Category: Nebula

I haven’t posted here for a while now. I post most initial looks at data sets on the Breckland Facebook page so this is the place to visit for the most up to date information. However, I will endeavour to keep this page reasonably current.

Last Saturday evening was crisp and clear with a waning moon. As I have an interest in dark dusty things I selected Barnard 15 as the target. Outside of the main plane of the Milky Way, this dark nebula is very black and sharply defined against a background of uniformly bright stars. Also in the frame are Barnard 16 & 17 along with much fainter dust clouds.

The lack of stars in front of B15 indicate that it’s pretty close to us. These clouds are dark due to the presence of sub-micrometre dust particles coated in frozen nitrogen and carbon monoxide. Also present is molecular hydrogen, atomic helium and C¹⁸O along with a cocktail of exotic molecules.

This is an update of the image I posted on Facebook with a more aggressive noise reduction process early in processing. Consequently, I’ve been able to stretch the contrast more to emphasise the fainter dust structures and apply a stronger colour saturation to the stars.

37 individual exposures of 10 minutes each were gathered before the moon rose for a total of a little over 6 hours.

After getting back to using my Astrotrac at the club’s Haw Wood star party I decided I’d like to do some more of the same at Kelling. There was an ulterior motive as well; since building and setting up the observatory there’s rather more work involved in stripping it all down to take into the field.

Once committed to the Astrotrac the choice of lens was made. The Canon 75-300 zoom works really well at shorter focal lengths and is ideally suited to unguided imaging with the Astrotrac. The camera was my QHY9 which had to be removed from it’s permanent home on the back of the Tak.

Once the sun set on Friday evening the sky cleared quite nicely, rather hazy with a lot of moisture but better than a lot of the skies we’ve had this year. As my pitch was completely over-hung with trees I negotiated with a neighbour for a corner of theirs. Once setup, Cygnus was close to the zenith so I started there aiming the red-dot finder between Deneb and Sadr taking some short exposures and then re-framing. Once done, I set a sequence of 5 minute exposures and left the Astrotrac to do it’s thing for the remainder of it’s 2 hour tracking time.

Once that had completed I moved the setup along the Milky Way towards Lacerta aiming for the dark nebula B168. The procedure was repeated and then, finally I moved to Auriga. By this time two things were apparent; 1) The skies were closing down and 2), after a week at work I was ready for bed so I cut this session short and headed for the van. Packing up with the Astrotrac consists simply of splitting it into parts small enough to fit in the van and stowing them in the cab in front of the seats.

So, just one night of imaging this time but rather more hours than we got at Haw Wood. That’s just the way it goes.

A conversation at the club about the problems caused by bright stars in photographs of faint objects led to a couple of sessions imaging IC443, the Jellyfish, in Gemini. Eta Gemini is a magnitude 3.3 star alongside the supernova remnant. Photo opportunities for this object this year are closing fast as it’s culminating as it gets dark. I’ve managed two sessions during this New Moon period for a total of 3hrs 20 minutes in my usual 10 minute subs.

Early attempts at processing were rather heavy handed with noise reduction so I’ve toned that down in this version and applied most of it when the image was still in it’s linear form. This has left more of the finer nebula structure intact.

A lot of the images of this nebula on the Internet are done with narrow band filters which suppress Eta Gemini but when using a One Shot Colour camera the star rather dominates. I’ve toned it down using the StarhaloReducer script in Pixinsight but I could probably be rather more aggressive with this.

I’ve been meaning to capture a new version of this nebula as the previous one, done on the Astrotrac exhibited quite pronounced trailing. This will be one of my final images done with the WO Zenithstar 70 as I’ve purchased an ex-demo Takahashi Baby-Q (FSQ85-ED). I’ve enjoyed working with the Zenithstar and I’ve learnt a lot in the years of using it but the time has come to upgrade to something with rather better colour correction and a flatter field.

Fifteen 10 minute subframes using my QHY9C.

While at Kelling Heath in October I took advantage of the darker skies to leave the scope collecting data until dawn of this area just to the west of Rigel in Orion. The Witch Head is very faint and being low in the southern sky is swamped by light pollution at home. This is a re-processed version of the image that appeared on the club Facebook page some time ago and I was planning to add more data over the course of the winter. However, having just purchased a new refractor this isn’t going to happen and I’ll start over with the new telescope.

Even from Kelling there were severe light pollution gradients on these images which I removed using Pixinsight. The club’s dark skies site at Haw Wood on the Suffolk coast will probably be the location of choice for any new attempt.

This is another image from the beginning of last week and I’ve reprocessed this from the version that I posted on the Breckland Facebook page. The background stars are a little less harsh, I’ve increased the contrast in the nebula and it’s a slightly closer crop. This is nine 10 minute subframes.

NGC 1499 in Perseus is a large, bright emission nebula created by the bright blue star Xi Persei irradiating a hydrogen gas cloud with UV. The brightest part of the nebula spans 5 degrees on the sky and just fits on the sensor of my QHY9 when used with my Zenithstar 70 and 0.8x reducer.

This is 110 minutes of 10 minute frames captured on Tuesday evening, processed with Pixinsight.

Friday night was clear until the moon rose at about midnight so I took the opportunity to add another 2 hours of data to that I’ve already collected on NGC 7000. The mount tracked well despite the brisk breeze and all 12 10 minute frames were good.

After calibration and stacking in Maxim DL, I opened Pixinsight for further processing. I’ve been playing with the Masked Stretch script but this has an unfortunate side effect of emphasizing the blue halos around bright stars and I haven’t worked out how to reduce this effect yet, so I used a basic histogram stretch. This was followed by an HDRMultiscaleTransform to push down some of the highlights and a LocalHistogramEqualisation (using a mask to protect the stars) to increase the contrast on dark structures. A morphological transform was used to reduce the intensity of the field stars.

After this, a TGVDenoise and saturation curves application completed the image.