by NoelC » Mon Jan 29, 2007 2:29 pm
Bear in mind I made this Witch Head image from IR, Red, and Blue exposures.
Looking at the original plate data, I'd say it is unlikely the spot at (2880,970) was dust or a plate defect, as its shape is round with a bright center, and its sharpness seems to resemble that of the other objects in the image. Notably it appears only in the infrared plate exposure, and so is colored deep red in the final image. It is possible it is an IR-only source, or it may be a phenomenon that showed up only when the IR plate was being exposed. Notably it's got a bit more of a halo around it than the surrounding objects. It does not appear on sky charts going down to magnitude 15 stars.
Keep in mind these DSS plates were exposed many years apart!
I actually removed most of the obvious plate defects during processing, including the shadow of a small thread or two. I missed a few, including that orange thread. Some of the dust/defects were on the plate when exposed (these show up as dark spots), and some during the scanning process (light spots).
Here are the IR, red, and blue exposures of the area containing this object, at full resolution from the plates, and without defects removed from the plate data. The object in question is at dead center. Judge for yourself.
IR exposure, November 12, 1987, UK Schmidt telescope:
Red exposure, October 21, 1993, UK Schmidt telescope:
Blue exposure, November 17, 1984, UK Schmidt telescope:
Portion of sky chart showing stars as dim as magnitude 15:
So... I'm thinking this [infra]red spot could be a true discovery. Good eye, cjet!
-Noel
Bear in mind I made this Witch Head image from IR, Red, and Blue exposures.
Looking at the original plate data, I'd say it is unlikely the spot at (2880,970) was dust or a plate defect, as its shape is round with a bright center, and its sharpness seems to resemble that of the other objects in the image. Notably it appears only in the infrared plate exposure, and so is colored deep red in the final image. It is possible it is an IR-only source, or it may be a phenomenon that showed up only when the IR plate was being exposed. Notably it's got a bit more of a halo around it than the surrounding objects. It does not appear on sky charts going down to magnitude 15 stars.
Keep in mind these DSS plates were exposed many years apart!
I actually removed most of the obvious plate defects during processing, including the shadow of a small thread or two. I missed a few, including that orange thread. Some of the dust/defects were on the plate when exposed (these show up as dark spots), and some during the scanning process (light spots).
Here are the IR, red, and blue exposures of the area containing this object, at full resolution from the plates, and without defects removed from the plate data. The object in question is at dead center. Judge for yourself.
IR exposure, November 12, 1987, UK Schmidt telescope:
[img]http://www.ourdarkskies.com/gallery2/d/813-1/IC2118_Spot_IR.jpg[/img]
Red exposure, October 21, 1993, UK Schmidt telescope:
[img]http://www.ourdarkskies.com/gallery2/d/816-1/IC2118_Spot_Red.jpg[/img]
Blue exposure, November 17, 1984, UK Schmidt telescope:
[img]http://www.ourdarkskies.com/gallery2/d/819-1/IC2118_Spot_Blue.jpg[/img]
Portion of sky chart showing stars as dim as magnitude 15:
[img]http://www.ourdarkskies.com/gallery2/d/822-1/IC2118_Spot_Chart.jpg[/img]
So... I'm thinking this [infra]red spot could be a true discovery. Good eye, cjet!
-Noel