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What's the big fuss about Dobs?


Guest Turtleboy
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Guest Turtleboy

As the title says really. I'm new to all this and have just ordered my first scope but I dismissed the Dobsonian mounts fairly early on because of their unweildy size. I have a dodgy back so I figured lugging one around probably wouldn't do me much good. Now I'm wondering if I made a mistake.


 


I understand that they are very stable and relatively inexpensive when compared to a good tripod mount, but is that all there is to it?


 


What I don't understand (having never used one) is how you make fine adjustments at high magnification without losing the object you're looking at.  As far as I understand it you simply push or pull the mount to where you want it, but how easy is that to do when you're looking at something light years away? My inital thought is that tracking an object would be a nightmare, but as it seems to be most people's mount of choice I guess I must be wrong.


 


I ended up going for a goto mount but once I have found my feet I may well look at upgrading, but the size and portability issue still puts me off.


Edited by Turtleboy
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Basically you get more bang for your buck. Take mine for example, it cost £375 2 years ago but for that I got a primary mirror size of 8". You pay for the size and quality of the optics and not for any computer wizardry.

Granted, when at high mag you have to constantly keep nudging the scope, where as a GOTO will track it, but you try and find a GOTO system that will have a primary mirror of 8" for less than £400, basically you can't.

I opted for the dob base as it forces you to learn the sky, because you have to find everything yourself, no computer to do it for you. Also, I think they are still portable, the weight of the dob base is similar I bet to a HEQ6 or similar, which you will need if getting into astrophotography.

End of the day all down to choice, I opted for a dob base so I could plough my cash into a decent sized primary, perfect for what I wanted, while still keeping it simple to transport.

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What Daz just said is pretty much on the money, but it does boil down to your preferences.


 


I bought a 12" Dob and loved the light gathering power of it, but I didn't get on with the Dob base, I didn't like tracking by hand (albeit I had the Auto which tracked well for a while) and I didn't go out often enough to actually learn the sky. Too many hobbies. :unsure:


 


I sold my Dob and bought a Celestron C9.25 which has less light gathering power than my Dob, stands on a tripod instead of a Dob base and has full GOTO. I love it. It's a great setup.


 


At the end of the day it's about your priorities and what you are most comfortable with.


 


Enjoy. :)


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Guest Turtleboy

Thanks for the replies.


 


At this point I have no idea what I would be most comfortable with. :lol:


 


It's all going to be down to trial and error. I can see the goto being a bit of a pain to set up (not actually picking it up until this weekend) and the battery issue is also a bit of a pain.


 


I do like the look of the larger reflector telescopes but at this stage it was mostly down to budget and the Nexstar came up at the right price.


 


Hopefully by the time I come to upgrade I will have been to a few meets and had a chance to play around with a few of the other set ups and know which way I want to go.


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You will see so much more with a bigger mirror. I used to have a 16" dob, saw almost everything worth seeing, I then had a triple heart bypass and that thing just became way to big to move so wenrt down to a HEQ5 mount with either a 81mm APO or a 152mm Bresser, and I couldn't see half of what I saw before.


 


Aperture is King when it comes to deep space.


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Being a refractor man I dont usually mess with reflectors and I always used to wonder this until I got an 8" newt and tried it on an EQ mount. Good grief! the contortions you have to get into at times when the scope has slewed putting the eyepiece upside down and 3 feet off the ground is very awkward. OK so you can slacken the tube rings off to turn the scope but then more often than not you loose the object or shift the mount off calibration so it looses it Goto. For a newtonian reflector the Dob base has got to be the simplest and easiest to use. 


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As mentioned - larger mirrors make for great light buckets and detailed views which you just don't get with affordable refractors. Glass optics in refractors are horrendously expensive compared to newtonian mirror based systems. A 6" mirror based scope may cost around £350 - but a 6" achro refractor will cost £1k - go appo and you're looking at approaching £8k'ish and upwards.


 


But the big distinguishing factor is astro photography as far as the mounts are concerned. You can get dobs that will track and also dobs that will goto. But they are essentially alt/az mounts and whilst ok for imaging planets which are bright and near, they will allways induce star trailing because they have to track in two planes.


 


Equatorial mounts can be polar aligned which means you only have to track in a single plane (RA). Polar aligning takes care of the Dec movement effectively making it zero (if accurate). This is essential for long exposure photography which is needed in order to capture  the dim and distant light from dso's - whilst avoiding star trails. Snapping planets is typically done in sub second exposures - snapping dso's means holding the shutter open 10 or 15 mins at a time keeping the image pixel perfect in position on a small camera chip. Hth :)


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Guest Turtleboy

Thanks Kim. Very good explanation.


 


So in a nutshell Dobs = cheap, easy to use and sturdy but fall down when it comes to astro photography and not the smallest of things to store. :screwloose:


 


It's becoming apparent that everything is a compromise with this astronomy lark. ;)


Edited by Turtleboy
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Not so much a compromise - more like buying cars - it's a case of horses for courses.


You wouldn't get a formula 1 race car to pop round the corner shop for 20 Woodbine and something pretty for her indoors.


Conversely you wouldn't get an 1100cc familly estate to race Jason Button round the M25. lol :)


 


(not that I'm advocating either of those hehehe)


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I would agree with the above answers.


I have a 12" Dob, which is a real pleasure to use, it sets up quick, and with a bit of dew control will keep you out all night. It excels at deep sky objects, and really drags in those faint fuzzies. I managed to find M51 through cloud last weekend, purely down the the light grasp it has.


On the other hand it isn't so good at planets and lunar, it's acceptable, but has poor contrast, and I can't get a pin sharp image.


My 5" refractor, although a Achro, does far better at Planets, Lunar and stars. The contrast is good, and when focused correctly delivers really sharp views. This makes a real difference on the Moon, bringing out fine detail, and on the planets can really get the best out of surface detail.


 


I have no axe to grind either way with goto or manual mounts, you buy what would suit you. If you want to learn the sky and you would be happy with manual, great.


But on the other hand, with our weather as it is, then why not have a goto, and maximise the amount of time you spend looking at a target rather than finding it.


 


It depends on what you envisage doing with you rig when you get it going, you mention imaging, so your mount will be crucial to you. If you purely want visual, then again it depends on what you want to see, as Kim mentioned all scopes aren't equal. 


Go and see the ELAC guy's and have a look through some scopes to get an idea of what will be of use to you.


 


Above all, enjoy it, don't let it get a chore. There is some amazing stuff out there.


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If you're concerned with not having any fine adjustment, you could try a decent manual alt az mount like the skytee 2. It's a bit more pricey than a dob, but more versatile as you can put any scope on it you buy. (up to 15kg per OTA) You can even put two on it at a time!

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On the other hand it isn't so good at planets and lunar, it's acceptable, but has poor contrast, and I can't get a pin sharp image.

 

That's the first thing I realised when I switched to the Celestron. Lunar and planetary are pin sharp and there's loads of contrast.

 

Of course, I lost light grabbing power... the trade-off!

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  • 4 weeks later...

Personally, as a beginner, half (or more) of the fun is manually finding objects for yourself - I like the challenge. Plus as Daz says, you seem to get more for your money, especially with the various Chinese-made Dobs now on the market.


 


Should you feel the need to go GOTO at a later date, you don't necessarily need to sell up, either. Just add a suitable mount.


 


But If, for instance, you've no interest in learning the night sky, I suppose a small SCT/MAK is fine.


 


Don't quote me though - I'm still pretty much a novice myself.


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Guest Turtleboy

Okay Okay I'm sold!


 


After having a go with Cosmic Dave's Skywatcher 200P Dob at the ELAC meet at Gib Point last night I have decided I NEED ONE!!! (It's all your fault Dave :lol:)


My initial worries about portability have been answered as a Dob of this size is easily portable, and a lot more controllable than I expected, and aperture fever has already set in as I was warned.


 


So after only a couple of weeks and half a dozen viewing sessions the Mak is on ebay and I'm in trouble with her indoors. :facepalm:


 


As soon as it's sold I will be ordering myself a shiny new Skywatcher 200p Dob. ;)

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Hi.

Glad you are settled at last on a scope that you actually like.

While I am not having a go or anything, I think this proves a valuable point to anybody out there who is thinking of buying a scope.

It shows that you need to think about what you want to observe, if you want it portable to ask loads and loads of questions and more importantly, if you can......

TRY BEFORE YOU BUY.

Welcome to the dob club, let the modding begin!!!

Edited by Daz Type-R
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Guest Turtleboy

Yeah I agree Daz. If at all possible I would suggest that anyone considering buying should go along to a meet and have a look at different Scopes and see what suits before committing.

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