[RCC] Medusa nebula Requests for constructive critique · Jure Menart · ... · 8 · 367 · 0

Dear forum

I finally got enough data to satisfy me (of course could be better, it can always be ) for the processing of Medusa nebula.

I would like to get some input from you what would you change in the processing. I know more data could be collected of course but as weather forecast is not best I will finish it with the data I collected. The conditions during this time really varied a lot (guiding was between from 0.5" RMS to ~1.2" RMS - so conditions were from good to mediocre I would say). I used first time 10 minute subs (usually I am going for 5 minute subs but with this low magnitude surface I found it better), luckily I didn't need to drop any frames so I think it was right decision at the end.

My flow is on PixInsight:
1. RGB stars
    - R, G and B separately GraXpert
    - R G B combination
    - RGB combined BlurXterminator (corr only is enabled by default for BlurXterminator 2)
    - RGB StarXterminator (used only stars)
    - RGB stars manual stretch with Histogram transformation
2. HOO starless
    - Ha, Oiii separately GraXpert
    - HOO combination (R=H, G=O, B=O)
    - HOO BlurXterminator
    - HOO StarXterminator (using only starless, performed StarXterminator only on H and O separately)
    - HOO stretch (Histogram transformation + STF data as input)
    - HOO curves (using starless H & O for masking, color masks & range selection - using convolution and  curves on masks), 'playing a lot with curves' (hard to describe but wanted to pull out weaker signals and not overblow stronger parts)
3. RGB stars + HOO starless combination
    - Using PixelMath with combine() and op_screen() function
    - NoiseXTerminator at the end
    - Final curve (difference between Revision 0 and Revision B)


Main question I can't decide upon I am putting to the poll - which of the two revisions you find better (either more pleasing or better because of more details). I find somehow darker (Revision 0) more pleasing but lighter (Revision B) is showing slightly more details. I tried few combinations in between but find these two 'extremes' best. I would be also glad if you comment your decision.

Revision O link: https://www.astrobin.com/du4nhz/#r0
Revision B link: https://www.astrobin.com/du4nhz/#rB

Riccardo Civati:
Hi Jure!!

first at all congratulation for the final result in both the images!!! on astrobin is one of the best!!! for me.

for me is better the darkest one but you could use curves trasformation on the lightest one ( block the point of the weakest signal and low the background signal), so you will have more contrast between medusa and background.

i am currently shoot on this nebula..80 hours SHO. hope....

ti mando il link della foto secondo me migliore esistente shooting by telescope mayall on kitt peak...4 meters mirror primary

https://noirlab.edu/public/images/noaoann09008a/

Hi Riccardo

Thanks for kind words!

I might try again to stretch a little bit as you suggested. I tried it already (I had like 5 combinations) and couldn't decide on any between the two I uploaded But today is another day and these details are best done after a while. Another issue I am seeing is that each monitor (or phone display) shows it a little bit different, so I have different favorites on different displays This is also the reason to start this poll - but as you proposed and I mentioned, there is still time to fine tune it.

I am sure with 80 hours you will get really nice details, I can't wait to see it!

I saw the image you linked and I agree - it's one of the best. I intentionally decided to go to HOO palette but next time maybe go also for SHO. You see so nice details on that image - the surrounding oxygen around the main body of medusa - I couldn't get it out, simply more data is needed

Riccardo Civati:

Jure Menart:

Riccardo Civati:
Hi Jure!!

first at all congratulation for the final result in both the images!!! on astrobin is one of the best!!! for me.

for me is better the darkest one but you could use curves trasformation on the lightest one ( block the point of the weakest signal and low the background signal), so you will have more contrast between medusa and background.

i am currently shoot on this nebula..80 hours SHO. hope....

ti mando il link della foto secondo me migliore esistente shooting by telescope mayall on kitt peak...4 meters mirror primary

https://noirlab.edu/public/images/noaoann09008a/

Hi Riccardo

Thanks for kind words!

I might try again to stretch a little bit as you suggested. I tried it already (I had like 5 combinations) and couldn't decide on any between the two I uploaded But today is another day and these details are best done after a while. Another issue I am seeing is that each monitor (or phone display) shows it a little bit different, so I have different favorites on different displays This is also the reason to start this poll - but as you proposed and I mentioned, there is still time to fine tune it.

I am sure with 80 hours you will get really nice details, I can't wait to see it!

I saw the image you linked and I agree - it's one of the best. I intentionally decided to go to HOO palette but next time maybe go also for SHO. You see so nice details on that image - the surrounding oxygen around the main body of medusa - I couldn't get it out, simply more data is needed

if you have the possibilitìy, try to use frame of 1200 s, this nebula is very weak. the image on kitt peak is a HOO but the detail goes from 4 meters of mirrors and the seeing better...

i hope in this month to pubblish my version

riccardo

Yeah maybe 1200s frames would be even better. I did step up from my usual 300s to 600s and it went well (didn't discard any frames), so I think 1200s would also work OK. Maybe you will change my mind about stopping with this project

Hello Jure,

First congratulations on both images! I think they are excellent images! Stars are round with good color and it looks like your tilt and backspacing are right there! I think the lighter one for me I like as it just glimpses a tad bit more around the nebula itself. But this may be somewhat a personal taste thing.

Over all great job!

Dale

Dale Penkala:
Hello Jure,

First congratulations on both images! I think they are excellent images! Stars are round with good color and it looks like your tilt and backspacing are right there! I think the lighter one for me I like as it just glimpses a tad bit more around the nebula itself. But this may be somewhat a personal taste thing.

Over all great job!

Dale

Hi Dale, thanks!

Yeah I am starting to get to know my old SCT (year 2006 but it still has some light in front of it obviously ), but still can't wait for my first refractor (waiting for it, already ordered ). But this SCT will always be special as it's my first

It seems that lighter one is also winning in the poll yeah, and I also started to agree the lightness is still better if it keeps more details. Maybe I will try to find middle way again (but failed before ).

Thanks again for nice words!