The Shark Nebula
LDN 1235 • Dark nebula • Cepheus • 650 light-years from Earth
🔭
Askar FRA400
📷
ZWO 2600MC Pro
🌃
Bortle 8
⏱️
20 hours
🗓️
April & May 2022
Overview
The Shark Nebula, also known as LDN 1235, is a faint cloud of interstellar gas and dust stretching roughly 15 light years from head to tail. It’s a dark nebula, visible only by the way it blocks and subtly reflects background starlight rather than emitting light of its own. With extremely low surface brightness, the Shark Nebula is a demanding target for astrophotography and particularly challenging to image from light-polluted urban skies.
Background
This was definitely the toughest target I’ve imaged to date! Astrophotographers wanting to capture the Shark Nebula tend to travel to the darkest skies possible, but my approach is always to try from a city and test what’s possible. For this, I used my faithful Askar FRA400 telescope and ZWO ASI 2600MC PRO camera. Being a broadband target, I didn’t use any filters, instead relying on a long total integration time. Well, I can now safely conclude the Shark can be imaged from Bortle 8 skies, but I wouldn’t necessarily recommend it!
It’s so incredibly faint that it didn’t show up at all in single 2-minute subs, and can’t really be seen even in a freshly integrated 20-hour image. Check the source data near the end of this page to see what I mean!
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Explore the field
Objects in this field 9 objects
9 objects
No matching objects.
- Shark NebulaLDN 1235
- Dark nebula
- vdB 150
- Reflection nebulaAlso catalogued as DG 178 · LBN 546
- vdB 149
- Reflection nebulaAlso catalogued as DG 177 · LBN 541
- Cr 471
- Open cluster
- 24 Cep
- StarAlso catalogued as HR 8468 · HD 210807 · HIP 109400
- A G-type giant star.
- 16 Cep
- StarAlso catalogued as HR 8400 · HD 209369 · HIP 108535
- An F-type main-sequence star.
- 78 Dra
- StarAlso catalogued as HR 8324 · HD 207130 · HIP 107230
- A K-type giant star.
- HR 8493
- Double starAlso catalogued as HD 211300 · HIP 109659
- A double star with a catalogued separation of 28.8 arcseconds.
- LBN 535
- HII region
About the labels and credits
Positions and outlines are calculated from a plate solution of this photograph. Outlines are catalogue guides and may not follow every visible filament. Additional catalogue objects may be faint or indistinct in this exposure.
Plate solving and annotation data: SkySolver, by Dominik Sito. Stars: Gaia DR3 and Hipparcos (ESA). Deep-sky data: OpenNGC © Mattia Verga (CC BY-SA 4.0), SIMBAD and VizieR (CDS). Names: Wikipedia (CC BY-SA 4.0) and IAU WGSN. Catalogue overlay adaptations, including styling and selected display names, are shared under CC BY-SA 4.0. Photograph © Lee Pullen.
Imaging details
- Total exposure
- 20 hours
- Dates captured
- April & May 2022
- Location and sky
- Bristol, UK (Bortle 8)
Equipment and software
- Telescope
- Askar FRA400
- Camera
- ZWO ASI 2600MC Pro
- Mount
- Orion Sirius EQ-G
- Guiding
- WO 32mm + ZWO ASI 120MM Mini
- Control
- ASIAIR Plus
- Software
- PixInsight, Lightroom
- Image by
- Lee Pullen
Exposure by filter
No filter
- Channels
- RGB
- Subframes
- 600 × 2 minutes
- Integration
- 20 hours
View subframe and stack
Single subframe and integrated stack, both with a simple stretch applied.
Kit list
This is the equipment I used to capture the image.
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Telescope: Askar FRA400
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Camera: ZWO ASI 2600MC Pro
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Guidescope: William Optics 32mm Slide-Base Uniguide
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Guidecam: ZWO ASI 120MM Mini
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Control: ASIAIR Plus
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Buy from Astroshop.eu
Buy from High Point Scientific
Processing
Once I began processing the data it was possible to draw out some details. The signal was still very weak though, and I ran into many problems.
First, noise. Normally I use Topaz DeNoise AI, but I’d heard good things about the recently released NoiseXTerminator plug-in for PixInsight. I gave it a go and wow, it’s impressive. See below for a before / after slider comparison. NoiseXTerminator will be my go-to noise reduction method from now on.
The next problem was controlling star sizes. There are countless pin-pricks of light in the image, and quite a few larger stars too. I find that Generalised Hyperbolic Stretch does an excellent job of stretching to non-linear while controlling stars, so used that to good effect. I then used StarNet2 to remove the stars, and did a bit of work to reduce their number before adding them back in.
The third big problem was with colour. To get any detail I was mangling the data quite hard, and as a result was producing lurid colours. I wrestled with this for a while, and in the end did a fair amount of desaturation. This helped, but unfortunately removed some nice blue nebulosity. Oh well.
In all, this was a really tough target to image and process. I can see that dark skies would really help to produce a much better end result, but hey, at least it’s possible for city astrophotographers to glimpse the Shark too.
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Seestar S50 image
This photo of the Shark Nebula was taken using my Seestar S50 telescope. It’s very difficult to make out, even with an integration time of over two hours.
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