Deep sky galaxy observing

[mdstuart]

I have been "reading" this book by a guy in the states...

http://www.amazon.com/000-Deep-Sky-Objects-Annotated-Catalogue/dp/1441994181

Its a very comprehensive listing of visual observing. He is way ahead of my efforts..

I have so far gone through up to NGC 3000 comparing my galaxy observations to his. The first obvious difference is I struggle below a dec of –10 and certainly below –15 but he goes way down so picks up all the Fornax galaxies etc...That’s my back garden and UK light pollution!

However for this sample his 170x250 brightness assessment is consistent with my <0.5 to 5 scale. The chart below shows really good consistency with the majority of scores following the green line below.

Count of BRIGHTNESSBRIGHTNESS170x250<0.512345Grand TotalEEB11EB11VBR469120BR3623941MB26119248MF14519F77VVF11XXX99Grand Total6026382111147

I think the ultimate visual list is however this one! He really is on another level!

http://www.astronomy-mall.com/Adventures.In.Deep.Space/steve.ngc.htm

I have a long way to go!

Mark

[mdstuart]

Oh tables do not come out on here!

Mark

[mdstuart]

Here you go

[andrew63]

The dedication of some of these guys is certainly very humbling.

andrew

[Mike73]

I think the ultimate visual list is however this one! He really is on another level!

http://www.astronomy-mall.com/Adventures.In.Deep.Space/steve.ngc.htm

I have a long way to go!

Mark

Blimey!

That is pretty amazing, just wish his observing list was laid out better and was easier to read.

Thats what I call dedication!

[ismangil]

For us mere mortals, how do you estimate 'brightness'?

On mobile (excuse the strange predictive words...)

[Tinker1947]

Dedication he has loads off, i also bet clear skys...

[Starlight 1]

For us mere mortals, how do you estimate 'brightness'?

On mobile (excuse the strange predictive words...)

Yes I would like to know how someone can work it out, I use my Starlight1-1 photometer ,But must be more ways to do it.

[swamp thing]

Great list Mark, that's bookmarked for future reference straight away.

[Double Kick Drum]

Thanks for sharing Mark.

That Steve Gottlieb list is going to take some going through. If I lived to 150 and kept my eyesight, i'd be doing well if I got half way through that lot!!!

Also book marked for future reference. I definitely need a bigger scope!

[mdstuart]

Brightness..now this is a challenge.

My scale is just a visual estimate. 1 is a galaxy you can see looking straight at it.. <0.5 needs averted vision to see. 2 is a brighter galaxy...its all estimate..

Now some say you can defocus a star of a known magnitute and then compare it to the galaxy and estimate its mag...There are of course electronic CCD methods which are far more exact.....or are they? The ease of seeing depends alot on surface brightness which is the average brightness of the galaxy accross its shape but then what if its not even...

So one galaxy mag 9 surface brightness 13 might be very different visually to another mag 9 surface brightness 13 due to its profile...so we are back to Steve and others actually looking at the things and giving an idea on how easy it is to see and hence back to my scale!

There are whole books on this subject!

Mark

[m_j_lyons]

I find trying to classify galaxy structures fairly challenging...I've assumed many face on spirals to be ellipticals...it's tough with low surface brightness objects. At least it's tough for me.

Sent from my Xoom using Tapatalk 2

[acey]

Yes I would like to know how someone can work it out, I use my Starlight1-1 photometer ,But must be more ways to do it.

Do you use it on DSOs? Would be interested to know what sort of results you get.

Historically, galaxy brightnesses have been measured in various ways. Herschel just labelled them "bright", "faint" or "very faint". Later there were attempts to compare galaxies with an artificial light source brought into the same field of view through an arrangement of mirrors. Disadvantages were variability of the source and the effect of atmospheric extinction. The most reliable method was felt to be comparison with defocussed stars: a second telescope was used for this, the observer being able to view both images simultaneously.

Visual classification of galaxies is certainly very challenging - though we can take heart in the fact that classification from photographs is not straightforward either. In my experience the easiest type to identify is face-on Sc, simply because of its low surface-brightness, and (in many cases) mottling that shows the presence of spiral arms. But I get it wrong plenty of times.

[umadog]

I think O'Meara discusses it in his Messier book. He has a different method from other people for certain object classes (e.g. those with bright core and suddenly dimmer surround). The point being that the integrated brightness is a bad estimate because it doesn't take into account size. This much is well known. Dividing by area (mean surface brightness) does to some degree address the issue but it assumes uniform brightness. For objects with very non-uniform brightness levels, this can lead to misleading numbers. O'Meara has tried to come up with an approach that tackles this to some degree. I don't know what it is, though, since he refers to it in the Caldwell book but doesn't describe it (I only have the Caldwell). So this is a perceptual magnitude estimate.