Integrating different exposure lengths in Pixinsight - Forums

Topic starter

Jan 10, 2022

Hi,

I have been putting together some images in Pixisnight with differing exposure lengths. I'm just looking for some confirmation that I'm doing it in a way to get the best result.

Right now I am using WBPP to create registered images then I use NormaliseScaleGradient and a subsequent ImageIntegration to create the masters for each exposure length. I duplicate the masters for each exposure so that I can get around NSG's 4 image minimum.

I have also used PixelMath to combine the masters for each exposure, but I find that it creates a noisier image that way.

Is there a better way to do this?

Thanks and all the best
Nick

Well Written Respectful

Michele Campini

Jan 10, 2022

1) only calibrate every light of each session with his flat (flatdark or bias) and dark
2) make a staralign for all the calibrated > debayered of any session so u've all the registered of all the session
3) using imageintegration u can integrate all the registered, u've to active the rejection (winsorized of what u prefer).

Do not merge master light with pixelmath, it's nonsense. If u want merge masterlight u need use hdr composition.

But after many test i prefer use imageintegration instead of hdr composition.

John Hayes

Frequent contributor

Exemplary contributor

Jan 10, 2022

I've never tried using NSG but your procedure sounds right.

Here's one that I've used:
1) I create two integrated masters for each exposure time.
2) Make a copy of each master so that you have a total of four images.
3) Load them into the ImageIntegration tool.
4) Use averaging and set the weighting to either "SNR Estimate" or "Exposure Time".
5) Turn off "rejection" and integrate the four frames. (PI won't let you integrate just two frames, which is why you have to copy the two integrated masters.)

This procedure will produce a weighted average to increase the SNR in the output. This is mathematically the same as just dumping all of your registered subs into the ImageIntegration tool and specifying using the same weighting option to combine everything in a single step.

John

Well Written Helpful Insightful

AstroNick

Topic starter

Jan 10, 2022

It sounds like I'm not too far off the money then. I'm fairly new at PI and it struck me that I hadn't done this before (previously I'd only used subs with the same exposure length) so just wanted to check that I wasn't missing out on something that made it fundamentally easier or the result better.

Thanks to you both for replying.

Nick

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