Hatched pattern in flat frame

szg

Please help me get through this problem.

I have hatched pattern in flat frame. This affected to my final image on object gradient trail.

My test flat took with minimal equipment, no 12VDC & external power supply connected (powered by notebook battery).

This flat took through telescope.

There're hatched pattern along gradient pattern.

2.jpg

This flat took without telescope, directly expose sensor to natural light. Sensor window covered by white 2" eyepiece dust cap as diffuser.

Hatched pattern shown lesser but still there.

4-BareCamera2.jpg

Sample final image. I remove stars and add increase the exposure to clearly show the pattern.

jelly patched.jpg

chad

Hi Paul,

Please check the email.

Thanks

Chad

Support@ZWO

flat frames is normal, could provide a original flat frame for us? put on dropbox.

Looks flat didn't calibrate the light well. Does the brightness of flat reach 25000-30000ADU?

szg

Sean.Wang wrote:
flat frames is normal, could provide a original flat frame for us? put on dropbox.

Looks flat didn't calibrate the light well. Does the brightness of flat reach 25000-30000ADU?

These flat are stretched. Original flats took around 30000 ADU.

Original flat at gain=300 submitted to Chad for analysis, Here is the same one I submitted to him.

https://www.dropbox.com/s/0jfwhl9f1794fir/Target%201_CLS-CCD_0.06sec_1x1_Gain300_Offset50_frame1_30C.fit?dl=0https://www.dropbox.com/s/0jfwhl9f1794fir/Target%201_CLS-CCD_0.06sec_1x1_Gain300_Offset50_frame1_30C.fit?dl=0

generalt001

Aren't the flats supposed to be taken around 12000-17000 ADU? 30000 seems extremely high?

Support@ZWO

30000ADU will be better, we got a lot of users tried this.

szg

I just close this call to ZWO. Thanks Chad & Wang for their good care.

What I found and summary to them:

1. After increase exposure from 2-min to 5&10-min, patterns are gone.

2. I used to stay with unity gain. With higher gain, patterns are less. However, I think increase exposure time is the better way to deal with, than just increasing gain.

3. Apart from exposure play, I found basic interpolation method for stacking each frame type (average, medium or else) should set to the same. So, flat & dark can efficiently clean unwanted low SNR pattern.

4. This pattern also appear in the other camera that use the same sensor (QHY163M). It's signature, not your production problem.

Support@ZWO

That's great, this solution is very important to us.