The weather really has been lousy this year! I’ve only managed ten imaging sessions in the past eight months; that’s just over one a month! Everyone in the astro-community has also complained at how despondent they have become due to constant clouds, or wild fires or raging storms. Even I have to admit, I’ve struggled to keep up the excitement of an impending clear night, only for it to be ruined by yet another cloudy evening.
Fortunately, this week has brought high-pressure weather systems over the UK, which finally resulted in a series of forecasted clear nights. Also fortunately, I’d got the week off work to make the most of it! It also gave me another night to test out IDAS NBZ filter on another target, IC 1848 – The Soul Nebula. I will come back to the Cygnus Wall, just fancied a little change.
The Soul Nebula, located 6500 light years away, is a large emission nebula found in the constellation Cassiopeia. IC 1848 and it’s sister nebula, the Heart Nebula (IC 1805), is located to the west of the characteristic “W” star asterism. Being around 100 light years from tip-to tip, if the nebula was a visual target it would span an equivalent area of four full moons. There are numerous star clusters within the nebula; CR 34, 632 and 634, including IC 1848, which the nebula is commonly designated as.
Learning from my previous imaging session on the 16th July, I decided to try out my own suggestion of 600-second exposures, and it was to great success!
At first I tried 600-seconds at ISO800, but the histogram curve was the same as it was previously; too far to the left, which resulted in an image that was way too dark. However ISO1600 resulted in a perfect curve which produced a great single sub-exposure.
As can be seen from the image above, the red Hydrogen-Alpha silhouette of the Soul Nebula can be seen in just a single image. Happy with the results, I stuck with those settings for the rest of the evening.
Throughout the entire evening, the one thing that kept blowing my mind was the AZ-EQ6-GT mount. It never put a foot wrong all night, not going above 0.70″ total RMS, and recovered from a dither within seconds, instead of minutes with my old EQ5 Pro. I’m so glad I upgraded!
If you can see the total RMS error on the image above, it reads only 0.5″, and this was near the end of a 10-minute exposure. To put that into perspective:
- 1-arc-minute = 1/60th of a degree
- 1-arc-second = 1/60th of an arc-minute
The mount was guiding at half an arc-second for 10 minutes straight – that’s 0.00013889º! I honestly believe that this mount could do 1-hour exposures, without breaking a sweat! I can only imagine what the accuracy of the Sky-Watcher EQ8-R would be like with my little 130-PDS.
Over the period of the first night, I managed to capture 13 exposures, equalling 2 hours 10 minutes. I started at at 22:08, just before astro-darkness with perfectly clear skies, however by 1AM the clouds were beginning to roll in, and by ten-past it was full blanket cloud cover, which never cleared. After 15 minutes of waiting for it clear, I called it a night, parked the scope and started taking the full set of calibration frames.
Editing this one was a little difficult when compared with my previous images, as the nebula fills the full image frame. Gradients were difficult to remove due to this, as there was very little area to clone out the nebula in Photoshop. However, with some nifty editing skills that I have developed, I managed to overcome those issues.
Overall, for only 2 hours on this target, I’m pleased with this image, but the high amount of noise in my images is starting to increasingly annoy me. When compared with other images that can be found on AstroBin and social media, their images seem ultra smooth and polished, whereas mine are grainy and pixelated. Admittedly, I’m only using a DSLR and comparing it to a dedicated cooled astronomy camera is like comparing apples to oranges. It is becoming increasingly apparent that the cooled route is the next step in my journey. Unfortunately though, that will have to wait until next year.
Over the next few clear nights, I’ll be adding more data onto this target to try and improve the signal-to-noise ratio, so we shall see what the next version will look like.
Till then, clear skies!