StarTools

Hi

Over new year I took 5 hours of Ha 3minute subs with my Samyang 135 and ZWO ASI183mm. So far so good, of course the weather closed in and when I got the chance to repeat the process with OIII subs the moon was waxing towards full. I stacked and checked out both in Startools, as you might expect there was a lovely teal coloured gradient on the moon affected subs (message to self choose a target well away from the moon). I was going to discard the OIII subs, but as Sirillic stores everything so neatly I kept them.

After rereading advice on the Compose module in the unofficial user guide (drawn by the description of a teal gradient) I decided to reprocess with an agressive wipe, 97%. The result is attached.

Questions

Can I wipe the two stacks separately, save and re-Compose. Thus using a NB wipe for Ha?
I am presuming the agressive wipe setting may take away some Ha colour?
Are the grey stars in the background caused by the agressive wipe?
I used Ha-Red O-Green O-Blue, how do I weight this in Compose i.e. do I load the Green and Blue both at 100% or 100% in total

Thanks

David

I believe you can certainly split the channels (if not already separated) and run different wipes, saving the results to then be re-composed. Off the top of my head I think you want to avoid a first AutoDev? That way when you hit keep leaving Wipe the image is back to linear for saving.

I am uncertain what ST will do though once you have the final composition, and how the early pre-Wiping may affect things. We know Wipe is mandatory, as I think it sets the color floors or something like that, so that color works right later on.

You may be able to shortcut it though - using the aggressive Wipe on your OIII first and saving that, then doing your HOO compose and one of the bicolor options, after which you would then run the lighter NB-strength Wipe on the whole thing. Maybe?

Curious myself what Ivo will think of it. Aggressive Wipes can erase data (if you are unable to protect with inverse mask), but different channels, particularly noisy blue, don't always warrant the same level of wiping. True also using NBA.

Hi David,

You can, indeed use Wipe on the individual stacks and save them away (while still linear), and re-open them in the Compose module.

That said, in widefields like these, you should be able to go quite aggressive with Wipe without losing real detail.

The reason for that, is that Wipe works by separating features based on how fast they undulate. Detail undulates much faster than a gradient. If most/all of your detail is small, then you can use a much higher Aggresiveness.

Without seeing/knowing how bad the O-III gradient was, it's a little tricky to provide specific advice though.

You could also contemplate using Ha for pure luminance and use the O-III and HA for coloring.

Topographic wrote: ↑Wed Jan 19, 2022 12:59 pm I used Ha-Red O-Green O-Blue, how do I weight this in Compose i.e. do I load the Green and Blue both at 100% or 100% in total

If you use "L + Synthetic L from RGB, R(GB)(GB) (Bi-Color)" for "L, RGB". You don't have to load O twice in both green and blue (but if you do, set one of their contributions/exposure times to 0). From the docs;

"L + Synthetic L from RGB, R(GB)(GB) (Bi-Color)" creates a synthetic luminance dataset from Luminance, Red, Green and Blue, weighted according to the exposure times provided by the "Total Exposure" sliders. The colour information will consists of red as imported, with an average of green+blue assigned to both the green and blue channels. This mode is suitable for creating bi-colours from, for example, two narrowband filtered datasets.

Hope that helps!

Ivo

I tried wiping the stacks individually, saving and re-loading but the images did not align correctly. The explanation seems to be that the separate stacks saved by Sirilic, looked different, the OIII had a area at the top that needed cropping, the Ha not so, I did use the same crop. The stacks aligned perfectly before copying them.

I will try your advice and see how it looks

thanks

David