Vela SNR Mosaic in 3nm NII and OIII

avandonk · #1 13-01-2014, 07:09 AM

This is just the start of what will be a 4x4 mosaic in NB and RGB. Even if it takes some years because of weather.

Full res image FoV 6.0 x 3.2 degrees. 12MB

http://d1355990.i49.quadrahosting.co...SNR_NB_NOO.jpg

Exposures were 20+ X 16 min for OIII and NII for both panels.

I am going for the maximum practical faint detail my system will record.

Bert

strongmanmike (Michael) · #2 13-01-2014, 08:27 AM

Pretty impressive field that Bert

Mike

gregbradley · #3 13-01-2014, 08:49 AM

Very nice Bert. One of my favourite objects. Lots of details.

Greg.

RickS (Rick) · #4 13-01-2014, 08:53 AM

Should be a stunning mosaic, Bert. The data looks to be fantastic.

batema (Mark) · #5 13-01-2014, 09:18 AM

Amazing photo.

avandonk · #6 13-01-2014, 11:50 AM

Thanks for the comments. I have been up all night now for three nights in four. What makes it worth it when you see something you've never seen before.

I tend to stack my data 1.5 times the native pixel count of my sensor. This with dithering and lots of frames increases the resolution due to the under sampling. One thing this allows me to do is then bin x2 or 50% which increases signal to noise by a factor of four. The image is now 75% of native pixel count about right for mosaics and the stars are now perfectly round.

This image is a starless version derived from binned x2 data and upsized to native sensor size. 9MB

http://d1355990.i49.quadrahosting.co...O_nostars_.jpg

Bert

astroron (Ron) · #7 13-01-2014, 12:16 PM

Incredible image Bert.

I always look at your images with awe.

Cheers

avandonk · #8 13-01-2014, 12:43 PM

Here is an image at native pixel size with stars derived from the x2 binned data. 11MB

http://d1355990.i49.quadrahosting.co...SNR_NB_B_N.jpg

The stars are a little bit bigger but now perfectly round compared to the image from the first post and the faint nebulosity is now far better defined.

Bert

RickS (Rick) · #9 13-01-2014, 01:10 PM

Quote:

Originally Posted by avandonk

I tend to stack my data 1.5 times the native pixel count of my sensor. This with dithering and lots of frames increases the resolution due to the under sampling. One thing this allows me to do is then bin x2 or 50% which increases signal to noise by a factor of four. The image is now 75% of native pixel count about right for mosaics and the stars are now perfectly round.

Have you looked at the Drizzle algorithm at all, Bert? Hopefully it will be implemented in PI before too long.

Binning x2 will increase signal by 4 times and shot noise by sqrt(4) times for a net improvement in SNR of 2 times. Suffering from too many nights at the scope?

Cheers,
Rick.

avandonk · #10 13-01-2014, 01:14 PM

Quote:

Originally Posted by RickS

Have you looked at the Drizzle algorithm at all, Bert? Hopefully it will be implemented in PI before too long.

Binning x2 will increase signal by 4 times and shot noise by sqrt(4) times for a net improvement in SNR of 2 times. Suffering from too many nights at the scope?

Cheers,
Rick.

What shot noise? Do you mean Poisson noise?

Bert

RickS (Rick) · #11 13-01-2014, 01:21 PM

Quote:

Originally Posted by avandonk

What shot noise? Do you mean Poisson noise?

Yes, shot noise aka photon noise aka Poisson noise: http://en.wikipedia.org/wiki/Shot_noise

avandonk · #12 13-01-2014, 02:04 PM

Quote:

Originally Posted by RickS

Yes, shot noise aka photon noise aka Poisson noise: http://en.wikipedia.org/wiki/Shot_noise

I am well aware of all sources of noise. I do have a degree in Physics.

Do you think that nutters such as myself would buy fast optics just to overcome these limitations of signal to noise if they did not work?

The only way to overcome or minimise Shot or Poisson noise is a fast optic where the stream of photons are like a river rather than a noisy trickle!

Drizzling is just upsizing and stacking!

Bert

cometcatcher (Kevin) · #13 13-01-2014, 02:29 PM

What an amazing, delicate looking cobweb of gasses. Suns definitely look prettier when they blow up.

RickS (Rick) · #14 13-01-2014, 02:37 PM

Quote:

Originally Posted by avandonk

I am well aware of all sources of noise. I do have a degree in Physics.

Do you think that nutters such as myself would buy fast optics just to overcome these limitations of signal to noise if they did not work?

The only way to overcome or minimise Shot or Poisson noise is a fast optic where the stream of photons are like a river rather than a noisy trickle!

Drizzling is just upsizing and stacking!

Bert

My comment on Drizzle applied to this:

Quote:

Originally Posted by avandonk

I tend to stack my data 1.5 times the native pixel count of my sensor. This with dithering and lots of frames increases the resolution due to the under sampling.

It seems like Drizzle may be a better way of doing the same thing, i.e. wringing some additional resolution from dithered data. It's a little more complicated than just upsizing and stacking.

My comment on shot noise and SNR applied to this:

Quote:

Originally Posted by avandonk

One thing this allows me to do is then bin x2 or 50% which increases signal to noise by a factor of four.

I was pointing out that you have increased your signal by a factor of four but not your SNR which has only increased by a factor of two. I was also kind enough to assume that you already knew this and had just made a silly mistake.

Cheers,
Rick.

avandonk · #15 15-01-2014, 04:30 PM

Quote:

Originally Posted by RickS

I was pointing out that you have increased your signal by a factor of four but not your SNR which has only increased by a factor of two. I was also kind enough to assume that you already knew this and had just made a silly mistake.

Cheers,
Rick.

It is a pointless exercise to argue about the intricacies of signal to noise here.

Let us just say that I do not need or want a lecture in statistics. If you want to be pedantic go to a more suitable forum or is that fora?

To tell the truth all I care about is a clearer image of heavenly bodies so my natural urges can be satisfied by a certain frisson of manipulation of my telescope.

Bert

David Fitz-Henr · #16 19-01-2014, 07:14 PM

Quote:

Originally Posted by RickS

My comment on Drizzle applied to this:

It seems like Drizzle may be a better way of doing the same thing, i.e. wringing some additional resolution from dithered data. It's a little more complicated than just upsizing and stacking.

I believe you are correct here Rick; whilst upsizing and stacking can result in smoother data and some marginal improvement in resolution, the drizzling process is not the same and can produce much larger gains in resolution for undersampled images. There is a lot of information on the web about drizzling - here is a good site that explains the concept quite well with a worked example: http://www.asiaa.sinica.edu.tw/~whwa...zzle/index.htm

Bert, what is the image scale of your system (arcsecs / pixel)?

Bassnut (Fred) · #17 19-01-2014, 07:38 PM

Spectacular Bert, interesting you went with Nii

Star Catcher (Ted Dobosz) · #18 19-01-2014, 09:11 PM

Fabulous capture and processing to show the structures.
Ted

DavidNg (David) · #19 19-01-2014, 09:22 PM

Wow, look really impressive already.

avandonk · #20 20-01-2014, 08:05 PM

Quote:

Originally Posted by David Fitz-Henr

I believe you are correct here Rick; whilst upsizing and stacking can result in smoother data and some marginal improvement in resolution, the drizzling process is not the same and can produce much larger gains in resolution for undersampled images. There is a lot of information on the web about drizzling - here is a good site that explains the concept quite well with a worked example: http://www.asiaa.sinica.edu.tw/~whwa...zzle/index.htm

Bert, what is the image scale of your system (arcsecs / pixel)?

My image scale is 3.08" per pixel.

I do understand information theory. Farting around with a single image is meaningless.

I dither my images by many pixels. This means I am sampling the same putative image many times.

I typically collect twenty plus images.

Bert