Calibration Issues -

[RodrigoQ]

Good Morning Everyone!

I hope I find some help here. I'm struggling really hard trying to understand what I'm doing wrong with my data. I got my very first mono camera ( ASI294MM Pro) and I shoot almost one hour on Ha for The Rossete Nebula. I follow the procedure and for some reason is impossible to me using the WPBB. If I just try to calibrate my light frames the result (Light Calibrated) are pitch black images, If configure the whole WPBB tool it get cancelled in the middle of the process .I feel frustrated because I don't know if I'm using wrong my camera and I took bad data or I'm not using PI property. I'm using N.I.N.A to acquire the images. Attached each type of each image vs histogram and the data information:

Lights : 20 x 180 s - Gain 180 - Offset 60
Darks : 15 x 180 s - Gain 180 - Offset 60
Flats : 30 x 3 s - Gain 180 - Offset 60
Dark Flats: 30 x 3 s - Gain 180 - Offset 60
Bias : 73 - Gain 180 - Offset 60

Also there is a google drive link so feel free to download the images and check them out, probably you guys will see something I'm missing:

Rossete Nebula - Troubleshooting - Google Drive

drive.google.com

I'm waiting for your feedback and learn from mi mistake.

Best Regards.

Rodrigo Quiroga

 

[bulrichl]

Hi Rodrigo,

I answered your post in the thread Image Processing Challenges, "My dark and bias median ADU is higher than my lights, pedestal not working.". I append it here again, in case you did not notice it:

Presumably your dark frames suffer from light leakage.

These are the statistics of a light frame and a dark frame:

            Light        Dark
count (%)   100.00000   100.00000
count (px)  11694368    11694368
mean        3984.8      4341.4
median      3972.0      4340.0
variance    118623.0    10377.7
stdDev      344.4       101.9
avgDev      69.8        90.2
MAD         65.2        89.0
minimum     3480.0      3776.0
maximum     65532.0     65532.0

The frames are captured at the same gain (180), offset (60) and exposure time (180 s). However, the median of the dark frame is greater than the median of the light frame by 368 ADU. The STF Auto-stretched dark frame (appended) shows nonuniform exposure to light. For recommendations how to avoid light leakage see my guide, https://pixinsight.com/forum/index.php?threads/for-beginners-guide-to-pis-imagecalibration.11547/ , chapter 5.3 Dark frames, bias frames and flat-darks: avoiding of light leaks.

Bernd

 

[RodrigoQ]

Thank you for help me out @bulrichl . I didn't see your replied it before so I deleted the older entry " "My dark and bias median ADU is higher than my lights, pedestal not working." to prevent duplication of information and keep everything in the same post. I'll remove my camera from my rig and wrap it on aluminum foil and take new darks and share with you the result.

 

[RodrigoQ]

UPDATE: @bulrichl As You suggested in your guide, I wrapped the camera with a double layer of aluminum fold in the front and take a new dark expecting to see a big difference. Following what I got:

	Old Dark	New Dark	Light
count (%)	100​	100​	100​
count (px)	11694368​	11694368​	11694368​
mean	4298.4​	3840.2​	3975.1​
median	4296​	3836​	3964​
avgDev	85​	17.8​	69.7​
MAD	83​	17.8​	65.2​
minimum	3720​	3428​	3452​
maximum	65532​	65532​	65532​

Good thing is the new dark look more uniform after perform the STF function but after take a look of the numbers the median of the light frame is greater of the median of the new dark just by 128 ADU. I'm not sure if I didn't cover correctly the camera (I guess a double layer is more than enough) or I got a defective camera but I was expecting to se a lower number on the median ADU on the new dark.

Please let me know your thoughts. Thank you for your help!

 

[bulrichl]

Your new dark frame looks promising. You should prepare a MasterDark from some new dark frames. Then use the new MasterDark for the calibration of a light frame and check whether clipping occurs. If no clipping occurs, avoiding the light leakage was the solution of the issue. Otherwise (i.e. if clipping still occurred) the application of a small output pedestal will be necessary in order to avoid clipping.

An output pedestal is configured in the 'Output Files' section of ImageCalibration. Normally a value of 100 to 200 DN is sufficient. The value must not be too low, but a slightly too high value doesn't do damage.

Bernd