M35 and NGC2158 - two open star clusters apparently side by side in the Constellation Gemini.

 

M35 and NGC2158 - two open star clusters apparently side by side in the night sky but
Ngc 2158 is light years further away than Messier 35. Image captured with the Seestar S30 'smartscope'. The lower image is a 'crop' of the one above and shows more detail particularly that associated with the fainter Ngc 2158.

                                                         

 " Kurt decided to re-work the data produced by our Seestar S30 of M35 and Ngc 2158 in the constellation Gemini" - Joel Cairo CEO of the JPO.

Messier 35 and NGC 2158: Scientific Description

By G.Gemini Coms Manager at the JPO.

An analysis of the visual field reveals a classic astronomical dichotomy: the open star cluster Messier 35 (M35)—which is identical to NGC 2168—appearing alongside the smaller, more compact open cluster NGC 2158 visible in the lower-right quadrant. Note that M35 and NGC 2168 refer to the same primary, widely scattered cluster. The comparison below evaluates the physical parameters that characterize M35/NGC 2168 in contrast to its line-of-sight companion, NGC 2158.

Key Physical Dynamics & Visual Morphology

Spatial Distribution & Density: M35 (NGC 2168) spans a physical diameter of roughly 24 light-years, presenting a broad, low-density distribution of bright blue-white massive stars across the field. Conversely, NGC 2158 appears extremely dense and visually resembles a globular cluster due to its vast distance, compact stellar packing, and smaller apparent area.

Evolutionary Differences: The blue-dominated light from M35 reflects its young stellar population, where massive main-sequence stars have not yet exhausted their nuclear core fuel. NGC 2158 is more than ten times older; its high-mass blue stars have long since evolved off the main sequence, leaving behind lower-mass main-sequence stars and red giants that give the cluster a distinctly yellower hue and higher interstellar extinction.

Perspective & Geometry: Though visually adjacent in the constellation Gemini, the two clusters do not form a gravitationally bound binary pair. NGC 2158 sits roughly 4 to 5 times deeper in the Milky Way plane, far beyond M35.

Comparative Astrophysics Analysis

Characteristic	Messier 35 (NGC 2168)	NGC 2158
Cluster Type	Loose Open Cluster (Trumpler III3r)	Highly Compact Open Cluster (Trumpler II3m)
Apparent Angular Diameter	~28 arcminutes	~5 arcminutes
Visual Magnitude ($V$)	+5.3 (Naked-eye target)	+8.6 (Telescopic target)
Distance from Earth	~2,800–2,970 light-years (~850–912 pc)	~11,000–16,500 light-years (~3.3–5.0 kpc)
Estimated Age	~100–175 million years (Young open cluster)	~1.0–2.0 billion years (Intermediate/Old open cluster)
Stellar Population Color	Dominantly blue-white (hot B-type main-sequence stars)	Dominantly yellow-orange (evolved giants, low-mass stars)

Digital processing or data reduction as it was called in the olden days.

 

Re-processed Messier 35 widefield Credit: Pip Stakkert

"Pip Stakkert decided to rework the data for this image we previously published. The original showed too many stars with pixelated shapes. 

Stars represent quite a challenge for astro-photographers. Nebulae and extended objects are much easier to image and represent. Stars are big, very big or enormous but all, other than the Sun, are far far away. As a consequence of their extreme distance, they should present as point sources of light of varying degrees of brightness and colour. Unfortunately, when the light from a star passes through a lens, be it on a telescope a camera or the ones in your eyes, the point source becomes a small disc. This is a physical and unavoidable feature of light and lenses! The colour, which is determined by the stars temperature, migrates to the edge of the disc leaving the brighter centre pure white and often saturated. To capture faint objects the astrophotographer primarily increases the length of exposures and consequently brighter stars are over exposed and colour is lost. Your eye and brain combination, may not be able to detect the light from faint objects that are easy for the cameras sensor to register, but working together  can compose a more coherent and dynamic view of the night sky. Getting the stars to look 'natural' in a widefield image requires the data processor to decide how many stars to show, how to ensure their disc shape is circular, how to differentiate between bright and dimmer stars and how much colour to display.

The new neural network based software StarFixer is an interesting development and is likely to improve over time. At the moment we use it in combination with other software in regulating the shape of stars. The new astrophotography V15 macros developed by James Ritson for Affinity Photo 2.0.0 are astoundingly good at rendering stars in a realistic and natural way.

The open cluster Messier35 is much clearer in this image version as is the fainter open cluster, NGC2158, to its immediate south west. Overall the image, fewer stars are on display and there is a bigger dynamic range between the dimmest and brightest stars. In a nutshell, this image of stars looks less busy, is a better representation of what the eye brain combination might see if it was more sensitive at low light levels and more naturalistic all round (excuse the pun)". - Kurt Thrust current Director of the Jodrell Plank Observatory.