The "No EQ" DSO Challenge!

[Nigel G]

2 minutes ago, Herzy said:

I remember posting a thread concerning one of my pictures and the lack of detail even though I integrated 4 hours. The object was very faint, but I thought my integration should've showed more detail than it did. 

I was informed by wimvb that my exposures (60s) weren't long enough to do the object justice. The one who explained it to me said that the reasoning for longer exposures making a difference is the amount of signal vs the amount of noise.

If I recall correctly, he gave this example:

Consider a REALLY faint object. It gives you roughly 1 photon (1 signal electron) per minute. At the same time, your cameras read noise will contribute 1 electron. It doesn't matter how many frames you take, your signal will remain 1 because stacking doesn't boost signal, it justs removes noise. SNR = 1.

Now consider you are imagin that same object with 10 minute exposures. Your capturing 10 signal electrons/photons and 1 read noise electron. SNR = 10.

Longer exposures give you more signal, and more of them give you less noise. The combination of long exposures and lots of them give you a really good SNR.

So in that regard, an alt/az mount user is limited. They can always remove more noise, but can never boost their signal much without field rotation. That doesn't mean they can't produce wonderful images - they certainly can. They are just limited to bright-ish targets. 

That's a good easy to understand example and my thoughts exactly , thanks

Nige.

[SteveNickolls]

Thanks Herzy for this explanation. There's still a lot of the brighter objects in the sky to image (thankfully) with 60 second exposures and as we don't here in the UK get many clear nights they should at least see me out (I mean to sound cheerful) :-)

Best Regards,
Steve

[Nigel G]

a quick question about onedrive , how do I share ?

Its ok I found out

 

Edited September 15, 2016 by Nigel G
silly billy

[Nigel G]

https://1drv.ms/u/s!Av3mI1-jgAvwa4nrxgPLQAAWX8U

I cropped this quite a bit, around 50% to work on.

If anyone wants to try please do,

Good luck, I hope someone can extract more, it will be interesting to see what other programs can do.

Nige.

[The Admiral]

I think this thread is worth a read: https://stargazerslounge.com/topic/245183-to-stack-or-not-to-stack-30-x-1s-1-x-30s/

I may be wrong but I get the impression that the 1 photon/minute example is a bit simplistic, because what you are stacking are images which are essentially sky background plus a little bit, and the signal to noise ratio for the wanted little bit of signal does improve with many subs. It is true, I think, that the longer the individual subs, the deeper you can go. Though perhaps that contradicts what I've just said . I still haven't got this noise thing fully under my belt! May be, what is a lot more important is the degree to which the wanted signal is above sky background. In other words, a dark sky produces the greatest gain. I look forward to the results of your experiment in this.

May be it's just me Nige, but I prefer your first image to the second longer total exposure one, less noise. They are round the right way are they? The trouble is, slightly different processing in ST can make all the difference. Do you think the gains from all the extra exposure time is proving worth while?

Incidentally, which of the 2 images have you uploaded?

Ian

Edited September 16, 2016 by The Admiral

[Nigel G]

26 minutes ago, The Admiral said:

I think this thread is worth a read: https://stargazerslounge.com/topic/245183-to-stack-or-not-to-stack-30-x-1s-1-x-30s/

I may be wrong but I get the impression that the 1 photon/minute example is a bit simplistic, because what you are stacking are images which are essentially sky background plus a little bit, and the signal to noise ratio for the wanted little bit of signal does improve with many subs. It is true, I think, that the longer the individual subs, the deeper you can go. Though perhaps that contradicts what I've just said . I still haven't got this noise thing fully under my belt! May be, what is a lot more important is the degree to which the wanted signal is above sky background. In other words, a dark sky produces the greatest gain. I look forward to the results of your experiment in this.

May be it's just me Nige, but I prefer your first image to the second longer total exposure one, less noise. They are round the right way are they? The trouble is, slightly different processing in ST can make all the difference. Do you think the gains from all the extra exposure time is proving worth while?

Incidentally, which of the 2 images have you uploaded?

Ian

I have uploaded the 2h 20 min exposure image, 

I think all that is needed is around 70 - 100 frames of the longest exp time you can manage with the kit one has using alt-az mount. Maybe even less, more experimenting to do ☺ 

I will try an experiment with one of my stacks of an easier target, using half the data for one and full data for the second, tonight's entertainment. 

In the second image I did over expose purposely to see if I could find the nebula so the noise level is higher but I  couldn't expose the first one as much as I  could the second I think due to the difference in total amount of frames, not exp time. That's my thoughts ☺I'm sure someone will disagree which only opens the door for more experimenting. 

Cheers

Nige. 

 

 

[Filroden]

I definitely need more processing practice. I really struggled with this one as the nebulosity was so feint. Here's my quick effort in PixInisght. I cropped the image to reduce the processing time.

Steps I ran included background removal, background neutralisation, colour calibration, noise reduction on background, deconvolution, a masked stretch to protect the stars, curves transformation, small histogram transformation and colour saturation.

[SteveNickolls]

Hi Nige,

I've had an attempt with your Cats Eye Nebula using StarTools-

i'll try a closer cropped one next.

Cheers,
steve

[happy-kat]

The background looks very noisy and splodgy. (Pixsinsight)

I prefer the original 45 minute one much quieter noise in the background.

Edited September 16, 2016 by happy-kat

[SteveNickolls]

Here's a closer cropped processing in StarTools-

I'd be happy with this, after all it is a faint, small object Nige.

Cheers,
Steve

[The Admiral]

Forgive me, but I really must show my ignorance here . What is the Cats-Eye in these pictures? Is it the faint blue whisp in the 7-o'clock position from the blue 'star', is it the blue 'star' itself, or is the blue 'star' just the centre of it? I'm having a lot of trouble matching up published pictures of it with what I'm seeing in your images!

Ian

[The Admiral]

Ah, I found this image from ESA's Digitized Sky Survey 2, taken in blue, red and infra-red. I see it is only about 20" across, so very small. This image is 1° square.

Ian

[Filroden]

Here's that image with mine rotated and resized to approximately match and one with it superimposed. In my original attempt I think I could just make out the outer boundary of the nebula against the background. I think another couple of hours of data might make it a lot clearer.

 

Edited September 16, 2016 by Filroden

[The Admiral]

Hmm, I can't do anything with this image, I don't know where to start with the gradients. This is a straight auto dev on the fts. Wipe doesn't seem to do a good job.

Ian

[Filroden]

13 minutes ago, The Admiral said:

Hmm, I can't do anything with this image, I don't know where to start with the gradients. This is a straight auto dev on the fts. Wipe doesn't seem to do a good job.

Ian

I cropped first to remove the vignetting and then removed the remaining background which was then much easier.

[The Admiral]

Well, by some very heavy cropping I managed to graunch it through, to get this:

The centre of the nebula seems to be saturated.

Ian

[Nigel G]

16 minutes ago, The Admiral said:

Hmm, I can't do anything with this image, I don't know where to start with the gradients. This is a straight auto dev on the fts. Wipe doesn't seem to do a good job.

Ian

After cropping and developing at about 92% and .90 gamma,  I  wiped using vignetting which made the image look really horrid but a re develop brings the image back nicely ready for next stage.

[Nigel G]

3 hours ago, Filroden said:

Here's that image with mine rotated and resized to approximately match and one with it superimposed. In my original attempt I think I could just make out the outer boundary of the nebula against the background. I think another couple of hours of data might make it a lot clearer.

[Nigel G]

Ken, you found more emissions than I did although it highlights more noise, maybe a mask around the nebula might help ☺ this is a very faint dso, so I'm happy with what's being extracted. 

Ian, the blue star in the centre is the centre of the dso with a galaxy up and slightly right and another faint and fuzzy near the bottom and left of my image.

Thanks for having a go at processing guys.  It's a tough one ☺

[SilverAstro]

3 hours ago, Filroden said:

 In my original attempt I think I could just make out the outer boundary of the nebula against the background.

Yep, I think you are right, just, mind u I sometimes see dragons in clouds

This is what I have experimented with (can the forum do animated GIFs ? ) :-

The same again but reducing the red noise a bit and upping the blue a tad :-

 

[Nigel G]

 

this is one I found showing the nebula and one of the galaxys ,

[Nigel G]

4 minutes ago, SilverAstro said:

Yep, I think you are right, just, mind u I sometimes see dragons in clouds

This is what I have experimented with (can the forum do animated GIFs ? ) :-

The same again but reducing the red noise a bit and upping the blue a tad :-

 

 

Nice , like it.

[Filroden]

10 minutes ago, Nigel G said:

Ken, you found more emissions than I did although it highlights more noise, maybe a mask around the nebula might help ☺ this is a very faint dso, so I'm happy with what's being extracted. 

Ian, the blue star in the centre is the centre of the dso with a galaxy up and slightly right and another faint and fuzzy near the bottom and left of my image.

Thanks for having a go at processing guys.  It's a tough one ☺

It's so feint there is little for me to run a mask from. I guess I could try extracting a mask from the Blue channel and see if I can protect the emission more.

[Nigel G]

Unfortunately another couple of hours data will make the stack around 400 to 500 frames and on my pc that's about 6 hours or more stacking on DSS 

237 frames took over 4 hours ☺

I'm going to try around 1.5 hours at a dark site next available weather window.  Stack them as a new image and maybe add older frames for an experiment. 

Nige.

[Filroden]

Just now, Nigel G said:

Unfortunately another couple of hours data will make the stack around 400 to 500 frames and on my pc that's about 6 hours or more stacking on DSS 

237 frames took over 4 hours ☺

I'm going to try around 1.5 hours at a dark site next available weather window.  Stack them as a new image and maybe add older frames for an experiment. 

Nige.

Yes, I found processing my 220 images of the Soul Nebula took longer then collecting them! The good thing with PixInsight is I can run calibration in batches and it's just the final integration that has to be done together. My biggest problem is that PixInsight saves all intermediate files and they are huge. Given each sub goes through about 4 stages, I think I ate about 100Gb of disk space doing 220 images.