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06/06/2003 04:55:48 PM · #1 |
Here are some TEST images I did with the D60 mounted piggy back on my meade LX90 telescope little over a month ago.
This test is to show the sensor noise at various exposure times.
I was in a nice dark sky enviroment so there is no light polution to affect the exposures.
The images are in pairs to show the unedited (just resized to 800x600) version and the version with the Auto Level performed.
Also included is a dark frame, and it was adjusted the same as the others.
There is one set of images to show the 150 second exposure and the 150 second exposure with dark frame subtract using ImagesPlus
To keep things consistant I used Ulead PhotoImpact 8 and did the Auto Level to bring out the noise.
D60 Noise
Im not to sure is the other D60 users have this level of Noise of not, so please provide me some feed back if the noise level in my camera is about the same of your D60
James
Message edited by author 2003-06-06 16:56:47.
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06/06/2003 05:08:06 PM · #2 |
I'm not too surprised at that level of noise, though the blooming on one particular side is possibly temperature related ?
this NASA site has a load of similar type of results doing long exposures with telescopes. |
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06/06/2003 05:11:55 PM · #3 |
Not surprised given your ISO is at 800-1000!
Try ISO 100 and those noises should disapppear. |
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06/06/2003 05:14:32 PM · #4 |
Originally posted by Gordon:
I'm not too surprised at that level of noise, though the blooming on one particular side is possibly temperature related ?
this NASA site has a load of similar type of results doing long exposures with telescopes. |
Im just wondering is its sensor temp, the air temp was between 55 and 65 degrees when those images were taken. I know that chip heats up fast.
James
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06/06/2003 05:15:25 PM · #5 |
| It could be near the battery or some of the electronics that are warming up over the longer exposure. |
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06/06/2003 07:44:48 PM · #6 |
James,
I agree it does seem that there may be some temperature thang going on here, but I'm a bit surprised by the sheer amount of the blooming. As for the general noise level, seems within reason especially with the high ISO's.
I tried a couple things in Photoshop, and found what may be a better method for subtraction. I used the images prior to levels adjustment, did subtraction by layering and using "multiply" as blending mode, then added adjustment layers on top to adjust levels. This resulted in an image with a bit more contrast than your subtracted image, and much less darkening along the RH edge. I did have trouble with the blooming, I think it was changing slightly with time in both severity and extent, so the dark frame does not compensate perfectly. I tried to adjust this by modifying the dark frame layer only, with only moderate success. Finally, I adjusted the color balance. The result looks like this:
I think you could greatly reduce noise by stacking multiple (shorter)exposures. If you're willing to manually "de-rotate" you could greatly decrease the field rotation as well. |
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06/06/2003 08:05:55 PM · #7 |
well since i was in a dark sky location I was taking lots of pictures, so I msure I never let the camera cool down much. the temps were between 55 and 65 degrees and low humidity.
since these images were taken I now have a wedge so my scope will track like the good equatorial mounts (its not as accurate, but its much better than the alt/Az method) and the images are much crisper and NO rotation , however they were taken from a not so dark area and show off the light polution very nicly, but the stars are much sharper.
I will post a sample so you can see the differance.
James
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