View Full Version here: : What are these stains?
jones
22-02-2011, 05:04 PM
Hi,
I took my second picture with my 50mm lens, being my guider cam broken. After processing with Iris and doing the asinh, I have tuned the visu to expose gradients, and look what I found!
http://i.imgur.com/228DS.jpg
What's going on there? It looks like there's a pattern. It's also visible with the image properly stretched:
http://i.imgur.com/gxdtS.jpg
Any idea what could've caused that?
Thanks!
jjjnettie
22-02-2011, 06:12 PM
It could be marks left from cleaning the sensor.
Taking flats should clear it up.
But I wonder if you've captured some very faint Northern Lights?
DavidU
22-02-2011, 06:20 PM
That's an interesting thought. The sun is flaring.
multiweb
22-02-2011, 06:23 PM
I reckon as well. The marks are rectangular and follow the sensor shape.
jones
22-02-2011, 06:26 PM
Hi everyone. I have taken flats, a number of them.
Also, I don't think those are northern lights because what you're looking at is the sigma-clip stacking of 51 pictures.
jones
22-02-2011, 06:27 PM
PS: I exclude this has anything to do with the sensor because it didn't happen when shooting at prime focus of my ED80 scope. So it must be the lens, mustn't it?
acropolite
22-02-2011, 08:32 PM
If there are city lights nearby, it could be skyglow off thin cloud. I have images with similar patches caused by skyglow from a nearby city.
jones
22-02-2011, 08:40 PM
LOL, acropolite, I am in a city. The light pollution is very evident. But I have to rule out the thin cloud hypothesis because of 2 reasons:
1) The imaging happened over 2 hours, so it should've been a very stationary cloud.
2) More importantly, the same pattern appears on another image taken the next night.
I wonder if there's a problem with my flats (both images share the same). I'll check that tonight.
jones
25-02-2011, 02:37 AM
I have checked my flats and they don't show that pattern. What on earth is it?
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