New to APP, very no...
 
Share:
Notifications
Clear all

New to APP, very noisy images

Page 1 / 2

(@matty)
White Dwarf Customer
Joined: 5 months ago
Posts: 15
Topic starter  

Hi all,

so using APP now and have a new QHY268C Camera, coming from a CCD background, so this is all new to me.

stacked and calibrated an image last night of the Pac-Man nebula, took 40 x 5 min lights and 20 each of Darks, Flats and Flat darks, all put in APP, but the image came out pretty noisy even with minimal stretch, so I then loaded all the same files in the stacking tool in Affinity Photo, and first of all it took 1/4 of the time APP took, and it also came out much less noisy on default settings…

Now I would prefer to use APP as I have paid and I am used to it now, but are there any of the settings on the left side i need to play with to get better cleaner results from APP

And one more thing, with this camera should I be using Dark flats instead of bias, or using both, as the consensus seems to be not to bother with bias, my flats and dark flats are 5.6 seconds long if that has any bearing

cheers all


ReplyQuote
(@matty)
White Dwarf Customer
Joined: 5 months ago
Posts: 15
Topic starter  

Wow, no replies…..so I guess I have asked in the wrong place…? Or is it a bad question….?? 🤔


ReplyQuote
(@sparna)
Molecular Cloud Customer
Joined: 1 year ago
Posts: 5
 

I have a QHY268C too, and had some problems with APP being picky about flats that other programs had no problem with....my routine now is flats and flat darks (of 2 seconds plus, as I believe these sensors are not totally linear at very short exposure speeds), and a master bias to subtract the offset from the light frames. I don't use darks with this camera as there is visually and statistically no difference in noise with or without them (and believe me, after spending hours making a comprehensive dark library when I got the camera, I really wanted to see a difference lol!). Since I don't use darks, I would have thought that I wouldn't need flat darks for the flats, but something about the way APP pre-processes means that my flats don't work without flat darks...meaning I then also have to at least use a bias on the lights.

I have a lot of issues with a lot of things in APP, but one of the reasons that I stick with it (beyond the fact that I spent so much on it) is that parts of it really are best in class - and the debayering algorithms and calibration are better than those in any other software, free or paid IMO. So I'm interested to see your results from the two, as Affinity is just about the only astro stacking software I haven't tried. If you load the unstretched Affinity stack into APP and apply the same DDP as the APP version, is it still less noisy?


ReplyQuote
(@matty)
White Dwarf Customer
Joined: 5 months ago
Posts: 15
Topic starter  
Posted by: @sparna

I have a QHY268C too, and had some problems with APP being picky about flats that other programs had no problem with....my routine now is flats and flat darks (of 2 seconds plus, as I believe these sensors are not totally linear at very short exposure speeds), and a master bias to subtract the offset from the light frames. I don't use darks with this camera as there is visually and statistically no difference in noise with or without them (and believe me, after spending hours making a comprehensive dark library when I got the camera, I really wanted to see a difference lol!). Since I don't use darks, I would have thought that I wouldn't need flat darks for the flats, but something about the way APP pre-processes means that my flats don't work without flat darks...meaning I then also have to at least use a bias on the lights.

I have a lot of issues with a lot of things in APP, but one of the reasons that I stick with it (beyond the fact that I spent so much on it) is that parts of it really are best in class - and the debayering algorithms and calibration are better than those in any other software, free or paid IMO. So I'm interested to see your results from the two, as Affinity is just about the only astro stacking software I haven't tried. If you load the unstretched Affinity stack into APP and apply the same DDP as the APP version, is it still less noisy?

Thanks for the reply…

interesting that you done use darks, I have not heard of that with this camera…I have heard that there is no need for bias, as the bias is already present in the flat darks, so I have just used Darks, Flats and Flat Darks.

I will try that with affinity, stacking and moving into APP for the DPP stretch…and let you know…👍🏼


ReplyQuote
(@mabula-admin)
Quasar Admin
Joined: 5 years ago
Posts: 3117
 
Posted by: @matty

Hi all,

so using APP now and have a new QHY268C Camera, coming from a CCD background, so this is all new to me.

stacked and calibrated an image last night of the Pac-Man nebula, took 40 x 5 min lights and 20 each of Darks, Flats and Flat darks, all put in APP, but the image came out pretty noisy even with minimal stretch, so I then loaded all the same files in the stacking tool in Affinity Photo, and first of all it took 1/4 of the time APP took, and it also came out much less noisy on default settings…

Now I would prefer to use APP as I have paid and I am used to it now, but are there any of the settings on the left side i need to play with to get better cleaner results from APP

And one more thing, with this camera should I be using Dark flats instead of bias, or using both, as the consensus seems to be not to bother with bias, my flats and dark flats are 5.6 seconds long if that has any bearing

cheers all

Hi @matty,

Thank you very much for posting your question.

Noise can only be judged correctly on the linear data result. Once you start to stretch the data, you will be stretching the noise and it is very hard to compare noise when you look at stretched data from different applications with different stretch tools.

Furthermore, APP will tell you hoe noise reduction is done in the FITS header of the stack. Have you checked the fits header of your integrations? On most datasets, APP will perform noise reduction close to the theoretical limit of noise reduction through data integration. So if you see clear differences between APP's result and from the other application then I can only assume something is not right somewhere in the workflow that you use in APP.

Well if you already shoot darks and dark flats, I would not add bias, no. Bias would only be usefull then if your sensor does not have any amp-glow and you would like to use dark frame scaling. But If your darks match your lights in terms of gain, exposure and temperature, you don't need dark-scaling 😉 so you don't need bias.

Do you want me to have a look at your data to explain what is happening in terms of noise? Maybe you can share a screenshot of the noise patterns that are bothering you? Is it random noise, are you referring to hot pixels/fixed pattern noise?

Mabula

 


ReplyQuote
(@mabula-admin)
Quasar Admin
Joined: 5 years ago
Posts: 3117
 

 

@sparna,

"Since I don't use darks, I would have thought that I wouldn't need flat darks for the flats, but something about the way APP pre-processes means that my flats don't work without flat darks...meaning I then also have to at least use a bias on the lights."

If you don't subtract any master from the flats, flats can never work properly. This is not an APP thing, this is fundamental because the flats have the sensor offset + the flat signal. That offset always needs to be removed and that can only be done properly and precisely with either bias or darkflats.

Maybe other applications subtract only an offset ADU value from the flats without using any master, but that will always be less good of course on pixel scale noise patterns and sensor characteristics, so I would not use that since creatings darks or dark flats or bias is not that hard with camera's like this.... why settle for a less precise way if the more precise way is easy to achieve?

Mabula

 

This post was modified 4 months ago by Mabula-Admin

ReplyQuote
(@matty)
White Dwarf Customer
Joined: 5 months ago
Posts: 15
Topic starter  
Posted by: @mabula-admin
Posted by: @matty

Hi all,

so using APP now and have a new QHY268C Camera, coming from a CCD background, so this is all new to me.

stacked and calibrated an image last night of the Pac-Man nebula, took 40 x 5 min lights and 20 each of Darks, Flats and Flat darks, all put in APP, but the image came out pretty noisy even with minimal stretch, so I then loaded all the same files in the stacking tool in Affinity Photo, and first of all it took 1/4 of the time APP took, and it also came out much less noisy on default settings…

Now I would prefer to use APP as I have paid and I am used to it now, but are there any of the settings on the left side i need to play with to get better cleaner results from APP

And one more thing, with this camera should I be using Dark flats instead of bias, or using both, as the consensus seems to be not to bother with bias, my flats and dark flats are 5.6 seconds long if that has any bearing

cheers all

Hi @matty,

Thank you very much for posting your question.

Noise can only be judged correctly on the linear data result. Once you start to stretch the data, you will be stretching the noise and it is very hard to compare noise when you look at stretched data from different applications with different stretch tools.

Furthermore, APP will tell you hoe noise reduction is done in the FITS header of the stack. Have you checked the fits header of your integrations? On most datasets, APP will perform noise reduction close to the theoretical limit of noise reduction through data integration. So if you see clear differences between APP's result and from the other application then I can only assume something is not right somewhere in the workflow that you use in APP.

Well if you already shoot darks and dark flats, I would not add bias, no. Bias would only be usefull then if your sensor does not have any amp-glow and you would like to use dark frame scaling. But If your darks match your lights in terms of gain, exposure and temperature, you don't need dark-scaling 😉 so you don't need bias.

Do you want me to have a look at your data to explain what is happening in terms of noise? Maybe you can share a screenshot of the noise patterns that are bothering you? Is it random noise, are you referring to hot pixels/fixed pattern noise?

Mabula

 

@mabula-admin

Thanks for the reply Mabula

here is a link to my stacked data from APP, it’s only 16 bit, i hope that is ok, I do have the 32 bit stack but not on this PC, it has a very light stretch from APP, and nothing else

104 x 2 min subs from QHY268c

Dropbox link

This post was modified 4 months ago by Mabula-Admin

ReplyQuote
(@matty)
White Dwarf Customer
Joined: 5 months ago
Posts: 15
Topic starter  

Oh well, so much for the help….☹️


ReplyQuote
(@vincent-mod)
Quasar Admin
Joined: 5 years ago
Posts: 4727
 

A bit of patience is maybe a good idea, we're a busy forum next to our work so answers are sometimes immediate, sometimes take a few days. At the moment I can't process data unfortunately, Mabula or Wouter will be able to in due time.


ReplyQuote
(@wvreeven)
Galaxy Admin
Joined: 4 years ago
Posts: 1647
 

@matty Can you upload the FITS file to

https://upload.astropixelprocessor.com/

using upload both for username and password? Create a directory matty_noisy_image and put the FITS file in there. Let me know here on the forum when the upload is complete and I'll have a look. Please do not upload a TIFF file.


ReplyQuote
(@matty)
White Dwarf Customer
Joined: 5 months ago
Posts: 15
Topic starter  
Posted by: @wvreeven

@matty Can you upload the FITS file to

https://upload.astropixelprocessor.com/

using upload both for username and password? Create a directory matty_noisy_image and put the FITS file in there. Let me know here on the forum when the upload is complete and I'll have a look. Please do not upload a TIFF file.

Sorry but that does not work, it starts asking me to sing in with a security key, and whether I use email or username it throws an error


ReplyQuote
(@matty)
White Dwarf Customer
Joined: 5 months ago
Posts: 15
Topic starter  

Tried everything and it will not let me sign in to make an account…..


ReplyQuote
(@wvreeven)
Galaxy Admin
Joined: 4 years ago
Posts: 1647
 

@matty Read my message again. You need to use upload for both username and password.


ReplyQuote
(@matty)
White Dwarf Customer
Joined: 5 months ago
Posts: 15
Topic starter  

Just says account is invalid, yet all details I enter are correct, as I just logged in with them….😡😡😡


ReplyQuote
(@vincent-mod)
Quasar Admin
Joined: 5 years ago
Posts: 4727
 

Like Wouter mentions, just use the word: upload as both the name and password


ReplyQuote
(@wvreeven)
Galaxy Admin
Joined: 4 years ago
Posts: 1647
 

@matty upload for both username and password is not invalid. I just tried. It works.


ReplyQuote
(@matty)
White Dwarf Customer
Joined: 5 months ago
Posts: 15
Topic starter  

Doesn’t work as it does not allow me to upload a Dropbox link to the tiff file…

I use  an iPad not a PC


ReplyQuote
(@vincent-mod)
Quasar Admin
Joined: 5 years ago
Posts: 4727
 

Using upload, works here as well. And you have to create a directory in there and upload the actual data in that directory


ReplyQuote
(@matty)
White Dwarf Customer
Joined: 5 months ago
Posts: 15
Topic starter  
Posted by: @vincent-mod

Using upload, works here as well. And you have to create a directory in there and upload the actual data in that directory

I have created the directly and it just asks me for the image, but it’s in Dropbox as i use an iPad not a PC, like many people 


ReplyQuote
(@matty)
White Dwarf Customer
Joined: 5 months ago
Posts: 15
Topic starter  

Ok, it’s uploading now to the Matty noisy images as you requested, it’s direct from app with a very weak stretch, and more and it’s riddles with noise, yet from affinity stacking software it was no where near as noisy….so have a look and see


ReplyQuote
Page 1 / 2
Share: