3 Messiers checked of my 2016 list

[glennbech]

From my balcony, I only have good visibility North and East. That limits what I can see form home, but the seasons bring enough diversity to keep my interest. I can get a peek through my roof and the house next door and I found Cheretan in Leo with my 33mm. I tried to spot the Leo triplet to get an idea of how good the skies where. I could see absolutely nothing, and knew that Mag 9+ objects were out of reach.  

Hercules is in a good spot nowadays, So I decided to check off a few brighter messier objects of my 2016 list. I have spotted M13 earlier this year in my 60mm 1960's refractor, but last Friday I went back with my 90mm Megrez to see if I could tease out some more detail.

I located eta-hercules with my 33mm 2" WO- SWAN and M13 is in the same field. I tried different magnifications all the way up to 132x, but I could hardly make out anything else than a fuzzball, even with averted vision. My skies are not that dark.

Moving west, finding M92 was a breeze. It was Also bright and difficult to miss, but smaller. 

M57 was easy to spot. I could clearly make out the ring, with the hole. It will be interesting to go back on a darker night, and observe it more in detail. I had some great views at M57 through a 8" dob I used to have. A real fascinating object!

As a novice observer ,I need to learn more about magnitudes. Stellarium (Software) lists M57 as Mag 9 about the same as the M66 galaxies). I could find M57 low in the sky. but not M66. Is it because the galaxies are larger ,and the magnitude in Stellarium is shown as the total light emitted from the object? It could explain why M57 was easy to see, at only 2 minutes and 30 seconds in size.

 

 

[laudropb]

Very nice report.

[YKSE]

Congratulasion to the new Messiers

As to these extended dso (galaxies, nebulas), surface brightness is a better measure than magnitude. As you have guessed, magnitude is the integrated surface brightness, the bigger an object, the brighter the magnitude will indicate, which is kind of miss-leading. A typical example is M33, the Triangulum galaxy, magnftude 5.5 or 5.7 by different sources, seems to be an easy target if looking only at the magnitude, but it's actually one of the most difficult Messier in light-polluted sites, its surface brightness 13.9 describes this difficulty much better.

[Astro Imp]

Congratulations and thanks for a nice report.

YKSE thanks for an illuminating explanation, really succinctly put.

[alan potts]

Nice report, I used to observe from the balcony of the apartment in town before I finished the house, I could only see east and a bit either side to north and south. I remember wanting to see Mercury in the west so I had to poke the 12 inch through the window.

Alan

[glennbech]

I sometimes set my telemator up on the front side of the house , facing south, to observe the moon and Jupiter. 

My megrez 90 is then at the balcony opposite side. After that I bother my family, turning out lights and running through the house, back and forth

Dark adaption is impossible anyway. We oversee a small town from our house and the lights from it constantly disturbs my night vision. 

 

[Special K]

Nice report on those Spring treats!  M92 is great isn't it?  To me it looks like a little galaxy that's been pulled apart a bit.  I've only recently tried for it and didn't realize how easy it is. Sometimes haze also gives me a non-event with M13....especially when I compare it with the good nights.  

M57 must have been a beauty in the 8" dob, and sure enough as YKSE says, the surface brightness is significantly higher than those galaxies.  That's one thing that gives globular clusters an edge as they are fairly compact to be easier to spot. In my 6" frac, M57 really comes across as a ring.  Love it!

[glennbech]

2 hours ago, Special K said:

Nice report on those Spring treats!  M92 is great isn't it?  To me it looks like a little galaxy that's been pulled apart a bit.  I've only recently tried for it and didn't realize how easy it is. Sometimes haze also gives me a non-event with M13....especially when I compare it with the good nights.  

M57 must have been a beauty in the 8" dob, and sure enough as YKSE says, the surface brightness is significantly higher than those galaxies.  That's one thing that gives globular clusters an edge as they are fairly compact to be easier to spot. In my 6" frac, M57 really comes across as a ring.  Love it!

3

It's very interesting that you said that about M92. I double checked the location. I thought I might a have come across a bright compact galaxy. I can imagine that is how they look in a larger telesopes

[YKSE]

21 hours ago, glennbech said:

It's very interesting that you said that about M92. I double checked the location. I thought I might a have come across a bright compact galaxy. I can imagine that is how they look in a larger telesopes

There wouldn't be any telescope to show a faint galasy as bright as M92 you saw, unfortunately.

There're two factors deciding the brightness of  faint fuzzies like galaxes or nebula: Contrast and exit pupil. 

Constrast is totally depended on the sky darkness, the darker the sky, the more visible these faint fussies. More or less magnification will not change constrast of extended DSO, the sky will dim or brighten exactly the same amount as DSO.

Exit pupil depends on the focal length of the scope and eyepiece you use. with the same exit pupil, a 4" scope will show EXACTLY the same brightness of a galaxy as a 20" scope does, the difference is that 20" scope will show 5 times larger image, therefore much easily for us to see some more details. A simple anology is reading a newspaper on a wall, with the same good illumination, standing 5 meters away(like a 4"), you wouldn't be able to read much, but in 1 meter distance(20"), you'll be able to read it without much difficulty. The only difference here is the angular size of letters are much bigger when you're close. An object needs to be of a certain size for our eyes to see. Making a object bigger is the main efffect of a larger aperture. 

But, if illumation is extremely low (e.g almost pitch black=very bad contrast), you still wouldn't be able to read anything even with your nose on the newspaper.

[glennbech]

On 4/5/2016 at 20:55, YKSE said:

There wouldn't be any telescope to show a faint galasy as bright as M92 you saw, unfortunately.

There're two factors deciding the brightness of  faint fuzzies like galaxes or nebula: Contrast and exit pupil. 

Constrast is totally depended on the sky darkness, the darker the sky, the more visible these faint fussies. More or less magnification will not change constrast of extended DSO, the sky will dim or brighten exactly the same amount as DSO.

Exit pupil depends on the focal length of the scope and eyepiece you use. with the same exit pupil, a 4" scope will show EXACTLY the same brightness of a galaxy as a 20" scope does, the difference is that 20" scope will show 5 times larger image, therefore much easily for us to see some more details. A simple anology is reading a newspaper on a wall, with the same good illumination, standing 5 meters away(like a 4"), you wouldn't be able to read much, but in 1 meter distance(20"), you'll be able to read it without much difficulty. The only difference here is the angular size of letters are much bigger when you're close. An object needs to be of a certain size for our eyes to see. Making a object bigger is the main efffect of a larger aperture. 

But, if illumation is extremely low (e.g almost pitch black=very bad contrast), you still wouldn't be able to read anything even with your nose on the newspaper.

This was totally new to me and very useful information! Thanks for taking the time to write it up. Terms floating around like "light bucket", can easily produce a mental model of aperture as an "opening" for light to "pour into". Larger aperture, more light.      

I have read up a bit on exit pupil. If I understand this correctly, the purpose of a larger scope is to get to higher magnification and at the same time  produce an image the size of our average pupils, when the light hits the eye. Exit pupil size is determined by how fast the scope is, not the size, but larger telescopes can have low f-numbers, but still have decent focal lengths. Correct?

[YKSE]

Exit pupil is calculated in two ways:

1. dividing the telescope's aperture by magnification, EP=Aperture/magnification, this means two telescopes with the same magnification, it will have the same size of exit pupil, i.e. the same brightness.

2. dividing the eyepiece focal length divided by telescopes focal ratio, i.e. EP=flep/F, since the telescope's focal ratio F is defined as telescopes focal length by aperture,  flscope/Aperture, we have
EP=flep/(flscope/Aperture)=Aperture/(flscope/flep), and magnification is defined as flscope/flep, so it leads to the same result.

Light buckets do collect more lights for point sources, such as stars, open clusters, globular clusters, also very small and (relatively) bright galaxies and planetary nebulas.  On these DSO, more magnification wouldn't reduce the DSO's brightness, only darken the sky brightness, therefore increased contrast. The effect of increased constract ends when the point sources reached the diffraction limit (showing diffraction rings), then these DSO are just like extended DSO, no more constrast gain by more magfication, it only leads to bigger size, which might still be of a advange for our eyes to detect though.

As mentioned in this post, there're people bagged all the Messiers with only 10x50 binoculars, and yet we have many observers with much bigger apertures couldn't see all the Messiers (even altitude allows it) in their light-polluted backyards.