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will5098

Newtonian V Dobsonian

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Hi all,

On a previous thread it had been suggested to me that a Skywatcher 150 Dobsonian would be my best option as a starter scope for £200 - which looks good.

Howevr, I have spotted the Newtonian SKYWATCHER EXPLORER-150 TELESCOPE costing £270 - Being an amateur, i'm not sure what the key differences are (looks aside) - is it just the tripod? what would the extra £70 give me and would it be worth it?:D

Any useful advice would be much appreciated (I suspect a dealer would reccomend the more expensive option!)...:)

Thanks

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Hi Will and welcome to the forum.

A Newtonian telescope is a Newtonian telescope and all will be broadly the same. What makes the difference as you alude to, is the mount.

generally, a Newtonian mounted on a basic wooden alt-azimuth mount (i.e. one that moves left right / up down) is referred to as a Dobsonian, after the inventor of this sort of design, John Dobson.

In terms of tripod mounted telescopes, there is one main type for astro use and this with an equatorial mount (sometimes referred to as an EQ mount or a German Equatorial Mount (GEM)).

On a tripod you can also have an alt-azimuth mount but these are less common and more expensive sometimes for a devent one. I have one like this called a GIRO II.

I find dobsonian mounts if well made (like the Skywatcher one is) provide a very easy to use, intuitive and stable platform for a telescope. This is by far my most favoured mount for visual use with Newtonians. There is no set up, you just put the scope on the ground and after cooling/collimation use it.

Some people like the slow motion controls of the EQ mount but I found when I used one that the eyepiece and also the finders can end up in some backbreaking positions. EQ mounts, when properly aligned, track in the same direction (well the opposite direction actually) to the rotation of the Earth either manually or via motors.

My issue with EQ mounts and tripods (as well as the positional issue above) is that they are often made to just about be adequate for the scope concerned with a small finder, a 1.25" eyepiece and if you start adding cameras and the like then the mount will possibly become inadequate.

Also, the more money you put into the mount and tripod, the less aperture you can afford and the more aperture you have the more you need to spend on your mount!

Either way and whatever scope you go for, I'd recommend a decent red dot finder as a way to much more easily locate targets. I would be lost without mine.

Edited by Moonshane

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This one First Light Optics - Skywatcher Explorer 150P EQ3-2 / EQ3 PRO GOTO has a focal length of 750mm and is better at viewing DSOs. This one First Light Optics - Skywatcher Explorer 150PL EQ3-2 / EQ3 PRO GOTO and this one First Light Optics - Skywatcher Skyliner 150P Dobsonian are basically the same Newtonian telescope. The difference being the simple altazimuth base of the dobsonian version and the equatorial mount of the EQ version.

Peter

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I am sure that Peter meant this but all three of the scopes will be as good as each other at observing DSOs. The only thing that governs light gathering is aperture. The difference with a shorter focal length is that you can fit in more 'sky' - ie they have a wider field of view so for larger objects (like some larger star clusters) more of the object will fit in the field of view with the same eyepiece.

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I am sure that Peter meant this but all three of the scopes will be as good as each other at observing DSOs. The only thing that governs light gathering is aperture. The difference with a shorter focal length is that you can fit in more 'sky' - ie they have a wider field of view so for larger objects (like some larger star clusters) more of the object will fit in the field of view with the same eyepiece.

Hi Moonshane / Peter,

Thanks for the advice - I think I'll go with the Dobsonin mount in that case - I'll use the change on some filters and maybe a Barlow.

Cheers - no doubt I'll be picking your brains again!!

All the best.:D

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You don't want to magnify the DSO to much, with the Dob you have to nudge the scope to follow your chosen DSO, with the newt, once polar aligned (quite easy and a one off) it will follow DSO's , so you get one in the EP centered, go have a cuppa tea and its still there when you come back.

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Hi Will, if you were considering buying the Explorer 150P for £270, it would wise to also consider the Skyliner 200P at the same price.

The extra aperture to begin with will be a good starting point for you.

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Cheers guys -

So, if I'm correct this is really a case of the EQ v Altazimuth mounts?

Is the EQ superior?

How long would it take a Messier object or a planet to passs accross a typical lens? Constant nudging of Dob sounds like it could be annoying?

Thanks :D

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Unless you get the tracking motors (extra £100), and polar align fairly acurately, you would have to manualy keep an object in the eyepiece with an EQ mount as well. Shane also makes a good point that for an EQ mounted Newt, the eyepiece normally ends up in the most uncomfortable position for viewing.

The higher the magnification and the smaller the field of view of the lens, the fast an object will cross it, but actually after about 10min with a Dob you just move it instinctively.

Where tracking motors can help, is when you want to show other people what you are looking at when using high magnifications.

Edited by RikM

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One other thing to bear in mind - if you're edging toward buying the Dob - is how you'll stand/sit whilst observing. You can adjust the height of a tripod mounted 'scope but, as far as I'm aware, you won't be able to with a Dob unless, like me, you have several different platforms to rest it on.

This probably doesn't concern most people, but if you've got back problems you may find it aggravates them.

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This probably doesn't concern most people, but if you've got back problems you may find it aggravates them.

I'm missing* a chunk of my spine but sitting on a folding camping stool means observing with a SW 200P dob is an easy and comfortable experience.

* I say missing but it was removed by surgeons at Nottingham Hospital last year and is probably sitting in a jar on a shelf somewhere :D

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I have used an EQ mounted Newtonian, but have found it to be unintuitive as I want to star hop to find my objects, it is do-able but not as easy. I'll be looking for a dob next for the ease of gliding around the sky it gives. I think it depends on your game plan, if you want to be abit more manual with finding and tracking objects (the bit I find fun!) then a dob is more suited to this kind of observations. If you wish to be able to find an object and track it accurately you will need an EQ mount with motors.

Another bonus of going for a dob, the mount is inexpensive so the extra cash can be spent on accessories, or better still a bigger mirror. Good luck :D

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There is a the extra tube ring mod to newts, found the mod on these forums, mine is a jubilee clip and a thin plastic strip above the top ring so the tube can be loosened and turned to bring the focusor to a friendly position, cost less than fiver..:D

post-29949-133877735686_thumb.jpg

Edited by Tinker1947

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Hi Will, if you were considering buying the Explorer 150P for £270, it would wise to also consider the Skyliner 200P at the same price.

The extra aperture to begin with will be a good starting point for you.

Thanks Ian - £250 is the max i can go to really ... and that includes other stuff i need like filters etc (i presume the scope comes with none...) i figure a 150dob will show me some messiers etc:headbang:

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I'm missing* a chunk of my spine but sitting on a folding camping stool means observing with a SW 200P dob is an easy and comfortable experience.

* I say missing but it was removed by surgeons at Nottingham Hospital last year and is probably sitting in a jar on a shelf somewhere :D

wow - i have a complete spine, but might go for chair as a back-up anyway!

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I have a 200p on a skytee 2 and imo it beats them all, EQ mounted newts are a nightmare for viewing positions. dobs can be a pain to balance and have a few height issues when viewing low in the sky.. but its a cost.. the alt az mout and tripod is 375 and the scope 270 so lots of money, if you dont have the money go for a dob i think. the eq mounts are just a pain for visual and are not needed.

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