Getting close to Carina

[MarsG76]

Hi Astronomers...

Sharing with you my latest completed astrophotography project which spanned across February and into March, targeting some close ups into nebulae within the southern sky constellation of "Carina".

I imaged 4 images concurrently all with my C8 at f6.3 with the QHY268M and tracked on a hypertuned CGEM mount.

All images are of objects within the constellation "Carina" but three of these images are closeups of the Great Carina Nebula, NGC3372, and the last image is the southern counterpart of the northern object in Aurgia, the "Tadpole Nebula", known as the "Southern Tadpoles" nebula, NGC 3572.

Total integration time for the first two closeups into the Carina Nebula were 20 hours, the third close up (one that looks like a profile of a face) was 13 hours and 55 minutes, and the Southern Tadpoles was 11 hours (and would benefit with a few more hours exposure through the SII and OIII filters... next time.)

All images were imaged in SII in the red, H-Alpha in the green and OIII in the blue channels.

Clear skies,

MG

 

[windjammer]

Fabulous. Absolutely amazing pics. Is there a short version of your processing path ?

Simon

[Zummerzet_Leveller]

Love to see these Southern Hemisphere targets.  So many intricate elements, especially in the first two images.  Keep 'em coming! 

[MarsG76]

11 hours ago, windjammer said:

Fabulous. Absolutely amazing pics. Is there a short version of your processing path ?

Simon

Hi Simon,

My workflow is quite simple as I do not want to muck around with my data too much and always aim for the best original stack I can record, always manually quality controlling all subs and rejecting all but the best of the night. I re-expose subs if I my data is all particularly poor or if I do not have enough for me to be happy with the integration time.
I like to aim for more than 30 subs per channel for more difficult objects or if imaging at over 1280mm focal length with my SCT.

The difference is visible in these latest 4 images... the first two were made up of exposures: Ha:50x300s, OIII:46x600s & SII:49x600s (20h00m), the third (Carina's Face Profile) exposures: Ha:35x300s, OIII:28x600s & SII:38x600s (13h55), which delivered quite a noise free stack even though the object is fainter than the first two BUT on the other hand the Southern Tadpoles were made of of exposures of only : Ha:26x300s, OIII:22x600s & SII:31x600s (11h00m), and it's a much fainter object.
The stacks resulted in being much dimmer, particularly OIII and SII was even weaker, and the stretched channels had a lot more noise which had to be dealt with... this particular nebula needs at least double the current image spent integration time and I will re-visit this object in the future.

 

Anyway, here is my processing work flow point form:

1. I align all of the stacked channels in Nebulosity

2. Crop the aligned stacked channels to crop out undesirable elements such as stacking artifacts.

3. Run all cropped channels through Starnet V2

4. In photoshop create starmasks using "Difference" between the Channel and starless channel.. I do this for all channels.

5. Stretch and process each Starless channel.

6. Combine into RGB.. these images were SHO... (Red<-SII, Green<-Ha & Blue<-OIII)

7. Generate a luminance channel before any color balancing

8. Color balance the RGB channel with using the generated Luminance channel.

9 Add the stars from the generated starmasks.

10. Final blacks and gamma level adjustment before exporting the final image... noise reduction as necessary, but at this stage I rarely have any noise in the image which needs to be removed.

Hope this was helpful,

Clear Skies,

Mariusz

 

Edited March 14, 2023 by MarsG76

[MarsG76]

1 hour ago, Zummerzet_Leveller said:

Love to see these Southern Hemisphere targets.  So many intricate elements, especially in the first two images.  Keep 'em coming! 

I imaged these regions in particular to compare the difference in detail recorded and overall image quality between my 8" SCT @ f6.3 and the same region imaged with my 80mm f6.25 refractor 2 years ago, almost to the month.

The first image is a comparison of the same area of the Carina nebula photos between the image completed recently and the cropped section of the same area from the full resolution photo taken back in 2021. The image taken with the C8 at f6.3 was scaled down to match the actual full resolution image from 2021.

 

The second image is a resolution and scale comparison of the same area of the Carina nebula photos between images taken with the 80mm refractor at f6.25 on the left and the C8 at f6.3 on the right. The image on the left is an unscaled full resolution image as recorded back in 2021 and the image on the right has been scaled down to 60% from the full resolution for presentation, effectively "BIN 2x2". Both images were taken with the QHY268M. and using the same filters.

 

I think that the bigger mirror makes a bit of a positive and sensitive difference.

 

 

 

[windjammer]

Very helpful work flow, thanks very much.  Interesting point about the number of subs - I rarely manage more than about 20 or so in each channel, just a factor of exp length (10mins) and number of clear nights.  Its better if the clear nights come in a row, otherwise I have to relearn how to drive the rig if left too long!!

Interesting too that you process each channel separately rather than as a colour combo - when I have done that I find it very hard to keep the channels 'in step'. 

Is the luminance just a b&w version of the colour combo, or is there a recipe for it ?

Great stuff

Simon

[MarsG76]

5 minutes ago, windjammer said:

Very helpful work flow, thanks very much.  Interesting point about the number of subs - I rarely manage more than about 20 or so in each channel, just a factor of exp length (10mins) and number of clear nights.  Its better if the clear nights come in a row, otherwise I have to relearn how to drive the rig if left too long!!

Interesting too that you process each channel separately rather than as a colour combo - when I have done that I find it very hard to keep the channels 'in step'. 

Is the luminance just a b&w version of the colour combo, or is there a recipe for it ?

Great stuff

Simon

Weather is a pain for all of us that is why I built a permanent setup, so that I can be imaging within 15 minutes of noticing a clear sky, this luxury makes exposing more subs or re-shooting data is easier... and if I stars and clouds come, than it's not as much of a infuriating event as spending a hour setting up for every imaging session... and we all know that weather forecasts are hardly ever accurate.

I find that processing each seperate channel independently gives me more fine details in the images as each filter records different details or parts of the details/feature. 

The luminance is one of two... either a "De-Saturated" version or a Grayscale version of the separately processed SHO image. Believe it or not those two versions do look different, more contrast than anything else tho. One looks better than the other, and this changes with images, so I keep the best looking version.