30 Oct 09 APOD: Bubble and M52

[Indigo_Sunrise]

Today's APOD

Shouldn't this:

Seen toward the northern boundary of Cassiopeia,

read as:

Seen toward the northeastern boundary of Cassiopeia

That is, if Polaris is used for 'north'.
Minor nitpick, I'm sure, but just curious......

Nice image, tho'!

[orin stepanek]

What I noticed on today's APOD was that the bubble seemed to be inset in the center of what appeared to be a swirl of pink clouds. These looked almost spiral in shape when the photo was enlarged.

Orin

[Geek-zer]

Every image is beautiful, and "Bubble and M52" is no exception. I have a problem with the explanation tho. If M52 is more than twice the size of the Bubble and less than half as far away, why does it look less than a third the size of the Bubble? I have been an amateur astronomer for over 60 years (thus, Geek-zer) but maybe I'm just dense.

[Geek-zer]

Scratch my question about the explanation. I answered my own question. The Bubble is the tiny object near the center of the red cloud and is not the cloud itself. I wonder if the red cloud itself (that contains the Bubble) has an NGC designation. .. Thanks to phpBB and NASA for providing these stunning images.

[bystander]

Every image is beautiful, and "Bubble and M52" is no exception. I have a problem with the explanation tho. If M52 is more than twice the size of the Bubble and less than half as far away, why does it look less than a third the size of the Bubble? I have been an amateur astronomer for over 60 years (thus, Geek-zer) but maybe I'm just dense.

That was kind of my first reaction, too, but the bubble is just the lighter circular outline in the pinkish area at the upper right (see APOD: 2009 Jan 24 - Bubble Nebula). M52 appears to cover more than four times that area.

[Chris Peterson]

Shouldn't this:

Seen toward the northern boundary of Cassiopeia,

read as:

Seen toward the northeastern boundary of Cassiopeia

Actually, these objects are right on the western edge of Cassiopeia, and closer to the southern border than the northern. If the caption is just referring to the "W" Cassiopeia asterism, and not the constellation boundaries, then the image could be described as a bit northwest of it.

[Indigo_Sunrise]

Thanx for clarifying, Chris.
The map I was using - here - somewhat confused me as to which way it was oriented.

Happens to the best of us, I guess.....

[Chris Peterson]

Thanx for clarifying, Chris.
The map I was using - here - somewhat confused me as to which way it was oriented.

Of course, it isn't all that obvious how the cardinal directions, which we normally reference to the horizon, map to the celestial sphere. North and south are pretty easy to figure out, since you have the poles for reference. For east/west, just remember that right ascension increases to the east (which makes sense, because RA is basically time, and the further east an object, the later it rises).

[bystander]

(which makes sense, because RA is basically time, and the further east an object, the later it rises)

What a confusing statement. I had to think about that for awhile. Since things rise in the East, why would things further East rise later? Seems counter-intuitive. I got it, but it did make me go, huh.

[Chris Peterson]

What a confusing statement. I had to think about that for awhile. Since things rise in the East, why would things further East rise later? Seems counter-intuitive. I got it, but it did make me go, huh. :? :oops:

Hmmm... seems intuitive to me. Just considering the simplest case of the part of the sky that is actually rising now, that is, right on the eastern horizon- surely it is obvious that "further east" from there must be below the horizon, meaning rising later.

[apodman]

A few years at sea with a sextant will cure ye. Arrrgh. Ye landlubbers could learn a lot from us sailors. We invented both sailing and the sextant right here in St. Petersburg no matter what the western consensus claims.

---

the northeastern boundary

Picky, I know: I'll buy the phrases "north end of the eastern boundary" and "east end of the northern boundary", but by intergalactic law all constellation boundaries run either due north-south or due east-west, so I have trouble reconciling actual orthogonal constellation boundaries with "northeastern" which I visualize as an oblique direction.

[darthdruid]

is there some misstake on the distances for oct 30 2009? they look to be wrong to me?

[Chris Peterson]

is there some misstake on the distances for oct 30 2009? they look to be wrong to me?

How so? Both the distances and object sizes seem about right. These objects are far enough away that there is some significant uncertainty in determining distance- probably 30% or more. But the values given are certainly reasonable.

[jerbil]

Is there not a further problem regarding orientation, Chris? Some astronomers seem to invert their images and some seem not so to do. Therefore some Norths are South and some Easts are West.

I have a video on a documentary about the First World War. The producers decided that, for simplicity, the allies should always be depicted on the left and the Germanic powers on the right. This required them to invert a large percentage of their archival footage (and then rotate by 180º.)

This explains why so many of the soldiers in this war appear to be left-handed.

[neufer]

Is there not a further problem regarding orientation, Chris? Some astronomers seem to invert their images and some seem not so to do. Therefore some Norths are South and some Easts are West.

I have a video on a documentary about the First World War. The producers decided that, for simplicity, the allies should always be depicted on the left and the Germanic powers on the right. This required them to invert a large percentage of their archival footage (and then rotate by 180º.)

This explains why so many of the soldiers in this war appear to be left-handed.

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• _A Simple Desultory Philipic_ by Paul Simon
  
  • I been Norman Mailered, Maxwell Taylored.
    I been John O'Hara'd, McNamara'd.
    I been Rolling Stoned and Beatled till I'm blind.
    I been Ayn Randed, nearly branded
    Communist, 'cause im left-handed.
    That's the hand I use, well, never mind!

[Chris Peterson]

Is there not a further problem regarding orientation, Chris? Some astronomers seem to invert their images and some seem not so to do. Therefore some Norths are South and some Easts are West.

The image is presented with north to the left, east down. That is rotated from the most conventional viewpoint, which is north up, east left. It isn't inverted or mirrored in any way, however.

It is pretty common for imagers with aesthetic goals to rotate their images freely to achieve the desired composition, or sometimes they need to do so to get a suitable guide star (with self-guided cameras).