Observing report.. Globular Clusters

[Nexus 6]

Hi SGL, in light of the limited oppurtunities for observing due to the weather, as always, I took the chance to test the go to of my 925 on a few globular clusters.

17. 06. 11

11:30-2:15

Seeing: 5/10

Tranparency: 5/10

Wind: light

Scope: Celestron cpc 925

Eyepiece: Televue 35mm Panoptic

Power: 67x

Targets: M2, M3, M5, M10, M12, M15, M92, NGC 6229

Impressions

M2 was on the way up to my east so it was not a particulary impressive sight but even still was unmistakable as a globular cluster.

M3 is certainly one of the brighter globulars with an approximate visual magnitude (vm) of approximately 6.4, it was setting to my west around 28 deg above my horizon. I was surprised by the amount of detail given its postition and with the Moon up but low on my southern horizon.

M5 was a very nice view with a vm of around 5.8 it was surprisingly luminous given the conditions.

M10 was not that far away from the Moon so I expected it to be difficult to observe even though it has a vm of around 6.6. I could make it out and although faint was still just about visable.

M12 another glob with an approximate vm of 6.6 I could not be sure I was looking at it due to the washed out sky from the Moon.

M15 was a very impressive sight, the core was obvious on this one and I was struck by its overall luminosity with a vm of around 6.4 it really stood out.

M53 not as obvious as the others but with a vm of around 7.7 and bearing in mind it is much further away than the other globulars in this report I was happy enough to be able to see it.

M92 was almost on my Zenith so I hoped for a good view on this one, with a vm of around 6.5 I was very impressed with it and was struck by its luminosity. When looking in Hercules for M13 try and have a look at this object too.

I also took the chance to have a look at NGC 6229 another globular in Hercules with a vm of only 9.4 it was visable to me but was very faint.

I had intented to have a look at M71 but it will have to wait untill next time.

The scope performed superbly with all targets falling into the fov of the Panoptic except M12 which I'm sure was there. I must check it out again to get an impression.

All in all a very enjoyable session. Have a look if you can, with conditions as they were it bode's well for nights with better skies when Im sure they would all be somewhat better

Clear Skies

[tbird]

Pleased you got out for some observing Alan.

I was using the 130p, but with the cloud and bright moon the limited light grasp of the 130 meant observing was confined mainly to Saturn.

I did manage a look at M57, but it was very faint, my 13mm Hyperion, the only EP I had with enough contrast to pick it out.

[northernnutter]

Sounds like you had a good night there Alan! Thanks for posting.

It's a great list as to what is visible at the moment...for newbies like me looking for inspiration!

(I also tried for some globs last night...but got absolutely no-where. What with the LP...moonlight etc...I knew I was on a losing battle:()

One question, if you don't mind?? You refer to VM? (Visual magnification??)..sorry I'm still learning...

I know 'mags' of objects are listed on Stellarium, for eg, but the mags you are listing...are they actually what you are estimating for the object on that particular viewing? If so...how do you work this out??

(Sorry for being a bit of a newbie pain!!)

Cheers

Vicky.

[Nexus 6]

Pleased you got out for some observing Alan.

I was using the 130p, but with the cloud and bright moon the limited light grasp of the 130 meant observing was confined mainly to Saturn.

I did manage a look at M57, but it was very faint, my 13mm Hyperion, the only EP I had with enough contrast to pick it out.

thanks mate, I knew it may be a few nights before I can next get out so just had to have a look for at least a few hours.

Try and get a look at M92 its pretty special considering M13 gets all the attention in Hercules

[Nexus 6]

Sounds like you had a good night there Alan! Thanks for posting.

It's a great list as to what is visible at the moment...for newbies like me looking for inspiration!

(I also tried for some globs last night...but got absolutely no-where. What with the LP...moonlight etc...I knew I was on a losing battle:()

One question, if you don't mind?? You refer to VM? (Visual magnification??)..sorry I'm still learning...

I know 'mags' of objects are listed on Stellarium, for eg, but the mags you are listing...are they actually what you are estimating for the object on that particular viewing? If so...how do you work this out??

(Sorry for being a bit of a newbie pain!!)

Cheers

Vicky.

Hi Vicky, the visual magnitude, vm, is a standard by which the luminosity of a given object is given as seen from the Earth. This can of course vary to the observer depending on their particular skies at that given moment of observing but when conditions are good that is as bright as it will appear to look to the observer.

[tbird]

There was a break in the cloud exposing M57, but Hercules was clouded over. I agree M92 is good but M13 is easier to find ;-). I should have stayed up later as I think the cloud was clearing but I was just too tired ( what a light weight lol ).

[northernnutter]

Ahhhh.....visual 'magnitude!!' (Close....but no banana!!)

Thankyou for the explanation Alan,

Much appreciated.

[Nexus 6]

Ahhhh.....visual 'magnitude!!' (Close....but no banana!!)

Thankyou for the explanation Alan,

Much appreciated.

Your welcome....apparent magnitude is also know as visual magnitude but is no different in its description.

By contrast Absolute Magnitude is a measure of a given objects luminosity from a set distance....32.6 light years or 10 parsecs.

As an example Deneb in Cygnus has a vm of about 1.5 but when using Absolute magnitude it is around -7.2!

[northernnutter]

Hey Alan...

just to clarify..(sorry:o)...measured as 32.6 light years from the object itself?? (Therefore far 'brighter' on the mag scale than we would see it as..)

(Who thought of 32.6 light years as a measuring point? Seems a bit random... )

vic.

[Nexus 6]

Hey Alan...

just to clarify..(sorry:o)...measured as 32.6 light years from the object itself?? (Therefore far 'brighter' on the mag scale than we would see it as..)

(Who thought of 32.6 light years as a measuring point? Seems a bit random... )

vic.

The measuring point is for you as an observer on the Earth and is set at the distance of 32.6 light years from the Earth. So on that basis many of what we observe as apparently bright objects are in actual fact much less luminous than they actually are in real terms.

Example, have a look at The Summer Triangle, Deneb in Cygnus, Vega in Lyra and Altair in Aquilla. To the naked eye it is obvious that Vega is the most luminous of the three and Deneb by far the less of the trio. Now imagine all 3 stars at the 32.6 light year distance, now it would show us that Deneb is in fact by some margin the most luminous star.

the factors to be concidered here are that every object we are looking at is at a certain distance from us and that its size and mass are linked to the total luminosity that the given subject is producing.

hth

[northernnutter]

Many thanks for the explanation Alan!

It's a real breath of fresh air to find a community with members, (such as your good self), who are prepared to give their time and knowledge to help less experienced members in their quest to learn more about this fascinating subject.

Wishing you clear skies,

Vicky.