Noise estimation in dark frames

[astropixel]

There are several math errors in astropixel's post (multiplication and failure to take square root):

Thanks Mike. Not sure how I missed that...

Thanks IanL, very aware of the problem. The alternative DSLR workflow goes some way to addressing the issues with consumer camera image calibration - though it may not be the complete answer.

[sharkmelley]

Because of the DSLR specific issues of estimating dark current referred to above, I wrote my own script.  It's not highly polished but it does the job.  A whole sequence of dark frames can be supplied, so the increase in dark current can be observed as the sensor warms up.

Here is some typical output (in the Process Console window):

=============================
DSLR Sensor Parameters v0.0.7
=============================
Camera: Sony ILCE-7S
ISO speed: 2500
Image Size: 4256 x 2848
Bias frames exposure time: 1/8000 sec
Flat frames exposure time: 1/100 sec
Dark frames exposure time: 297 sec
Channel order:             []
Gain per channel(e/ADU):   [ 1.672, 1.676, 1.682, 1.65 ]
ISO for unit gain:         [ 4179, 4190, 4205, 4125 ]
Read Noise(e):             [ 1.37, 1.38, 1.4, 1.36 ]
Dark Current (e/pixel/sec) [ 0.1207, 0.1198, 0.1203, 0.1181 ]
Dark Current (e/pixel/sec) [ 0.1285, 0.1269, 0.1287, 0.1271 ]
Dark Current (e/pixel/sec) [ 0.1353, 0.1348, 0.1356, 0.1336 ]
Dark Current (e/pixel/sec) [ 0.1456, 0.1385, 0.1409, 0.1389 ]
Dark Current (e/pixel/sec) [ 0.1497, 0.1445, 0.1457, 0.1429 ]
Dark Current (e/pixel/sec) [ 0.1499, 0.1493, 0.1489, 0.1476 ]
Dark Current (e/pixel/sec) [ 0.1556, 0.154, 0.1538, 0.1515 ]
Dark Current (e/pixel/sec) [ 0.1573, 0.1566, 0.1569, 0.1517 ]
Dark Current (e/pixel/sec) [ 0.1598, 0.1582, 0.1584, 0.1558 ]
Dark Current (e/pixel/sec) [ 0.1622, 0.1598, 0.1609, 0.1586 ]
Dark Current (e/pixel/sec) [ 0.1644, 0.1621, 0.1632, 0.1596 ]
Dark Current (e/pixel/sec) [ 0.1654, 0.163, 0.1635, 0.1603 ]
Dark Current (e/pixel/sec) [ 0.1677, 0.1625, 0.1647, 0.1628 ]
Dark Current (e/pixel/sec) [ 0.1681, 0.1647, 0.1666, 0.1642 ]

Noise estimates for 297sec exposure
Read Noise(e):             [ 1.37, 1.38, 1.4, 1.36 ]
Thermal Noise(e):          [ 7.07, 6.99, 7.03, 6.98 ]

Mean values in ADU
Bias Frame 1: [128, 127.9, 127.9, 128 ]
Bias Frame 2: [128, 127.9, 127.9, 128 ]
Flat Frame 1: [323.3, 279.2, 279.5, 170.1 ]
Flat Frame 2: [328.9, 283.7, 284, 171.3 ]
Dark Frame 1: [ 126.9, 126.7, 126.9, 126.6 ]
Dark Frame 15: [ 126.8, 126.5, 126.6, 126.5 ]

DSLR Sensor Parameters v0.0.7 Completed.

To install it, put the unzipped file in your PixInsight/src/scripts folder and run it from the menu using Script->Execute Script File

Regards,
Mark

[msmythers]

Thanks Mark

Now I have another test to verify that my old original Nex-5's are poor, haha.


Mike

[astropixel]

I will give it a shot with the frames used in this discussion thread.

[sharkmelley]

I forgot to include an image of how it looks:

I will give it a shot with the frames used in this discussion thread.

That will be interesting.

Mark