For an upcoming Echelle spectrograph I bought a new detector, an ASI294MM-Pro. This is my first CMOS chip. I want to present my observations on this detector to show the effect of technical progress.
Please find a more extensive evaluation of the asi294mm-pro at Christian Buil's site.
The ASI294 is operated under Linux on an INDI server. indi_asi_ccd is used as the driver. The client is ccdciel. Gain was 200, offset 8. I have reproduced all measurements also with my old Atik460EX with the driver indi_atik_ccd.
I took 30 bias shots with an exposure time of 0.00032 sec at a temperature of -20°C. The arithmetic mean of these frames give the particular meanbias. The results in the meanbiases and the particular single biasframe bias004.fits are
Frame | ASI294 | Atik460 | |
---|---|---|---|
Num Pix | all | 11694368 | 6045051 |
Mean | meanbias | 561 | 320 |
Std Dev | meanbias | 3.9 | 3.2 |
Mean | bias0004 | 572 | 320 |
Std dev | bias0004 | 16 | 17 |
ADU ≤ xxx | meanbias | ≤400: 0px | ≤200: 0 |
ADU ≥ xxx | meanbias | ≥740: 16px | ≥400: 0px |
I show you the 10th column from the right border.
I took 30 dark frames of 600s exposure time at a temperature of -20°C with my ASI and 23 with my ATIK. 29 rsp. 22 of them were mean averaged and also also a median average of these frames was computed. See the meandark:
There is a light in the dark to better find your way home at night.
The two mean darks are not very different.
Property | ASI294 | Atik460 |
---|---|---|
Mean | 570 | 321 |
Std Dev | 41 | 104 |
ADU ≤ xxx | ≤400: 0px | ≤300: 0px |
ADU ≥ xxxx | ≥1200: 735px | ≥1000: 463px |
I made a simple data frame to see what the unwanted lantern does to weak data. My weak signal is 4096 ADU all over the chip. \[\mathrm{sim\_data} = 4096 + \mathrm{remaining\_dark}\] \[\mathrm{pure\_data} = \mathrm{sim\_data} - \mathrm{meandark}\] This simple data reduction removes the glow of the amplifier leaving some noise that comes with every signal. See characteristics of the resulting frame \(\mathrm{pure\_data}\) in the table below and following a plot of the 10th rightmost column in \(\mathrm{sim\_data}\) and \(\mathrm{pure\_data}\) from the asi cam. At last 10th last column of \(\mathrm{pure\_data}\) from cmos vs. ccd.
Property | ASI294 | Atik460 |
---|---|---|
mean | 4087.020 | 4095.983 |
median | 4086.483 | 4095.958 |
std dev | 31.66 | 19.59 |
Last modified: 2023 Jan 13