2218 replies to this topic

[Dave Mitsky]

Its OK - I found this great list with the Messiers in order of surface brigthness.  Seems the second one is the Whirlpool in Triangulum.  Too bad I have to wait till fall!

http://www.messier.s...rg/dataMag.html

That list is arranged in order of integrated or apparent visual magnitude.  M33 actually has the third lowest surface brightness figure of the Messier galaxies.

Here's a list of the Messier galaxies, their integrated visual magnitudes, and their surface brightness figures in magnitudes per square arc minute:
 

M31 3.4 13.6
M32 8.1 12.7
M33 5.7 14.2
M51 8.4 12.6
M58 9.7 13.0
M59 9.6 12.5
M60 8.8 12.8
M61 9.7 13.4
M63 8.6 13.6
M64 8.5 12.4
M65 9.3 12.4
M66 8.9 12.5
M74 9.4 14.4
M77 8.9 13.2
M81 6.9 13.0
M82 8.4 12.8
M83 7.6 13.2
M84 9.1 12.3
M85 9.1 13.0
M86 8.9 13.9
M87 8.6 12.7
M88 9.6 12.6
M89 9.8 12.3
M90 9.5 13.6
M91 10.2 13.3
M94 8.2 13.5
M95 9.7 13.5
M96 9.2 12.9
M98 10.1 13.2
M99 9.9 13.0
M100 9.3 13.0
M101 7.9 14.8
M104 8.0 11.6
M105 9.3 12.1
M106 8.4 13.8
M108 10.0 13.0
M109 9.8 13.5
M110 8.1 13.9

To convert magnitudes per square arc minute to magnitudes per square arc second add 8.9.

[Eliserpens]

Hmmm, so I still got it wrong.  Then the Virgo sombrero (M104) is the visually brightest?  But I guess it also depends on the darkness of the sky around it.  Bode's is at least in a very dark part of the sky...

Edited by Eliserpens, 13 April 2020 - 03:35 AM.

[Rajput]

That list is arranged in order of integrated or apparent visual magnitude.  M33 actually has the third lowest surface brightness figure of the Messier galaxies.

Here's a list of the Messier galaxies, their integrated visual magnitudes, and their surface brightness figures in magnitudes per square arc minute:
 

M31 3.4 13.6
M32 8.1 12.7
M33 5.7 14.2
M51 8.4 12.6
M58 9.7 13.0
M59 9.6 12.5
M60 8.8 12.8
M61 9.7 13.4
M63 8.6 13.6
M64 8.5 12.4
M65 9.3 12.4
M66 8.9 12.5
M74 9.4 14.4
M77 8.9 13.2
M81 6.9 13.0
M82 8.4 12.8
M83 7.6 13.2
M84 9.1 12.3
M85 9.1 13.0
M86 8.9 13.9
M87 8.6 12.7
M88 9.6 12.6
M89 9.8 12.3
M90 9.5 13.6
M91 10.2 13.3
M94 8.2 13.5
M95 9.7 13.5
M96 9.2 12.9
M98 10.1 13.2
M99 9.9 13.0
M100 9.3 13.0
M101 7.9 14.8
M104 8.0 11.6
M105 9.3 12.1
M106 8.4 13.8
M108 10.0 13.0
M109 9.8 13.5
M110 8.1 13.9

To convert magnitudes per square arc minute to magnitudes per square arc second add 8.9.

Thanks. These are very helpful. Some of the surface brightness numbers seem a bit off though...

 

M51 is listed at 12.6 - almost as bright as M32(12.7). In practice, I can barely see the cores of it and its companion even on the best of nights.

M81 & 82 are listed as having low/average surface brightness (13.0 & 12.8). In practice they seem brighter by a huge amount.(I've seen them with the full moon out.)

M104 (11.6) seems right though - saw it the other day and it did stand out very well.

Edited by Rajput, 14 April 2020 - 07:38 AM.

[Dave Mitsky]

Integrated magnitude, surface brightness, orientation, and morphology all have to be taken into account.  Unfortunately, there is no simple metric for determining how easily visible a galaxy will be.

[Eliserpens]

Thanks. These are very helpful. Some of the surface brightness numbers seem a bit off though...

 

M51 is listed at 12.6 - almost as bright as M32(12.7). In practice, I can barely see the cores of it and its companion even on the best of nights.

M81 & 82 are listed as having low/average surface brightness (13.0 & 12.8). In practice they seem brighter by a huge amount.(I've seen them with the full moon out.)

M104 (11.6) seems right though - saw it the other day and it did stand out very well.

What kind of light pollution do you have Rahput?  M81 sure is not bright here (Bortle 'suburban').

[Rajput]

What kind of light pollution do you have Rahput?  M81 sure is not bright here (Bortle 'suburban').

I live in a suburban area too. Light Pollution is not terribly good but not as bad as a city either. I used this site and it says I'm in a Pink/Red zone - https://www.lightpol...0FFFFFTFFFFFFFF.

 

I'm able to see Mag 4.5 stars . e.g. Sagitta has a couple of 4.5 stars I can see without issue and a 5.25 which I rarely ever see.

 

One note - I'm playing a bit fast and loose with the words  "bright" and "seeing" here   I see M81 as a core with a halo around it and M82 is just a line with a slightly brighter middle. Never been able to see any detail beyond that. It is fairly obvious in my 10inch though. Once I find the location it is always visible directly, never had to use averted vision or anything.

[Eliserpens]

Hmmm... not sure why I am having such difficulty with M81 then.  The other night was pretty dark.  Part of it is the EQ mount for sure but I was there long enough I must have traversed the area at least once!

 

Could you see it in the finder scope first?  (assuming you have one of course).

Edited by Eliserpens, 14 April 2020 - 11:47 AM.

[Dave Mitsky]

Here's the section on M81 and M82 from my post at https://www.cloudyni...ur-astronomers/

 

M81 (Bode's Galaxy) and M82 (the Cigar Galaxy)

 

M81 (NGC 3031) and M82 (NGC 3034) are two bright galaxies in the northwestern section of Ursa Major. M81, a type Sb spiral galaxy, has an integrated magnitude of 6.9 and a surface brightness of 13.0 magnitudes per square arc minute. M82, a type Ir II irregular galaxy, shines at magnitude 8.4 and has a slightly brighter surface brightness of 12.8 magnitudes per square arc minute. M81 and M82 were discovered by the German astronomer Johann Bode on December 31, 1774. Together they are sometimes known as Bode's Nebulae.

 

To locate this galactic pair, pan from "above" Dubhe (Alpha Ursae Majoris) towards the "front" of Ursa Major. The next fairly bright star is 23 Ursae Majoris (magnitude 3.5). To the northwest of 23 Ursae Majoris lies a moderately bright isosceles triangle of stars consisting of Sigma 1 and Sigma 2 Ursae Majoris and Rho Ursae Majoris. Northeast of the triangle is 24 Ursae Majoris, which shines at magnitude 4.5. Southeast of 24 Ursae Majoris is a magnitude 5.7 star. M81 is immediately to the southeast of that star. M82 is situated about 2° southeast of 24 Ursae Majoris and just 38 arc minutes, a bit more than the width of a Full Moon, to the north of M81. Extending a line from Phecda (Gamma Ursae Majoris) to Dubhe the same distance beyond Dubhe places one approximately one degree south of M81.

 

Finder charts for M81 and M82 are posted at the following URLs:

 

http://www.seeintosp.../M81-81Wide.pdf

 

http://www.backyard-.../top100/10.html

 

http://www.dreistein...=A&id=50767&on=

 

http://www.dreistein...=A&id=50791&on=

 

An MP3 guide to locating M81 and M82 can be found at http://ia600708.us.a...ongtheStars.mp3

 

Telrad finder charts for M81 and M82 are available at the following URLs: 

 

http://www.custerobs...cs/messier2.pdf (map 5)

 

http://avila.star-sh...charts/m081.htm

 

http://avila.star-sh...charts/m082.htm

 

For more on M81 and M82, see the following sites:

 

http://messier.seds.org/m/m081.html

 

http://messier.seds.org/m/m082.html

 

http://www.nightskyi...1_m82_galaxies/

 

http://www.universet...054/messier-81/

 

http://www.universet...071/messier-82/

 

http://www.messier-o...1-bodes-galaxy/

 

http://www.messier-o...2-cigar-galaxy/

 

http://www.cloudynig...s/mar/M_81.html

 

http://www.astrofoto...AP155_U16M.html

 

http://www.deepskyvi...essier/M82.html

 

https://tonyflanders...rly-spring/#M81

 

https://oneminuteast...piral-galaxies/

 

https://www.universe...ng-m81-and-m82/

 

http://www.hawastsoc...ps/uma/uma2.gif

https://astrobackyar...d-m82-galaxies/

 

M81 and M82 are the major members of the M81 group, which is one of the closest galactic congregations beyond the Local Group. NGC 2976 and NGC 3077 are two other member galaxies that are good targets.

 

http://messier.seds....ore/m081gr.html

[Rajput]

Hmmm... not sure why I am having such difficulty with M81 then.  The other night was pretty dark.  Part of it is the EQ mount for sure but I was there long enough I must have traversed the area at least once!

 

Could you see it in the finder scope first?  (assuming you have one of course).

Never been able to see it in my finder (my 70mm has a 5x24, the Dob has a red dot). It shows up very faintly in my 70 mm but it needs a really good night.

 

From your Sig, it looks like you have a 190mm so it should definitely show up in yours. Did you try M104 or M94? They are easier starhops and should be fairly easy to see as well.

Edited by Rajput, 14 April 2020 - 12:34 PM.

[Eliserpens]

Never been able to see it in my finder (my 70mm has a 5x24, the Dob has a red dot). It shows up very faintly in my 70 mm but it needs a really good night.

 

From your Sig, it looks like you have a 190mm so it should definitely show up in yours. Did you try M104 or M94? They are easier starhops and should be fairly easy to see as well.

M104 was the plan - but its over the horizon, unless I get up v early!  M94 should definitely be doable, thanks for the suggestion.  Now, how do I clear the clouds out of the way?
 

[Dave Mitsky]

M94 is compact and has a bright core, which makes it a fairly easy target.  It was one of the handful of galaxies that was more than just the faintest bit of "lumpy darkness" that my wife and I observed from our red-zone driveway last night using a 6" f/10 Celestron NexStar Evolution SCT.

[Eliserpens]

Another vote for '94   And my Telrad arrived today, so I have great hopes!

[river-z]

Couple good nights with clear skies here in Southern California and my double star project is plugging along with 20 more.  I did have some trouble resolving a split in some of the stars in Bootes: Izar and Zeta.  Not sure if they were too tight or what.

 

Some favorites:

-tight and bright: Algieba in Leo & Porrima in Virgo

-nice color contrast: 19 in Lynx

-rose color pair: 17 in Hydra

[kjkrum]

Yesterday I spray painted the inside of the focuser draw tube on my Meade AZ70-ADS. Tonight my nose told me the volatiles were gone, so I reassembled it and took it out despite some atmospheric haze. Pointing it near Venus confirmed a dramatic reduction of internal reflections. I also replaced the tiny, straight through finder scope with a green laser. Another big improvement. Took a peek at M42 and M41. Also saw five satellites in half an hour. :-/

[Cape_sundew]

A slight newbie here, and hello CN. I am using a Z12 in a bortle class 4 area. Eyepieces are all factory basics at the moment.
Two nights ago I finally found M51 and M52, and got some structure out of them while my eyes adjusted to the darkness. I had searched for them before but honestly was under the impression they would be much bigger than they turned out to be. Still an amazing find, but a star test showed viewing wasn't too great either. Then it was off to Venus. A thin layer of clouds came rolling by and actually provided a natural light filter to venus, allowing me to easily make out the dark back side of the planet as well as the front. It was amazing watching a glowing orb float through my eyepiece. It was also dusk so the sky wasn't dark yet, but I will always remember it.
Next was crab nebula, which I have now spent the equivalent of 3 hours searching for but still no luck. It happens, so I moved on. The behive cluster, amazing and full of orange/red stars.
After more coffee and some laundry I went back out a few hours later to watch Jupiter and Saturn rise. Jupiter eventually got high enough to get ok contrast from, Saturn just wont let the horizon go yet. Mars was a multicolored marble, still not impressive yet either.
Last night back to venus, mag x300 during dusk showed the orb shape of the planet again, so I got a chair and spent at least an hour staring as the sun set. Then to orion for one last goodbye, a tree now blocks my view. Then I started doing naked eye observations and saw a ton of satellites, so I chased a few... Then...

I look up here in Missouri, and here comes a string of satellites. About the time the third one appeared my brain realised what was going on, and it was off to tell my family to look outside. One by one, 60 satellites in a row came across our skies. I learned then my family has no interest in astronomy, they had no idea what they where and I got to explain 4 times to 4 people about starlink. They took a good 5 to 10 minutes to all pass by.
Few minutes later clouds rolled in. I have a telrad on its way to me which will help tremendously. All in all, still very hooked and counting down the hours already because tonight is clear too. Tonight I am going to go cluster hunting until my hands are too numb to move eyepieces hopefully. I love space, I have learned so much about it that it is more than amazing finally seeing the things I have spent years hearing of in person. Hope this wasn't too long of a reply, and clear skies.

ATS

[jap201]

used the new scope early this morning for mars, saturn and jupiter.  everything looked really nice at 180x.  maybe i didn't let the scope and EP's cool down long enough, or it wasn't great viewing in the upper atmosphere, but could not make out the cassini division at 300x.  

 

is it me, or is it getting crowded up there?  been seeing an awful lot of satellites lately.  seems to be more than normal.  ahh, i forgot about starlink...

 

next up m52 and m97.  need to wait for some clear skies, snow tonight, followed by another front.

[Eliserpens]

I look up here in Missouri, and here comes a string of satellites. About the time the third one appeared my brain realised what was going on, and it was off to tell my family to look outside. One by one, 60 satellites in a row came across our skies. I learned then my family has no interest in astronomy, they had no idea what they where and I got to explain 4 times to 4 people about starlink. They took a good 5 to 10 minutes to all pass by.


ATS

Astronomy can be lonely inside as well as out!  That's why we have CN....  Sounds like a fruitful session though

[Eliserpens]

...but could not make out the cassini division at 300x.  

 

Don't know this one - some hints?

[Dave Mitsky]

Don't know this one - some hints?

Are you asking what the Cassini Division is or hints about observing it?
 

https://astronomy.co...ets4.jpg?mw=600

 

http://www.damianpea.../beltsrings.jpg

 

https://www.britanni...ystem#ref514933

[jap201]

Don't know this one - some hints?

Sorry, that's the diviion between some of the rings on saturn.  i thought i'd be able to make it out pretty easily at 300x.  I thought I'd make out more bands on jupiter also.  could be my eyes, maybe the viewing wasn't as good in the upper atmosphere when i was out, or maybe I just have to get more used to this scope.  still, I was never able to get the old c102 past 200x, so this is real nice.  the stars lie on black velvet...

[SeaBee1]

Don't know this one - some hints?

 

Hello Elise! I am assuming your question is about the Cassini Division? This is a distinct, but thin (in a scope) line dividing the two main rings of Saturn. It was first chronicled by the French observer Giovanni Cassini in 1675 using a 2.5 inch refractor at 90X magnification. It is quite the sight and quite doable in most modern scopes at similar or better aperture. It does need a steady atmosphere to see it well, however.

 

As a side note, my best view of the Division was in my ten inch reflector a few years ago, but now, due to cataracts, I am having trouble seeing it at all. So, if your eyes are good, and your skies are steady and transparent, your equipment should give you a nice view of the Cassini Division.

 

Keep looking up!

 

CB

[Eliserpens]

Thanks!  I knew I'd come across it but didn't recall where (and a bit lazy to not look it up myself!).  Unfortunately, Saturn is way off my current visible sky so will have to wait for that one.  Venus is setting and the only 'planet' I currently have a chance of seeing is the moon!

[Eliserpens]

Whoopee.  Nice dark sky tonight - no moon, though a bit hazy.  Excited to try out the Telrad - aligned this afternoon.  With the Telrad, a very nice ARCI, and also a wide angle 31 mm I have no excuses left!

 

Fortunately, did not need one.  The Telrad is like cheating!  I sighted the scope to my best guess for M91 - and then looked in the 31 mm.  And there was a fuzzy spot off centre.  I had the sidereal on (just pointed the mount north using a compass) with negligible drift so could go back in the house for my 11 mm EP.  That was rewarded by a dusky, but clear galaxy with a bright core.  One in the bag (not counting Andromeda of course)!  I also made sketches and my star pattern was perfect - once I realized that the scope was inverting the image.

 

Very pleased!

[Eliserpens]

That list is arranged in order of integrated or apparent visual magnitude.  M33 actually has the third lowest surface brightness figure of the Messier galaxies.

Here's a list of the Messier galaxies, their integrated visual magnitudes, and their surface brightness figures in magnitudes per square arc minute:
 

M31 3.4 13.6
M32 8.1 12.7
M33 5.7 14.2
M51 8.4 12.6
M58 9.7 13.0
M59 9.6 12.5
M60 8.8 12.8
M61 9.7 13.4
M63 8.6 13.6
M64 8.5 12.4
M65 9.3 12.4
M66 8.9 12.5
M74 9.4 14.4
M77 8.9 13.2
M81 6.9 13.0
M82 8.4 12.8
M83 7.6 13.2
M84 9.1 12.3
M85 9.1 13.0
M86 8.9 13.9
M87 8.6 12.7
M88 9.6 12.6
M89 9.8 12.3
M90 9.5 13.6
M91 10.2 13.3
M94 8.2 13.5
M95 9.7 13.5
M96 9.2 12.9
M98 10.1 13.2
M99 9.9 13.0
M100 9.3 13.0
M101 7.9 14.8
M104 8.0 11.6
M105 9.3 12.1
M106 8.4 13.8
M108 10.0 13.0
M109 9.8 13.5
M110 8.1 13.9

To convert magnitudes per square arc minute to magnitudes per square arc second add 8.9.

Hi Dave; after imaging M94 I wonder if these numbers are as useful as they could be.  The issue is how do they calculate the surface brightness?  I presume they take the total brightness and and divide it by the area.  But this assumes the object is evenly illuminated.  M94 has a very bright core but a faint halo - the 'surface brightness' calculated by the above would be very misleading - it is infact rather easy to find because you only see the core first.  What we need is a brightness figure that reflects the most easily observed element.  Perhaps this will not be so different for many of the objects but in this case it certainly is.

[Waddensky]

I presume they take the total brightness and and divide it by the area.  But this assumes the object is evenly illuminated.

Exactly. The surface brightness is an average value for the 'size' of an object (usually based on a certain constant brightness level). Most deep-sky objects are not equally bright in this way. M31 for example has one of the lowest average surface brightnesses in the list provided by Dave, but the bright core is easily seen by the naked eye from a moderately dark location. There's much more to it than just integrated or surface brightness, although the latter will give you at least a better idea of the visibility.