M45- Interstellar dust or gradient?

[Icesheet]

I recently imaged M45 for the first time in years and in all honesty my first proper try. Even at that I only managed just over an hour due to clouds. When I came to process it I had real challenges with gradients. I knew there is a lot of dust in the ara but I seemed to have a strange radial gradient that I was not fully able to remove. I found an Adam Block video that had something similar and I tried his process but I'm not sure I have been successful. I can see I have some of the dust I expected there and more exposure would help obviously but there is also something else. Still looks like a radial gradient? Please comment if you have seen this too.

Tak FS60 with X.72 reducer

Zwo ASI2600MC

23x300sec

Processed in PixInsight

 

 

 

Edited January 15, 2023 by Icesheet

[ONIKKINEN]

Did you take flats and did you take them directly after the session (or is your setup permanent so that you dont have to fiddle with gear every time you set up)? And if you did, did you calibrate those flats with matching darkflats while also calibrating your lights with matching darks.

Another option would be some kind of local light source reflecting/leaking into somewhere. This kind of darkness surrounding M45 and then a sudden increase is definitely not natural and is some kind of aberration from your setup or your location.

[Icesheet]

Thanks for the reply. I should have mentioned that. I used darks and flats but they weren’t shot on the night. I just used ‘master’ ones. That could very well be the problem . I’ll shoot new ones tomorrow but it may already be a lost cause. At least it wasn’t a full night of data wasted!

[markse68]

I think it could be real- there are several images on Astrobin which show a similar bubble around them- could be from their combined stellar winds blowing the nebulosity they’re in outward or perhaps the collapsed cloud they formed from? I heard that the nebulosity  is only meant to be something they’re passing through but how can they tell that? Nice image anyway

Mark

Edited January 16, 2023 by markse68

[Magnum]

You have plenty of real dust but also the radial gradient ( reverse vignetting ) overlayed with it.

What Bortle location are you, Ive just shot this are myself and although I have the IFN / dust mine doesnt have the golden colour I was aiming for, maybe my light polluted Bortle 5.5 location.

Lee

[alacant]

Hi

Nice shot. You've some nice detail emerging.

Why not just remove the halo? The extraction takes most of the bg magenta with it too. This is with the .jpg. On a linear file, this would be far better.

Cheers

[Icesheet]

7 hours ago, Magnum said:

You have plenty of real dust but also the radial gradient ( reverse vignetting ) overlayed with it.

What Bortle location are you, Ive just shot this are myself and although I have the IFN / dust mine doesnt have the golden colour I was aiming for, maybe my light polluted Bortle 5.5 location.

Lee

I’m Bortle 4 where I’m located but mainly shooting towards Bortle 3/2 which helps. The IFN is nice but a pain to process!

 

57 minutes ago, alacant said:

Hi

Nice shot. You've some nice detail emerging.

Why not just remove the halo? The extraction takes most of the bg magenta with it too. This is with the .jpg. On a linear file, this would be far better.

Cheers

If you tell me how I will! That looks great 😊 

[ONIKKINEN]

Try Siril?

The background extraction tool in Siril can work with difficult gradients. Yours doesnt look too difficult, just have to mind the sampler placements so that the tool doesnt sample actual signal like the faint dusty parts.

[Icesheet]

51 minutes ago, ONIKKINEN said:

Try Siril?

The background extraction tool in Siril can work with difficult gradients. Yours doesnt look too difficult, just have to mind the sampler placements so that the tool doesnt sample actual signal like the faint dusty parts.

I would have hoped DBE on PixInsight could have handled it. Probably user error as sample placement is important there too. Is Siril free? Looking forward to hear what @alacant done as that looks more like what I was expecting. 

[ONIKKINEN]

18 minutes ago, Icesheet said:

I would have hoped DBE on PixInsight could have handled it. Probably user error as sample placement is important there too. Is Siril free? Looking forward to hear what @alacant done as that looks more like what I was expecting. 

It is free. I have had better success with Siril background extraction than DBE in PI, but i am a beginner with PI so wouldnt have had time to learn DBE properly.

[gorann]

Very nice, but yes you have (or had now) a radial gradient. Somtimes DBE or GradXT creates them if not set properly. Have a look at this image by @ollypenrice to see what the dust around M45 looks like.

https://www.astrobin.com/a7j34x/

Edited January 18, 2023 by gorann

[ollypenrice]

I wouldn't wouldn't want to offer the image that I took with Paul Kummer as being somehow definitive, but it was taken as a mosaic in which four of the panels met at the cluster itself. Since vignetting is panel-specific and the mosaic went together happily, I'm inclined to think that there is no dark region around the cluster, though the idea of radiation pressure creating one is plausible in principle. I've always found the same shapes in the outlying dust clouds whenever I've done M45 in widefield. It is a popular target with guests.

ABE, in particular, is prone to taking background samples which are too close to a bright central object. This often happens when it's applied to galaxy images. The result is that it over-corrects on the basis of having read outer glow as background sky. This may well have happened in your (excellent) image. Increasingly, I follow the advice of Rogelio Bernal Andreo and place as few background samples as possible in DBE, keeping very well clear of any nebulosity. The idea is to find broad gradient, not localized lightpath irregularities.

Olly

Edit: another candidate for your dark circle would be over-correcting flats, which are quite common. If this were the cause, you'd also get over-correction of dust bunnies, but there's no obvious sign of that. Perhaps you didn't have any significant dust bunnies on your flats, though? If you did, the fact that they are not over-corrected in the image suggests that over-correction won't be the cause.

 

Edited January 18, 2023 by ollypenrice
False click.

[ollypenrice]

On 16/01/2023 at 02:01, markse68 said:

 I heard that the nebulosity  is only meant to be something they’re passing through but how can they tell that? Nice image anyway

Mark

I think it's done by finding the radial velocity of the stars from their Doppler shift. When the stars of a cluster share a radial velocity and an approximate distance, it's a safe bet that they are moving together and, therefore, formed together. If their proper motion is fast they would have moved well away from their birthplace and from any relic hydrogen left over from then. On top of that, the presence of hydrogen is strikingly absent in this region. There is Extended Red Emission (ERE) but no significant Ha. Compare this with what we see in the Rosette nebula which surrounds the cluster NGC2244.

Finally, and this may be an amaeurish remark, I think we can see in the dust surrounding the M45 cluster, a kind of wake left by the stars as they move through it.

Olly

[Icesheet]

Thanks. I think I have managed to get something more realistic. I hope you don't mind that I downloaded and manipulated your image in PI to help with DBE @ollypenrice. I cropped the fov similar to mine, removed the stars and based on your image, selectively placed my DBE points. You can see the comparison below. Leaving aside the huge quality difference in the images I can now start to see similar structures in the dust now. Btw fantastic image Olly. Removing the stars realy emphasises the amount of dust around here!  I'll need significantly more integration to get close to this, if I ever can!

 

[ollypenrice]

7 hours ago, Icesheet said:

Thanks. I think I have managed to get something more realistic. I hope you don't mind that I downloaded and manipulated your image in PI to help with DBE @ollypenrice. I cropped the fov similar to mine, removed the stars and based on your image, selectively placed my DBE points. You can see the comparison below. Leaving aside the huge quality difference in the images I can now start to see similar structures in the dust now. Btw fantastic image Olly. Removing the stars realy emphasises the amount of dust around here!  I'll need significantly more integration to get close to this, if I ever can!

 

No problem. I've done something similar myself, ie use other images to estimate where the DBE samplers could realistically be placed. It's reassuring to see more agreement betwenen the images, too.

Olly

[Icesheet]

Ok, got some more data tonight and have got this. Not sure I can get better than this. 
 

 

Edited January 21, 2023 by Icesheet