Preprocessing and bias causing lines on the image

[swag72]

Here's something that I don't understand in my preprocessing stage, I've attached an image of the problem. I am pre processing using just lights and bias at this stage and when I use the bias frames I get lines down the image. When I preprocess without bias and just use the image integration tool the lines disappear. 

Is there a setting that I am using incorrectly with the bias frames? Both the bias and light frames are captured in Maxim.

I hope someone can help as I do want to use bias frames, but at the moment it's better without them.

[pfile]

is it a dslr, and how many bias frames did you use? if it is a dslr you may need 100s of bias frames due to banding issues.

[swag72]

No it's a CCD - Atik 460EX mono and I used 25 bias frames and 11x1800s lights.

[Andres.Pozo]

How did you calibrate the images? Did you use BatchPreproccess? Did you create the Master Bias with PI or Maxim?

[swag72]

I calibrated the images in the PI BatchPreprocess script, so the master bias was created in PI. I only use Maxim for capture, nothing else.

[pfile]

i don't know about that camera, but i routinely use 200 bias frames and 100+ darks with my 8300M... i have a lot of cloudy nights to take darks.

[jerryyyyy]

Can I ask a question in here?  Do you really need 100+ darks?  I though the value decreased with the square root of the number. 

Also I assume PI can process images that are say 600s with darks collected at 1800s.  It does not go in the other direction does it?  Calibrate 3600s images with 1800s darks? 

[Andres.Pozo]

Can I ask a question in here?  Do you really need 100+ darks?  I though the value decreased with the square root of the number. 

http://pixinsight.com/forum/index.php?topic=4112.msg28652#msg28652

[gvanhau]

Hello

Have you tried to calibrate manually using the indicidual proceses?
I have so far never used the batch processing script, instead I do all calibration using the individual processing May be I'm wrong, but I feel I have more control doing so.

In this case it should be something like:
first Integrate bias there is a tutorial here for settings http://www.pixinsight.com/tutorials/master-frames/en.html
Next step is calibrate lights
Then align
finally integrate.

I have a Atik 450 (similar) and had no problems with it.

Regards
Geert

[sreilly]

I guess it's important to know if you are scaling your darks? Or are you using darks of the same temperature and time? If you aren't scaling the darks then I don't think you need the bias frames. I may be wrong but I seldom use bias frames to calibrate my ST10XME or STL-11000M cameras.

[swag72]

I don't use darks, and up antil now the bias has worked well. I have integrated the subs without the bias and the lines have disappeared, so it's something to do with the bias.

I may have a look at doing it manually - Thanks for the tip.