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What should I expect from my 8-inch Dob?


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Hello everyone,

Over the last few months, I've been researching instruments and finally purchased my first telescope, an Orion XT8. This 8-inch Dob seemed like a great scope to start with, given its good performance for both planets and deep sky objects. At least, that's what I read; now I'm afraid I made a mistake, particularly because of my frustrations trying to find galaxies.

After a few weeks of getting comfortable with the major players in the night sky, I've begun trying to pinpoint smaller objects, particularly galaxies. I began with M81, M82, M108, and the Whirpool Galaxy. Two nights and 3.5 hours later, and all I have to show for my troubles is frustration. Once, when looking for the Whirlpool Galaxy, I found a light haze in the correct area. Is that what I should expect galaxies to look like? I'm not expecting Hubble-like images or anything, but without at least an idea of what I am looking for, I'm afraid I'm overlooking them.

Should I expect trying to find all smaller objects to be this difficult? Similarly, what other limitations should I expect from my scope, and where can I expect it to excel? Can you guys help alleviate my fears and frustration? Thanks so much.

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hi there

I am no expert (and have scopes either side of yours) but can answer your queries as follows:

you have a great all round scope so don't worry - there's lots to see

galaxies are not generally that small - this is part of the problem as although they might be e.g. apparent magnitude 6, this unlike a star is spread over a wide area so they really are usually quite dim - probably the only exception to this is Andromeda which you might just see with the naked eye depending on your local skies

what you can see really depends on how dark your site is. light pollution affects galaxies more than most things so unless the sky is very dark and with little light pollution they will always be tricky - I live in quite bad light pollution though and can still pick out galaxies with my dob. it's not always essentially accurate but as a

general rule if you can see the Milky Way naked eye you should be able to pick out brighter galaxies with binoculars. I can pick out M81 and M82 with binoculars.

even when you see galaxies, they will generally be a faint whiff of cloud, often with a bright core like a fuzzy star.

use your lowest power eyepiece. a 25mm should be ok but lower is better still.

you really need fully dark adapted eyes - also, I don't even bother when the moon is up - look at the moon instead :D

I have only seen M51 once and it was a vague twin spot in the sky (with it's NGC companion) like a pair of dim eyes staring out of space.

think about what you are seeing rather than the detail you can see - it will amaze you despite the 'faint fuzzy' (they are called this for a reason :p appearance of the subject.

once you see a few, you'll be able to detect them more easily as you know what to look for.

to me it sounds like you found M51.

good luck and hope you find more soon.

cheers

Shane

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You are only looking for very dim smudges with maybe a slightly brighter core. They are very diffused and can very often be overlooked. The only major galaxies that show any detail and this will only be from a dark site will be M81/82, M31, M51, and a few of the Virgo galaxies.

Try hunting for some edge on galaxies as these can sometime be easier to spot as it's a sliver of light it's easier to spot, try for example Ngc4565 in Coma Berenices.

But remember don't expect alot and you must have dark adapted vision, what I find helps from a light polluted sky is a blackout blanket draped over your head.

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All I would add is that the finer details in galaxies come out the more you study them in the eyepiece. If you can get to grips with star hopping down to stars of 8th or 9th magnitude then you'll be able to pinpoint the location of hundreds of galaxies with ease. What you can see, as Shane pointed out, depends on how dark your local sky is.

From a rural site your scope will easily pick up M81 as a large diffuse oval of light with a bright core. M82 will look like a stubby cigar of grey light with a dark cut across its plane at higher magnification.

From a light polluted sky however M81 will look quite small as you may only pick up on the core.

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Stick at it. Once you know what to expect visually the thrill is in the chase. Remember that M51 may look light a faint smudge (or two) but you are a seeing something 15 million light years away, 50,000 light years across and shining with the luminosity of 10 billion suns. Not much to look at but amazing what you can find in the night sky really.

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I can only add some weight to what the others have said. I have the same scope as you but a different brand name, it's an incredibly good scope. So no need to feel you have made a bad choice.

From a light polluted backyard galaxies are perhaps the least satisfying of all the objects you could possibly track down. They are competely dependent on a dark background sky for maximum contrast, which isn't possible from an urban location. That's not to say you can't track them down but a faint hazy patch is all they will amount to.

Drag your scope out to a dark site and its a completely different ball game. It's like you've had a scope upgrade to something much larger. Taking M51 as an example. From my back garden M51 is a difficult object to see in the 8" dob, a very faint patch is all. But from a dark site my local group use, M51 comes alive. Suddenly both cores are easy objects to see and now there's hints of spiral structure too.

And galaxies like M81/M82 are better still. From home they are very easy to see and still quite pleasing due to their contrasting shapes. But from the dark site they are like bright beacons and better still a third fainter galaxy pops into view as well.......3 galaxies in one eyepiece view.....awesome!

Globular clusters make a much better target from the back garden and with the help of a narrowband filter, planetary nebula too.

Edited by russ
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My first "grown up" scope was an Orion Skyquest 8" dob, and the first time I saw M31 through it I was disappointed. Dim little smudge, just glad I found it at all. From my light-polluted garden, star clusters and planetary nebulae were far more interesting to look at (M57 was tiny but awesome). I hunted down the brighter Messier galaxies and was pleased to see them, but they were all faint fuzzies.

I started driving regularly to a dark site (mag 6), read some books that helped me learn how to look more closely at galaxies (e.g. O'Meara, The Messier Objects), and realised that if I worked at it, I could see spiral structure in M51. With the 8" I logged something like 500 DSOs before stepping up to the 12" I now use. The 8" is a great scope, but to get the best out of any scope you need a dark sky, and you need to be patient in teasing out whatever tiny details you can discern. Mostly it comes down to looking at how the brightness increases as you go from the edge to the centre: whether it's continuous, suddenly increasing, varying, etc. That way it can be possible to tell a spiral from an elliptical, even if you can't see any arms.

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You have a good scope, I would echo all the above post's regarding light pollution, and finding a dark site. I live near Nottingham and the LP is bad, but I go to a dark site with other EMS members, although not totally dark, way better than my garden. It is amazing the difference it makes, other than M31, I have no chance of other galaxies from home, but there I have seen most of the more prominent one's. Have a look at M13, the globular cluster in Hercules, that should be good and will take magnification.

At SGL5 a good number of people had "Sky and Telescope, Pocket Sky Atlas." It's small (A5), spiral bound and laminated. So I purchased one and have found that to be useful.

( Thanks Dobserver!)

Happy hunting.

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When i am hunting galaxies i use a 32mm EP on my scope. Its not ideal but it saves a bit of time then if i used a smaller EP because i can scan larger areas of sky. Its easy for people (including myself) to tell you what to look out for but galaxies are VERY easily missed unless you have a Go-To setup or you manually scan the sky very very slowly.

Essentially they look like small fuzzy whispy "clouds". Patches of lighter sky against the normal background sky. Once i think i have found one.......i will gradually increase the magnification of the scope. You dont want to increase it too much or you will be too close to the galaxy and it will most likely vanish. They are best observed with averted vision (looking directly slightly left or right of the actual object enhances detail in your peripheral vision).

As has been said above..................the fun is in the chase. Unless you have a Go-To scope which eliminates the chase to a certain degree but thats not saying it takes the fun away.

The REAL thrill is knowing that the light from the object you are looking at has been traveling through the void of space for hundreds of thousands of years just to reach your eyeball.

Your telescope is really a kind of time machine. It lets you look back into the past.

That is truely astounding.

P.S.~~~an 8" Dob is a nice choice of weapon for the hunt.

Edited by LukeSkywatcher
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defo not a fan of the galaxys though have to say counting the fuzzys in marcian chain is unreal also leo triplet and m81 and 82 is quite something though i never get bord of globs m3 is a corker with high mag

toby

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I agree, try some globular clusters (M3 and M13 are mandatory :)) and M57 is a nice little smoke ring in the sky.

I do love galaxies for what they are and the challenge of finding them but the truth is they don't show detail, unless you have perfect conditions, dark skies and some patience. I also have a XT8. Only galaxy where I was able to detect some structure was M51 with excellent seeing conditions and a dark sky.

Edited by pvaz
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  • 6 years later...

On my second night out I saw many faint DSO's including many faint ones like crab nebula, m78, and other galaxies. But they all look like very faint smudges

But I used a 4.5 inch telescope

 

Edited by Bhuvan
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