Imaging at different exposure lenghts

[Mav359]

Hi guys

Ive seen people talking about imaging a DSO like M42 with two sets of subs at different exposure lenghts, one longer set to gather the detail of the nebula and a second set of shorter exposed subs to gather to detail of the core.

I understand the reason why you would do this but how do you process that information.....

1) Do you stack all the subs together regardless of their exosure times?

2) Do you need to take two sets of darks?

Cheers

[Star Gazer]

Hi Mav359,

If you see my thread:

http://stargazerslounge.com/imaging-image-processing-help-techniques/171282-hdr-merge.html

You'll see that I am about to merge multiple exposures for M42 for the very reasons you state. I think I might have gone a bit over the top with the number of exposures to merge but I am experimenting.

Anyhow you can find PS tutorials that show you how to blend using layers and masks, but I don't want to do that, so I am going to use PixInsight. There is a process in PixInsight called HDRComposition (high dynamic range) that I am going to try later today. I think Harry page was going to post one of his famous tutorials (essential if you new like me to PixInsight) on this but he's had a bit of a problem with the video not being ready, or something like that.

I think you could also try just about any HDR software out there including things like Photomatix which is normally used for daylight type HDR photography.

Have you tried DSS? Just put your different groups of exposure in different groups (tabs at the bottom of the window) and leave DSS to do the normal stacking and then merging. I'm not using this as I don't like what DSS does to the colours.

[steppenwolf]

I haven't tried the HDR approach although I can see some advantages to using it. I have tried layer masks as shown in this excellent tutorial which even features M42.

[Mav359]

Cheers guys i'll start having a read