Elephant's trunk widefield

[alexbb]

Hello all,

I've been capturing photons lately on the IC1396 with a Canon 300 F4 L lens on an ASI 1600 MMC. I did that for about last month during which I didn't take the camera and the filters off the lens.

My balcony is pointed towards ~NEE so I can only see and image the sky between ~30 and ~140 degrees in azimuth and up to ~50 in altitude (with some tricks I can extend that). I shot the Ha sometimes also with the moon still up in the sky, sometimes without, when the trunk rose above ~25 degrees in altitude, the O3 above ~30 degrees and the S2 above ~25 too. In total I have 10h of Ha, 6h of O3 and 5h of S2 taken during 4, 3 and 2 nights respectively. Last night was a pain with the S2, the download from camera freezing twice and guiding going weird. Anyway, this was the last clear night, the forecast says that is going to be cloudy for a while and even if it clears, the moon will interfere so I won't get more data for a while. Perhaps I will switch to something else.

All subs are 300s at gain 139 (unity) and cooled to -15C. All calibration frames. The O3 flats looked a bit weird so I took them twice and combined the 2 results.

I can't really describe the final combination as it was more trial and error / like/dislike. The L is ~75-80% Ha and O3 and S2 equally filling the rest. The RGB was combined in StarTools and in GIMP, the layer combined in StarTools having a much higher percentage in the final blend. All processing done in StarTools and GIMP and the resizing/aligning was done manually in GIMP.

I don't know if I missed something about the acquirement and the processing.

The lens seems to have some element tilted, you can see some coma in the bottom-left corner and bloated stars in the top-right one. Better than no lens/scope though and at F/4 is quite fast.

This would be my longest project and the most detailed one (highest resolution).

I think I could get a better result from processing, but it takes ages at full resolution. Therefore I call this the final result (for a while at least).

I'm also attaching the Ha, O3 and S2 channels.

Comments and critics are welcomed.

You can also follow the progress and the testing for this target at bin2x2 here:

Thanks for looking and clear skies,

Alex

 

[Allinthehead]

Very nice Alex.

[alexbb]

8 hours ago, Allinthehead said:

Very nice Alex.

Many thanks!

I think I could have enhanced the contrast a bit more.

And I didn't mention the filters. They were Optolong Ha 7nm, O3 6.5nm and S2 6.5nm, 1.25".

[gnomus]

That is a pretty decent result, and I don't think the issues you see in the corners are worth bothering about.    All in all, I would say it was a triumph and I would be quite happy with it.  Whilst I am sure you could increase the contrast (you can always increase the contrast ), I am not sure this would improve things.  Indeed, there is a hint of black-ring-around-the-stars going on, which would probably become more obvious if you pushed harder.  Indeed, I wonder if it might be worth trying to deal with the ones you have either by a less agresive stretch or less aggressive star reduction.  

The other palette you might like is a straightforward bicolour HOO combination.  The Ha looks lovely and clean.  I wonder if the OIII could be denoised a bit more?  (I don't know if it is adding any significant 'detail' so it might not matter if it was a little 'soft'.)

[alexbb]

Hi, Steve, and thanks! I was wondering too about the stars' rings, where do they come from?! I didn't apply too much star reduction. I did only 1px star shrinking in StarTools which I combined in the final layers at <30%. I did apply though a less stretched layer with a mask containing only the stars. But the non altered stretches showed the same halos. I also excluded the stars and a considerable area around them when I sharpened a little the image and I looked carefully for this not to impact the halos. I thought then they were more because of the lens' reflections as you can see around the Garnet star. But they look centered on the stars, not eccentric towards the image sides. I'll try another approach next time.

Anyway, I don't think I'll spent too much time to reprocess these layers as I plan to gather more data on O3 and S2 in some weeks when the moon goes away. Hopefully it will clear out too by that time. I don't expect too much from this, but I hope that the noise will get down significantly. On these layers I added back some noise after the aggressive noise reduction as it looked too artificial for me. As usual, more data would have made it better.

Alex

[PatrickGilliland]

I like that, subtly processed and colour is very nice - well done.

[alexbb]

1 hour ago, PatrickGilliland said:

I like that, subtly processed and colour is very nice - well done.

Thanks, Paddy! After processing it, I decided that I will acquire more data, at least on the O3 and S2 bands. Surprise, surprise, last night it cleared out after midnight so I gathered almost 2 more hours on S2 after the moon descended to a lower altitude. Even though the moon was bright, I think the conditions were better last night after the rain compared to the previous S2 nights. I plan to gather ~10h for each channel.

Clear skies!

Alex

[PatrickGilliland]

1 minute ago, moise212 said:

Thanks, Paddy! After processing it, I decided that I will acquire more data, at least on the O3 and S2 bands. Surprise, surprise, last night it cleared out after midnight so I gathered almost 2 more hours on S2 after the moon descended to a lower altitude. Even though the moon was bright, I think the conditions were better last night after the rain compared to the previous S2 nights. I plan to gather ~10h for each channel.

Clear skies!

Alex

 

That'll certainly help out some more - look forward to the next iteration then

[alexbb]

On 4/7/2017 at 15:45, PatrickGilliland said:

That'll certainly help out some more - look forward to the next iteration then

I got about 2 more hours on each channel for a total of 12 for Ha, 8 for O3 and 7 for S2. Now, I don't know if 10h for O3 and S2 would make a real difference. I might give them a try if I get clear skies. At this resolution, processing takes a while. I should have enhanced maybe better the nebula and try to control better the stars on the O3 and S2 layers. I got some blue/brown-ish halos around the larger stars. I did no apply any kind of star reduction.

Anyway, I think this is the next iteration, not the last one, I think I'll have time to process it again, especially since my internet provider decided to "upgrade" their equipment and therefore there's no more internet for me. But I might try to throw some more subs to it.

Thanks for looking,

Alex

[Guest]

All of your pictures are, Very nice Alex.. 

[alexbb]

Many thanks, @artem! Glad you like them!

Regards,

Alex

[alexbb]

Ok, one more iteration. Now with 2.5 extra hours on O3 for a total of 10h 25min on the O3. The others are the same. This one has slightly better controlled stars, but less contrast. Which one do you prefer and what would you change about them?

Thanks,

Alex

[alexbb]

Processing day today. More contrast on this image too and more saturation. I didn't restart the processing from the beginning.

Clear skies!

[MikeODay]

Wonderful image Alex - great detail and lovely colours 

[alexbb]

Thanks, Mike!