View Full Version : M 74 reprocessed

2012-Nov-22, 11:03 PM
M74 is a face on grand design spiral galaxy located in Pisces about 32 million light-years away according to the HST website. Most sources say it is 100,000 light-years across but including the outer plumes to the north and south in my image I get 125,000 light-years assuming the 32 million light-year distance is correct. Redshift puts it only 17 million light years away which is highly suspect. It is thought to be a member of the same galaxy group as the polar ring galaxy NGC 660 I posted October 9, 2010.

I originally posted my black and white version of this data back on September 26, 2006 and added color data a few weeks later. Then in January, 2007 I had learned more about color processing and tried again adding H alpha data. There the image sat in a lost directory. I recently ran across it and decided to see if I could improve it any. I really need to retake the data as my calibration data back then was of much lower quality than I obtain today. Unfortunately old images must be calibrated with old calibration data so I can't use modern calibration data, that would be worse than using the old but poor data.

Since then the Gemini telescope in Hawaii has taken an image of it with a newly designed camera. That image was done through narrow band filters that isolate different elements and displays these in artificial colors. For instance ionized Hydrogen seen as pink in a typical "true color" image is colored green in their image. The image is at: http://apod.nasa.gov/apod/ap011004.html .

While dealing with the poor calibration frames I had to sacrifice some of the fainter out parts of the galaxy but I was surprised at how much detail was in the data that I failed to pull out with my limited processing skills of early 2007. Note H alpha was added only to the red and blue channels, not the luminance channel. Adding it to the luminance as well seemed to overpower the image so went with it only in the color channels. Looks like I have hundreds of images from back then that could use similar reprocessing. But then in a few years I'd probably have to do it all over yet again.

14" LX200R @ f/10, L=4x10' R=3x10'+80%2x30'Ha G=3x10' B=3x10'+20%2x30'Ha, STL-11000XM, Paramount ME.

Sorry, only the heavily cropped image would fit bandwidth limits without loss of color and detail.


2012-Nov-23, 02:52 AM
It's not fair to compare to compare a 14" scope to an 8 meter one at 4000m elevation, but in this case, I'll allow it. :)

Very nice photo! I really like the H-alpha details and the darker nucleus. The dust lane detail right down to the center is a very nice touch.

Out of curiosity, have you done NGC-660? I'm not able to search using 3 letter terms.
edit: scratch that, I found it.

2012-Nov-23, 05:55 AM
Now you know why I didn't include the link to it. I couldn't find it either. The search engine here is worthless as you can't put in a catalog designation unless it is a long one. It assumes anything short is too common to be searched on when, in fact it is unique. Other forums don't have that issue making them far more useful -- to me at least. Lots of things here are poor for imaging posts. File size is too small for today's chips. I could only include one fourth if the image and meet bandwidth limits without loss of resolution and color with added artifacts. Most of the experienced imagers who used to post here have gone to more reasonable forums for that type of post. I'll likely join them. I have to prepare special versions for this site, just not worth it.

Most beginners (like I was in 2006 and 7) burn in the cores of galaxies when stretching sufficiently for the outer parts. It takes some skill to learn how to control the stretch to prevent that from happening. There are several ways, all take practice and experience to master however. I'd not learned that obviously in January 2007. Most think they over exposed the core when the detail is there, just lost due to how the image was stretched.

BTW, a good friend of mine and past president of our astronomy club when he was an engineering student in 1976 was the head of the optics team that designed and built the Gemini scopes and now is now the Telescope Department Head for the Thirty Meter Telescope which will join Gemini North so he'll have two scopes on the old volcano. I like to push that scope when I can. His first observatory scope was an 8" used at our public observatory. It wasn't designed for wheel chair patrons so has been replaced to meet Federal guidelines the city said we had to meet for the handicapped. His budget was $200 and he met it doing all the machining himself with two high school kids doing the optics (which were excellent after a few retries as they'd never made a mirror before). His budgets are a bit larger now!


2012-Nov-23, 07:03 PM
Please do me a favor. Before you leave the forum devoid of eye candy, message me a link to where I can find your photos.