The Rotten Fish Nebula | LDN 1251

The Rotten Fish Nebula LDN 1251 in Cepheus, imaged from a light polluted urban sky

THE ROTTEN FISH NEBULA

LDN 1251 • Dark nebula • Cepheus • 1000 light-years from Earth


🗓️
Sep & Oct 2023

Overview

The Rotten Fish Nebula is a dark nebula, a type of object defined by what it obscures rather than what it emits. The darkest regions in this image are dense clouds of gas and dust that block the light from background stars, creating areas that appear almost starless. Interwoven with these shadows are faint wisps of nebulosity that reflect light from nearby stars. The object is also known as the Angler Fish Nebula, and is catalogued as LDN 1251.

Background

This is an incredibly challenging target to tackle from city skies! It’s very faint, and is actually close to the Shark Nebula. Like the Shark, the Rotten Fish is a broadband target and so doesn’t benefit from narrowband filters like the Optolong L-Ultimate. So, very long integration times are needed to achieve a respectable signal-to-noise ratio — although this image is a bit of an experiment…

Optolong Optics have kindly sent me one of their brand new filters, the L-Quad Enhance. This is a broadband light pollution filter, so in theory ideal for targets like the Rotten Fish. Click here to read my review. For this target, I captured 10 hours of data with no filter; and 14 hours with the L-Quad Enhance. I’ll show a fair comparison in the eventual review, but for now this image is the result of integrating all 24 hours. To be honest it could do with longer, as it’s still fairly noisy, but hopefully that’s not too noticeable so long as you’re not pixel-peeping. I was also plagued by tech issues — specifically, my camera disconnecting — that knocked a few clear skies on the head.

The Rotten Fish Nebula LDN 1251 in Cepheus, imaged from a light polluted urban sky
Framed astrophoto taken from a light-polluted city, available to buy as a fine art print

Close-ups

  • Close-up view of the "head" of the Rotten Fish
  • Close-up view of the "tail" of the Rotten Fish
  • Close-up view showing dark nebulosity

Imaging details

Date

22 September to 15 October 2023

Location

Bristol, UK (Bortle 8)

Telescope

Askar 130PHQ Flatfield Astrograph

Camera

ZWO ASI 2600MC Pro

Mount

Sky-Watcher EQ6-R Pro

Guiding

WO 50mm + ZWO ASI 120MM Mini

Control

ASIAIR Plus

Software

PixInsight, Lightroom

Image by

Lee Pullen

Filter

Channels

Exposure

No filter

RGB

300 × 2-minutes (10 hours)

Optolong L-Quad Enhance

RGB

420 × 2-minutes (14 hours)

24 hours

Imaging details

Date
22 September to 15 October 2023

Location
Bristol, UK (Bortle 8)

Telescope
Askar 130PHQ Flatfield Astrograph

Camera
ZWO ASI 2600MC Pro

Mount
Sky-Watcher EQ6-R Pro

Guiding
WO 50mm + ZWO ASI 120MM Mini

Control
ASIAIR Plus

Software
PixInsight, Lightroom

Image by
Lee Pullen

Filters

No filter
RGB
300 × 2-minutes (10 hours)

Optolong L-Quad Enhance
RGB
420 × 2-minutes (14 hours)

Total exposure: 24 hours

Kit list

This is the equipment I used to capture the image.
Affiliate links help support the site at no extra cost to you.

William Optics 50mm with ROTO Lock guidescope

Guidescope: William Optics 50mm with ROTO Lock
Read my review

Buy from Astroshop.eu
Buy from High Point Scientific

Processing

I used GraXpert for the first time when processing this image. It’s a free piece of software that removes gradients from an image (like ABE or DBE in PixInsight). It’s not a PixInsight plugin, so needs to be run separately. I tried the beta, which features an AI algorithm that I found to be effective. If you want more info, I recommend this video by YouTuber Cuiv.

Example astrophotography image promoting one-to-one online astrophotography masterclasses

Example source data

Here are example single subframes and freshly integrated stacks, just with simple stretches applied.

Seestar S50 image

Here’s an image of the Rotten Fish Nebula taken using a Seestar S50 telescope. It’s just about possible to make out the head of the fish. The easiest point of reference is the brightest star, easily visible in this Seestar photo, and the main image.






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