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DRT

A new Dob - bigger or better?

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This is a long-burn question for me as something wonderful has to happen to my employers bonus scheme before it will be acted upon but I need lots of advice before taking the plunge.

I recently sold a 12" SW FlexTube Dob because I wanted to experiment with other types of scopes. When I sold it I knew for sure I needed another one, and it had to be a big one. I have been looking at the new SW 18" truss Dob, the Explore Scientific 16" and various others but can't help thinking that £3-4k from a mass market supplier might be a mistake.

I have also been looking at various threads about specialist optics/Dob manufacturers and am completely baffled by the choice of what to spend my money on. Orion Optics UK look particularly interesting as I like the idea of them being close to hand.

So, let's say the bonus and share scheme come into perfect alignment next March - which Dob should I spend from £5k to £6k on?

Should I go for a bigger scope from a mass market supplier or a smaller but better scope from a specialist?

Relatively light weight and portable are premium requirements - as is being absolutely enormous :grin:

Note: I am a visual observer, not a photographer.

Edited by DRT
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It's not a practical proposition for me even if I had the funds but if my circumstances change (ie: better observation site and easier storage) I think I'd be looking at something like the 18" Sumarian that Alan Potts has recently acquired with the best quality mirrors that I could afford in it.

I guess, if I'm going to "push the boat out" 16" is a little tame and, having seen a couple, 20" is perhaps just too large so 18" seems to be a "Goldilocks" aperture to me.

But it wouldn't get used in my current circumstances wheras my 12" dob is practically "grab and go" and a very competant scope so I'm not unhappy with what I've got now :smiley:

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18", f4, Nichol mirror in this size,  Sumerian structure for portability. Mod Alan has a great scope. This is my vote.

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I'm thinking you will need at least an 18" scope to make a really striking difference versus the C11 you already have.  Having spent big $ (those are the £ we use over here) on a premium ultralight Dob myself, and then spent time and effort engineering the ultralight compromises out of it, I'd suggest:

  • Look for a used "premium"  telescope to buy - you'll pay much less than new, and get a much better product than a mass-produced Chinese scope
  • Prioritize great optics - you can fix/improve the structure as needed, but the mirror you have to live with or spend big money to have re-done
  • Get a "traditional" Dob structure - the extra weight is worth it for the extra rigidity versus an ultralight/ultra-portable design
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All below should start with 'In my opinion..'  ;)

I've had an Obsession 18, Orion (US) 14 and now own a Sumerian 16 Alkaid.  Also much experience with Obsession and Sumerian 15, 18, 20 & 22s (UC or Classic).

Assuming that you are going for new.  Sourced within the EU.

Avoid the mass market scopes.  They may weight a ton and be just not well constructed.  My 14 Orion weighed more than my current 16...

The 18 is a very useable size.  Take one step back from the biggest that you can afford and go up in quality e.g. mirror coatings. A more portable solution.

The 18 Canopus structure from Sumerian is great.  Then you have to deal with OO UK...can be a pain but produce good optics.  Also match your good optics with good eyepieces.

Yours (and others) mileage may vary!

Good luck!!!

Cheers

Paul

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Thanks all for the very helpful advice.

It's not a practical proposition for me ... it wouldn't get used in my current circumstances wheras my 12" dob is practically "grab and go" and a very competant scope so I'm not unhappy with what I've got now :smiley:

What is it about your current viewing site that would make a larger Dob impractical, John?

you have to deal with OO UK...can be a pain but produce good optics.

What's the issue with OO-UK? I have looked at their site and found it very difficult to work out what I would need to buy but I can't say I have read any bad reports about dealing with them. I like straightforward people to deal with so any advice would be appreciated :wink:

Has anyone tried the new SkyWatcher 18"? I know it bucks the trend of the advice given above but at £3.5k looks a much cheaper option. What is it missing that the more expensive options would give me?

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Thanks all for the very helpful advice.

What is it about your current viewing site that would make a larger Dob impractical, John?

What's the issue with OO-UK? I have looked at their site and found it very difficult to work out what I would need to buy but I can't say I have read any bad reports about dealing with them. I like straightforward people to deal with so any advice would be appreciated :wink:

Hi Derek,

Our house and gardens are quite small and rather overlooked, My scopes live in corners of the dining room and I observe on a small patio and patch of lawn. I need to be able to move any scope that I'm using around the garden quite often during a session to dodge trees and minimise the effects of local lighting. Also I don't want long set up / tear down times so essentially as "grab and go" as possible. I had a Meade 12" Lightbridge for a while which was much heavier and more bulky than my current 12" Orion Optics / Moonshane dob. The Meade LB did not get out a lot wheras my current dob is the most used of all my scopes. If I'd not come across the OO 12" tube assembly I guess I'd still have a 10" as my largest aperture.

On Orion Optics, I've never bought a scope from them but I have bought smaller items and made enquiries about other things. I found them rather unhelpful and inflexible. They also seem to regard deadlines for delivery as someone elses problem :rolleyes2:

I've read plenty about similar negative experiences but some positive as well, to be fair. It almost seems to depend on the mood you catch OO in !

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Some people would think me mad for using my 16" only once or twice a year but I have my 12" for most observations at home (similar reasons to John) and am happy I do. If I didn't then I'd use the 16" more.

Based on what I have seen and made, I would suggest a John Nichol 18" f4 mirror in a sumerian frame. They are really excellent. Larger structures like the standard obsession are possibly more rigid but at the cost of weight.

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Re oouk I think the service depends on who you get and when you call.

I once called out of interest to collect a spider and secondary and got a warm welcome and even a tour. All was quiet though so maybe they were less stressed out. He even agreed to print a replacement test report for my used bought mirror.

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Hi Derek, you might need a ladder or step with the 18" Sumerian, you probably won't with the 16". My 16" is easy to set up, use, store & transport, but I couldnt move it around the garden once set up, as it's too awkward to move once fully built. Hope this helps. Btw I've never had any trouble dealing with OO and their scopes are easy to move around. :)

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Thanks all - really helpful stuff and it seems that OO-UK is a bit hit and miss when it comes to service so I will probably avoid using them.

The 18" Sumorian seems to be getting the most votes so I might end up joining the Sumo-squad in the spring :grin:

I've emailed Obsession to ask about the practicalities of importing an 18" UC to the UK. Their stuff looks fantastic but I suspect the cost of shipping and import taxes will knock the price up substantially.

The search for knowledge continues...

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This one seems right on your budget Derek :), with ServoCat tracking too!

http://www.astrobuysell.com/uk/propview.php?view=99583

I think I would go along with the other advice, 18" f4 Sumerian with a Nichol mirror. At f4 I don't think you will need a step, my 16" f4.5 is ideal height at the Zenith.

I saw that last night Stu - unfortunately it's at least six months before the funds could become available :-(

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On your quest to import from USA you will have to factor in import tax and then VAT!!!!!!!!!!!!!! all said and done your looking at around £1,000 to import a well speccd Obsesssion.

Hth

Regards

Mike

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Just had a quick look at the u/c18 on abs if the guy has got all the bugs out of the frame it is keenly priced.

Regards

Mike

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Derek,

I took a lot of notice of your reasoning now take some of mine

Dig deep buy the trouble and strife some shoes, get a F4.3 mirror ordered or near from J Nichol and a Canopus from Sumerian, with the euro weak the difference will not be so massive.

Goldielocks is a happy bunny.

Alan

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Sound advice, Alan - I had forgot to work the shoes into the budget :lol:

I'm guessing that one of these things will be difficult to slip through the domestic net so some forward planning definitely required on that front!

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Shame, was tempted myself but funds definitely say no, without selling a lot of what I've got!

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Derek,

I measured this the other day for someone that was asking by PM.

The floor to eyepiece on mine is 186cms, I need a 12 cm building brick to see easily overhead ( don't worry it is a TV building brick) . I would think with an F4 this may not be required if it were me but then I have no idea how tall you are. I am about 5 feet 10.5 though I was talker when I was younger, a tad over 6 foot, at least that what the Police had me down as..

I guess the mirror would take longer than the scope, my scope took 3 months but that was across Christmas and New year and I impressed that I didn't want a rush job, so I may well have been knocked back if other orders were pressing. I know at the time he was waiting for a delivery of mirrors to him and was having to make others wait.

Alan.

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I'm about 5' 9", Alan. Might be 5' 10" when I get my new knees later this year :grin:

I've had a look at Telescope House but they don't seem to stock those TV building blocks - are they black and green and six times more expensive than the grey ones in B&Q? I'm sure they must make a big difference to the view!

Is it a Nichol mirror that you have?

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Thats a fantastic amount of money for a new system, and if you can afford it / write that amount off,  and get the maximum use  permitted from the scope against the UKs weather and seeing conditions, then go for it, you may not have another chance, but don't regret the expense afterwards?

I share your excitement with the windfall, I have two biggies  to collect this Year!  I know what I would like to get, but not sure how I will spend it?

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Thats a fantastic amount of money for a new system

Indeed - but it feels like an itch that I can't resist scratching :rolleyes:

I've been looking at the Nichol's website and see that all of his "stock" mirrors come in variants of F3.6, F4 and F4.5.

What are the pros and cons of each of these for visual use?

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Does David Lukehurst still make Dobs? These get good reviews are and in the ballpark for price.

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Indeed - but it feels like an itch that I can't resist scratching :rolleyes:

I've been looking at the Nichol's website and see that all of his "stock" mirrors come in variants of F3.6, F4 and F4.5.

What are the pros and cons of each of these for visual use?

This is my take on it.

The faster mirrors will be dearer and you need to be more precise when collimating. Collimating the Sumerian is very easy but at f3.6 I'd be worried about a small shift when moving the scope, but I don't know how much might cause a problem or be noticed. You'll definitely want a coma corrector at f3.6 but probably will at f4.5 as well, but maybe not.

The pros of the fast scope are a shorter scope and wider fov.

I think I'd be happy at f4 or above :)

One more thing I've thought of, the exit pupil of a given eyepiece will be larger at f3.6.

Edited by Scooot
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