M31 Mosaic (Peter Hannah)

Celestial hemisphere: Northern · Constellation: Andromeda (And) · Contains: Andromeda Galaxy · M 110 · M 31 · M 32 · NGC 205 · NGC 221 · NGC 224

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M31 Mosaic

Link: https://astroworkshop.com/the-great-andromeda-galaxy/

Powered byPixInsight

M31 Mosaic

Link: https://astroworkshop.com/the-great-andromeda-galaxy/

This image is a mosaic of 8 panels taken through the 14-inch telescope at my remote site in Spain. Since the galaxy spans over 3° on the sky (or about 6 full moon widths) and the telescope’s field of view is 49 arc-minutes, a mosaic is the only way to image the entire galaxy with this setup.

Each panel was exposed through red, green, blue, luminosity (clear) and hydrogen-alpha filters: 4 hours each for the broadband filters and over 6 hours for the H-α. This adds up to over 180 hours’ total exposure time.

The processing was quite challenging. The issues included uneven background illumination (gradients) which varied with each filter, making it difficult to match the backgrounds (and this can lead to unnatural colour effects). Fortunately PixInsight has some excellent tools for both planning and assembling mosaics, and for dealing with gradients.

The image, in which north is to the right, shows the spiral arms with their predominantly blue younger stars and dark dust lanes, and the satellite galaxies M110 (NGC 205) below and M32 (NGC 221) above (M31 is NGC 224). In addition the H-α narrowband filter has brought out a number of H-II regions in the spiral arms.

The link below is to my web page that includes a zoomed area of this image showing M31-V1, the first Cepheid variable identified in another galaxy which proved that Andromeda was a galaxy in its own right, far beyond the boundaries of our Milky Way.

Please note: The following tables are updated every 24 hours.

Distribution of astrophotographers

This table shows the number of distinct astrophotographers who have been assigned and IOTD/TP award compared to the total number of images awarded.
	Distinct awarded users	Total awarded images
Image of the day
Top picks
Top pick nominations

Distribution of subject types

This table shows the distribution of awards per subject type, compared to the popularity of images of that subject type.
	Image of the day	Top pick	Top pick nominations	Total submitted
Deep sky
Solar system
Extremely wide field
Star trails
Northern lights
Noctilucent clouds
Landscape

Distribution of data sources

This table shows the distribution of awards per data source, compared to the popularity of images acquired from that data source.
	Image of the day	Top pick	Top pick nominations	Total submitted
Backyard
Traveller
Own remote observatory
Amateur hosting facility
Public amaeteur data
Professional, scientific grade data
Mix of multiple sources
Other
Unknown

The “AstroBin Image of the Day and Top Picks”, or IOTD/TP, is a long-running system to promote beautiful, interesting, peculiar, or otherwise amazing astrophotographs, with a focus on technical excellence. Learn more.

Submitted The date and time when you submitted this image for IOTD/TP consideration.	...
Views by Submitters (available since September 19th, 2023) Every image is assigned to 50% of available Submitters. In the event that at least 80% of them don't view the image before its time in the IOTD/TP process expires, it's assigned to the other 50% of Submitters and the process begins anew.
Promotions by Submitters When 3 distinct Submitters promote the image, it moves on to the next stage of the process: evaluation for Top Pick status. This requirement, in addition to anonymization of images and distribution to only a subset of them, prevents biases and ensures that the best images are selected.
Promotions by Reviewers When 3 distinct Reviewers promote the image, it moves on to the next stage of the process: evaluation for IOTD status.
Early dismissal Staff members have a lot of images to inspect on a daily basis, and they can dismiss images if they believe they don't meet the requirements for IOTD/TP selection. If an image is dismissed 5 times, it's removed from the process. This streamlines the process and ensures that any bias present in promotions could be overruled by other staff members.

Status	Basic success
Started	...
Astrometry.net job	8362412
PixInsight job	n/a
PixInsight queue size	n/a
PixInsight stage	n/a

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M31 Mosaic

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