View Full Version : What is this artefact?

2014-May-02, 12:13 AM
These are from, Lunar Orbiter Photographic Atlas of the Near Side of the Moon by Charles J Byrnes.
The white spots appear to cast shadows in both directions so I assume they are a by-product of cleaning and restoring the author did or its the result of a light effect.

2014-May-02, 08:43 AM
That looks bad

ETA: I saw from an online preview that the author (Byrne, not Byrnes) discusses many of the artifacts early in the book. Does he mention these?

Did your copy come with a CD of images?

O, and welcome to Cosmoquest forum!

2014-May-02, 10:13 AM
Wow. Not knowing what the media is - I'd say it is either a MAJOR photochemical error in the case of a film transfer or a really dreadful mag roll or photo roll issue from a xerographic machine. Close viewing shows the "shadows" or dark lines going both left and right from the white splotches which would indicate... I'm not sure.

2014-May-02, 11:16 PM
Ok, I believe it's Light Dithering (http://wiesmann.codiferes.net/wordpress/?p=15527). Unfortunately I don't have the book or cd, but I was able to find a database of the originals (http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1971NASSP.206.....B&db_key=AST&page_ind=352&plate_select=NO&data_type=GIF&type=SCREEN_GIF&classic=YES). There's 722 pages there to look through but I found 88,132,146,148,156,259,260,269,279,352,594, and 717 to be most similiar in effect but 594 is the best. It gives a neat effect. What do you think?

2014-May-04, 07:01 PM
I'm an expert at dithering...oh you mean for