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What size scope do you need to see all Messiers?


iamjulian
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Quite an interesting night under the stars last night. It wasn't exactly a clear night, but there were gaps so I went out anyway. Lots of thin strips of high cloud meant the image through the eyepiece went from showing perhaps a dozen stars to a hundred stars, and back, in the space of a few seconds. After realising I had spent the previous night out looking for M1 in completely the wrong place, it was the first target last night and it took about 30 seconds to find. No detail, but the cloud wasn't going to help. The other targets were all in Ursa Major, namely M109, M108 and M97. I couldn't find the first, probably not surprising given that the map I had in my head told me it would be down and bit and left a bit from Gamma Ursae Majoris. However I did find the other two, bringing my Messier count to 40.

I found M97 first. I only spotted it because of the three stars close by that I recognised from a star map. And sure enough, with averted vision it was there, though no sign of the two dark spots that give it the owl moniker. Heading backward towards Beta Ursae Majoris I spotted the thin galaxy form of M108, again more with averted vision. So what gives? I'm using a 12 inch telescope and I can only just see these two. I am on the southern edge of a town of 300k people. When the "bowl" of Polaris is pointing down, as it was last night at about 9pm, I can just about see all four stars. So that's mag 5 ish. Hardly bad light pollution compared to people living near cities. I just wonder how on earth people with light pollution worse than this can even begin to do the messier list without moving to a dark location. It is so sad.

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  • 2 weeks later...

I guess we all just make the most of our situation. It would be great to live in an area that is truly dark but very few of us do. I can see M31 with the naked eye (on a good night) from my back garden so i am not sure where that puts me on the grand scale of LP. Its not the most obvious object in the night sky so i am thinking that where i live really cant be that bad compared to where others live.

I live about 20 miles south of Dublin city almost right on the border with County Wicklow. The dark skies of the Dublin/Wicklow mountains are a 10-15 minute drive away. Even with the level of LP that i have i find that the SkyWatcher LPF i have works wonders.

I guess the larger the scope you use the greater the magnification of light pollution there is?. My biggest scope is only 130mm diameter.

On the flip side:

When i am imaging with my camera (on a fixed tripod), i find that i can not take exposures of any length longer then about 6-8 seconds. Anything longer and the whole image just becomes orange. At 5 seconds...............the sky is black and the stars are nice and bright.

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Hi Juliam

French astronomer Charles Messier in 1771 at that time scopes were hand made but was not as good as a 4" or may be a 6" scope as today so as Messier found M1 to M103 and the rest added later I would say 8" should let you see at least smudges

One guy on here as seen them all, remember reading it last year and as your is a 12" well good luck with that hope you make it with the weather we have been having :)

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I have managed to see some of the Messiers that are regarded as the most difficult with my 8" 'scope from a reasonably light polluted site, these include: M74, M97, M101 and M108. The limiting factor for me now is the lack of a clear southern horizon.

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as hinted at by John I think the requirement is more one of dark skies and a good all round view to the horizon (especially south) than the size of the scope. I'd wager the vast majority could be seen with 15x70s at a good dark site, and I bet the remainder could easily be seen with a 6" reflector. Seeing them and seeing decent detail though are not the same of course :)

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iamjulian, what sort of magnification are you using? I'm observing with an obviously much smaller scope from the middle of a city, and I fight the light pollution with magnification. My sky gets 'dark' at a magnification of around 100 (an exit pupil of 1mm). If you were observing from where I'm at with your scope you would need a mag of 300 to get the same sky darkness.

EDIT: Obviously, that's not a fair comparison, as the stars will be much brighter in the 12 inch! So less contrast is needed in a bigger scope arguably.

Since moving to the city, I've seen a number on Messiers - 36, 37, 38 and 42 - in the couple of short sessions I've managed. I found M37 particularly difficult. I've tried but failed to find some Messiers in the Plough - it is due north of me and low down, directly in Amsterdam's light dome.

Edited by Ags
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Some messier types are less affected by light pollution than others. Star clusters (open and globular) can at least been seen despite some light pollution. Nebulae and especially galaxies seem to do a "disappearing act" pretty sharpish if there is light pollution (man made or lunar) in the sky.

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Hi julian, good point you make, the same one crossed my mind recently, I had a good look to check which ones I will not get from my latitude to start with, I then took into to account some darker skies and lastly the size of my scope. I have only just decided to have a go at as many as I can, hense the change to my signature listing my Messier count. I am sure I have seen a few more than I list but want to make sure I get a proper observation of the ones I see from now on.

In my favour.... good dark sky location 5 mins from my doorstep as well as reasonable skies at home, decent Horizon in all directions when I take the bins out.

Aim to go through Virgo for a start although I may struggle to get them all, I hope to update my count in the weeks ahead and will report my observations.

Clear Skies. :)

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I would start making detailed records, keep an accurate log of what you see noting size, star positions, colour etc.

It really does help to make you examine what you are looking at in greater detail.

Even better start sketching some of the galaxies, this really helps.

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Hi Doc, my Messier count is taken from my limited obervation notes over the past 3 years,( doesn't time fly, of course the number of nights I have been out observing is probably less than 1 month in total, British weather, work, illness makes up for the lack of nights out.

I come into the New Year with the intention of making more of my chances, thats why I wanted a grab and go, was thinking a diffreent way at first but in the end decided to go with the bins rather than a scope.

My note book will indeed be having some more info logged. :)

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Thanks for all the feedback. Ags, magnification about 48x but you make interesting point and I shall have to experiment with that, thank you.

I cannot see the southern sky due to a north facing garden, but I have deepest darkest Wales on the doorstep so I know I will have to head out to complete the messier list. Would be nice to get as many as I can from the back garden though.

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According to some, a 3" scope from a dark site is enough. Most objects on my list can be seen with my 15x70 from a dark site, but some are very hard, due to lack of magnification. From my back garden I often need to get out the C8, though a 4" may well be able to do the trick, depending on transparency of the sky, which affects the level of LP. Even so, with an LP filter, some are hard: M74 and M108 in particular.

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