Eagle Nebula and DWB 192

[Allinthehead]

Hi all, it's been a few months since i had a chance to image due to losing astro dark in the south of Ireland, but happily it has returned which gave me the opportunity to image the Eagle Nebula which i thought would be impossible from my location. I took a chance and slewed to it and there it was although extremely low down with hfr readings of 2.4 and above. I decided to give it a go and after two nights and only 2 hrs of data i'm delighted to tick this one off my list of iconic objects.

150 second subs at unity gain with the asi 1600 and esprit 100

Captured with sgpro and processed in PS.

 

Dwb 192 and Sh2-116

This is an area of Cygnus that i couldn't find much information on. It's quite feint and i need to get a lot more data on it. Bottom right is Planetary Nebula Sh2-116 

If anyone has any information on this area i would appreciate it.

6 hrs in 300 second subs at unity gain with the asi 1600 through an esprit 100

Captured with sgpro and stacked in APP. Processed in PS.

Richard.

[vlaiv]

Just a quick question, why did you drizzle M16?

[Allinthehead]

12 minutes ago, vlaiv said:

Just a quick question, why did you drizzle M16?

Hi Vlaiv. I was playing around with different settings in APP and found that a drizzle integration gave the best results. I know data should be undersampled to really see a benefit but nothing like a real world test to see what works. 

[vlaiv]

I'm just wondering, since drizzle can lower SNR. With ASI1600 and Esprit 100 you will be sampling at 1.43"/px, and that is sort of optimum resolution for ~ 2.3" FWHM stars. What is your average FWHM in subs, have you measured it?

[Allinthehead]

5 minutes ago, vlaiv said:

I'm just wondering, since drizzle can lower SNR. With ASI1600 and Esprit 100 you will be sampling at 1.43"/px, and that is sort of optimum resolution for ~ 2.3" FWHM stars. What is your average FWHM in subs, have you measured it?

Average was about 2.8 

[vlaiv]

I guessed it was something like that - that is why I asked about drizzling. You say you feel it is better when you drizzle, can you tell me why? I'm interested because you should have better SNR without drizzle and there is nothing to be gained from drizzling (no detail) - according to theory.

[groberts]

Like the Eagle but particularly impressed by DWB 192. 

As you say it is feint even with 6-hours integration time but rather  intriguing and would be good to see with greater time and other wavelengths - if you have the conditions & patience?  Thanks for posting.

Graham     

[Allinthehead]

On 01/08/2019 at 11:26, vlaiv said:

I guessed it was something like that - that is why I asked about drizzling. You say you feel it is better when you drizzle, can you tell me why? I'm interested because you should have better SNR without drizzle and there is nothing to be gained from drizzling (no detail) - according to theory.

Hi Vlaiv. I tried processing standard integration and drizzle. I just liked the drizzle better. Seemed sharper and the stars were less soft.

On 01/08/2019 at 12:11, groberts said:

Like the Eagle but particularly impressed by DWB 192. 

As you say it is feint even with 6-hours integration time but rather  intriguing and would be good to see with greater time and other wavelengths - if you have the conditions & patience?  Thanks for posting.

Graham     

Thanks Graham, i'm hoping for clear skies soon to add some colour. 

[Datalord]

On 01/08/2019 at 11:14, vlaiv said:

I'm just wondering, since drizzle can lower SNR. With ASI1600 and Esprit 100 you will be sampling at 1.43"/px, and that is sort of optimum resolution for ~ 2.3" FWHM stars. What is your average FWHM in subs, have you measured it?

I often drizzle my images as well, even though I'm imaging at 0.52"pp. Like Richard, I compare the two outputs and more often than not, the drizzled image just looks better, theory or not. Added bonus is that the resolution enables poster size prints.

[Rodd]

Looks great.  I have tried drizzle and really like the scale increase--4x larger.  But I have not really tested the difference between drizzle and just upsampling to make bigger.  

Rodd

[vlaiv]

3 hours ago, Datalord said:

I often drizzle my images as well, even though I'm imaging at 0.52"pp. Like Richard, I compare the two outputs and more often than not, the drizzled image just looks better, theory or not. Added bonus is that the resolution enables poster size prints.

I was not going to pursue this any further, after all, if one finds that drizzle indeed produces better image than that is fine with me. However, now I'm intrigued to understand this better and would like to ask you to provide an example if that is ok?

Same piece of image side by side - one drizzled one not, at 1:1 resolution with emphasis on what looks better - can be written in words (tighter looking stars, deeper nebulosity, whatever you find better in one image vs other). This would be really helpful for me to understand this topic further.

[Datalord]

37 minutes ago, vlaiv said:

This would be really helpful for me to understand this topic further.

Hmm, infuriating I can't find this exact example I know I had on one of my images a few months ago. I did exactly the side by side and for some reason the drizzled seemed to have better control over the dark areas. Less noise, more smooth. I can't find it now. 😞

[Allinthehead]

On 04/08/2019 at 16:36, vlaiv said:

I was not going to pursue this any further, after all, if one finds that drizzle indeed produces better image than that is fine with me. However, now I'm intrigued to understand this better and would like to ask you to provide an example if that is ok?

Same piece of image side by side - one drizzled one not, at 1:1 resolution with emphasis on what looks better - can be written in words (tighter looking stars, deeper nebulosity, whatever you find better in one image vs other). This would be really helpful for me to understand this topic further.

Hi Vlaiv. Sorry for the delay in this. These images have been auto stretched in APP no further processing. 

Drizzle

No Drizzle

 

Drizzle crop

 

No Drizzle crop

[vlaiv]

21 minutes ago, Allinthehead said:

Hi Vlaiv. Sorry for the delay in this. These images have been auto stretched in APP no further processing. 

Still not seeing it ...

Upper is enlarged no drizzle version, lower is drizzle version. If anything, upper looks like it has better SNR, but I'm not seeing added sharpness in second one (drizzled).

[Allinthehead]

7 minutes ago, vlaiv said:

Upper is enlarged no drizzle version, lower is drizzle version. If anything, upper looks like it has better SNR, but I'm not seeing added sharpness in second one (drizzled).

Looks to me that you have mixed up the which one is the drizzle version

[vlaiv]

28 minutes ago, Allinthehead said:

Looks to me that you have mixed up the which one is the drizzle version

No, I'm pretty sure I got it right - you can see it yourself in above images - enlarged no drizzle version is lacking sharp per pixel noise (because it was enlarged, and I did not use any sort of sophisticated rescaling algorithm - I just pressed ctrl+ in fire fox to get it to 200% display size).

Mind you, lack of high frequency noise might seem like sharpness - but actual signal is lacking sharpness - no additional detail is there, which is to be expected as drizzling will not work in amateur setups. Although majority of people disagree with this, drizzle in fact requires such a guiding/dithering precision that you need to make half pixel offset between subs. This is possible for Hubble and it's pointing and stabilization, but it's not possible for amateur setups (drizzle was developed for Hubble undersampled images).

On the other hand drizzle will definitively lower SNR, because you are stacking less samples per each output pixel, and that can be seen in above images.

[Allinthehead]

I know this is subjective but to my eye the drizzle version i posted above looks better. Very little difference until zoomed in. I also found it easier to process. The stars were easier to control, again purely subjective.

However the crop you posted shows almost the opposite, that's why i thought you had mixed them up. 

[Datalord]

I think they show exactly why I find the drizzles better. Very notably, the contrast is larger, because the dark areas are darker.