Hemisphere:  Northern  ·  Constellation: Cepheus (Cep)  ·  Contains:  The star 16Cep  ·  The star 24Cep
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LDN1235: Dust around the Shark Nebula, 


            Alberto Ibañez
LDN1235: Dust around the Shark Nebula
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LDN1235: Dust around the Shark Nebula

Technical card

Imaging telescopes or lenses: Borg 101ED f/4

Imaging cameras: QHYCCD 163M

Mounts: SkyWatcher HEQ 5 Rowan Belt Mod

Guiding telescopes or lenses: DYI Guidescope

Guiding cameras: QHYCCD QHY5 R - II

Software: PinInsight 1.8  ·  Main Sequence Software Sequence Generator PRO  ·  Stellarium  ·  PHD2 PHD 2.6.5

Filters: Optolong B 36mm  ·  Optolong G 36mm  ·  Optolong R 36mm  ·  Optolong L 36mm

Accessory: QHYCCD QHYCFW2-M-UltraSlim

Dates:Aug. 19, 2020

Optolong B 36mm: 44x300" (gain: 174.00) -10C bin 1x1
Optolong G 36mm: 44x300" (gain: 174.00) -10C bin 1x1
Optolong L 36mm: 163x300" (gain: 174.00) -10C bin 1x1
Optolong R 36mm: 48x300" (gain: 174.00) -10C bin 1x1

Integration: 24.9 hours

Darks: ~50

Flats: ~15

Flat darks: ~15

Avg. Moon age: 0.44 days

Avg. Moon phase: 0.22%

Bortle Dark-Sky Scale: 3.00

Temperature: 15.00

Basic astrometry details

Astrometry.net job: 4236264

RA center: 22h 9' 32"

DEC center: +73° 7' 26"

Pixel scale: 1.875 arcsec/pixel

Orientation: 49.595 degrees

Field radius: 1.451 degrees

Resolution: 4438x3368

Locations: Alto Mijares Observatory, Castellon, Castellon, Spain

Data source: Traveller


2020 Summer Project (version: LRGB_eroRGB_v5nr_redo5)

Adquisition Notes:
The adquisition was my first serious attempt imaging outdoors. I drove 30km from my second's residence (suppossed SQM21.5) until I found a place quite high (1400m) and supposed to be very dark (SQM21.87). The idea was to stay 2 nights gathering photons, but also testing my AstroHub 2.0 with a 100Ah LifePo4 battery and a 300W solar panel. Everything worked like a charm and now I know that I can rest for days or weeks with plenty of power. I gathered 8h of LRGB on this dark site, and the rest was taken from my backyard.

Processing Notes:
I needed 6 months to achieve the result I was looking for on this target. It has been a really challenging processing because the goal of the image wasn't the shark nebula itself but the surrounding dust. To pull out the dust was not a problem itsef, because the data was pretty clean. The real difficulty was the lack of contrast and to reduce the stars.
The processing of the LRGB non-linear stage has been quite simple using mainly curves and histogram transformations, no LHE, MMT, MLT or HDRMT enhacements.
The hard work was done previously, where I implemented new techniques that I think that worth to mention:

-Multiscale Gradient Removal: I had very bad gradients that didn't allowed me to push the data. I was struggling with this form months... and then I used this procedure, and fixed it in 1h. Simply perfect.

-L to RGB starmatch:
L channel always has higher FWHM so stars grow when combining L with RGB. In this image was specially disturbing because the nebula, and the surrounding background is very faint so it needed and agressive star reduction. To try to avoid artifacts, I worked on the L channel before combining and I used a special contour mask produced by the difference between L stars and RGB ones, to apply erosion over the L stars. After this "L to RGB starmatch" there were 3 additional iterations of erosion, one of them specifically focused on small stars, another on medium stars, and a third overall to compensate a late black point adjustment.

-Image Slicing:
Although no Starnet++ was applied to this image, it was used to create specific masks using the procedure that I published recently. For example to create an absolute starmask that I sliced in different star sizes to process them individually, or many other masks to isolate the DSOs involved in the image and be able to process them properly.
A discussion can be found here:
...and a more in deep information of this procedure can be found in my website:

-Refining procedure:
I used a procedure to refine the processing workflow using Process Containers. It allowed to change specific parameters of specific processes and see the influence in the final result in an easy and quick way. I'm just finishing a tutorial about it.