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Imaging the Orion Nebula

Acquisition Deep Sky M42 Messier Objects Emission Nebula
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Jerry Gerber avatar
Jerry Gerber avatar
My very first astrophotograph of the Orion Nebula isn't bad for a first attempt (https://www.jerrygerber.com/photography/M42.jpg ) but I would like to try again without overexposing the core element.  Instead of taking multiple 180 second subs, here's what I am thinking of doing:

15 subs at 30", L-Enhance filter
15 subs at 60", L-Enhance filter
15 subs at 90", L-Pro filter
15 subs at 120" L-Pro filter
15 subs at 180". L-Pro filter

After calibrating and integrating each group of subs, can I then take the master subs taken at 30", 60", 90", 120" and 180" and integrate them into one final unstretched image?   I think that way I'll have the data for the dimmest areas as well as properly exposed core data.    I've checked my earlier image and the core is overexposed on each sub, so there's no way to get that detail using those subs. 

Thanks!
Jerry
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Roger Nichol avatar
Roger Nichol avatar
For the core, think more along the lines of 5s with the L-Pro.

For my rendition, I used the following.  In retrospect, I could achieve a similar result with 180s stack, lightly stretched 180s stack OR a 30s stack and the 5s stack. 



https://www.astrobin.com/fvzdlx/B/?nc=&nce=
jewzaam avatar
jewzaam avatar
Look into High Dynamic Range (HDR) processing.  You're on the right track but you take the bright area of a higher exposure time and substitude data from a shorter exposure.  For RGB I take 15s and 120s subs and H-alpha 60s and 600s subs.  For my latest go I also took some 5s subs RGB but don't think it was needed.  Was just a "why not" experiment.  https://www.astrobin.com/ptwzja/B/
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Jerry Gerber avatar
Jerry Gerber avatar
Roger Nichol:
For the core, think more along the lines of 5s with the L-Pro.

For my rendition, I used the following.  In retrospect, I could achieve a similar result with 180s stack, lightly stretched 180s stack OR a 30s stack and the 5s stack. 



https://www.astrobin.com/fvzdlx/B/?nc=&nce=

Thanks Roger!  Your image looks really good.  Why use the broadband filter on the core when the narrowband filter (L-extreme) blocks more light?
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Roger Nichol avatar
Roger Nichol avatar
Jerry Gerber:
Why use the broadband filter on the core when the narrowband filter (L-extreme) blocks more light?

Well, the core is very much broadband so merging a narrowband core with the surrounding broadband might lead to some undesirable consequences.  Not saying it can't be done though, perhaps using a 3nm Ha stack of short exposures as a luminance applied to the broadband core... ?  

FYI, I found blending the different stacks much easier in Photoshop as it is easier (for me) to mask and interactively adjust the transparency of the various layers rather than relying on iterations of PixelMath or similar.
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Jerry Gerber avatar
Jerry Gerber avatar
Roger Nichol:
Jerry Gerber:
Why use the broadband filter on the core when the narrowband filter (L-extreme) blocks more light?

Well, the core is very much broadband so merging a narrowband core with the surrounding broadband might lead to some undesirable consequences.  Not saying it can't be done though, perhaps using a 3nm Ha stack of short exposures as a luminance applied to the broadband core... ?  

FYI, I found blending the different stacks much easier in Photoshop as it is easier (for me) to mask and interactively adjust the transparency of the various layers rather than relying on iterations of PixelMath or similar.

OK, I'll consider that.   I find that Pixinsight is great for calibration, integration and stretching, and a few other post-processing tasks.  But I always use a program called ACD Ultimate Photo Studio to do my sharpening, cropping, color balancing, tonal balancing and, if desired, working with hue, saturation and color brightness.  At the post-processing stage of image creation, a stacked, aligned and integrated image is not unlike any other photographic image.  Of course things like star reduction are best handled by PI, but even gradient removal is a lot more intuitive in a traditional photo editor, at least if it's a good one.
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KIJJA JEARWATTANAKANOK avatar
KIJJA JEARWATTANAKANOK avatar
Hi
I share the same opinion about the shorter exposure for nebula core. My last M42 image the nebula core was burned with 30s subs (https://astrob.in/javd8l/0/). And for HDR blending, if you already have Pixinsight, try HDR composition tool. It works great!

CS
Kijja
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Stuart Taylor avatar
Stuart Taylor avatar
+1 for a 5 or 10 sec sub for the core. It's very bright, even with a filter.
Ryan Abbott avatar
Ryan Abbott avatar
In my opinion (even though it's quite inexperienced), you only really need 2 sets of exposures, one for the core and one for the rest of the detail.
Whether it's 5s or 10s subs for the core and 120s or 180s subs for the details, it doesn't matter too much. It only matters that you have a non blown out version of the core to mask into the longer exposed stack.

Below is my latest version (only version i've ever uploaded here) which uses 10s for the core and 120s for the details, just to help you gauge a bit.
I didn't use the HDR tool in PixInsight and i purposely left the core fairly bright without clipping anything just to capture the more natural look. I'm personally not that keen on HDR looking versions but it's all preference.

https://www.astrobin.com/12yzsp/

CS,
Ryan
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