subtle processing rings

[Cleon_Wells]

I took 41-120sec subs of M51 the other night with my 10”RC/Canon T1i, iso400 . I noticed after I did a quick PI processing (Hist_Trans and Curves) that I have subtle rings in the lower right hand corner of this image, the + is the center of the most predominate ring. I show the Master Flat and a single flat sub Calibrated,  the flats show the same lower right hand corner as the integrated master. What could cause this problem?
Cleon

[pfile]

maybe your flats didnt actually match the lights perfectly? like whatever dust was there during the light fell off before you took the flats? the picture is quite small - i cant really see the ring and can't tell if it looks like overcorrected from a flat or not corrected.

not to derail too much but when was "the other night"? there is a supernova in M51 that just appeared around june 1st.

http://www.astropix.com/HTML/SHOW_DIG/M51_Supernova.HTM

http://www.cbat.eps.harvard.edu/unconf/followups/J13303600+4706330.html

[Cleon_Wells]

pfile, I tried to dig out the faint rings, but it was a lost cause, I'll have to create a new flat for the Canon and see if I see these rings in the Master Flat.
On the date and time, I got the first image on 5/31/2011 at 04:41:52 UTC.
It is amazing how the Super Nova is brighter then the core of M51 and brighter then most of the stars in this image.
I did a crude check on brightness and think the visual output dropped a small amount over the 94-minute time of my image session.
Cleon

[pfile]

you should send your raw images in to the palomar transient factory. they have been posting this info around the web:

This is a very exciting scientific discovery, to which amateurs can further significantly contribute! We at the Palomar Transient Factory seek more image data of M51 obtained between May 30 and June 2, 2011. So, if you have imaged this galaxy using a telescope and a digital camera, your data may be very useful to this project!

Helpful data would be:
* only if it is of M51 between May 30 and June 2
* only if it is has an accurate time stamp.

In case such data exists, please send the raw images, specify the filter(s) used and if possible send images of the same field taken with the same instrument and telescope before May 30, all to: ptf11eon@gmail.com Your help could be crucial for great scientific discoveries! we will not use any data without permission, and will of course credit all useful images.

[Alejandro Tombolini]

Excellent Celon, you had very good luck with this photo. !!!

Regards, Alejandro.

[Cleon_Wells]

Alejandro, here's 41-subs of M51, not the greatest but for me and my location, I'll take it.
pfile, I sent two images in, the first and the last of the night.
Cleon

[Alejandro Tombolini]

Hi Cleon, it is very good and with many details in the galaxy and colors perfect for me.

I see that there are some lines that stay in the background like happen to me.

I am sure that they are the product of the hot pixels not removed in calibration routine in some of the channels.

I know that it is very laborious, but in my case I am checking image for image and re-calibrating manually those who stayed with hotpixeles 
(The Animation is the perfect tool to visualize them)
 
What I do in PixelMath is: Image - MasterDark(BiasSustracted)*ki

ki: normally the same one that PI calculated in the well calibrated images.

Regards, Alejandro.


Hola Cleon, quedó muy buena y con muchos detalles en la galaxia y los colores perfectos para mi gusto.

Veo que hay algunas líneas que quedan en el fondo tal como me pasa a mí.
 
Estoy seguro que son producto de los hot píxeles no removidos en la rutina de calibración en alguno de los canales.
Sé que es muy trabajoso, pero en mi caso estoy revisando imagenpor imagen y recalibrando manualmente las que quedaron con hotpixeles
(El Animation es la herramienta perfecta para visualizarlas)

Lo que hago en PixelMath es: Image - MasterDark(BiasSustracted)*ki

ki: normalmente el mismo que PI calculó bien en las fotos bien calibradas.

Saludos, Alejandro.

[Cleon_Wells]

Alejandro, the banding to the right of the galaxy core is caused my over use of Georg's CanonBandingReduction Utility.
I also had a large left to right gradient with the right side being the light side.
I hope to get more subs tonight, weather permitting.
Cleon

[georg.viehoever]

Alejandro, the banding to the right of the galaxy core is caused my over use of Georg's CanonBandingReduction Utility.
...

Glad to hear it is still in use :-)
Georg

[Alejandro Tombolini]

Hi Georg, I use it a lot, is a very goog tool!!!

Cleon, I was not referring to the banding. I was referring to the soft diagonal lines in the background that are mixed with the thin details of the galaxy.

(I am not good in english, I am sorry).

Regards, and good luck with the weather tonight


Hola Georg, Yo lo uso un montón, es una herramienta muy buena.

Cleon, no me refería al banding, Me refería a las lineas diagonales en el fondo que están mezcladas con los finos detalles de la galaxia.

Saludos, y buena suerte con el clima esta noche.

Alejandro.

[Cleon_Wells]

Alejandro, I don't see the banding your talking about; could it be a jpg artifact?
Georg I use your Utility all the time; do you see any diagonal banding in the image?
Check this image that has a different pixel per inch setting.
Cleon

[pfile]

cleon, the "banding" is definitely there - maybe your monitor black point isnt right. there's streaks oriented about 15 degrees off of the vertical - angled about at 1 o'clock. i think Alejandro is right, these are the result of hot pixels not being totally calibrated out and then are not being rejected during stacking. you might want to adjust your stacking parameters to reject more pixels...

[Cleon_Wells]

pfile, I was looking for a 45 degree band, but I see what Alejandro is talking about when I stretched the image and can see the streaking caused by the camera noise more then hot pixels.
I'll try and lower the pix rejection points back to 4 and 2, I had used 5 and 3.
Cleon

[Cleon_Wells]

Well I tried to get more sub of M51 but between the guiding errors and the focus change, the night was a bust. Today I tried changing the MasterDark by subtracting the MasterBias (25-iso100@1/4000 BatchFormatConverted subs and then integrated into the MasterBia file)  from each of the ten CR2 dark  subs. There is a noticeable difference between integrating the ten dark .fit subs into a MasterDark and then subtracting the MasterBias from the Masterdark file during the Calibration of the lights, compared to subtracting the MasterBias from each dark sub CR2 file creating the .fit dark subs and the integrating the _c dark subs into a MasterDark.
I know Vicent’s direction tells us to calibrate each dark raw./CR2 sub before integration, creating the MasterDark, I’m just surprised I can see this much difference between the two procedures. Bottom line, I have recalibrated the CR2 subs of M51with the calibrated MasterDark and see less  noise/hot pixel banding in the master light, it’s still noisy but more random.
Cleon

[Cleon_Wells]

I think this is an example of my banding noise problem that’s caused by Flexure. The noise striping/banding is created when Star Registration corrects my Flexure problem.
Integration1 is not cropped and has no Low or High noise rejection. The top rejection maps, (low & high)  are from another integration of the same 43 subs. I think this is what caused the banding that Alejandro and pfile saw in my M51 image.
Cleon