Messier Like Objects

glenc (Glen) · #1 23-11-2008, 08:01 AM

I have been working on a catalogue of Messier Like Objects.
The faintest open cluster in Messier's catalogue is magnitude 8.0. (M26)
The faintest globular cluster in Messier's catalogue is magnitude 9.2. (M72)
The faintest planetary nebula in Messier's catalogue is magnitude 11.0. (M97)
The faintest galaxy in Messier's catalogue is magnitude 10.1. (M91 and M98)
That is according to the SAC database. http://www.saguaroastro.org/content/downloads.htm

If we use the above magnitude limits and SAC v8 we get 288 OC, 79 GC, 50 PN and 133 Gxy brighter than those magnitudes.
If we use a different database the numbers will be a bit different.

But you need to take other things into account too.
For open clusters the number of stars and richness need to be considered. I don't want 288 OC, it is too many.
Globular clusters are fairly straight forward and 79 is a good number.
For planetary nebulae size is a factor. The smallest is M57 (86" diam), should we go smaller than that?
There are only 7 non-Messier PN brighter than mag 11 and larger than 80", and 24 non-Messier PN brighter than mag 11 and larger than 18".
For galaxies we need to look at surface brightness. (M101 has the lowest SB)

And the hard one is nebulae, how faint should we go?
Which NGC and IC nebula are brighter than M1, M8, M16, M17, M20, M42-43 and M78?
The smallest Messier nebulae are 8' across, should we go smaller? M1 and M78 are the smallest and faintest M nebula.
What do you thinK?

glenc (Glen) · #2 18-04-2009, 06:29 AM

The faintest galaxies in Messier's catalogue are magnitude 10.1.
The attached list is from the SAC ver 8 database and contains 135 galaxies brighter than magnitude 10.2. Dwarf galaxies are not included.
If Messier and Mechain had searched both the northern and southern sky "properly" they would have seen most of these galaxies.

The columns in the list are:
OBJECT Name, NGC or IC number
OTHER Messier number (there are 40 Messier galaxies)
TYPE galaxies
CON Constellation
MAG Magnitude (faintest are mag 10.1)
SUBR Surface brightness (mag 15 is difficult)
SIZE_MAX in arc mins
SIZE_MIN in arc mins
PA Position angle
CLASS elliptical, spiral, irregular etc
RA Right Ascension
DEC Declination
N-S 20 galaxies are north of dec +45, 13 are south of dec -45
TI Tirion star atlas map (there are 26 maps)

Refr: http://www.saguaroastro.org/content/downloads.htm

dannat (Daniel) · #3 18-04-2009, 08:35 AM

Glen, another terrific list - i will have to give up work full time so i can make it thru your lists which i have downloaded

glenc (Glen) · #4 18-04-2009, 09:09 AM

Thanks Daniel.
The faintest globular cluster in Messier's catalogue is magnitude 9.2.
The attached list is from the SAC ver 8 database and contains 81 globulars brighter than magnitude 9.3 including 29 Messier objects.
If Messier and Mechain had searched both the northern and southern sky "properly" they would have seen most of these globulars.
Class I globulars are hard to resolve, class XII are easy to resolve.
BRSTR is the brightest star.
16 GC are south of dec -45, none are north of dec +45.
Globulars in bold print are the brightest 40.
The attached file contains M like globulars and galaxies.

hickny (Peter) · #5 18-04-2009, 10:25 AM

Thanks Glen. Having had my scope for nearly 2 years now and as my skill level (star hopping) improves, your lists will help me find more of the delights in the night sky. Last night I am almost sure I saw M104 near the zenith around midnight. A little disappointing in my 8" DOB but judging by the star patterns in the vicinity and the view in Stellarium it had to be M104. I think I need a bigger scope!

Robh (Rob) · #6 18-04-2009, 10:43 AM

Glen,

Great project and very time consuming.

One of the brightest PN is NGC 3242 (Ghost of Jupiter), size 25". The Blue Planetary (NGC 3918) is about 12" diameter. You can't exclude these.

Don't forget the eta Carinae nebula (NGC 3372)!

For all objects, I'd be inclined to go for observed brightness rather than size as a criteria. As you have mentioned Vmag is not a great indicator for large objects so Surface Brightness will come into play.

Regards, Rob

glenc (Glen) · #7 18-04-2009, 04:02 PM

The attached file now includes 80 globular clusters, 31 planetary nebulae and 135 galaxies. I have include planetary nebulae larger than 12" across down to magnitude 11.0. Sizes for PN are in arc-secs not arc-mins. C STR is the magnitude of the central star. PN in bold are the brightest ones. Six PN are north of dec +45.
Refr: Saguaro Astronomy Club Database version 8.0
Planetary nebula are often typized for their appearance, according to the Vorontsov-Velyaminov scheme:
1 Stellar Image
2 Smooth disk (a, brighter toward center; b, uniform brightness; c, traces of a ring structure)
3 Irregular disk (a, very irregular brightness distribution; b, traces of ring structure)
4 Ring structure
5 Irregular form, similar to a diffuse nebula
6 Anomalous form
http://seds.org/messier/planetar

glenc (Glen) · #8 19-04-2009, 05:35 AM

Which NGC nebula are as bright as or brighter than M1, M8, M16, M17, M20, M42-43 and M78?
They need to be visible in a 6" Newtonian and brighter than magnitude 11. http://picasaweb.google.com.au/dunlop1826/NGCNebulae#

glenc (Glen) · #9 19-04-2009, 06:07 AM

Here is some information on Messier's telescopes. http://seds.org/messier/xtra/history/m-scopes.html
Speculum has a reflectivity of about 63% after 6 months in a damp atmosphere. http://www.iop.org/EJ/abstract/0950-7671/24/9/308
Aluminium has a reflectivity of 87%. That means Messier's speculum 8" is equivalent to a 5.8" aluminium mirrored Newtonian.
(8 squared x 0.63 squared = 5.8 squared x 0.87 squared)

glenc (Glen) · #10 19-04-2009, 03:42 PM

The attached file now includes 40 nebulae as well as 80 globular clusters, 32 planetary nebulae and 135 galaxies. (287 total)
Let me know if I missed any bright nebulae or if any of the 40 I have included are too faint for Messier to see.

erick (Eric) · #11 19-04-2009, 04:02 PM

Persist with the 8" and M104, Peter. Under good dark conditions you can get a good view of it.

Quote:

Originally Posted by hickny

Thanks Glen. Having had my scope for nearly 2 years now and as my skill level (star hopping) improves, your lists will help me find more of the delights in the night sky. Last night I am almost sure I saw M104 near the zenith around midnight. A little disappointing in my 8" DOB but judging by the star patterns in the vicinity and the view in Stellarium it had to be M104. I think I need a bigger scope!

Robh (Rob) · #12 19-04-2009, 04:39 PM

Glen,

You've done a marvelous job. Nice and useful reference material.
You've pretty much got all the brighter objects here.

Galaxies are a tough one.
Consider these:
The galaxies in the Grus Quartet (NGC 7552/7582/7590/7599) fall outside your magnitude limit of 10.1 but have a surface brightness between 12.2 and 13.2. So would match others in your list.
Similarly NGC 1326 in the Fornax cluster with mag 10.5 but SB 12.9.

Top job, Rob.

Chippy (Nick) · #13 19-04-2009, 11:49 PM

Excellent stuff Glen - thanks for posting this. Now I need some clear dark skies!

glenc (Glen) · #14 20-04-2009, 04:14 AM

Rob, NGC 7552 & 7582 are mag 10.6. If I went to mag 10.6 I would have more than 260 galaxies.
I could restrict it to mag 10.6 and SB 13 but that cuts out the LMC, SMC, M31, M33, Cen A, N55 etc. Where do I draw the line?
The most difficult part of this project is choosing nebulae, because they have no magnitudes, and open clusters because they can be bright and unimpressive.
I will look for the best NGC & IC OC brighter than mag 7.5.

andrew2008 · #15 20-04-2009, 08:09 AM

Hi Glen.

Great work on the list, will definitely use it as soon as i sort out my Argo Navis.

Just a question though. Down to which magnitude should i expect to see in a fairly light polluted part of Bris? Probably around Mag 5 skies at best on a few occasions.

Robh (Rob) · #16 20-04-2009, 11:24 AM

Quote:

Originally Posted by andrew2008

Just a question though. Down to which magnitude should i expect to see in a fairly light polluted part of Bris? Probably around Mag 5 skies at best on a few occasions.

Andrew, have a look at the Bortle Dark Sky Chart ...http://en.wikipedia.org/wiki/Bortle_Dark-Sky_Scale

Glen, point taken based on your criteria.
Again, great work, Rob.

glenc (Glen) · #17 20-04-2009, 03:20 PM

Andrew, what size is your scope? It's best if you can get out of Brisbane.
Some say limiting mag = 9.1 + 5 times log D where D is the scopes diameter in inches.
The limiting mag for a 6" is about 13, so Messier might have seen mag 13 stars.

glenc (Glen) · #18 30-05-2009, 09:07 AM

I selected 72 open clusters from a list of 165 OC.
I looked at all the 165 OC using Desktop Universe.
Some OC were included because of associated nebulosity.
The attached file contains 72 OC, 80 GC, 40 Neb, 32 PN and 135 Gxy.
That is a total of 359 Messier like objects.
If you look at 30 every month you will see them all in a year! Look around RA 13 this month.

Robh (Rob) · #19 30-05-2009, 10:10 AM

Quote:

Originally Posted by glenc

The attached file contains 72 OC, 80 GC, 40 Neb, 32 PN and 135 Gxy.
That is a total of 359 Messier like objects.
If you look at 30 every month you will see them all in a year! Look around RA 13 this month.

Glen,
This is a fantastic resource!

Much appreciated, Rob

glenc (Glen) · #20 30-05-2009, 03:56 PM

Thanks Rob.
At 10pm the best time to see:
Gxy is April.
GC is July.
OC is Feb & July.
Neb is Jan.
PN is Sept.
April has 65 objects and July 61 objects.