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Noreik

8" or 10" Dobsonian - Skyliner or other

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Hello all,

I'm trying to decide between an 8" and 10" Dobsonian, for most DSO but also occasional planets.  Not worried about astrophotography for the time being and would not be worried about this scope being able to produce pictures of any quality.  I was thinking either:

http://www.firstlightoptics.com/dobsonians/skywatcher-skyliner-200p-dobsonian.html

or

http://www.firstlightoptics.com/dobsonians/skywatcher-skyliner-250px-dobsonian.html

But if people have recommendations of others, e.g. :

http://www.telescopehouse.com/revelation-10-f-5-m-crf-premium-dobsonian-white.html

I'm open to suggestions.

It might be a question for a separate thread, but what is the difference (apart from the size, obviously!) of 1 1/4" EPs and 2" EPs?

Thanks in advance,

Noreik

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Hi Noreik,

If deep sky objects are your primary interest then you need all the aperture you can get so 10" over 8" I think makes sense.

Not a massive difference between the Skywatcher and the Revelation dobsoninan in terms of performance to be honest with you. I've owned both. The Revelation / GSO ones are slightly better equipped but I found the Skywatchers had perhaps slightly more consistent optical quality about them. Overall I'm sure you would enjoy either though.

The 2" eypiece size can show a wider field of view, around 50% wider, than a 1.25" of the same focal length and thats it's main advantage. Usually they are used in longer focal lengths (eg: 20m and longer) because the 1.25" eyepieces can go wide enough in the shorter focal lengths. Often folks have a set of 1.25" for high / medium / lowish magnifications and a 2" eyepiece for the lowest power / widest field views.

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It's the same conundrum you buy the 8 then you will always wonder if you should have bought the 10 so as what's already been said go for the 10.

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I recently had the same issue you did... An 8" or 10" Dob were my options, just like you. I opted for the 10" personally just because of the bigger aperture. In amateur astronomy, more aperture is never bad... EVER. As was said above, if transportation, storage room, and portability isn't an issue, go for the 10". If you do decide to transport the 10", just make sure you do it safely and correctly. I actually have my box that it was shipped in with all of the foam inserts for transportation to some of the bigger local star parties in my area. 

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All good advice. If you can afford and handle the size of the 10" then by all means go for it. Before deciding its a good idea to see both size scopes "in the flesh", so you have a very real understanding of their size and possibly of their weight also. Most people simply think "How big and heavy can a 10 inch diameter be!!!!".

Large Dobs dont suit me physically (wheelchair user), so thats why i went for an 8" SCT. Its as light as light can be for a scope with 8" aperture. 

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I was looking at the choice between 8" and 10". I eventually went with 8" as I have a bit of a back problem, and I'm glad I did. I can carry it down the garden OK, but I think I would have struggled were it any bigger.

They are bigger in the 'flesh' than they look in pictures. And heavier too!

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The 8" or 10" is a dilemma many seem to have had - including myself. I went with the larger one in the end despite getting worried over my perceived difficulty in keeping a 10" collimated due to the shorter focal length. This turned out to be quite false, it was easy to set up and has been a joy to use ever since.

If DSOs are your thing then you'll want all the aperture you can get. The difference between an 8 and a 10 won't be incredible, but it will be there and you'd notice it in a side by side comparison. In terms of size there's no difference between them other than the slightly wider tube of course. The only other consideration is weight. I haven't tried lifting an 8" dob so I can't help here, but looking at the specifications I don't think there's all that much difference between the two. If you're comfortably lifting something like a large sack of potatoes or a bag of concreting sand, it won't be a problem.

As to Relevation vs Skywatcher, I believe the optical difference between them is negligible. The former has a finer focuser, but that's about it really. Whichever takes your fancy.

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I have also gone through the 8" / 10" question.

I have had 3 Dobsonians....

1. Skywatcher 8"

2. Skywatcher 10"

3. Orion Optics 8"

The SW10" was better than the 8" for all observed targets (deepsky and planetary) but was very heavy for my bad back.

So I sold it and bought the 8" 1/10th wave Orion Optics  which is VERY light - with hindsight I wish I had bought  the Orion Optics 10" which weighs the same as the SW8"

Hope that helps

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Thanks for all the advice.

I don't have a bad back (yet!) and would be storing the telescope in a cool location most of the time, which should minimise the cooldown time needed, so I'm going for the 10" Skyliner via FLO.  Fingers crossed it's here for Friday's (seemingly) clear skies!

Thanks again all.

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For DSO observing 10" is the minimum, you can do it with the 8" but you'll be limited to less objects and also in therms of zooming and angular resolution. But if you are total beginner I might advise you to buy the 8" because of lower price and later buy something much better like 12" or 16". And you have pretty compact scopes from Explore Scientific.

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For DSO observing 10" is the minimum, you can do it with the 8" but you'll be limited to less objects 

You'd better tell Mr Wilkiinson about that then. He does reasonably well with his old C8. :D

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I've done far less DSO than Michael has, my DSO are all bagged with the scopes I currently have, nevertheless. Bigger scopes have surely advantage in seeing small DSO (sub 1 arcmin e.g), but there're so much more larger DSO out there, the sky darkness is much more important than scope size IMHO.

Acey's post here is a very comprehensive summary about DSO observing, worth a good read of ALL who's interested in understanding and using the tools (scopes, eyepieces etc) properly.

http://stargazerslounge.com/topic/259888-light-pollution-vs-surface-brightess-being-able-to-see-the-object/?p=2844817

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The length between a 8" and a 10" is very similar (if not the same), so I do not think that the 10", being 5cm wider, causes an additional issue for storage. 

Portability can be instead. It seems to me that while many people can move a 8" without major issues, a 10" is considered at the limit. It would be good if you could see them in a shop before buying one, and think how much you feel yourself comfortable at lifting a large object weighing about 15kg from your storage room to your car or to your backyard. 

Another thing is how your sky is. If you observe from a light polluted area, I doubt you will see a major difference between the two. In this case, an 8" could be a better choice as it is more manageable. However, if you can access to a dark place relatively often, then a 10" is certainly worth as it can show you more DSO and these will be brighter at the same magnification. 

Finally, what about the future: with an 8" you can step up to a 12"; with a 10" you should realistically step up to a 14"/16" which are really large tools. Of course you might not step up at all, and many people actually don't. 

Realistically, you cannot go wrong with either. They are both very good and they can both show you many many targets if you are patient, have dedication and passion. :)

I would visit your local astronomy club or a shop (but don't buy anything immediately.. have a thought first! Choosing a telescope takes time and this time pays you back eventually). Check the size, the weight, have a thought about where to store it and at the size of your car. Think about how you would lift from your storage area to your backyard if you have one. Consider how much money you intend to spend. Eventually you will have to buy some extra-accessories (first of all a collimator and possibly some book/atlas too - Turn left to Orion and Sky and Telescope Pocket star atlas are very good references). A 10" is generally <F5, so it will be more demanding on eyepieces. This means that eyepieces must be good otherwise you might see a few aberrations. Wide field ones are more expensive of course. A 8" is generally F6, so it will be easier on this (meaning that you can spend less). 

Take your time and good luck! :)

Piero

Edited by Piero
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