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Messages - Sedat

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Any guesses as to why the less than 1 sec flat subs are noisier than the 600 sec light subs ?

Phewww! I knew I was making a stupid mistake somewhere... never looked at the exponential figures :(

Thank you both!


I have started using PI for calibrating, aligning and stacking very recently. Instead of using the BPP, I'd like to use the dedicated tools to have a better control on the whole process. Thanks to the Noise Evaluation script, I was able to track the noise levels after each step. The following data belongs to Luminance images shot by Atik 460 EX Mono camera:

Uncalibrated sub
Calculating noise standard deviation...

* Channel #0
?K = 2.304e-03, N = 157934 (77.90%), J = 4

Calibrated sub - with Bias and Flat Masters
Calculating noise standard deviation...

* Channel #0
?K = 2.297e-03, N = 4647476 (76.88%), J = 4

CosmeticCorrection applied sub
Calculating noise standard deviation...

* Channel #0
?K = 2.295e-03, N = 4786605 (79.18%), J = 4

StarAligned sub
Calculating noise standard deviation...

* Channel #0
?K = 2.030e-03, N = 4484671 (74.19%), J = 4

Stack of 30 frames
Calculating noise standard deviation...

* Channel #0
?K = 4.611e-04, N = 3256902 (53.88%), J = 4

So, I'm getting more than 2x more noise in the final stack.

On the other hand, the situation with flat frames is like the following:

Uncalibrated flat sub
Calculating noise standard deviation...

* Channel #0
?K = 5.214e-03, N = 5910648 (97.78%), J = 4

Calibrated Flat sub - with Bias Master
Calculating noise standard deviation...

* Channel #0
?K = 5.214e-03, N = 5910693 (97.78%), J = 4

MasterFlat - Stack of 40 frames
Calculating noise standard deviation...

* Channel #0
?K = 1.400e-03, N = 5864821 (97.02%), J = 4

With the flats I'm getting almost 1/4th of the noise of the individual frames.

The BiasMaster used in the calibration of these light and flat frames - Stack of 200 frames
Calculating noise standard deviation...

* Channel #0
?K = 2.791e-05, N = 5170396 (85.53%), J = 4

The SuperBias produced from the above BiasMaster
Calculating noise standard deviation...

* Channel #0
?K = 9.400e-06, N = 2611685 (43.20%), J = 4

The subs at the beginning and end of the bias capture
Calculating noise standard deviation...

* Channel #0
?K = 3.089e-04, N = 5915885 (97.86%), J = 4

Calculating noise standard deviation...

* Channel #0
?K = 3.092e-04, N = 5913929 (97.83%), J = 4

Can somebody please explain me what's going on here ? Also, why is the SuperBias more noisy ?

I've started reading the relevant chapter in The Handbook of Astronomical Image Processing but it will take some time to go through all the details there. I thought I could get some quicker response from the gurus here.

Many thanks


General / Re: What happened to my STF icon on the Toolbar
« on: 2012 December 24 00:35:06 »
Yes, v1.8 returned my favorite icon to the toolbar :)

General / What happened to my STF icon on the Toolbar
« on: 2012 December 24 00:21:30 »
During one of the recent updates, this icon disappeared from my toolbar on the Windows 7 installation. My Mac OS installation still has it.

I have even reset all the settings but this icon is not coming back. Today I will install version 1.8 and I hope it comes back :)

Any help will be appreciated.



Hi Lex,

Thank you for willing to take the time to work on my data.

Currently, I am in the US for NEAIC and NEAF and I don't have the un and pw information with me. Could you please send an email to Juan so that he can give access to you for the file sharing site.

Thank you again.


Were you able to download the files ? Please let me know.

Woooohooo! I guess I said the magic words :)

Hi Harry,

Thanks for chiming in.

I have just checked and saw the files are still there @ under "forum shared files/Sedat"

Please let me know if this works for you.



Ola Alejandro,

Thank you for processing my data.

Take your time please.

Best wishes


Hi Rüdiger,

Well, maybe it's only me but I am seeing hints of the flux. Please compare my version below , however ugly looking it is, with Harry's image. I am sure you will see what I mean. If I had one tenth of Harry's skill I am sure I would make mine much better.

and this is Harry's



Hi Rüdiger,

Thank you for taking the time to work on my data. I guess I was expecting too much from this data :) My flats are not perfect I believe. This results in that terrible looking data. Denoising methods are not helping as you say.

Our friends are all CCD guys I think and they don't want to spend their times with the worries of us, the poor mortals :) Maybe we should move to CCD cameras :)

Any volunteers ? No one ?  ??? ::)

When trying to download your files, I only get "Cannot find file!".

Oh! Either I am doing something wrong or the system is not up and running yet to produce the correct link. I have tried to download the files myself and got the same response.

The files are under Forum Shared Files, within the folder named "Sedat". You can reach the files at

I hope you can download the files this time. If not, please try the rapidshare links I gave in my original post.



Hi Rüdiger,

I am not very comfortable with PI image integration yet. I can use Images Plus to do the integration of these 2 files.

When I mix the ISO800 images with the ISO1600 ones, what happens to Dark frame matching ? Can I work without Dark frames, is this possible in PI ?

Sorry for too many questions but I am a newbie indeed.

Hi Rüdiger,

At the time of shooting, it suddenly occurred to me  that 6 minutes sub exposure might have been to much at ISO 1600 which would lead to saturated galaxy core and I switched to ISO 800 for the rest of the session. When I shoot with my C11 Edge+Hyperstar, this can easily happen. This FSQ belongs to a friend and it was my second attempt to shoot with it. So I am not very familiar with its outcome yet. There was another scope mounted on the side bar for testing and comparison purposes, coupled to my Canon 450D camera. Due to this, I was not able to dither properly. I believe some of the problems are related to this.

At the first attempt, with the help of dithering, I managed to obtain a nice Leo Trio:

Leo_Triplet2 by bilgebay, on Flickr

If you are suggesting that I should stack the outcome of the 2 sets via Pixel Math or any other tools, I can do that too. Please let me know.

Thanks for taking the time to look at my data.


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