Disk Detective Talk

Artifacts in DSS images

  • TED91 by TED91 moderator

    You probably noticed, that some DSS images contain "strange objects".

    DSS images are scanned photographic glass plates. Impurities such as dust or scratches on the original glass plates can cause that some DSS images may contain strange artifacts.

    Here are a few examples:

    Speck of dust:

    enter image description here

    AWI0000504, AWI00006as, AWI00003iq, AWI00009tc, AWI00000sv, AWI00005bg

    Scratches:

    enter image description here

    AWI00000q4, AWI000052q, AWI00003q5, AWI00002xy, AWI0000d0t

    Posted

  • onetimegolfer by onetimegolfer

    No possibility the black hole could be a "black hole"?

    Posted

  • onetimegolfer by onetimegolfer

    How about the one with the tear drop scratch : "Event horizon" just curious?

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  • jdebes by jdebes scientist, admin

    Sadly, no. Black holes have no hope of being resolved with optical imaging. Too small and too far away.

    Posted

  • onetimegolfer by onetimegolfer

    Thank you; Had to ask

    Posted

  • onetimegolfer by onetimegolfer

    Rather than a corrupted plate could this be "lighting strike" in the dust clouds around the target. Such as the tear drop photo

    Posted

  • lrebull by lrebull scientist, translator, admin

    No lightning, sorry. Just dust motes.

    Posted

  • Artman40 by Artman40

    How are those object called which look like a faint ring which is empty inside? I accidentally skipped over one of these.

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  • onetimegolfer by onetimegolfer

    http://talk.diskdetective.org/#/subjects/AWI00005eg Now here is one you can see the spot in the DSS & 2MASS ranges; almost a bulls-eye missed only by that much. It may have been stated but are there three different telescopes taking photos of these objects?

    Posted

  • lrebull by lrebull scientist, translator, admin

    I'm not sure what you mean by a faint ring that is empty inside. The one you linked, AWI00005eg, doesn't appear to have any dust motes that I can see, but it does look to me like a galaxy (in this case, elongated smear) at the shortest wavelengths. It is faint at JHK (in 2MASS) so the mottling noise in the background is more noticeable, given the stretch of the images.

    Posted

  • onetimegolfer by onetimegolfer

    http://talk.diskdetective.org/#/subjects/AWI00005eq This is a correction to an earlier post :Is this a "blackbody" and in http://talk.diskdetective.org/#/subjects/AWI000030x : Is this gravitational lensing? Sorry for the wrong link earlier and do we have an image of the real McCoy or its image

    Posted

  • lrebull by lrebull scientist, translator, admin

    Re: is this a blackbody: No, neither of the sources you most recently linked have an SED that looks like a blackbody. All the blackbodies in the WISE data should have been weeded out by our selection process, so no plain blackbodies should be in Disk Detective. See my blog post here for examples of plain blackbodies : http://blog.diskdetective.org/2014/02/01/spectral-energy-distributions-seds/

    Re: is this lensing: While I admit I am not an expert on gravitational lensing, I'm not seeing anything that looks lens-like in either of the sources you linked. One source you linked has something that looks a black dust mote on one of the frames; it isn't a dust mote, though, because the things that are truly dust are on the DSS frames, and this black thing appear on a 2MASS frame. I still strongly suspect that it is an image artifact, however. The other source you linked has a source that appears in the same image (at sloan, 2mass, and even the shorter WISE bands) but could be closer/same distance/further away; we don't know anything from just the images aside from the fact that it appears (in projection) nearby on the sky. It is more likely another random star or galaxy - those are far more common than lensing (which is one reason people get excited when they really do find a lens - it's a rare thing!).

    Hope this helps.

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  • onetimegolfer by onetimegolfer

    thanks Irebull

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