16" Dobs

[Moonshane]

Oh no, the dreaded aperture fever is beginning to rear its head.

I have concluded that the absolute maximum for portability either into the back garden or the back of the car is a 16" mirror.

I have in my mind 1) a 16" Meade Lightbridge with the base replaced by a home made 'Orion Optics UK style' one made with either 3/4 good quality ply or 10mm sheet ali or 2) a mirror set inside a home made 'obsession' style or 'skeleton' truss dob. I can do all the work for this myself so whether or not I go for a mirror or a full scope does not really matter. I just don't want to end up with something worse than my 12" dob which I consider to be excellent and really enjoyable to use. I'd need to sell this if funding a larger scope.

my main query is the quality of the lightbridge mirrors at 16".

Does anyone have any direct comparisons with the LB mirrors and other mirrors such as those you can maybe buy from Oldham Optics or OO UK?

Thankfully I need to save some cash first so have time to research this properly. That said, if anyone is looking to sell a mirror set or a 16" dob over the next few months then do let me know. It's possible that I may even grind a mirror myself if I can do so for DSO viewing quality where I understand the quality of mirror/polishing etc is not as critical as higher powers?

Thanks for any comments

[pvaz]

I never tried any of them so I can't really say which is better.

From what I read so far the LB haves some issues to address which will make it cost more in the end. The orion optics comes with a better base for an extra 100 and you can ask them to upgrade the focuser and other bits.

Another option is to wait for skywatcher to launch their new 16" dob with tracking and GOTO. Orion US is also launching a truss tube version of it.

[Moonshane]

cheers Paulo

I am mainly interested in optics as I can pretty much fix anything cheaply myself and I am not really interested in GOTO etc as I prefer to locate things myself using maps as this is a big part of the fun (and frustration!) for me.

you make a good point about the OOUK version. in my mind is a mirror set or a 16" LB used for maybe £1000 approx but as you say, by the time I have added a base, maybe new coatings etc etc I could possibly have bought an OOUK which I know I will be happy with based on my experience of the two I have. perhaps I need to save for a little longer and just get the OOUK.

[Chris H]

Don't know what the top end of your budget is but have you thought of a David Lukehurst Dob David Lukehurst - astronomical telescopes - Links not the cheapest but he uses top quality mirrors and the scopes look really well made.

[Moonshane]

cheers Chris

not a supplier I was aware of!

this is just the sort of thing I was considering although what frustrates is that the cost of a mirror set seems to be around £1600-2000 and the scope is almost free! (i.e. is it worth making one!?) suppose that's where the money always goes though.

[Peter Drew]

With the greatest of respect, a 16" mirror of the short focal length needed for a Dob, is a pretty difficult project even for an experienced amateur mirror maker. A "so-so" large mirror will certainly produce a larger, brighter fuzzy blob but many good DSO's have fine structure and/or faint stars requiring at least 1/4 wave accuracy for good results. Best to look for s/h, IMO, if you want a 16" any time soon. .

[Moonshane]

cheers Peter

I agree with you actually and really didn't relish trying to make a mirror of this size/figure. I am rapidly coming to the conclusion that a used one (preferably an OO UK or Oldham Optics or similar quality mirror) is the only option other than save a lot longer and increase my budget to maybe £2500.

[haitch]

Have you actually had the chance to get to grips with a 16"?

I'm only asking as it's really bigger than it sounds. My 14" (granted it has a solid tube) is plenty to handle.

[pvaz]

...not really interested in GOTO etc as I prefer to locate things myself using maps as this is a big part of the fun (and frustration!) for me. ...

Likewise, but don't forget about tracking! And as far as I know the new Skywatcher 14" dob comes with 1/4pv optics similar to the standard OOUK optics, on a much better package (dual speed crayford, collapsible tube, motors, goto, tracking, EP rack and the base can be easily dismantled). Besides sometimes you may want to use GOTO. I turn mine on, when I get excelent seeing conditions so I won't loose time. The way it works, if you decide not to use goto on a target, even though it's on, you can always point the scope manually.

I think the question now is: Can SW price match the OOUK standard 16" with their new dob?

If you do wan't a higher grade optics (1/6+pv) with hilux then OOUK is probably the way to go.

Dobsonians - Skywatcher Skyliner 350P FlexTube GOTO

[Moonshane]

Have you actually had the chance to get to grips with a 16"?

I'm only asking as it's really bigger than it sounds. My 14" (granted it has a solid tube) is plenty to handle.

cheers Haitch

good point but I am working on the basis that a truss 16" if well designed will be readily handled and portable. I'd not consider the solid tube OOUK as this would be like carrying an oil barrel.

the good thing is I am nowhere near affording one yet so I'll hopefully have chance to see one before I do. my mate has a 22" which is not yet constructed but this does not scare me too much.

[Moonshane]

Likewise, but don't forget about tracking! And as far as I know the new Skywatcher 14" dob comes with 1/4pv optics similar to the standard OOUK optics, on a much better package (dual speed crayford, collapsible tube, motors, goto, tracking, EP rack and the base can be easily dismantled). Besides sometimes you may want to use GOTO. I turn mine on, when I get excelent seeing conditions so I won't loose time. The way it works, if you decide not to use goto on a target, even though it's on, you can always point the scope manually.

I think the question now is: Can SW price match the OOUK standard 16" with their new dob?

If you do wan't a higher grade optics (1/6+pv) with hilux then OOUK is probably the way to go.

Dobsonians - Skywatcher Skyliner 350P FlexTube GOTO

cheers Paulo

all good advice. yes, the tracking would be more useful but honestly I don't like relying on anything electronic mainly as I think your skills diminish if you do. that said, when trying a sketch of Jupiter recently I confess that tracking would have come in handy. the advantage I have is time