PI Problems: MLT

[Baskevo]

Hi everyone,

I have always had this issue, and it is starting to get really annoying... Especially with narrowband where I have entire frames filled up with nebulosity that make it hard to use DBE. I'm going to post this up on CN and the PI forums, but I was wondering if maybe any of you have run into this issue.

So, after stacking my images, I run dynamic crop, and then I run ABE or DBE (I always try for DBE). I have had this issue, mostly when I run ABE but also with DBE sometimes, where after background extraction, I run MLT. The image looks fine and less noisy, until I restretch the image and my image looks 1000x more noisy... See the link below for images.

It happens whether I use more noise reduction or less, whether I use Starlet Transform or the MLT algorithm... I have tried using the linear mask but it does nothing to my images. I have to go back to background extraction and run DBE until I find the sweet spot, otherwise when I actually stretch, the image will be super noisy like it is when I run STF after running MLT.

Has anyone else had this problem?

Here are 4 images:
https://photos.google.com/u/1/album/AF1 ... 8Miw8wpZOg

1) Image before MLT, with autostretch
2) image immediately after MLT, autostretch still applied
3) Image restretched after MLT
4) MLT settings

Clear skies, Y'all.

[UlteriorModem]

Re-Stretch? Do you mean STF? Not an actual stretch?

If so the solution is to not do that No seriously I have run into this too and have learned that once a good STF has been applied don't change it Apply that initial stretch to your Histogram for the actual stretching.

Also ABE and DBE have problems with frames that are filled from corner to corner with nebulosity and or noise. Sometimes in that case it's best to just skip background neutralization.

[Baskevo]

Thanks for the tip UM! I figured that out the hard way... I save the process icon for the original STF, and was able to apply it to the image after MLT to get a similar, less noisier result Thanks for the help!

[UlteriorModem]

I'm not sure why this happens but it does from time to time. The idea of keeping a process icon is a good one.

[STEVE333]

Hi James - I use MLT for noise reduction on every image while still in the Linear state. It always reduces my noise.

I have an idea about what may be happening with your images. Before ABE or DBE your image may have some significant gradients that limit how much stretching STF can apply. After ABE or DBE is applied the gradients will have been removed (or greatly reduced) so when STF is applied it will apply a stronger stretch. This stronger stretch will make the noise appear larger. The noise has been reduced by using MLT, but, the stronger stretch makes it appear larger.

One easy way to test this is as follows:
1) Run ABE or DBE on your image (let's call the resulting image the Master).
2) Make a copy of the Master image, and, run the MLT on the copy.
3) With STF open, left-click in the Master image.
4) Drag the STF triangle button onto the copy. This will apply the same stretch that is applied to the Master image to the copy image.
5) Compare the noise in the two images.

Hope this helps.

Cheers,
Steve