Author Topic: M51 from Cooperation Project public files  (Read 6561 times)

Offline Carlos Milovic

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M51 from Cooperation Project public files
« on: 2010 May 19 19:42:44 »
Hi all

I was kind of bored... so I downloaded the data from the M51 Cooperation Proyect (see this topic:
http://pixinsight.com/forum/index.php?topic=1878.0  )

I didn't want to spend too much time, so just a mild color saturation, and almost no multiscale enhancement (just hdrwt).

By the other side, one thing I did try was deconvolution of the L image, by using the data from ReadPSF as input. That worked very nice :) Since I picked a well resolved star, I'm pretty confident of the measurements... and the deconvolution worked quite fine with it as PSF. So, even when it is not perfect, I would say that the StarStatistics class is useful :D

Hope you like the image (see atach).

All credits for the guys of the project... maybe I'll try a serious rework with newer data, gathering more frames :D (if released, of course). Thanks Yuriy! ;)

Regards,

Carlos Milovic F.
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Offline Nocturnal

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Re: M51 from Cooperation Project public files
« Reply #1 on: 2010 May 19 21:39:48 »
That looks real good!
Best,

    Sander
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Offline Yuriy Toropin

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Re: M51 from Cooperation Project public files
« Reply #2 on: 2010 May 20 04:05:55 »
Hi Carlos,
Thanks for putting your effort in post-processing, it came out really nice!

Also, keep eyes on initial post, there probably will be some new "grand sum" releases late May/early June.

Offline Jack Harvey

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Re: M51 from Cooperation Project public files
« Reply #3 on: 2010 May 20 04:43:26 »
Great job with terrific resolution.  A tad bit green n my monitor?  But other than that it is great with a super bit of background detail!
Jack Harvey, PTeam Member
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Offline Carlos Milovic

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Re: M51 from Cooperation Project public files
« Reply #4 on: 2010 May 20 06:12:09 »
Thanks :)

Yuriy: I certainly will check them again. Was a real pleasure to work with this data, so I really am looking forward a reprocess with even better SNR.

Jack: Yes, I left a bit of green. Also, it may look greener since it has only a mild color saturation. If I rise it, it becomes more bluish.
Regards,

Carlos Milovic F.
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Offline georg.viehoever

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Re: M51 from Cooperation Project public files
« Reply #5 on: 2010 May 22 11:41:36 »
Hi,

I used Carlos version (http://pixinsight.com/forum/index.php?topic=1943.msg12155#msg12155) of this M51 image and sent it through the Blind Solver http://pixinsight.com/forum/index.php?topic=1857.msg12021#msg12021 to obtain coordinates, scale and orientation. I then used the software Aladin http://aladin.u-strasbg.fr/aladin.gml to create and overlay with the Nasa Extragalactic Database (NED) http://nedwww.ipac.caltech.edu/. I filtered it for galaxies (blue circles) and labeled those that have well known names ("IC", "Messier") in red. Attached is the result.

The amazing thing is the number of galaxies that are visible on this picture. Maybe about 50% of the blue circles are actually related to some faint "star", down to mag 22.3 or so. Below this, the blue circles are usually empty.

Amazing!

Georg


Georg (6 inch Newton, unmodified Canon EOS40D+80D, unguided EQ5 mount)

Offline Carlos Milovic

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Re: M51 from Cooperation Project public files
« Reply #6 on: 2010 May 22 13:11:20 »
Wow, there are so many objects :) Good work, Georg
Regards,

Carlos Milovic F.
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Offline Yuriy Toropin

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Re: M51 from Cooperation Project public files
« Reply #7 on: 2010 May 31 03:39:07 »
Georg,
can you please do the same trick with the latest M51 "grand sum" published? (see this message)

You can try to work with presented 900x900 fragments (scale is ~0.455"/px on them) or can dowload initial sum in FITS and work wit it.

Unfortunately, it looks like NED is not enough there...

Offline Yuriy Toropin

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Re: M51 from Cooperation Project public files
« Reply #8 on: 2010 May 31 04:43:13 »
Stretched L channel of the currect version of M51 from cooperation project files (see details and link to download data here).



Needless to say that all pre-processing of individual contributions (if needed), alignment and stacking/post-processing has been done in PI.

Offline Carlos Milovic

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Re: M51 from Cooperation Project public files
« Reply #9 on: 2010 May 31 06:20:21 »
Looks like I have material for next weekend ;)
Regards,

Carlos Milovic F.
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Offline georg.viehoever

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Re: M51 from Cooperation Project public files
« Reply #10 on: 2010 June 02 09:53:07 »
Yuriy,
Georg,
can you please do the same trick with the latest M51 "grand sum" published? (see this message)
...

See http://pixinsight.com/forum/index.php?topic=1878.msg12491#msg12491. I am afraid that beyond 24 mag, data becomes very sparse, and I am not sure how reliable data beyond this limit is.

Does anyone have an idea how many photons a typical CCD cell (e.g 5.7 um *5.7 um) will register per second on an amateur telescope (e.g. 6 inch f/5 newton) for such faint objects?

Georg
Georg (6 inch Newton, unmodified Canon EOS40D+80D, unguided EQ5 mount)

Offline Nocturnal

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Re: M51 from Cooperation Project public files
« Reply #11 on: 2010 June 02 10:05:02 »
Georg,

if you know the QE of the sensor and gain of the ADC and have raw captured data that is properly dark subtracted you can get a decent estimate of the number of photons collected in each pixel. This is probably hard to do with a DSLR unless you know exactly how ISO settings affect gain. To get truly accurate numbers you'd need to calibrate your sensor with a light source of known photon flux. A bit beyond the typical amateur.

I suppose you could also calibrate using an accurately measured target (star) but atmospheric extinction is an unknown so I doubt that any degree of accuracy is achievable.
Best,

    Sander
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Offline vicent_peris

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Re: M51 from Cooperation Project public files
« Reply #12 on: 2010 June 02 10:17:23 »
Georg,

if you know the QE of the sensor and gain of the ADC and have raw captured data that is properly dark subtracted you can get a decent estimate of the number of photons collected in each pixel. This is probably hard to do with a DSLR unless you know exactly how ISO settings affect gain. To get truly accurate numbers you'd need to calibrate your sensor with a light source of known photon flux. A bit beyond the typical amateur.

I suppose you could also calibrate using an accurately measured target (star) but atmospheric extinction is an unknown so I doubt that any degree of accuracy is achievable.

Hi,

you have a calculator here:

http://www.tass-survey.org/richmond/signal.shtml

According to this calculator, a 15 cm f/5 scope captures these photons per second in R band:

mag  24.00:  0.0223
mag  24.50:  0.0140
mag  25.00:  0.0089
mag  25.50:  0.0056
mag  26.00:  0.0035

I've put these parameters:

Filter:     R  <-- This Johnson filter has about the same light trhoughput as a 100 nm photographic R filter.
Tel_diam:   15 (cm)
Overall QE: .5
Pixsize:    1.57 (arcsec/pixel)
Readnoise   13 (electrons)
Sky mag:    21 (mag/sq.arcsec)
Airmass:    1
Ext_coeff:  0.1
Exptime:    10000 (sec)
FWHM:       .1 (arcsec)
Aper_rad:   .886 (arcsec)   <-- a circle with the area of one squared pixel.


Regards,
Vicent.


Offline vicent_peris

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Re: M51 from Cooperation Project public files
« Reply #13 on: 2010 June 02 10:57:35 »
Using the aperture photometry module by C. Milovic, I've done photometry on a known SDSS source and on the 26.1 mag object. The reference object is SDSS J132919.23+471328.4:

http://nedwww.ipac.caltech.edu/cgi-bin/nph-objsearch?objname=SDSS+J132919.23%2B471328.4&extend=no

I've joined B and G signal to emulate a g' filter; OTOH, a photographic R filter is something like a r' filter with 50% less bandwidth. Following these premises, in our image the fainter object appears to have these magnitudes:

g': 24.9
r': 23.9

But in our R filter we're detecting an object 50% fainter than r' mag. So we're going to r'=24.4.

So we're not going to mag 26 but 25. Anyway, measurements at this signal level are very uncertain...



Vicent.

Offline vicent_peris

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Re: M51 from Cooperation Project public files
« Reply #14 on: 2010 June 02 11:07:17 »
OTOH, to me it seems that there are two adjacent tiny objects:



The catalog coordinates gave me exactly the image coordinates of the lower object. So perhaps they are two nearly 26 mag objects. But you are looking at a integrated 25 mag object because you're not resolving them. Aperture photometry cannot be done in this case... I integrated the brightness of the two objects to do the aperture photometry. To separate them you need to do PSF photometry.


Vicent.