Notty wrote:Please feel free to merge this with the similar thread on the same subject, but as that one seems to have gone cold I thought I'd start afresh. Background is DSLR, 5y elapsed experience but limited hands on in that time. Previous Photoshop user. I've not moved to mono CMOS cooled cam w.filters and had a chance this week to have a play. Moonlight so went for NB. Attempted a Hubble palatte on the Elephants Trunk and California news respectively. Here are a list of my questions, if anyone could help that would be great. Naiive and not much capture time and I went for same amount of each channel, which I suspect is not enough!
1. I have heard it said that with NB processing it is worth pre-stretching the weaker channels before merging. My data suggests this might be sensible as my Sii and Oiii are way weaker compared to Ha as one would expect. Maybe I wouldn't need to pre-stretch the Ha as it's already a strong signal. In Star Tools would we process each channel separately thus, then re-import in the RGB module, or would we do something clever in layers/masks? (my weakest subject!)
2. Colours. I can't seem to manipulate my colours to get the lovely golds and blues in the Hubble palette via ST's colour module. In Photoshop NB tutorials I've seen, you are able to manipulate the individual colour channels within themselves... does this feed into the question above whereby we would process each channel separately? If so, I imagine it would be extremely hard to gauge the effect of changing one colour on the summed effect when they are merged?
3. Is the "Cap Green" setting only relevant to LRGB imagine as we are playing with visible wavelengths? Obviously most of my image is green due to the dominance of the Ha.
4. General ST question: I can not and have never been able to use the Deconvolution module, as I can't ever get ST to create a mask for me. The alternative seems to me to create a manual one by individually selecting every single star on my image, which can't be right so I must be missing something in my understanding! I have even read the section in the unofficial user manual and am still none the wiser!
5. I have read the very helpful post on the Autodev module and am I correct that it should only be used as a temporary reveal for those of us with less than perfect data? This seems to be born out by my experience and I use Manual Dev, but can someone explain if the GAMMA is used with or instead of the DEV slide? I understand GAMMA is a preset shaped curve stretch applied, but it always seems to wash out my data so I'm not sure what the point of it is?
6. Hue/Saturation? For colours. I assume these are the function in the "LIFE" module, but none of the preset buttons seem to increase the hue or saturation, and invariably make my image look worse!
I tried to attach the best I've managed of the Elephant but once I've attached it and loaded it on the form, if I press submit the BB software just clears the screen of my entire post. Anyway I'm happy enough for a first attempt but it'd be good to know if my colour control is limited by my data or lack of technical skill on Star Tools. Thanks for any help in advance.
Notty wrote:Chris, thank you so much for taking the time to give me such excellent information. I'm going to digest what you've written and have another play and see what I can achieve. To be fair I'm starting with pretty weak data anyway as I was only giving the new camera 1st light but I was blown away with the Ha I got from a mere 50 mins worth of data low in the sky with pollution and moonlight! I'm slowly getting to grips with Start Tools as well, but my ambition is to one day be able to do everything I need in ST and ditch the (expensive) Photoshop.
ChrisLX200 wrote:You really need to normalise the background levels first, then you could stretch the signal if one channel is particularly weak.
Notty wrote:ChrisLX200 wrote:You really need to normalise the background levels first, then you could stretch the signal if one channel is particularly weak.
I'm feeling a bit thick here, but I keep reading this section and though I know what it means and what needs to be done, how/what do you use to do this bit of preprocessing Chris? Many thanks again.
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