This is a composite image of M101 showing the appearance and brightening of supernova SN2023ixf.  I was excited to hear about the discovery of this SN because I had been spending the previous week imaging M101 despite smoke from those fires up in Canada infiltrating my air space.  I wondered if perhaps I had imaged the SN even before the discovery was made, and much to my surprise and delight, I had indeed caught it starting some 12 hours before its discovery by Koichi Itagaki!  If only I had been more attentive, I could have spotted it earlier, and fame (but likely not fortune) would have been mine!  Alas, the morning of the 19th I had to get up and go to that pesky day job of mine!  I couldn't look at the last night's frames until after work.

With the help of Howard Ritter on the ap-gto forum, I learned how to measure the SN's magnitude in my frames using this write-up by Harriet Dinerstein.  I had 23 x 300s luminance frames from that night.  Using the integrated image, I annotated the magnitudes of many of the stars using PixInsight's AnnotageImage script.  Then, for the first frame, I used Dynamic PSF to mark 36 stars whose magnitudes I knew.  Last, I marked the SN.  The results were saved to spread sheet, which included normalized fluxes.  I saved the script to an icon.  I then loaded the other frames one at a time and restarted DynamicPSF from the icon.  (If you wish to repeat this, be sure to rename the image Identifier to the same thing each time before restarting DynamicPSF.)  There's a refresh button which updated the measurements for each frame.  With all the results in spreadsheets, I combined them and calculated the magnitudes using this formula:

m_sn = m_star - 2.5 log10( f_sn / f_star )

Finally, I calculated the magnitude average and standard deviation for each frame and then plotted the results vs. time:

(UPDATE: Several have suggested that I invert the Magnitude axis so that the data shows increase in brightness over time.  Here is the modified graph.)



As you can see from the graph, the SN was undergoing its rapid brightening phase during this time.  I thought this information may be of interest to those wishing to track the luminosity of the SN, so I learned where and how to upload the results.  I filed a report here.  This was loads of fun!

The L frames for each of the images were taken during the time frames indicated.  The RGB data was taken last night, 2023-05-27 UTC, and applied to all the frames.  I had to do something tricky with the color data for the supernova.  When I first applied the color data from last night to the earlier frames with no SN and early SN, a blueish patch showed up in the LRGB image.  I went back to the RGB frame from last night's data and removed the SN completely using CloneStamp.  My preferred method for adding color to the luminance is to process the RGB image separately, use ChannelExtraction to get the L, a and b channels, discard this extracted L and then combine a and b with my full luminance image.  With the SN color removed, I was content to show it as white without any color here.

I also provide the full frame LRGB images from each of the three nights in the revisions.  I intend on producing a glamor image of M101 eventually using all the data from before the SN as well as this latest data with it.  This may end of producing an odd, ghostly image of the SN, but I'll see if I can still make something nice out of all of it.

I hope you enjoy these images and magnitude results, and perhaps you will be inspired to go do some measurements of your own.  Thank you for your attention and interest!