[Solved] Drizzle and Interpolation in 1.083-beta2

@blanshan91 This question is unrelated to the contents of the post where it was placed in, so I created a new topic for it.

@blanshan91 Can you please explain how you came to this conclusion? How many lights are you integrating? Is, as the help tool tip for drizzle indicates, your data well dithered and undersampled? Please give us as much info as possible to better help you with this.

I have 99 calibrated light frames that are undersampled and well dithered, and regardless of the scale and droplet size I use, the image resolution stays the same, no difference between the image versus a none drizzle image, which was why I was asking if you see the same thing. I didn't notice this until I installed latest beta

I installed the previous version of APP and drizzle works with my data, so drizzle does not seem to be working on your latest beta release.   Thanks for not testing this on your end and letting us know. 

@blanshan91 Bill, what previous version of APP did you install? Also, please note that this is a beta version and not an official release. I will pass on your findings to Mabula. In the mean time, please do not make any assumptions on what is being tested and what not. Thank you.

Version 1.082 was version I used to confirm drizzle worked.  The 1.083 beta it does not.

I understand it is a beta which was why I was letting you know of the problem.   

Any news on when this will be fixed and BETA3 will be released?

No exact deadline no, Mabula is working on the various issues and requests made for the beta.

Thanks Vince, hopefully very soon as I do like the features better in beta2 but because I am working on long focal length stuff, I really need Drizzle to work.  Is it possible to have both versions installed on the same PC?   When installing the beta it over writes the previous version I believe.  Would be nice to have the ability yo install a separate instance.  

Also, it would be really nice if Mabula would add a feature to SAVE all setting values so they can be recalled with ease, or at least automatically save all values from previous use.   IMHO, APP is still the best stacking software available, but could be faster if we didn't have to set all the settings over again

Posted by: @blanshan91

Also, it would be really nice if Mabula would add a feature to SAVE all setting values so they can be recalled with ease, or at least automatically save all values from previous use.

This is foreseen for either 1.084 or 1.085.

Hi Bill @blanshan91, @wvreeven, @vincent-mod,

I will test right now and let you know if this is indeed a bug in beta2 😉

Will report back soon!

Mabula

Hi Bill @blanshan91, @wvreeven, @vincent-mod,

I have tested drizzle in APP 1.083-beta2 with 100 monochrome frames and everything seems to work as expected. If I alter the drizzle droplet size I clearly see differences between the results. And I clearly see drizzle artefacts as a sign that the data is drizzled instead of interpolated. The metadata of the fits files also report that drizzle was used and so does the APP console.

What kind of data are you processing, is it monochrome or OSC data? What happens if you set the drizzle kernel to pointkernel (this makes the droplet size irrelevant and thus very small) ? Have you set integrate mode to drizzle instead of interpolation?

Mabula

@mabula-admin   I am doing mono and my first test was mode: Drizzle, Scale 2, Droplet of 0.9.  I have tried increasing and decreasing the droplet but doesn't change anything. I have been using TopHatKernal as I believe this was default.  Works fine in 1.082 but beta not working for me.  

Whatever I do Bill @blanshan91, all works as expected. 3 screenshots from 1.083-beta2

Interpolated:

Drizzle with tophat kernel, scale 2.0 droplet 0.9, showing clear drizzle artefacts

Drizzel with pointkernel, scale 2.0 (thus droplet infinitely small), showing a lot of drizzle artefacts because of too little data... (and too small dither steps as well)

Perhaps you can show us some screenshot between stacks that are interpolated, drizzled with different settings, and all zoomed in on the same star so we can see what happens on pixel level ?

Mabula

@mabula-admin   That is so strange.   I just tested this again, here are my screen shots which shows no change.

Is there information in the FITS Header you use to make this work so I can look this up on my end here?

Bill

@mabula-admin    Can you test something on your end.    Calibrate your lights, then save them.    Clear all files and the load your calibrated light frames back in, then run the the other processes i.e star align, normalize, etc, then test drizzle.

@mabula-admin   One more question, I noticed after you save calibrated or normalized light frames, the original fits header info is gone and replaced by APP info.  Is it possible to have both so no information is lost?

@mabula-admin   I just confirm it, if you run steps 1-6 it will allow drizzle.  If you run step 1-2 and save, then reload files and complete 3-6, it wont drizzle.   Same goes for running step 1-5 and then save normalized files, then reload and run 6, drizzle doesn't work.  

Dear Bill @blanshan91,

I will test tomorrow but I can already explain a problem here. Drizzle will not work if you load already registered (so saved at step 4 or step 5) frames. Drizzle will only work if they still need to be registered in the current APP version. This is due to the nature of how Drizzle works.

To make it possible that Drizzle works on already registered data, the registered data needs to include so-called drizzle maps and APP does not yet provide this ;-). The registered frame will then include a separate image with drizzle information needed to correctly drizzle the data.

So that would explain the behaviour that you mention I think.

Please have a look in this screenshot, you see the FITS metadata mentioning the applied integration settings including drizzle or interpolation :

Mabula

@mabula-admin  Ok, then that is the problem.   I have 4 nights of imaging and I saved all the normalized files (step-5).   Then when done, I loaded all normalized lights and reran step 5 again so all files were normalized together, then tried to process Drizzle.   

Question, is there a way to save the drizzle information within the header so drizzle could work in this process?   

Posted by: @blanshan91

@mabula-admin  Ok, then that is the problem.   I have 4 nights of imaging and I saved all the normalized files (step-5).   Then when done, I loaded all normalized lights and reran step 5 again so all files were normalized together, then tried to process Drizzle.   

 

Question, is there a way to save the drizzle information within the header so drizzle could work in this process?   

Dear Bill @blanshan91,

The drizzle maps are images themselves, they are way to large to include them in the header. It is on our todo list to make it possible to save registered data including these drizzle maps though ;-). THen if you load the registered frames and the drizzle maps, you will be able to still drizzle.

Mabula

@mabula-admin   Ah, makes sense, that would be awesome!!!