First narrowband image not very impressive!

[BrendanC]

Hi all,

I've recently made the leap from DSLR (modded EOS1000D) to mono (ASI1600MM Cool with EFW).

After the expected teething troubles, everything seems to be working OK. However, the first results are in and they're a bit disappointing!

This is the very last shot I got with the Canon - SH2-155, the Cave Nebula, in HaRGB (10:40 of Ha and 3:45 of RGB):

Honeyview_Honeyview_cave (1).jpg (185.07 KiB) Viewed 3257 times

This is what I just got with the ZWO, which I have processed as HOO because HSO looks even worse:

Honeyview_Honeyview_hoo-DeNoiseAI-low-light.jpg (191.46 KiB) Viewed 3257 times

This is from 8:44 of Ha and 4:04 O3. It's a combination of 240s and 540s exposures, because I didn't really know what I was doing with the histogram (I think I do now). Also, this was shot during a full Moon - I wanted to do it under challenging conditions just to see what came out.

There's more nebulosity I guess, but on the whole, I'm a little disappointed. The stars aren't great, and the image is generally kind of washed out.

I completely get that I knew the DSLR inside out after two years, and could get results I was really pleased with, and that hopefully, ultimately, the same will happen with the ZWO camera. Also, the DSLR version was under better conditions. But I did expect quite a lot more from kit that costs quite a lot more!

So can anyone please point in the right direction for what I might be doing wrong here, at any stage from capture to processing? Kit list is 130PDS, NEQ6, ASI1600MM with 7nm Baader narrowband filters, APT, PHD2, APP, StarTools, Topaz DeNoise AI, Bortle 4 sky, and I used 25 flats, 25 dark flats and 50 darks.

I guess for now my questions are:
* Am I right that HOO is more usually the better way to create natural colour images, rather than HSO?
* If so, should I be loading H into the red channel in Compose, and then O into both the green and blue channels?
* Should I consider using a luminance channel too? If so, would that be the Ha?
* Or... do I just need lots more data and/or should I accept that shooting during a full Moon is just too tough (which would be unfortunate because my understanding was that this was possible)?

Thanks
Brendan

[Mike in Rancho]

Nice start. I'm sure there's a learning curve to astrocams just like there was getting experienced at the DSLR.

I think the 1600 is an older model camera, so you might do some reading on best practices for exposure settings and calibration. Or perhaps you already did so.

I would have to look up your target here to see what it has to offer in terms of Ha, OIII, and SII. But OIII can be a bit impacted by the moon moreso than Ha and SII I imagine.

Still, with enough exposure time and if the target actually has those wavelengths to give, I would think you should be able to put together a decent HOO or SHO. The ST club here can certainly give things a go to see what's in the data if you want to link your three filter stacks.

I'm not sure what "natural color" means from narrowband acquisition, if anything. But HOO does sort of fall in the same general spectral locations as visual, if that's what you are looking for.

H is red and then O into G, or B, or both, and select the bicolor setting. If you put the O into both I think you have to zero out one of the exposures so that the Synth L isn't double weighted.

Putting the same Ha file into the luminance slot will just give it extra weighting, I believe, if you are choosing one of the L+Synth L options. A number of different ways of getting to the same place, if that is your goal.

Not so sure on the separate denoising program there.

[BrendanC]

Thank you Mike! I managed to get some more Ha last night under better conditions, before the Moon came up, so let's see what I can conjure up this time.

You're right about the learning curve... all over again...!

The separate denoising software is really a throwback to my DSLR days. I would really love to use the ST denoise but after having used the Topaz on some of my shots, I have to say it was a step up, at least for me. But I'm definitely open to jettisoning that and doing everything in ST.

I've looked for recommended starting points with the ASI1600. Seems a popular combination is to shoot narrowband with a gain of 200 and offset of 21 (broadband with gain 75) so I'm taking that as my starting point rather than unity gain (139).

I just did another run with the data from last night and I think I'm getting closer to something respectable, although now I think the colour is over-saturated! The stars are still a bit of a problem with those halos though. It also seems that adding Ha as a lum layer does bring out more detail, but tends towards pink rather than red (it's all subjective I know, but I prefer the deep red). I'll be taking a look at those other combos you mention too.

cave.jpg (107.03 KiB) Viewed 3215 times

[firebrand18]

Hi Brendan,

Narrowband processing is certainly a learning curve and a rewarding one once you get the hang of it, especially with ST v1.8 awesome features.

On the topic of Topaz Denoise, I also used it a while back and was initially excited with the "improvement" until I started to look real close at what was going on with the sharp/denoise process; unlike ST, Topaz DN has no real knowledge of stellar/DSO detail; it is very good with daytime/regular photography but we're talking a different animal with AP.

When you start zooming in, you will see It makes a mess of stars and starts to "create" "warp" or "alter" detail where none existed in nebulae and galaxies.

As I got more savvy and comfortable with ST, I stopped using it altogether as recognized its limitations. Your experience may differ of course but just my two cents.

CS

[Mike in Rancho]

For sure Brendan, adding extra power to the luminance of the Ha target is probably going to wash it out to pink. So no surprises there I think.

Does each individual filter stack show that you acquired decent structure in each band?

If so, a proper compose and then SHO settings in Color really should produce a good result. And probably same with bicolor.

I imagine that, as usual, either will require a throttle back of the Ha in order to help reveal OIII and SII.

[BrendanC]

Thanks again Mike. I took a shedload of S2 and O3 last night to see if I can balance things out a bit, as you suggest. I've decided to concentrate on this one object so that I can compare like with like - different channel combos, Moon phases, exposure times etc - and learn how my kit behaves. I think that after this latest batch I'll have enough to know what's working and what isn't.