Orion Optics UK 150L Dobsonian

[Neil English]

Hi folks,

I was wondering whether anyone has had a chance to look through or better still, reguarly use, the 6" F/11 Dob sold by Orion Optics UK. Here's a link for reference:

Dobsonian OD150 L

Any info on this would be greatly appreciated.

Many thanks,

Neil.

[stafford_stargazer]

I havent used it,but knowing orion optics im sure the quality is there and you will have nothing to worry about in that department.

Will make an excellent planetary scope with the longer f ratio.

G

[John]

I've not used one but Ade Ashford reviewed one a while back. I expect you have seen this Neil but here is the link anyway:

Orion Optics OD150L De-luxe

[Hypernova]

The only OO I have had the pleasure of peering through is their 12" dobsonian, at 120x M13 was absolutely stunning, best I've ever seen it

The 6" f11 possessing quite a lslow focal ratio and with their superb optics it should a great performer on the moon, planets and double stars. I think

[brianb]

it should a great performer on the moon, planets and double stars. I think

Yeah, IMHO it would be a waste of money to order without top grade (1/10 wave PV) optics. If the tube they supply is the same as the other OO scopes I've seen (thin walled aluminimum) lining the inside with 2mm thick expanded polystyrene or cork (to improve the insulation, thereby reducing tube currents) would be a worthwhile "upgrade". And fitting a fan to assist cooling of the primary mirror.

[Neil English]

Hey folks,

Thanks for all your feedback. This is certainly a bit of a mystery scope. I have read Ade Ashford's review, thanks. I've been looking for feedback from owners of the OO 6"F/11 Dob but thus far I have only found one. That chap is very happy with it. Indeed, he has recently told me that he split Zeta Bootis with it; which is quite an achievement.

I wonder whether folks have side stepped this scope in favour of larger models such as 8"F/6 models? That said, I have recently put a 6" F/8 Skyliner 150P through its paces and I must say that I'm very impressed with its performance. The optics on this scope are very well figured, maybe 1/6th wave with no obvious roughness or zones. Despite its 1.5 inch central obstruction (25%), it gives very nice images of the Moon, planets and double stars, though to get more mileage out of it, a cooling fan is probably a good idea. But for £180 UK, it's a great bargain in today's market.

The owners of the Orion scope are remarkably reticent! Maybe the 1/10th wave optics and 15% central obstruction has stupified them all.

I see other companies offering their own rendition of the planetary Dob. OPT are offering an 8" F/9 truss tube Dob for $995 USD;

OPT 8" f/9 Planetary Dobsonian Telescope - OPT Telescopes

Portability aside, I’m not sure whether a truss tube design is as a good as a closed tube model although it would cool off quicker.

And Discovery continue to offer their split tube 8” F/7 PDHQ for about the same price at $999USD

Discovery Telescopes

Looks like the market is heating up for ‘plantetary’ Dobs,

Best wishes,

Neil.

[brianb]

I’m not sure whether a truss tube design is as a good as a closed tube model although it would cool off quicker.

The basic issue with a truss tube at high power is that heat current from the observer's body tend to blow through the tube, causing awful "tube currents". Dewing of both primary and secondary mirrors tends to be an issue too. A latticework truss tube is probably superior to a metal tube in holding the optical components, the obvious thing to do is to wrap it in a light insulating jacket (neoprene?) to act as a dew shield & keep local heat plumes out of the line of sight.

Wooden tubes work very well, too, but tend to suffer from collimation drift ... not too much of an issue at f/10.

[John]

.... I have recently put a 6" F/8 Skyliner 150P through its paces and I must say that I'm very impressed with its performance. The optics on this scope are very well figured, maybe 1/6th wave with no obvious roughness or zones. Despite its 1.5 inch central obstruction (25%), it gives very nice images of the Moon, planets and double stars, though to get more mileage out of it, a cooling fan is probably a good idea. But for £180 UK, it's a great bargain in today's market....

I've seen those OTA's for sale used for ridiculously low prices - sometimes well under £100 !. I'd be interested to know how the Skywatcher 6" F/8 compares with a TAL 6" F/8 - the OTA from the TAL2M model. I know the TAL would be a lot heavier

[Neil English]

Hi John,

I used to own one of those old Tal 6" F/8 instruments. As you say; it's built like a proverbial tank and consequently very heavy. The Tal mirror is/was spherical though, and while at F/8 it was just about "diffraction limited" it sure served up some pretty nice views. I don't know for sure, but I'd wager the SkyWatcher (with its well figured paraboloid) just might edge it out at high powers.

Brian, I see the OPT scope comes with a light shroud. I wonder if that would keep body thermals at bay once the miiror has had time to cool off?

Cheers,

Neil.

[Peter Drew]

If you want a really good 6" F8, look out for an AstroSystems scope with David Hinds "A" quality optics.

[Moonshane]

I have been going through this same debate in my head. The OO scope looks amazing and with the upgraded optics, and dual speed crayford etc it's about £700 new! I don't suppose they ever come up used.

I am also now considering the 6" f8 OTA from SW and maybe mounting this on my altaz converted Vixen GP mount. I don't suppose there's any reason you couldn't decrease the size of the secondary?

top tip from Brianb re lining the tube. I might also do this with my 12" dob.

[Moonshane]

ps

I even started to think about grinding my own f11 mirror and making my own newt but it appears likely to be as expensive (if not more so - especially cf the SW 6" f8) as buying one! I think this is likely to be the case for smaller mirrors and I bet I could not do as good a job as Skywatcher!