LDN 1622 - The "Bogeyman" Nebula...

LDN 1622

Object: Lynd's Dark Nebula (LDN) 1622 (vdB 62)
Type: Dark nebula 
Constellation: Orion
Distance: 500 light years

Date: 28th January 2020

Equipment: ATIK 460EX with EFW2, Skywatcher f5.5 Esprit 100 ED refractor, Avalon Linear mount, guiding with Lodestar X2/PHD

Subframes: 23 x 600s H-alpha, 6 x 300s each for RGB (2x2 binned), no flats/darks (hot pixel removal in Astroart).

Stellarium map showing location of LDN 1622

Lynds’ Dark Nebula (LDN 1622) is a dark molecular cloud approximately 10 light-years across on the eastern edge of the constellation of Orion close to a dim arc of nebulosity known as Barnard’s Loop, near the plane of our Milky Way Galaxy.

It has the popular (though not with me!) nickname of the Bogeyman nebula, presumably because of the shape of the lower part of the dark cloud, which resembles a hooded figure.

LDN 1622 is highlighted against the faint and more distant background of nebulosity, which is obscured by the dust of the dark nebula in front of it.

Parsamian 3, from main image.

At the bottom of the image, there can be seen evidence of a blue smudge of reflection nebulosity surrounding what appears to be a somewhat misshapen star.  This object is known as Parsamian 3 (HD288313), a pre-main-sequence star.​

Pre-main-sequence (PMS) stars are young stellar objects that have not yet begun to burn their hydrogen core, but instead are fuelled by gravitational contraction and deuterium fusion. 

As it contracts, its internal temperature rises and the resultant radiation blows away much of its birthing cocoon material of dust and gases gathered earlier in their life as a proto-star. Once this envelope has been blown away, the star becomes optically visible. The gravitation contraction continues until it begins fusing hydrogen and joins the main sequence of conventional stars.

All of the subframes in this image were plagued by noise, possibly due to high cloud. The Ha data was used as a luminance layer over the RGB combined data and had to be hit hard with noise reduction (edge preserving smooth in PSP), hence the soft look to the final image.

The Heart of the Heart: Melotte 15...

Star Cluster Melotte 15

Object: Melotte 15
Type: Open star cluster 
Constellation: Cassiopeia
Distance: 6000 light years

Date: 19th January 2020

Equipment: ATIK 460EX with EFW2, Skywatcher f5.5 Esprit 100 ED refractor, Avalon Linear mount, guiding with Lodestar X2/PHD

Subframes: 12 x 600s H-alpha, 1 x 600s OIII, no flats/darks (hot pixel removal in Astroart)

Stellarium map showing location of Melotte 15

Melotte 15 is an open cluster of stars, containing a few bright stars nearly 50 times the mass of our Sun and many more dim stars that are only a fraction of our Sun's mass.

It lies in the distant Perseus arm of our Milky Way galaxy at the centre of the Heart Nebula (IC 1805, Sharpless 2-190). Its stars provide the source of radiation that causes the surrounding clouds of hydrogen gas to fluoresce.

Across the region are strewn dark bands of dust, which are believed to be the birthplace of new stars.  Melotte 15 itself is a relatively young star cluster, estimated to be around 1.5 million years old.


I had previously imaged this part of the sky back in November 2007 as a wide field mosaic of two frames using a 135mm camera lens: the image below shows Melotte 15 in relation to the surrounding extensive nebulosity in the area.

Nebulae in the region of Melotte 15

The main image is a work in progress: clouds rolled in before I could get any RGB or more than one frame of OIII data!  Below is the stack of the 12 x 600s H-alpha frames, which gives a better idea of the detail in the region.

Melotte 15 in H-alpha light.

NGC 896 & IC 1795: The Fish-Head Nebula...

NGC 896 & IC 1795 - The Fish Head Nebula

Object: NGC 896, IC 1795
Type: Emission Nebula 
Constellation: Cassiopeia
Distance: 6000 light years

Date: 15th and 17th January 2020
Equipment: ATIK 460EX with EFW2, Skywatcher f5.5 Esprit 100 ED refractor, Avalon Linear mount, guiding with Lodestar X2/PHD

Subframes: 25 x 300s H-alpha, 20 x 300s OIII (2x2 binned), 6 x 300s each for RGB (2x2 binned), no flats/darks (hot pixel removal in Astroart).

Stellarium map showing location of IC 1745

High in the winter north-western sky (close to the Double Cluster in Perseus), NGC 896 is a relatively bright knot of nebulosity which forms part of a wider area of nebulosity designated as IC 1795, itself part of the larger IC 1805/IC 1848 complex ( the “Heart and Soul Nebula”). It is approximately 20 arc-seconds across, appearing to occupy an area in the sky around two-thirds of the full moon. 

Discovered by William Herschel in 1787, NGC 896 lies at the edge of a large molecular cloud located in the distant Perseus spiral arm of the Milky Way Galaxy. The area around NGC 896 is also a strong source of radio emissions.

The hydrogen alpha frames were taken on the 15th. I took some 300s unbinned OIII subs the same night, but a combination of high haze and a rising gibbous moon washed them out. The OIII signal of IC 1795 is also comparatively weak compared to the Ha, so I went for 2x2 binned subs at the next available opportunity.  In hindsight, I should have gone for longer exposures in narrowband as both Ha and OIII stacks were pretty noisy, as were the RGB subs.

I prepared an RGB colour frame from red, green and blue stacks and a HOO frame from the narrow band stacks, both in PaintShop Pro.  I then combined the two to give a balanced colour mix, and then overlaid the Ha stack as a luminance layer. Selective sharpening and curves in PaintShop gave the final image.  I had to hit the narrowband stacks with noise reduction a bit harder than I would have liked as they were fairly noisy, so the stars are a bit fuzzy. This is a bit frustrating as sky conditions were (for once) excellent on the 17th, and I could easily have taken much longer exposures.

I had previously imaged this area in December 2007 as a two-frame wide-field mosaic using a 135mm camera lens. The image below shows the relation of IC 1795 to IC 1805 and IC 1848.

Emission nebulae IC 1848, IC 1805 and IC 1795 in Cassiopeia.