11 replies to this topic

[gps1539]

Hi, the online Siril documentation for manual preprocessing is well written, but it seems to be for an older release as it shows a "Pre-processing" tab rather than "Calibration" in the newer releases.
https://siril.org/tu...ls/tuto-manual/

 

The above documentation has a step for Pre-processing Flats with a stacked Bias sequence and then stacking a "Master-Flat" with normalization of "Multiplicative". For Darks it suggests stacking with "No normalization".

For Pre-processing Lights the guide shows using the Flats and Darks from the above steps with your lights. However the guide shows no line to add Biases as we have in the newer releases.

 

My Question(s)

 

1. In newer Siril releases what are the recommended steps for stacking Biases (are they needed?), Flats and Darks :

- How to stack Darks?

- How to stack Biases?

- How to stack Flats?

- Should Flats be Pre-processed with stacked biases?

 

2. I've recently started using NINA and the Flat wizard does not capture Biases. I see in the forum many folks believe they don't need Bias frames. Is there a recommendation one way or another for Siril? and if Bias frames aren't needed does it change how Flats should be stacked i.e. No normalization or Multiplicative?

 

Sorry for the long question and thanks in advance.

[rj144]

Where do you see many say you don't need bias?  You need bias so you can subract from the flats.

 

I don't manually stack my calibration frames, I just run the script.

[Stylistic007]

If you are following the steps, you have used the Bias's to preprocess Flats: ergo "pp_Flat.seq" 

 

Bias's are the first sequence you stack of all the sequences.

 

Unless I don't understand your question?

[Stylistic007]

Here is my working document on preprocessing:  https://1drv.ms/u/c/...1LnTxQ?e=MVjfmn

 

You can follow it along with the website if its confusing.  Just focus on the red arrows.

 

PS- I use LibreOffice so it is in .odg file type

Edited by Stylistic007, 23 March 2025 - 01:29 PM.

[gps1539]

Where do you see many say you don't need bias?  You need bias so you can subract from the flats.

 

I don't manually stack my calibration frames, I just run the script.

Thanks

In the NINA forums I saw folks reply that they don't use Bias frames to a question about the NINA Flat Wizard (which doesn't include Biases). I will continue to take biases.

[Stylistic007]

Ya...I'm in the same boat.  I don't know if they are "needed" but I feel that best practices say you do.... so I too, will take them...and its quick.

[gps1539]

Here is my working document on preprocessing:  https://1drv.ms/u/c/...1LnTxQ?e=MVjfmn

 

You can follow it along with the website if its confusing.  Just focus on the red arrows.

 

PS- I use LibreOffice so it is in .odg file type

Thanks for the two replies. Super helpful and it solved my confusion.

 

I was adding the stacked biases, along with Darks and pp_Flats when calibrating Lights. I'd missed that "Offsets" in the old UI is the same (I think) as "Bias" in the newer releases.

[Stylistic007]

Thats why I did the document....its basically an updated version of the original.

 

To your original post...

 

Those are great questions.  I too would like to understand, fundamentally, what they are, if they are needed, etc.  However, I found to just follow a process, get used to it, then the important questions come.

 

For now, I know SIRILs processing works for me, and my questions are about drizzle, deconvolution, dither,.....

[Drothgeb]

Thanks

In the NINA forums I saw folks reply that they don't use Bias frames to a question about the NINA Flat Wizard (which doesn't include Biases). I will continue to take biases.

 

Thats why I did the document....its basically an updated version of the original.

 

To your original post...

 

Those are great questions.  I too would like to understand, fundamentally, what they are, if they are needed, etc.  However, I found to just follow a process, get used to it, then the important questions come.

 

For now, I know SIRILs processing works for me, and my questions are about drizzle, deconvolution, dither,.....

The bias frame calibrates the flat in the same way a dark frame calibrates a light frame. If you don’t use a bias frame, the flat won’t correct properly.

 

In Siril, you can also use a synthetic bias. Which is just the ADU value of a bias frame. Or, you can use flat darks. Which are essentially  bias frames that match your flats in exposure length. They are the best frame to use, but usually aren’t necessary. 

[rj144]

Thanks

In the NINA forums I saw folks reply that they don't use Bias frames to a question about the NINA Flat Wizard (which doesn't include Biases). I will continue to take biases.

You only need to take biases once for a long time.  And they take like 20 seconds.

[Stylistic007]

I just had, I think, a bias issue my last session.

 

ASIAIR set the bias to 1 ms. I took more at 0.5ms for some moon footage I was playing with.

 

When I went to stack I had to set the Low windsorized sigma to its max (10) and got 1.250% or something.  I can usually adjust to get the recommended 0.100%.  So I used the 0.5ms set and it worked fine.

 

I see my camera can do 0.32ms.  Should I override the ASIAIR and set it to its maximum frame rate?  I'm thinking so....?

 

Again, I'm not sure if this is a huge issue or not, but I'd like to get into some good habits.

Edited by Stylistic007, 23 March 2025 - 03:32 PM.

[danny1976]

I see in the forum many folks believe they don't need Bias frames

What they mean (I think) is you can take darkflats instead of biases. The whole process of calibrating stays the same. You just place the darkflats in the biases folder (if you use the OSC_Preprocessing script). 

 

Darkflats have the same exposure/gain as your flats but with the lenscap on. 

 

I've used darkflats and biases and I don't see any difference. There are some camera's which require darkflats. 

Edited by danny1976, 23 March 2025 - 04:50 PM.