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Help with observing M31


tomys
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I really really want to see that galaxy. Tried 4 times, 100% failure. Which star should I start with and start hopping from? My finderscope is around 4-5 degrees wide and my lowest power eyepiece is half a degree wide. My highest power eyepiece goes all the way down to 1/30 a degree wide. I can see quite a fair bit of the east and the mountains go all the way up to around 8 degrees altitude, and the roof starts at around 20 degrees altitude. I am forced to see out a window. That's east.

What time and how do I star hop to M31? :)

Info

Finder: 4-5 degrees

lowest power: 1/2 degree

highest power: 1/30 degree

range to the east which is not obstructed: 8 to 20 degrees

dimmest star approx mag: 2

Thanks in advance!

Edited by tomys
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It is a bit low at the moment when it gets dark so you need to look after midnight. Use Stellarium to see where it is. I tend to find the top left star of the Pegasus square. Then go for the next bright star to the left...Then up and slightly to the left past two other reasonably bright stars. If you are using binos it shoudl then be pretty obvious as a blob...

Buy turn left at Orion and use that would be my next suggestion..

Mark

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It took me ages to find it, think mainly the reflection from the street lights around me reflecting on the lens stopped me. I put up a screen last week and lo and behold came upon it almost at once, was dancing for joy :) , so good luck with your search. I came upon it by following the bottom star of Cassiopea, using the constellation like an arrow!!

Jim

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Yes, follow the right V of the Cassiopeia W to a bright (2nd mag) star of Andromeda (Mirach). Then, at around midnight, another fainter (4th mag) star (mu Andromeda) is 4 degrees above Mirach. Then, another 4 degrees up you'll find M31. There's a 4.5 mag star (nu Andromeda) marking the way at 3 degrees up from mu just before you get to M31.

post-13420-133877463036_thumb.jpg

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M31 is 2.6 x 1.1 degrees... i think part of the problem might be your relatively narrow fov. I've attached a simulated view of a 1/2 degree fov overlaid on the galaxy. Maybe the bright core is totally filling your fov and you're not recognizing it for what it is?

Also attached is a horizon simulation of London at midnight, when M31 will be 33 degrees from the horizon. It's indicated by red crosshairs, and i've marked a search-pattern in yellow. If you have a pair of binoculars (or maybe you could try this with your finder scope), make a visual straight-line sweep between Alpheratz and Shedir, and slowly work down towards the horizon while remaining parallel to the yellow line. When you see a fuzzy spot, that's M31... there's nothing else like it in the area. Or you might try just going straight up from Mirach. Whichever way you choose, keep in mind that the graphic is based on Alt/Az at midnight... things won't look the same before or after that time.

Best of luck, and i hope you bag it. :)

post-13732-133877463098_thumb.jpg

post-13732-133877463103_thumb.jpg

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Tomys, M31 will be North East, at around 22 degrees elevation @ midnight. That's going off my location in the South China Sea. I'm about 130 miles south of you, but that should give you a clue.

Here's a screen shot from Stellarium, set to Hong Kong (ish):

930ccd0340d9bf76b99ca4915282c44e_5660.jpg?dl=1279344820

(clickable).

HTH.

YM

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It'll be quite high by the end of August / start of Sept during the late evening hours. Last year I saw it in binocs from a fairly light polluted area during a full moon, so you should have no trouble - right now though you'll have to wait till around 3:00 - 3:30 am for the best chance :)

Edited by brantuk
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I have also never managed to see M31 through a telescope, I may have glimpsed it once as a very faint fuzzy patch through my 15x70 binoculars. I am sure this is due to the light pollution in London.

Thanks for all the useful information, especially the simulation of the sky as seen from London!

M31 should appear above the roof of my house at around 3a.m. so I will try to spot it tonight, if there are no clouds!

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Tomys, the most crucial piece of data you give is your limiting magnitude, 2, which means you are in a heavily light-polluted area. This will make it very hard to see M31.

The visibility of galaxies depends on the darkness of the sky. There has to be sufficient contrast otherwise you won't see it with any instrument. A telescope makes galaxies bigger and dimmer: the brightest view (meaning highest surface brightness) is with naked eye - you use a telescope to make the object big enough to make out against the sky (about half a degree). You will need to use your lowest possible power in order to get the brightest view. Additionally, you should aim to see galaxies when they are highest in the sky (i.e. due south), as they are dimmed by Earth's atmosphere when close to the horizon; and you want the sky to be at its darkest. So autumn is a better bet for attempting to view M31.

The innermost part of M31 (out to about a third of a degree) has a surface brightness of around 21.5 magnitude per square arcsecond (MAS), and in order to see this you would need a limiting magnitude of about 5. However the very centre of M31 (out to about 0.03 degree) has a surface brightness of about 17.5MAS, suggesting a required limiting magnitude of only 1.7. So this tiny innermost part might be visible in a sky as bright as yours. It would require a magnification of about 20, which is the lowest useable power of a scope of around 6" aperture.

However you would need to make sure your eyes are truly dark adapted, which is difficult in heavy light pollution. First find the object using the finder charts, then acquire the area in the main scope. Keep your head covered to block out all stray light and keep the scope aimed at the required location at lowest power. Eventually you might be able to make out a faint fuzzy blob: the centre of the galaxy. To see more of the galaxy you will need to travel to a darker site. With a limiting magnitude of 6, the galaxy is easily visible with the naked eye and binoculars show the dark lane of the spiral arm.

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M31 is JUST within the realm of naked eye objects from my location during the darker months when it is higher in the sky earlier. I've seen it in my 20X90 bins but failed to find/see it in my 90mm scope.

I'm hoping to see it later this year with my 130mm scope.

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I use the same as Rich, the "steep" V of Casseiopia acts like an arrow pointing at M31.

Try by eye and if nothing very, very vague :eek::eek: registers then try with a set of binoculars.

It won't exactly jump out at you.;):evil6::icon_eek::evil6:

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Thanks! I am in a much darker place and 20 degrees up I can make out all the constellations there. Below that are blocked by fog + city lights. I will see it TONIGHT! Grrrrrrrrrrrrrrrrrrrr

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Hiya Tomys, I have pinched one of Talitha's graphics (hope you dont mind Carol :eek:) to show my 3 right and 3 up method. Start in Perseus with its brightest star Mirfak, look to the right and you should see a ring of bright star's ending in Pegasus, So 3 stars right Mirfak, Almach and Mirach, now 3 stars up and BINGO there is M31.

Note, try binoculars frst of.

post-13880-13387746347_thumb.jpg

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To find M31, I use the most equilateral triangle of the two in Cassiopeia, which points down to Mirach (easy to see - basically the next brightest star in the general direction the triangle points). Then, I pick out the other two stars that make a noticable line with Mirach, and M31 is just a little offset from the last star. This whole process (including seeing the galaxy) is easy to do with the naked eye under dark skies.

M31pointer.png

Edited by george7378
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Last night I missed my opportunity as I didn't dare to go outside at night, especially in a foreign area. Now that I know China is safer than I thought, and that I know that it is GIGANTIC, I will now go and see it tonight.

Many people say that the ring nebula in Lyra is easy to find, but really! After MANY tries I have still failed.

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A lot of the time, the Ring Nebula is mistook for another star (especially as it is in a large star-field), so the thing to do is explore the area slowly at low magnification until you see a fuzzy and circular object. Use averted vision at higher magnification to see the dark bit in the middle - you will know it's the ring then.

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Then I think I just saw it without your helpful tips. I was swinging it wildly around until I saw something strangely out of focus. Turning the knob led me nowhere. Then I thought: The nebula... and then I was overjoyed! :eek:;):icon_eek::D:( :(

I got to see the wild duck cluster too, and now I am so happy I will wait for a darker day to see it. Thanks!

At my position it is best for me to wait all the way to 3 am now. M31 would be overhead! But obviously sleepiness is in charge now. Goodnight!

(I lied twice about seeing M31 already, ouch... Gonna have bad dreams)

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