RASA 8 is back: Iris Nebula chased by some dark nebulosity

[ollypenrice]

1 minute ago, gorann said:

Hi Olly,

I am in the middle of the Friday night dinner so this is a short response. The 400 mm FL does not give super resolution to the Iris so I could allways add that later from old data I have. And seeing was not the best and the scope is not on my Mesu but on a NEQ6, so I was tempted to add old data to the Iris. But what I think is amazing is how deep you can ho with this sytem in just 8 hours. I really had to suppress some of the faint stuff not to overwhelm the image with dust - it could have been so much more dusty.

Bon appétit!!! I like the high contrasts in the dust and wouldn't hesitate to blend in high res Iris. That's exactly what I did.

Olly

[gorann]

1 hour ago, ollypenrice said:

Bon appétit!!! I like the high contrasts in the dust and wouldn't hesitate to blend in high res Iris. That's exactly what I did.

Olly

Yes Olly, I will make an ultimate blend with old data. I here just wanted to show what the RASA 8 could do in 8 hours (and soon there will be 12 hour nights up here😁). So I see this scope as a deep diver and not big resolutioner, and not a competitor of  big mosaics. But, as I think you have said, images should be looked at the pixelscale they are presented at (although we image proessors are all by habitat pixel peepers). Back to dinner and a discussion about fish genomes (my wife is also a biologist).

Edited October 16, 2020 by gorann

[Erling G-P]

52 minutes ago, gorann said:

..., and not a competitor of  big mosaics.

On the other hand, you could do an entire mosaic in a single night... 😁

[gorann]

1 hour ago, Erling G-P said:

On the other hand, you could do an entire mosaic in a single night... 😁

that is a thought😉, but for now a bit too complex and exchausting since I usually run a second rig with two refractors and are costantly fighting with computers that don't do their jobs, like last night....

[ollypenrice]

9 hours ago, gorann said:

that is a thought😉, but for now a bit too complex and exchausting since I usually run a second rig with two refractors and are costantly fighting with computers that don't do their jobs, like last night....

Yes, I too find that enough is enough!

😁lly

[tomato]

12 hours ago, gorann said:

that is a thought😉, but for now a bit too complex and exchausting since I usually run a second rig with two refractors and are costantly fighting with computers that don't do their jobs, like last night....

Yes, I don't know how you guys manage to  run multiple observatories at the same time, not much of the software seems robust enough to run unattended for long, but maybe that's me not being rigorous enough in the set up.

I am taking tiny steps towards unattended operation, but clear sky is currently so scarce I don't want to waste it playing around with the kit, there is only so much you can do in daylight.

[gorann]

2 hours ago, tomato said:

Yes, I don't know how you guys manage to  run multiple observatories at the same time, not much of the software seems robust enough to run unattended for long, but maybe that's me not being rigorous enough in the set up.

I am taking tiny steps towards unattended operation, but clear sky is currently so scarce I don't want to waste it playing around with the kit, there is only so much you can do in daylight.

Seems like every time I leave the obsies unattended for an hour or two something happens, often a computer that decides to stop downloading. Tonight I am going to try AstroImager to control the cameras. Hopefully more stable than ASICAP but I am sure there will be some hours of complete confusion🥴

[wimvb]

23 hours ago, ollypenrice said:

 

On 16/10/2020 at 00:00, gorann said:

Thanks a lot Andrew! Yes I am pleased about how it turned out. Maybe it is the amount of photons the RASA collects (7.8 hours at f/2 corresponds theoretically to 96 hours af f/7) that makes the "dark" nebulosity look quite bright.

Now you know what I'm going to say to that! 🤣  How did the photons entering your objective know the focal length of the system that followed? What matters is aperture and pixel size. F ratio is hot air. You proved this with your Liverpool Telescope images!

Olly

Well, actually...

The photon capturing ability of an  imaging system is proportional to the square of (pixel size / f-number). That’s why the f-rule works in day time photography; you can swap lenses and keep the exposure time if you don’t change the f-number. But this relationship can also be stated as: the capturing ability of an imaging system is proportional to the square of (aperture x imaging scale (”/pixel)). A lower f-number will either mean that you have a larger aperture, or you put more sky on each pixel. Both will get you more photons on each pixel.

In Görans case, if he had used a 400mm telescope with a 56 mm f/7 aperture, he would probably still be collecting photons.

The reason why the Liverpool telescope is so good at collecting photons, is its 30 um pixels at f/10, giving it an imaging scale of 0.3”/pixel at 2 m aperture.

[ollypenrice]

15 minutes ago, wimvb said:

Well, actually...

The photon capturing ability of an  imaging system is proportional to the square of (pixel size / f-number). That’s why the f-rule works in day time photography; you can swap lenses and keep the exposure time if you don’t change the f-number. But this relationship can also be stated as: the capturing ability of an imaging system is proportional to the square of (aperture x imaging scale (”/pixel)). A lower f-number will either mean that you have a larger aperture, or you put more sky on each pixel. Both will get you more photons on each pixel.

In Görans case, if he had used a 400mm telescope with a 56 mm f/7 aperture, he would probably still be collecting photons.

The reason why the Liverpool telescope is so good at collecting photons, is its 30 um pixels at f/10, giving it an imaging scale of 0.3”/pixel at 2 m aperture.

Yes, but I read 7.8 hours at f/2 corresponds theoretically to 96 hours af f/7 as a statement making no reference to pixel size. If it is a statement in which we are to consider pixel size as a constant then that's another matter.

Olly

[gorann]

9 minutes ago, ollypenrice said:

Yes, but I read 7.8 hours at f/2 corresponds theoretically to 96 hours af f/7 as a statement making no reference to pixel size. If it is a statement in which we are to consider pixel size as a constant then that's another matter.

Olly

Hi Olly! Yes, I made no reference to pixel size since I kept that constant in my comparison. In my mind I was thinking that nothing else was changed but aperture, so comparing two scopes with the same FL but different aperture, and with the same camera. Of course few would probably buy 400mm FL f/7 telescopes so it may be a bad comparison, but compared to an Esprit 80 with 400 mm FL (and I love Esprits), the RASA collects 6.25 times more photons per unit of time, so 7.8 hours with the RASA 8 corresponds to 49 hours with an Esprit 80.

Edited October 17, 2020 by gorann

[wimvb]

2 minutes ago, ollypenrice said:

If it is a statement in which we are to consider pixel size as a constant then that's another matter.

Olly

I think we have to consider pixel size. We need to include the complete geometry of the system, and that includes pixel size. Otoh, if the system is extremely undersampled, pixel size is irrelevant, and so is f-number. If the light from a star falls on only one pixel, no matter what size that pixel is, aperture is the only parameter that determines photon capturing ability.

[gorann]

On 16/10/2020 at 21:10, ollypenrice said:

Bon appétit!!! I like the high contrasts in the dust and wouldn't hesitate to blend in high res Iris. That's exactly what I did.

Olly

So here it is Olly @ollypenricewith blended in high resolution data on the Iris (952mm FL refractor) I had from 2016. I like the result.

[The Admiral]

1 hour ago, gorann said:

So here it is Olly @ollypenricewith blended in high resolution data on the Iris (952mm FL refractor) I had from 2016. I like the result.

Could it have got any better? Yes, clearly it can! I like the result too .

Ian

[gorann]

48 minutes ago, The Admiral said:

Could it have got any better? Yes, clearly it can! I like the result too .

Ian

Thanks a lot again Ian! Good to know I am on the right track😁

[ollypenrice]

2 hours ago, gorann said:

So here it is Olly @ollypenricewith blended in high resolution data on the Iris (952mm FL refractor) I had from 2016. I like the result.

 

Ooh yes, much nicer. Well blended. (What did you use? The PI Inquisitors regard this as 'painting.')

What continues to impress me (and make me curious) is the level of contrast between brown dust and background sky. I would say that I have as much signal in mine but the contrast, particularly in distinguishing brown from dark background blue, is far less.

Olly

Edited October 18, 2020 by ollypenrice
Typo

[gorann]

26 minutes ago, ollypenrice said:

Ooh yes, much nicer. Well blended. (What did you use? The PI Inquisitors regard this as 'painting.')

What continues to impress me (and make me curious) is the level of contrast between brown dust and background sky. I would say that I have as much signal in mine but the contrast, particularly in distinguishing brown from dark background blue, is far less.

Olly

I first resized (reduced) the high resolution image in PS (I usually do it by measuring the distance (in pixels) between the same two stars in the images to calculate a reduction factor). I then just did a star alignment in PI using the RASA image as template. Then I added it as a layer to the RASA image and used the dreaded brush too to let about 50% through on the nebula.

I am also amazed how bright the images turn out initially and I think it is not only the RASA but also have to do with the camera, the ASI2600 is just a fantastic camera with virtually no noise, thus allowing a lot of stretching. I also often increase the brightness and dustiness using a trick you taught us here on SGL: I add an Equalize layer selectively, usually just a few %.

Did you see the quite dusty M45 that I posted yesterday? Your "Equalize method" helped a bit on the dust there.

 

[ultranova]

Most impressive, for me it has to be the best take 

I have seen of this area, 

superbly processed and framed

well done 

Paul

[gorann]

22 minutes ago, ultranova said:

Most impressive, for me it has to be the best take 

I have seen of this area, 

superbly processed and framed

well done 

Paul

Thanks Paul! You are much to kind😊

[wimvb]

2 hours ago, ollypenrice said:

What did you use? The PI Inquisitors regard this as 'painting.'

All other PI users call it 'High Dynamic Range Composition', or possibly just 'Pixelmath'. 😉

Fabulous blend, Göran.

This camera is one of the first (with the ASI6200) astro cmos cameras to have a 16 bit ADC, and a dynamic range of 14 stops (bit). I suspect that this is the reason why you can achieve such amazing depth in only a short time. The camera can handle the photons that the RASA sucks in, in both the bright and the dim areas.

Edited October 18, 2020 by wimvb

[gorann]

15 minutes ago, wimvb said:

All other PI users call it 'High Dynamic Range Composition', or possibly just 'Pixelmath'. 😉

Fabulous blend, Göran.

This camera is one of the first (with the ASI6200) astro cmos cameras to have a 16 bit ADC, and a dynamic range of 14 stops (bit). I suspect that this is the reason why you can achieve such amazing depth in only a short time. The camera can handle the photons that the RASA sucks in, in both the bright and the dim areas.

There you go Olly @ollypenrice, it is the 16 bits of the camera - but then also CCDs are 16 bit, but they may be old and noisy😉 and not so stretchable.

[ollypenrice]

2 hours ago, gorann said:

I first resized (reduced) the high resolution image in PS (I usually do it by measuring the distance (in pixels) between the same two stars in the images to calculate a reduction factor). I then just did a star alignment in PI using the RASA image as template. Then I added it as a layer to the RASA image and used the dreaded brush too to let about 50% through on the nebula.

I am also amazed how bright the images turn out initially and I think it is not only the RASA but also have to do with the camera, the ASI2600 is just a fantastic camera with virtually no noise, thus allowing a lot of stretching. I also often increase the brightness and dustiness using a trick you taught us here on SGL: I add an Equalize layer selectively, usually just a few %.

Did you see the quite dusty M45 that I posted yesterday? Your "Equalize method" helped a bit on the dust there.

 

Although it's not cheap, Registar would do this job in a couple of clicks and do it infallibly. If you're going to do a lot of composite imaging I think it would be worth it. I don't combine the component images in Registar for the reasons implicit in your workflow. I do it in Photoshop so I can feather in the high res gradually and control the opacity of the blend. https://aurigaimaging.com/

Splendid M45.

Olly

[gorann]

15 minutes ago, ollypenrice said:

Although it's not cheap, Registar would do this job in a couple of clicks and do it infallibly. If you're going to do a lot of composite imaging I think it would be worth it. I don't combine the component images in Registar for the reasons implicit in your workflow. I do it in Photoshop so I can feather in the high res gradually and control the opacity of the blend. https://aurigaimaging.com/

Splendid M45.

Olly

I have seen you talk warmly about Registar and would have it if it was not that I do all my processing on a Mac and I think Registar is just Windows. I do use some Windows machines for controlling the Mesu and some cameras but that is a constant fight for me and my wife (a Windows person) is getting tired of having to regularly rescue me.

Edited October 18, 2020 by gorann

[tomato]

APP is not too shabby at registration and frame resizing. Couldn’t you use this then move the frames into PI/PS?

[gorann]

1 hour ago, tomato said:

APP is not too shabby at registration and frame resizing. Couldn’t you use this then move the frames into PI/PS?

Thanks but actually there is no problem - It is just Olly that loves Registar. PI did it for me in 5 minutes😉

[ollypenrice]

15 hours ago, gorann said:

Thanks but actually there is no problem - It is just Olly that loves Registar. PI did it for me in 5 minutes😉

I think our wires are crossed! (Probably my fault.) I was talking about the resizing and aligning of the high res over widefield which I understood you to be doing in Photoshop when you said,  'I first resized (reduced) the high resolution image in PS (I usually do it by measuring the distance (in pixels) between the same two stars in the images to calculate a reduction factor). I then just did a star alignment in PI using the RASA image as template. Then I added it as a layer to the RASA image and used the dreaded brush too to let about 50% through on the nebula.' When you do this in PI does it re-curve the high res to match the widefield? On small regions this might not be an issue but therre will be different field curvature in the two images, something which Registar adjusts.

When Rodd contacted the PI developers about including a facility for resizing and aligning high res for inclusion on widefield they replied by insisting that this was 'painting,' and not something they'd get involved in. Since neither image is 'painted' I fail to see why they should say this.

Olly

Edited October 19, 2020 by ollypenrice
clarification