Eratosthenes (Bruce Rohrlach)

Contains: Solar system body or event

Eratosthenes

Acquisition type: Electronically-Assisted Astronomy (EAA, e.g. based on a live video feed)

Eratosthenes

Acquisition type: Electronically-Assisted Astronomy (EAA, e.g. based on a live video feed)

Skywatcher 200mm/f5 with Televue 5x (ASI 224mc).

Eratosthenes crater (59 km wide and 3.6 km deep) lies at the western terminus of the Montes Apenninus. With terraced walls and central peaks, it has a thick ejecta blanket but lacks rays.

Named after the Greek astronomer Eratosthenes of Cyrene (275-195 BC), Eratosthenes was chief librarian of the Great Library in Alexandria - which contained over a million books as papyrus scrolls.

At one point Eratosthenes calculated the diameter of the earth using deductive reasoning. To do this he employed a measuring unit called stadia, and hired a guy to pace out the distance between Alexandria and Syrene (in Libya) in units of stadia, a distance of 5000 stadia which was around 500 miles. That, combined with the angle shadows cast during midday at solstice in Alexandria, and knowing the sun shone vertically to the bottom of a well in Syrene without casting a shadow, he was able to calculate the earth’s diameter to be 25,000 miles, an accuracy of 99.6% using basic trigonometry. So interesting to see how these two proximal craters have suitably been named Eratosthenes and Stadia.

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

Image Index:

Contribution Index (beta):

Eratosthenes

Eratosthenes

Equipment

Acquisition details

Description

Comments

Histogram

		...
You have no new notifications.

Image Index:

Contribution Index (beta):

Eratosthenes

Eratosthenes

Equipment

Acquisition details

Description

Comments

Histogram

Notifications

AstroBin is in READ ONLY mode

Sorry :-(

Sorry :-(

Sorry :-(

Are you really sure?

Warning!

Warning!

Are you sure?

Report abuse

Slideshow settings

IOTD/TP stats (last [x] days)

Distribution of astrophotographers

Distribution of subject types

Distribution of data sources

Sorry

Sorry

Share

Upload new revision

Upload uncompressed source (XISF/FITS/PSD/TIFF)

Delete image and all its revisions?

Delete original image?

Delete all other versions?

Delete all revisions?

IOTD/TP stats

The following people like this image

The following people bookmarked this image

Warning

Flag malfunctioning thumbnails

Contains

Remove yourself as a collaborator

Plate-solving information