I Shot NAN…

Okay first off, granny is absolutely fine, even though she set about me with her handbag first! I didn’t shoot her. At all. In this instance NAN is an acronym for North America Nebula, or NGC 7000 to give it it’s New Galactic Catalogue designation.

The North America Nebula (note it’s “America” NOT “American” as I keep seeing online) is an emission nebula in the constellation Cygnus, very close to the star Deneb, one of the Summer Triangle.

I first imaged this region a couple of years ago using the stock Nikon D5300 at 250mm. It wasn’t a great shot and there wasn’t a huge amount of integration time either, but for my first go, I was happy enough.

My first go at NGC 7000 using a stock D5300. Not a lot of integration time but you can just make out the Pelican Nebula next door to it.

My second go at this one was not long after, but this time I decided to go for far longer using the modded 450D.

Another go, this time with the modded 450D. Loads more to see here with a camera that’s been modified for astrophotography.

As you can see, there’s a huge difference between a stock camera and one that’s been modified for astrophotography.

This time, I’m going to go back to using the modded 450D, this time on the 72ED. But now I’m going to use the ZWO Duo Narrowband Filter as well, and go for imaging this one in the HOO palette.

So join me as we return to shooting elderly relatives, this time in narrowband.

Setup

I’m going to be shooting this not long after a full moon. Normally this would be a non-starter using a DSLR, but I’m interested in seeing how much difference shooting with that duo narrowband filter makes. And I’m shooting far enough away, at least to start with, that I should have a fighting chance.

For this one I’m going to be using my tried and tested 72ED on the Star Adventurer. Imaging will be with the modded Canon 450D and the ZWO Duo Narrowband Filter. My field of view will be a lot closer than the first two images and I’ve gone for 1 minute subs at ISO 1600 as I think this will be long enough to get some okay data, but not too long that light pollution will cause me too many issues. I’m also concentrating primarily on an area of the nebula known as the Cygnus Wall, a very distinctive location that shows up well with good detail when imaged in narrowband. In fact in that first image you can quite distinctly make out the Cygnus Wall, despite the very short exposure.

Stellarium showing that my FoV (field of view) will be ideal using the 72ED and 450D

Imaging

Aside from a slight camera hiccup at the start, I managed to get on target quite quickly. It helps that the bright star Deneb is so close to the area I need to be as I use this as a point of reference. This is where it pays to have at least some knowledge of what is where in deep space when you’re not relying on computer assistance.

When I first started this hobby…sorry, PASSION…I started off by star hopping, and using a mount such as the Star Adventurer this previous experience is now paying off. It almost feels “old school” and I love it. But in fairness I still platesolve to target for the final framing, but in this case, with this mount, you can do it in the APT software by obtaining the coordinates from the objects database, and then manually moving the mount and taking test images and running each image through the platesolve routine until the coordinates of where you are match those of where you need to be.

With the nebula where it currently is, I had to do a manual meridian flip after an hour and a half, and also took the opportunity to swap out the camera battery after my dummy battery mains adapter cable snapped. All went well after the flip, then I had three and a half hours worth of data to go through, stack and process. Guiding seemed okay(ish) but there were still plenty of spikes in there. During the flip I also moved the counterweights to keep things as “east heavy” as possible. This helps in that it keeps the gears meshed in the mount and theoretically reduces backlash in the system. My setup is much too heavy for this mount if I’m honest, so any advantage, no matter how small, that I can gain can only be a benefit, although the one thing I didn’t do was to calibrate PHD2 to the area I was shooting, either before or after the flip. Can’t recall at this moment in time where I read it, but apparently if you’re using an ST-4 (as opposed to ASCOM) cable for guiding then you need to recalibrate PHD2 every time you change your target.

Eventually cloud rolled in, but it was still good to be able to not just get out and image, but to just sit out and look into the depths of space again. There’s an indefinable “something” that draws me to it time and again. Something that I never find boring or tiring. It’s not just the peace and quiet or the stillness. My brain has issues shutting down but sat out there under the stars, I can allow it to wander. I have an often busy, and sometimes complicated, life and this place I can go to is incredibly important to me. It’s where I go to give myself some reset time, and I’m truly thankful for it. I’m also grateful to Amanda for her patience and understanding. Although she shies away from the technical parts, she’s witnessed the unparalleled majesty of deep space with her own eyes and seeing her reaction to it was simply beautiful. She gets it, she understands WHY the wonders of our universe are so compelling a pull. It’s like a call home.

Stacking & Processing

This is my first time using the duo narrowband filter with a DSLR, but in all honesty, the processing won’t be any different from using my ZWO ASI178MC dedicated astronomy camera. For now, I’ll explain how I went about the processing.

In both cases I stack the data plus full set of calibration frames in AstroPixel Processor (APP) using the Ha-Oiii Colour algorithm and then extract the individual wavelengths separately, saving each version as 16bit TIF files. As a point to note, when setting up the stack you need to let APP know that you’re using an OSC (or DSLR) with a duo narrowband filter. So you need to set your bayer matrix (in my case RGGB usually), and then click “Force Bayer Matrix.” On that same initial tab you then need to change the algorithm to “Ha-Oiii Colour.” Once the stack has done, MAKE NO CHANGES! Merely save the output as a 16 bit TIF file. At this point, go back to the initial tab and change the algorithm to “Extract Ha” and then hit “Integrate.” Again once the stack has done, make no changes and just save the output file again as a 16 bit TIF. Rinse and repeat for the Oiii.

If you start making changes before you save the files, such as cropping etc, then you’re merely going to increase your workload by needing to manually realign the three output images when you take them into the next stage.

From there I import all three into Photoshop and run star reduction, deep space noise removal, and sharpening on each frame before putting the Ha into the red channel and Oiii into the blue/green channels. This is where it helps to have made no previous changes because at this point you can just CNTL-A/CNTL-C the individual Ha/Oiii images and paste them straight into the appropriate channels. After this point, crop away to your heart’s content.

Clarity, contrast and saturation are done in Lightroom before exporting as PNG.

Unfortunately I seem to have some sort of mark on the camera sensor as can be seen around the 10 o’clock position from the Cygnus Wall. I’m not sure if I’ll be able to do any content-aware clone stamping out of that but if I manage it, I’ll post it up.

The Final Images

When all was said and done, I managed to keep a paltry 147 minutes of 60 second frames. But considering the again limited exposure time, mount restrictions, etc I’m quite happy with this go at shooting an elderly relative in deep space. This will be my only go at it this season as I’m keen to move onto other projects, but I’ve already started compiling my #2022goals list and this is one I’ll be returning to next year.

So, for the time being, thank you for taking the time to read, and clear skies all!

NGC 7000 North America Nebula in HOO. 147×60 sec, modded 450D at ISO 1600, ZWO Duo Narrowband Filter, SkyWatcher 72ED
A tighter crop of the Cygnus Wall, somewhat over processed.

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