Cheshire cat galaxy group, SDSS J1038+4849, gravitational lens (Morten la Cour)

Cheshire cat galaxy group, SDSS J1038+4849, gravitational lens

This iconic target represent a gravitational lens, where the two foreground galaxies SDSS J1038+4849 lens four background galaxies into arc shaped structures, where the weakest is ABmag 23.55. The entire lens is known as Hubble's smiling lens. More data about this lens and several others can be found here https://www.researchgate.net/publication/231037045_GeminiGMOS_Spectroscopy_of_26_Strong_Lensing_Selected_Galaxy_Cluster_Cores

This image is taken in several nights in Feb->March 2021 from a SQM-L 21.3->21.6 sky in Denmark. The elevation is 17 above sea level.

The electron flux into the 4.54x4.54 micron pixels from the weakest arc is 0.65 electron pr minute. The background flux was 92.5 electrons pr pixels. The pixel resolution of the setup is 0.846 "/pix, and the gain is 0.156 electrons/ADU. Hence with a QE of 60% this corresponds to an photon flux of the weakest arc of 1.5 photon/min on a background of 215.4 photons/min. Some integration time is needed in order to obtain a resonable image.

The image is assembled from 321 300s L + 24 600s RGB subs. Also around 35 5s RDB subs were included to improve star colour. Drizzle integration in PI. The final image is resampled 200% to a resolution of 0.22 2/pix. The lens itself is around 20” in diameter.

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 failed
Started	...
Astrometry.net job	4465660
PixInsight job	n/a
PixInsight queue size	n/a
PixInsight stage	n/a

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