IC 1396 (Elephant Trunk) in Narrowband with a Nikon D5300a

[Xiga]

Hi Fellow Gazers!

 

I’ll cut straight to the chase. This is:

 

7 x 600s Ha

15 x 900s OIII

Total Exposure time 4 Hrs 55 mins

2” Baader filters.

30 Flats and 50 Bias. No Darks. Dithered every frame.

Nikon D5300 (modded by JTW Astronomy)

Skywatcher 80ED

Skywatcher HEQ5 Pro Mount (with Rowan Belt Mod)

Guided using an absolutely ancient QHY5 through PHD2 (using the new PPEC algorithm, which I found did lower my RMS slightly)

Captured with SGPro

Pre-Processed in APP

Post-Processed in PS

 

This wasn’t actually meant to be a full process tbh. I just started quickly playing with the data, and once the classic Hubble golden hues started to appear I was addicted and just couldn’t stop! Lol. So I didn’t even bother doing any gradient reduction on the Ha and OIII stacks.

I used one of Annie’s Astro Actions (Hubble Palette Creation) to build the image. Obviously this requires an SII image, so for that I just layered the OIII over the Ha and blended at 80% opacity (so 20% Ha and 80% OIII) to create a synthetic SII. Does anyone know if it’s better to use the ‘Channel Mixer’ option instead for this?

I then used Bob Franke’s excellent colour-mapping tutorial to bring out the classic Hubble Palette colours.

Once I was happy with the colours I then added back in the Ha-only image as Luminance, and blurred the colour layer to remove the noise. Adding the Ha back in as Luminance made a huge difference to the noise and really reduced the truly massive stars from the OIII image (which had to be stretched aggressively).

Then the usual final tweaks, star reduction, minor levels & curves, a hint of further noise reduction, etc

 

The OIII subs showed virtually nothing on screen, even with SGP’s auto-stretch set to High. The moon was also a major factor over the 2 nights, it was in the region of about 85% - 95% illuminated! (the OIII subs did have a noticeable gradient as a result) .I probably shouldn’t have bothered with the OIII in fairness and just concentrated on getting Ha, but I hadn’t actually used the OIII filter since I bought it so I just couldn’t resist! I need to capture a LOT more Ha for this though, hopefully I can add to it soon.

 

When I do a re-process (hopefully soon) I will make the following corrections:

 

1. Remember to add in the last 2 OIII subs (total 30 mins) that I somehow missed out on this version (doh!)

2. Use a better blend for creating the synthetic SII. The OIII image is so much noisier than the Ha one, so it probably makes more sense to use a higher percentage of Ha than OIII, probably something like 60% Ha and 40% OIII.
3. I actually have another 5 600s Ha subs that I omitted due to them being affected by thin high-level clouds. I did a stack using all 12 subs, and I was amazed at how good it still looked (APP’s ‘Quality’ setting seems to work really well at weighting the subs accordingly). So I think next time I will use all 12 Ha subs as it should lead to significantly lower noise (which is excessive at the moment).
4. Do gradient reduction on the Ha and OIII stacks.

Narrowband imaging is all a bit new to me so C&C, and any tips, will be most welcome.

Clear skies folks!

 

https://flic.kr/p/Dbtyvj

 

[sloz1664]

Hi Ciarán

Given the shortish imaging time you have used for this image, I think you have done very well and is a really good image. I would increase my Ha to 15 - 20 min to get as much detail as you can. This could be done whilst the moon is in view. Oii and Sii similar exposures but you need to be aware the moon will have an effect on them. love the hubble colours BTW.

Steve

[Xiga]

Thanks Steve!

I was just thinking the same thing myself. This was my first attempt at going beyond 8 min exposures, and the mount seemed to handle the 15 min ones just fine, so I think next time I will aim to just capture 20 min subs regardless of whether it is Ha or OIII. And even though I don't think my camera benefits from darks at all, i'll experiment with a few just to see if the longer exposures are more dependent on them.

Even though the OIII exposure makes up about 75% of the total, the vast majority of the actual signal is coming from the Ha, and 70 mins just isn't cutting it yet. So I definitely need to add to it (Sunday night is looking promising so hopefully then!)

[tooth_dr]

Stunning Ciaran. Can’t wait til see what you can do with 15-20 minute subs.  

[newbie alert]

I'm not usually a fan of the Hubble pallete..but I really like this..job very well done

[Rico]

1 hour ago, Xiga said:

And even though I don't think my camera benefits from darks at all

I take you have no amp glow of any kind ?

[Xiga]

55 minutes ago, tooth_dr said:

Stunning Ciaran. Can’t wait til see what you can do with 15-20 minute subs.  

Thanks Adam!

 

23 minutes ago, newbie alert said:

I'm not usually a fan of the Hubble pallete..but I really like this..job very well done

Cheers sir :-P

 

3 minutes ago, Rico said:

I take you have no amp glow of any kind ?

That's right Rico. I've never seen any with my D5300, which is an absolute blessing, as I would really hate having to deal with taking darks with an uncooled camera! I normally just use Bias and Flats, along with heavy dithering, and the stacks come out clean and free of any walking noise.

[Uranium235]

Very interesting image, and it provides encouragement for me in regard to the idea of caputing OIII with a DSLR.

[Xiga]

22 hours ago, Uranium235 said:

Very interesting image, and it provides encouragement for me in regard to the idea of caputing OIII with a DSLR.

Cheers mate! :-)

Yes, OIII is doable with a DSLR, but you need looong exposures, and lots of them to boot! Not exactly efficient, but certainly possible.

ps - I was out again last night. Managed to grab another 13 * 900s of Ha. I reeeally wanted to go for 1200s, but after initially getting rained on (!) and frantically dis-assembling everything and getting it all back inside, it then cleared up, and being the insane person that I am I went back out again (cue another hr of setup). Didn't want to risk losing any subs to clouds, so decided to compromise at 900s. And wouldn't you know it, the skies were perfect for the next 4 hrs! Will post up the new version when I get a chance to process it later in the week.

[MartinB]

Wowsers, looks great, love the colour.  The noise does take over a bit when looking at the larger image so worth getting more data