What mag dso's could i see?...

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hey all.

i was just doing some planning on what dso's to look for using stellarium when im out in my yard at night and just wondered what magnitude dso's im likely to see?

my scope is a skyhawk 114 with standard 10 and 25mm eyepieces.

my yard gets quite dark as there is no street lights in the allyway and no neighbours lights, but i am in the middle of a quite light polluted town, possibly a 3 or 4 on the stallarium scale.

i was out the other night and was able to see m35 in gemini quite nicely which is magnitude 5.10 (stellarium)

i was making plans to view dso's as low as 8.60 will this be possible with the conditions and gear i have said?

thanks for taking the time to view this.

martin

[acey]

Best thing is to try it and see. Difficult to say without knowing your limiting magnitude, and in any case DSO magnitudes are deceptive because there's also the issue of size (i.e. surface brightness). Moon's in the way at the moment but will be less troublesome at the end of next week.

DSO limiting magnitudes become a bit more meaningful once you go to fainter levels (e.g. mag 11+) because you're then talking about lots of objects, and averages make more sense. At the very brightest end (e.g. Messier objects) binoculars are sufficient if the sky is dark enough, but if the sky is bright and there's not enough contrast of object against sky, no aperture will suffice (i.e. you can't see galaxies in daytime).

Judging sky darkness is also difficult, because the eye adjusts to whatever light there is. From a suburban garden the sky may look black, but that might be because the eye has adapted to a high level of light. A sky of the same inherent brightness, seen from a truly dark site with fully adapted eyes, might look twilit. Hence it make sense to judge sky quality by the faintest visible stars: for example look at Ursa Minor and check on Stellarium to find the magnitude of the faintest stars you can see.

Another test is the Milky Way: if it's not visible to the naked eye then galaxies will not show their full glory through a telescope, though clusters will still make good targets.

[John]

The Orion Nebula (M42) would be a "must see". The galaxies M81 and M82 in Ursa Major should be reasonably well positioned later in the evening and make a nice pair in a low power eyepiece - they should be easily within range of your scope.

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thanks acey. ive got a few jotted down (old school pen and paper style w/diagrams ) that i am planning to view so will defo find out on the ext clear night.

john the orion nebula was the 1st thing i pointed my scope at on christmas night, its an amazing thing to view. im glad you mentioned m81 and m82. those are the ones im most looking forward to seeing.

thanks alot

[E621Keith]

Adding to John's list, M31 Andromeda galaxy and M45 Pleiades are the other two 'must see'.

Apart from that, it depends on your local light pollution (limiting magnitude), weather, the moon and the date.

[Per167]

I also thought a lot about this problem when staring out in the hobby. I found this website Tony Flanders' Astronomy Site - Surface Brightness very helpful in judging what I was supposed to see. It has a list of all Messier objects and how they are affected by light pollution.

When searching for the faint fuzzies the magnitude listed in compilations of e.g. the Messier objects does not really say that much if you observe under moderate-heavy light pollution.

It's quite easy to get frustrated searching for 5 objects and not having any idea if there is even a chance you will be able to see them with your scope at your current location!

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hey keith ive seen m31 and m45 they were both great in my scope, the pleiades are my fav so far.

great link per167. thanks for that.

[Double Kick Drum]

Magnitude is a guide but can sometimes be a bit misleading.

Two good examples are M33 and M101 which I believe have respective magnitudes of 6 and 7.5. In actual fact these both have low surface brightness and are only possible in decent skies (I have only ever seen M101 once in a dark sky with 15x70s).

Magnitude is a measure of the total light emitted from an object. Where nebulae and galaxies are not stellar points, the light is spread around. Subsequently some larger objects are fainter than their advertised magnitude.

At the other end of the spectrum are a couple of planetary nebulae - M57 (the Ring nebula) and NGC 2392 (the Eskimo nebula). These are rated as mag. 9 and 10 but both are surprisingly bright and should be within reach of a 4.5 inch scope due to their comparative smaller size.

M81 and M82 make a good pair. M105 in Leo is a small but bright galaxy that should be within reach.

Also, have another look at M31. It has a bright smaller elliptical companion M32 that should be visible.

Regards