‘SEP - MultiStar’ used to be my chosen guiding algorithm, I’ve been using ‘Smart’ and it’s been much better. So until I can get this resolved, I’ll stick with ‘Smart’ (rather than ‘crap’) guiding. That’s not to say ‘Smart’ is any better - the guiding still turned to crap and required an auto-recalibration after each dither operation. So something is not right. Somewhere…
I’ll have to see if I can roll things back to an older version, or move to a different guiding package. (PHD2 is supported by KStars/Ekos and has some pretty cool features that might make life easier. I’ll have to see.)
Anyway, after all that, I was confident that I could capture some good images - despite dodgy guiding.
So, the skies cleared for once, my target was visible all night long, and I didn’t have to go to work the next day. Except for the full moon. Oops. And my target was very close to the moon. Double oops.
Not to worry, the L-Enhance filter was able to strip out some/most of the moonlight. The individual light frames were quite washed out and didn’t have much contrast. (I had a frame from 2 weeks ago and the difference in contrast is very noticeable.)
I only got a bit over an hour of data this time because I decided the moon was getting too close to my target. So I bailed out and packed everything away.
Surprisingly, the stacked data came out a lot better than I thought it would. Sure, the amount of detail is pretty low, and the contrast between the nebula and the background could be better.
Affinity’s noise reduction routine made a great job of killing all the salt-n-pepper speckles, and I was then able to tweak the brightness/contrast and colour saturation to get something that looked half-way decent. Similarly, the starmask got a similar treatment that gave me good contrast between the stars and the background without too much fringing or bloat.
Overall, I’m happy with the image. It came out quite well and I can’t wait to try this one again when conditions are better.
Image data:
- Gain: 100
- Offset: 10
- Temperature: 0 degrees C
- Exposure: 180 seconds
- Frames: 26 Lights, 25 Darks, 25 each of Flats and DarkFlats (78 minutes integration in total)
- Filter: L-Enhance
- Processed with SiriL (stacking, pre-processing and star removal with Starnet++) then finished in Affinity Photo v2
Equipment: SW72ED @ 420mm / HEQ5-Pro / ASI183MC-Pro / SV165+SV305 / Kstars/Ekos