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):

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

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 Baader 7nm 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?
* 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

[vlaiv]

11 minutes ago, BrendanC said:

Am I right that HOO is more usually the better way to create natural colour images, rather than HSO?

No, both are equally false color. Difference is in having only color gamut - one is inherently bicolor and other is tricolor. Much more color variety can be produced with three components as opposed to two.

13 minutes ago, BrendanC said:

Should I consider using a luminance channel too? If so, would that be the Ha?

This is generally good practice if Ha represents object well. Most objects have Ha component in everywhere, but there are some objects where Ha is very separated from OIII and with these objects you will loose out if you use Ha only as luminance.

Best way to tell is to stretch both Ha and OIII as mono images and just look if OIII signal appears where Ha appears as well - if they match in location (Ha is likely to be much more spread) - then you can use Ha as luminance.

Other way would be to just do it and see if you like the result

15 minutes ago, BrendanC said:

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)?

It is myth that you can properly image narrowband with moon out. Yes, narrowband helps with LP and moonlight - but that simply does not mean that results will be anywhere as good as in proper darkness.

Narrower the passband of filters - more it helps. 7nm is not very narrow.

[BrendanC]

Thanks @vlaiv, all great advice, as always.

7nm is what I've got, unfortunately! It would also appear that, well, shooting in the poorest of conditions is giving me the poorest of images.

The next few nights are very clear, with some windows of opportunity while the Moon is still below the horizon, so I'm going to try and get fresh, clean data during those times and see what happens.

Cheers, Brendan

[bomberbaz]

I am new to ths imaging game but thought some bias would help clean up the image!