RCC: Please critique my dumbbell nebula (I’m new to mono imaging).

Médéric Hébert (sgthebert)The stars color looks weird to me, maybe try getting some RGB data for them?

Agreed.  Isn’t the nebula weird too.  I mean it doesn’t look like the common dumbbell shape you see in most images.

Tommy Mastro:

Médéric Hébert (sgthebert)The stars color looks weird to me, maybe try getting some RGB data for them?

Agreed.  Isn’t the nebula weird too.  I mean it doesn’t look like the common dumbbell shape you see in most images.

Not sure what you are on about here, it’s the perfect shape for the Dumbell Nebula, and it’s exactly how it should look shape wise, with the extra faint nebula showing around the outside, I agree the colour is a tad off, but a superb image all the same…

Tommy Mastro:
Hi all,

I’m new to mono imaging and would like some honest feedback about my latest image.  I use a very basic, straight forward SHO workflow in pixinsight. I usually struggle with stars and my background.  In this case, I feel like the whole image just came out . . . weird. 

https://app.astrobin.com/i/1ono76


Dumbbell Nebula in SHO 2025 (Rev1)
by Tommy Mastro

Published: Jul 12, 2025

Total integration: 25h 20m

Integration per filter:
- Hα: 10h (150 × 240")
- SII: 6h 40m (100 × 240")
- OIII: 8h 40m (130 × 240")

Equipment:
- Telescope: Celestron C9.25 SC XLT
- Camera: ToupTek ATR585M
- Mount: Sky-Watcher EQ6-R Pro
- Filters: Astronomik H-alpha CCD 6nm 2", Astronomik OIII CCD 6nm 2", Astronomik SII CCD 6nm 2"
- Accessory: Starizona SCT Corrector 0.63x
- Software: Pleiades Astrophoto PixInsight, Stefan Berg Nighttime Imaging 'N' Astronomy (N.I.N.A. / NINA)

For more information, visit AstroBin:
https://app.astrobin.com/i/1ono76


Thanks in advance!

Hey Tommy, to my eyes the stars look a tad bit out of focus. 
CS!
Rajat

Médéric Hébert:

Tommy Mastro:
I mean it doesn’t look like the common dumbbell shape you see in most images.

Did you have interesting data for S2? (aka should I try to get some too?)

I'm not an expert on anything so I'll let other shim in for the more detailed/complicated critique.

I only noticed that SII didn't have a lot of nebulosity around the main center like OIII and HA had.  I was basically just the ball in the center.  But I did combine them all equally, then I used Narrowband Normalization in PI to boost the OIII a bit.

Tommy Mastro:

Rajat Kumar:

Tommy Mastro:
Hi all,

I’m new to mono imaging and would like some honest feedback about my latest image.  I use a very basic, straight forward SHO workflow in pixinsight. I usually struggle with stars and my background.  In this case, I feel like the whole image just came out . . . weird. 

https://app.astrobin.com/i/1ono76


Dumbbell Nebula in SHO 2025 (Rev1)
by Tommy Mastro

Published: Jul 12, 2025

Total integration: 25h 20m

Integration per filter:
- Hα: 10h (150 × 240")
- SII: 6h 40m (100 × 240")
- OIII: 8h 40m (130 × 240")

Equipment:
- Telescope: Celestron C9.25 SC XLT
- Camera: ToupTek ATR585M
- Mount: Sky-Watcher EQ6-R Pro
- Filters: Astronomik H-alpha CCD 6nm 2", Astronomik OIII CCD 6nm 2", Astronomik SII CCD 6nm 2"
- Accessory: Starizona SCT Corrector 0.63x
- Software: Pleiades Astrophoto PixInsight, Stefan Berg Nighttime Imaging 'N' Astronomy (N.I.N.A. / NINA)

For more information, visit AstroBin:
https://app.astrobin.com/i/1ono76


Thanks in advance!

Hey Tommy, to my eyes the stars look a tad bit out of focus. 
CS!
Rajat

Yep, I solved that issue the night before last.  I wasn't using filter offsets and my auto-focus runs for the SHO filters didn't have a long enough exposure.  So when there was a filter change, the AF routine would fail.  I didn't realize this because I sleep through it, but I eventually figured out what was happening.  Now I have the ight exposure times for each filter.  Although I also have the filter offsets now, so I really will only be using my Luminance filter for focusing.  Last night's focus routines were perfect and the images sharp.

Normally in NINA, when you set up your filter offsets so that everything is referenced to the L filter. That way, if your offsets are accurate, you only have to focus for the L filter and never will have to focus the others.

Tony Gondola:

Tommy Mastro:

Rajat Kumar:

Tommy Mastro:
Hi all,

I’m new to mono imaging and would like some honest feedback about my latest image.  I use a very basic, straight forward SHO workflow in pixinsight. I usually struggle with stars and my background.  In this case, I feel like the whole image just came out . . . weird. 

https://app.astrobin.com/i/1ono76


Dumbbell Nebula in SHO 2025 (Rev1)
by Tommy Mastro

Published: Jul 12, 2025

Total integration: 25h 20m

Integration per filter:
- Hα: 10h (150 × 240")
- SII: 6h 40m (100 × 240")
- OIII: 8h 40m (130 × 240")

Equipment:
- Telescope: Celestron C9.25 SC XLT
- Camera: ToupTek ATR585M
- Mount: Sky-Watcher EQ6-R Pro
- Filters: Astronomik H-alpha CCD 6nm 2", Astronomik OIII CCD 6nm 2", Astronomik SII CCD 6nm 2"
- Accessory: Starizona SCT Corrector 0.63x
- Software: Pleiades Astrophoto PixInsight, Stefan Berg Nighttime Imaging 'N' Astronomy (N.I.N.A. / NINA)

For more information, visit AstroBin:
https://app.astrobin.com/i/1ono76


Thanks in advance!

Hey Tommy, to my eyes the stars look a tad bit out of focus. 
CS!
Rajat

Yep, I solved that issue the night before last.  I wasn't using filter offsets and my auto-focus runs for the SHO filters didn't have a long enough exposure.  So when there was a filter change, the AF routine would fail.  I didn't realize this because I sleep through it, but I eventually figured out what was happening.  Now I have the ight exposure times for each filter.  Although I also have the filter offsets now, so I really will only be using my Luminance filter for focusing.  Last night's focus routines were perfect and the images sharp.

Normally in NINA, when you set up your filter offsets so that everything is referenced to the L filter. That way, if your offsets are accurate, you only have to focus for the L filter and never will have to focus the others.

Well that depends. I have it focus on my green filter because it's the highest offset.

Quinn Groessl:

Tony Gondola:

Tommy Mastro:

Rajat Kumar:

Tommy Mastro:
Hi all,

I’m new to mono imaging and would like some honest feedback about my latest image.  I use a very basic, straight forward SHO workflow in pixinsight. I usually struggle with stars and my background.  In this case, I feel like the whole image just came out . . . weird. 

https://app.astrobin.com/i/1ono76


Dumbbell Nebula in SHO 2025 (Rev1)
by Tommy Mastro

Published: Jul 12, 2025

Total integration: 25h 20m

Integration per filter:
- Hα: 10h (150 × 240")
- SII: 6h 40m (100 × 240")
- OIII: 8h 40m (130 × 240")

Equipment:
- Telescope: Celestron C9.25 SC XLT
- Camera: ToupTek ATR585M
- Mount: Sky-Watcher EQ6-R Pro
- Filters: Astronomik H-alpha CCD 6nm 2", Astronomik OIII CCD 6nm 2", Astronomik SII CCD 6nm 2"
- Accessory: Starizona SCT Corrector 0.63x
- Software: Pleiades Astrophoto PixInsight, Stefan Berg Nighttime Imaging 'N' Astronomy (N.I.N.A. / NINA)

For more information, visit AstroBin:
https://app.astrobin.com/i/1ono76


Thanks in advance!

Hey Tommy, to my eyes the stars look a tad bit out of focus. 
CS!
Rajat

Yep, I solved that issue the night before last.  I wasn't using filter offsets and my auto-focus runs for the SHO filters didn't have a long enough exposure.  So when there was a filter change, the AF routine would fail.  I didn't realize this because I sleep through it, but I eventually figured out what was happening.  Now I have the ight exposure times for each filter.  Although I also have the filter offsets now, so I really will only be using my Luminance filter for focusing.  Last night's focus routines were perfect and the images sharp.

Normally in NINA, when you set up your filter offsets so that everything is referenced to the L filter. That way, if your offsets are accurate, you only have to focus for the L filter and never will have to focus the others.

Well that depends. I have it focus on my green filter because it's the highest offset.

Interesting.  Why would the higher offset matter?  Thanks.

For the stars, use the Seti Astro NB to RGB star combination script. 

The Seti Astro Perfect Pallet Picker is also a great script to see which pallet will work best with your data. 

In Scripts -> Toolbox there is NarrowbandHueCombination that can work well for some data. 

https://astro-photographie.fr/traitement_pixinsight.html

For the stars, use the Seti Astro NB to RGB star combination script. 

The Seti Astro Perfect Pallet Picker is also a great script to see which pallet will work best with your data. 

In Scripts -> Toolbox there is NarrowbandHueCombination that can work well for some data. 

https://astro-photographie.fr/traitement_pixinsight.html

*Awesome, thanks!

Tommy,
I haven't read through this entire thread so forgive me if I'm repeating what others might have said.  Here's what I see:

1) The stars are out of focus.  When the focus is good, the stars will be pinpoints.  Fix this first before going any further!

2) The some stars show chromatic errors, which could come from a stacking error or a problem with tracking and/or image rejection.  When you are doing this properly, the stars will have radially uniform colors.  Figure out why this is happening and fix it.

3) The stars are not well processed.  Some of them have color but they are all presented as flat-topped disks.  This is most likely because you sharpened them.  When you sharpen the nebula features, you must not touch the stars!  They should have a peaked brightness profile.  The only way to properly sharpen the stars is through deconvolution--and you should only do that once.

4) If you use NB star data (i.e. you don't insert RGB star data), you should neutralize their colors so that they all appear white.  Properly done, all white stars in a NB image look just fine.

5) The colors are indeed a little "weird" but for NB images you are allowed to map the colors however you like.  The thing you want to do is to figure out how to map them into a generally more pleasing palette.  An RGB HOO combination might work better, but there are a lot of options.

6) Pay close attention to how you set the black point.  Your background is an unappealing gray/magenta color that doesn't look anything like the blackness of space.  For this object, the black level should be roughly R=G=B and in the darkest regions, it should sit at around 18-25 for each of the color channels (in 8 bits).  25 will probably be too bright but that's something that you'd have to experiment with.

As an example, heres what I did with NB data on the same object using a HOO palette and with white stars.   https://apod.nasa.gov/apod/ap161102.html

Good luck with it!

John

Tommy Mastro:
6)  Okay, this one is over my head a bit. I'm not sure what you're referring to when you say "it should sit at around 18-25 for each of the color channels (in 8 bits).". Are you referring to the numbers within Histogram Transformation?  And what would this translate to for a 14/16 bit camera?

I was referring to sampling the brightness at a point in an eyedroper tool like the one in Photoshop.  What are you using for processing and how can you sample brightness and color?

John