Author Topic: DR7 - DR8 Oddity  (Read 1109 times)

waveney

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DR7 - DR8 Oddity
« on: November 09, 2011, 08:25:33 pm »
This is what I see in DR7:



and this with exactly the same options in DR8:



In DR7 it failed to show the Photometric objects and where it has spectra (it has one of the central galaxy), in DR8 the Photometric objects and location of the spectra are shown, but half the image is missing!   (You have one guess as to why I was looking at that galaxy)

Me thinks there could be something amiss...
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RandyC

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Re: DR7 - DR8 Oddity
« Reply #1 on: November 09, 2011, 10:33:14 pm »
This is what I see in DR7:

and this with exactly the same options in DR8:

In DR7 it failed to show the Photometric objects and where it has spectra (it has one of the central galaxy), in DR8 the Photometric objects and location of the spectra are shown, but half the image is missing!   (You have one guess as to why I was looking at that galaxy)
Me thinks there could be something amiss...

It seems DR8 did an excellent job of adding spectra to DR7's coverage. I believe the spectum "holes" in the SDSS mask were placed based on DR7 data. Many times I find a DR8 spectra where there is no image. So I use the DR8  spectra and DR7 image. The DR8 imaging seems a little less clever. First off, they decreased the image resolution. Yes, it's brighter, etc, but it's also blurrier. Secondly, as in your example, the image coverage is confusing. I am not sure how much of what was imaged in DR7 was reimaged in DR8. They may have needed to do double imaging to stitch DR7 and DR8 together. But many times, DR8 is just blank where there is a DR7 image.

btw, 'met thinks' is 70s Popeye talk, you must have picked that up from Paul R. ackkkkk!   :' ;) 
Randy