PixInsight Forum (historical)

PixInsight => Tutorials and Processing Examples => Tips & Tricks => Topic started by: jeffweiss9 on 2010 November 06 13:10:16

Title: Help with StarHaloReducer
Post by: jeffweiss9 on 2010 November 06 13:10:16

I've not been able to get that to work successfully and could use some advice on how to use it to successfully reduce halos.
When I adjust R, G B upward to reduce the halo and then try to blend the outside regions with the background using the RGB/K slider, I'm unable to match the background and, if I get anywhere close, I've cancelled out the halo reduction.  What is the proper workflow to use this?

Also, I've tried to reset setMinSize to get a big enough image of the star shown by the tool but couldn't get that to work either. Is there a good setting to use that lets you actually see the halo and star radii that you are trying to set?

Thanks very much.  This should be an extremely useful tool if I can figure out how it is supposed to be used.
-Jeff

Title: Re: Help with StarHaloReducer
Post by: Silvercup on 2010 November 06 18:09:41

Hi Jeff:

If you could upload a jpg of your image I'll try to fine-tuning the parameters.

Best, Silvercup

Title: Re: Help with StarHaloReducer
Post by: jeffweiss9 on 2010 November 07 08:39:05

Thanks, Juan Manuel-
 I attach a jpg and would love to know the right settings as well as a bit on how to get to them using the displayed image, if possible.
-Jeff

Title: Re: Help with StarHaloReducer
Post by: sigurd on 2010 November 07 10:02:34

I gotta' say, those don't really look like haloes in the usual sense (internal reflections). I think if they were they'd have a more sharply defined boundary.

Nevertheless, I'd also like to see some examples, since I also haven't really gotten the halo reducer to work well for me either. :)

-esy

Title: Re: Help with StarHaloReducer
Post by: jeffweiss9 on 2010 November 07 10:35:42

Not sure if the flares on these bright stars weren't worsened by the fact that I forgot to extend the SVR90T lens shade / dew shield for this data collection so the objective was exposed to nearly 180 deg of light.  But I wouldn't think that affects the optics.
-Jeff

Title: Re: Help with StarHaloReducer
Post by: harist on 2010 November 08 04:11:41

Well, after  a few unsuccesfull attempts with the HaloReducer (couldn't match the background, couldn't even get close), I decided I like Halos and I left them alone!

Tasos

Title: Re: Help with StarHaloReducer
Post by: Silvercup on 2010 November 09 07:48:14

Hi all:

Well, let's go.

I developed SHRscript for individual halos on brighter Stars.

Jeff, in your image you has gotten halos in every big and medium star, prehaps due to humidity. You must be very carefull masking your star to avoid halo growth.

I always advise a double HistogramTransformation. In a first step I use MaskedStrech Script with a Target Median of about 30%-40% of the Median we want to reach if we manualy strech the image (duplicate image, manual HistogramTrasnformation, see statistics and the median value) an then do a second manual HistogramTransformation in the usual way.

Anyway, this is the procedure to reduce Halos.

You need to run several script iterations. In the case of this example 3 iterations are necesary. You need to precisely place star center and halo center. To do this move RGB/K slider to darken the halo so yo can see if it is centered. for the star darken any r, g or b slider and check star center.

First Step:

(http://farm5.static.flickr.com/4017/5161572920_f636492687_b.jpg)

Second Step:

(http://farm5.static.flickr.com/4133/5161573044_f9dc3013bc_b.jpg)

Third Step:

(http://farm5.static.flickr.com/4015/5161573154_3dbaa6d09c_b.jpg)

Image comparation:

(http://farm2.static.flickr.com/1392/5160970575_70ee7bae48_b.jpg)

I hope this helps.

Best. Silvercup

Title: Re: Help with StarHaloReducer
Post by: Jack Harvey on 2010 November 10 06:16:02

Interesting  Are you going to put the script on the Scripts gallery?

Title: Re: Help with StarHaloReducer
Post by: Silvercup on 2010 November 10 07:04:00

Hi Jack:

Where is script gallery?.

Script is included in the PI utility scripts.

Silvercup.

Title: Re: Help with StarHaloReducer
Post by: Jack Harvey on 2010 November 10 13:22:01

Thanks I missed it

Title: Re: Help with StarHaloReducer
Post by: jeffweiss9 on 2010 November 12 10:59:21

Thanks for posting that, Silvercup-
 I'll need some more practice with it, as (since I already had changed the image slightly from what I posted) I had some difficulty doing as good a job of matching the background as you did.  I still leave square (and other) discontinuities.  It's not the reason for my problem, but it might be helpful for sight-challenged people like me if we could increase the displayed image size by a factor of 2 or 4 to more-easily see that crucial boundary.  I tried doing that in the source but for some reason it usually reverted to the default image size - just as I was getting closer to the larger image I was seeking.
Thanks again.
-Jeff

Title: Re: Help with StarHaloReducer
Post by: Nigel Ball on 2010 December 16 03:23:43

Jack, I hope you don't mind me resurrecting your opriginal thread but I also need some help with halo reduction

I've taken a set of HaRGB on the area around Gamma Cass - see screenshot below for an idea of the problem I will face. These are STF auto stretched combines as follows

R,G,B  2x2 6x5 mins

Ha 1x1 13x20 mins

I'm looking for some guidance on workflow more than anything

Thanks in advance

Nigel

Title: Re: Help with StarHaloReducer
Post by: Nigel Ball on 2010 December 16 06:40:35

**** UPDATE ****

I've had a play in my lunch hour and had some success. However, I seem to get a hard edge is there a softness setting somewhere?