Wow there appears to be a lot of globulars that I have captured. Not out of the ordinary I am sure but I had no idea that there were so many. It being a smaller galaxy than our own from what I have read; I expected not many would be present. Thanks for putting that up.
Oh maybe a slight misunderstanding here. The data I used was from my scope since I had the FITS file with WCS fields (what Aladin wants). We would have to feed in your FITS file into Aladin to get the markers on your image. (I suppose I could try plate solving the JPG from your website).
Hi Paul,
OK here is your image plate solved in Maxim (after fooling it with a fake FITS header) and loaded into Aladin with the glob magnitudes. I put the cutoff for globs at Vmag 20.5, best I could do with the JPG.
BTW why is your image reversed left-right, artistic license?
(Normally a two mirror scope, or refractor, flips the image upside down)
Oh maybe a slight misunderstanding here. The data I used was from my scope since I had the FITS file with WCS fields (what Aladin wants). We would have to feed in your FITS file into Aladin to get the markers on your image. (I suppose I could try plate solving the JPG from your website).
EB
Ah, that's ok Eric, I thought you had used my image.
Quote:
Originally Posted by ericwbenson
Hi Paul,
OK here is your image plate solved in Maxim (after fooling it with a fake FITS header) and loaded into Aladin with the glob magnitudes. I put the cutoff for globs at Vmag 20.5, best I could do with the JPG.
BTW why is your image reversed left-right, artistic license?
(Normally a two mirror scope, or refractor, flips the image upside down)
Best,
EB
Thanks Eric. There is still a lot of globs there. Thanks for going to that trouble.
I don't know why it came out that way. I was imaging at 283 degrees and it was originally on its side. Not flipped either in processing. Just rotated 90 CW and cropped to suit.
It's basically the same orientation as that Hubble image. Just a little more skewed. And I know you took it Paul, because the diffraction spikes on yours are a little further rotated compared to Hubble's!
d.
Thanks Robert for your comments. Quite interesting. I will go and take a look at that thread. It might help with my processing of halos in future.
Hello Paul,
Halo studies are really hotting up, at present, in the professional community. They have pushed integrated-light imaging of halos to about 30 magn. per sq. arsecond, and they are currently trying for 32 magn. per square arcsecond.
See for instance work done with this interesting array of small refractors:
I am pretty sure that the professionals have figured out some pretty good tricks and techniques for reducing the effects of sub-optimal flatfielding, scattered light in the optics, and other factors that could make it difficult to detect extremely low surface brightness light.
I am not, however, familiar with the literature on this!
cheers,
Robert
And now, just for fun and profit.....
Very Deep Image of the Virgo Cluster to 28.5 V magnitude per square arcsecond, by Mihos and Harding of CWRU::
Last edited by madbadgalaxyman; 25-04-2015 at 10:58 PM.
Wow there appears to be a lot of globulars that I have captured. Not out of the ordinary I am sure but I had no idea that there were so many. It being a smaller galaxy than our own from what I have read; I expected not many would be present.
See my comments in this thread as to the apparent magnitudes and angular sizes of the globulars associated with M104 ::
Rhode and Zepf, in a 2004 paper, estimated a total population of 1900 globulars belonging to M104, but I am unsure how well this estimate has held up since then. They also estimated that the system of globular clusters stretches to about 19 arcminutes from the centre of M104.
cheers,
Bad Galaxy Man
I shall shortly "weigh up" the Milky Way Galaxy vs. M104, in terms of the relative luminosities of these two galaxies.
Hint: in any fight between the MW and the Sombrero, the Sombrero wins by a large margin.
Last edited by madbadgalaxyman; 26-04-2015 at 05:05 PM.
Your question about the relative sizes and luminosities of the Milky Way and the Sombrero Galaxy has had me working on this problem for a couple of hours every day, for the last week.
The Sombrero has a rich (1900 +/- 200) globular cluster population for two reasons:
(1) It is more luminous than our own galaxy
(2) It has a gigantic spheroidal bulge/halo component(s)
vs. our galaxy which has only a very small central bulge. And there are more globulars per unit of galaxy luminosity in those galaxies dominated by a bulge or spheroid.
The luminosity data on the Sombrero has been relatively easy to find, but in an odd sort of way, assessing the total luminosity of the MW has been an unpopular problem in the professional literature (only about 4 attempts to do this, in the last 20 years).
So I am going to ask a couple of Milky Way specialists if they have some recent data on the luminosity of our own Galaxy.
There is an old figure of about absolute blue magnitude -20 for the luminosity of our own galaxy which has been endlessly rehashed in the textbooks, but this figure does not really cut it any more......it is disappointing for the amateur to realize that the textbook writers do not usually utilize the most up-to-date data!
cheers,
Robert Lang
P.S.
Relative diameter of the two galaxies is going to be easier to assess. Our own galaxy is certainly no more than 80,000 light years across.
The diam. of the sombrero can be assessed from the catalog angular diam. plus there is a good recent estimate of its distance. However, M104 is very very different from our own galaxy, as our own galaxy has only a very very very faint halo! Indeed, there are strong arguments for M104 being earlier than type Sa in the orthodox Hubble Sequence of :
E - S0 - Sa - Sb - Sc - Sd - Sdm - Sm - Irr
Wow, thanks Robert for all the reading and interest you have taken in the topic. You're comments always make for interesting reading and I am sure I can speak for all; are always appreciated too.
Wow, thanks Robert for all the reading and interest you have taken in the topic.
Thanks, Paul, I am glad people appreciate the information I provide.
But I will leave the imaging and most of the image processing to experts like yourself and others in this forum....your imaging discussions increasingly have the specialized sound of a discussion between professional astronomers!
Hargis and Rhode, in a 2014 paper, claim that the bulge (or the extended spheroid..... including the bulge and also the halo) is actually much brighter (in terms of its total amount of light) than the flat disky component , leading to an overall falloff of light with increasing radius, in M104, which is more typical of an elliptical galaxy!
They regard the spheroidal component of The Sombrero as being totally dominant over the planar disk component, though I personally have some doubts about this interpretation. There are several assessments in the literature that state that the integrated light of M104 is dominated by the light from the bulge/spheroid, so the numbers cannot lie.
Certainly, our own Galaxy is very much different from M104, as it has a prominent disk and a small bulge.
I will probably do a bit of a quick MW vs. M104 comparison in the Science Forum, though this project is snowballing and there is a great deal to know about M104.
Thanks Geert. Several people have suggested that, but I know there are a lot of good ones out there. However, for a scope that cost very little (not counting the other equipment which makes a huge difference too), I am quite pleased with the result.
