16" f4 Orion Optics UK Dobsonian Project

[Moonshane]

I couldn't resist starting this thread even though I have not yet even been down to collect my mirror! You may guess I am quite excited.

I have committed to an OOUK 16" f4 primary mirror with 1/8PV and 0.984 strehl so it seems to be a good one. I am selling some gear currently to fund it, for collection possibly next week sometime.

One of these items is my 12" f5.3 OOUK dob and I love this so much being so easy to set up and use. Therefore I felt I should try and copy the design and build a solid tube 16" f4 dob. This is to be based on the solid tube version that OOUK actually sell.

The focal length is 1600mm the same as my 12" and therefore I am assuming the OTA will be wider (of course) but the same length and therefore also fit in my car without the need to split the tube a la Discovery Telescopes. I may eventually do this but will see how it goes. The identical focal length also means the magnifications in my eyepieces will be unaffected - although I may need a paracorr which will actually improve the images and reduce the exit pupils in all of my eyepieces but especially those of longer focal length.

My first consideration was cost. A new 16" OOUK dob with the same spec as my mirror on a dob base and with a dual speed focuser would be a shade under £4000 inclusive of the dreaded VAT. This is WAY above my budget.

Thankfully due to the decent price of the vendor of the mirror (and his kind willingness to allow me some time to raise the funds) and his willingness to sell me the bare tube and rings at a keen price (he used the other parts on his current other project), it may just be possible to build my (currently at least) dream scope for a grand total of £1200. This should be covered completely by the funds raised by selling the gear so technically it 'won't cost me anything'.

I will be looking to source (probably from OOUK):

Secondary spider

Secondary mirror (82mm minor access)

Dual speed focuser

9 point mirror cell

Once I have these I can then re-create the OOUK dob base (or something quite similar) in 18mm exterior grade plywood, paint it black and add some teflon blocks and I will be ready to roll. I may also make another equatorial platform but not sure at this point.

I anticipate this will be completed by early summer and in good time for the Peak Star Party and also the autumn observing.

In the interim I can spend time on Lunar, Planetary and double star observing with the 6" f11.

I will add some pics as I go (i.e. once I have actually returned with the mirror!

Cheers

Shane

[johninderby]

It will be interesting to see how you get on.

BTW Telescope service has some usefull bis and pieces.

GSO 27 Point primary mirror cell for 16 "mirror

£17.83 plus postage

http://www.teleskop-express.de/shop/product_info.php/language/de/info/p3521_Rohling-fuer-16--Hauptspiegelfassung---fuer-den-Selbstbau.html

http://www.teleskop-express.de/shop/index.php/cat/c64_Selbstbau-----mechanische-Teile.html

John

[GazOC]

The best upgrade on my 14" f4.5 Dob is the upgraded mirror cell. It saves a lot of aggro messing about with a big, fast mirror.

[Moonshane]

wow! cheers John. that's an amazing price. I think I will order one of those immediately assuming the ID of the OOUK tube is big enough. then again at that price, I can always make it fit!

the spiders seem pretty reasonable too.

if I can save that much on a mirror cell then maybe I can afford a Baader Steeltrack focuser or a Moonlite after all.

[Moonshane]

The best upgrade on my 14" f4.5 Dob is the upgraded mirror cell. It saves a lot of aggro messing about with a big, fast mirror.

cheers Gaz. I wonder whether the TS one would be as good as the 9 point CNC OOUK one at £140+ vat (I presume not).

[johninderby]

The TS (GSO) one won't be as good as the proper OO one but it's cheap. The TS one apparently needs a minor bit of work to convert it into a true 27 point cell. They also do the GSO 18 point cell that replaced the 27 point cell but it's about £100.00.

If the funds are available yes then do get the OO one. It's a much more substantially made bit of kit.

John

[Moonshane]

cheers John

you are probably right. I'm waiting for a price from OO for a few things (cell, alt rings, spider, secondary) and will see if they'll do a deal.

if I can afford it then I'll definitely go for the OO one as it does look well crafted. for a 16" mirror I suppose a good quality 9 point is better than a semi decent 18/27 point. then again, if I get the spider and the cell now from TS then I can always replace it in the future and get the shipping all in one.

[johninderby]

Yes, where do you draw the line.

If cost were no object I'd go for this one as you could then build a square mirror box.

http://www.teleskop-express.de/shop/product_info.php/info/p4119_TS-HS-Fassung-eckige-Basis---18-Punkt-fuer-Hautpspiegel-bis-D-16-.html

Only about £526.00 with the mounting sling for the mirror

John

[Moonshane]

blimey. if I were going this route, I'd make one as my father in law's a decent welder.

[Moonshane]

I have established the internal diameter of the OOUK 16" tube is 430mm so the cheaper option would be no good. I may as well therefore go for the OOUK cell as I will know this fits and maybe even in the same fitting holes as will be on the OTA.

the TS secondary looks very good as does their monorail focuser. may also get a square of ebony star too while I am at it.

oooh, I'm getting going now.

[swamp thing]

Warning!

Aperture fever is not cured by a 16" scope.

Good luck with the build.

Regards Steve

[Moonshane]

Warning!

Aperture fever is not cured by a 16" scope.

Good luck with the build.

Regards Steve

ha ha

cheers Steve

not looking for a cure, just a 'patch' for a few years before I can afford and go for the 20". then my 16" will be a grab and go.

[ollypenrice]

Great project. You are dead set on a solid tube? Tube currents can be a real hassle...

Olly

[Moonshane]

Great project. You are dead set on a solid tube? Tube currents can be a real hassle...

Olly

hi Olly

Cheers. Initially I thought of a truss and then as I was offered the shell of the tube and the rings by the vendor for next to nothing, I thought well I may as well make a solid tube dob. The good thing about this though it that I will make the alt bearings and rocker/ground board in such a way that I can reuse them if I ever decide to split the tube and create a truss dob a la Lightbridge using the top and bottom sections of the OO tube but cut out the middle. I'll see how it goes with some flocking etc for a while and then decide.

at least this way I can get a scope running quite quickly and than can be readily modified in due course. if the tube does work out, I don't need to buy truss tubes, shroud etc. but in the long run that route may be preferential due to portability convenience I suppose.

[spaceboy]

If you do get it finished in time for the Peak Star Party I think I'm gona have to get myself a pitch after all.

[Moonshane]

hi mate

it will definitely be finished by then (and I'll be there) and hopefully within a couple of months.

here's a pic of the tube compared with a 6" f5. the 16" is the one on the right (by the way, the lines at the top and bottom are a fault in the card I am using which seems to take ages to process images).

I am determined to make as much as I can for this (mirror cell, spider, base, alt bearings) as this will allow me to buy better quality items of things I cannot make (focuser, secondary mirror) and also possibly provide enough funds for converting it to a split tube or truss dob in due course.

the mirror is lovely and will last me for years.

I had to jump on this as I have never seen a mirror of this quality for sale in the UK or they are very rare at least so I think I have got myself a further bargain and the seller has enough funds to refigure and recoat a 17.5" f5 he bought, and the buyer of my scope got a fab scope for less than half the cost of a new one so everyone's a winner.

cheers

Shane

[spaceboy]

That's gona be a right handful Shane. I take it the kids have left home and you planning on using their bed room to store it. Look forward to the updates.

[Moonshane]

ha ha

nope, the beauty of the OO design (and the one I'll copy) is that the base will have a foot print of only about 22" so it will sit in a corner where there's a gap left by my 12" (sniff).

[John]

I've seen a solid tube OO 16" F/4 on an equatorial mount Shane - the Widescreen Centre have, or had, one in their London shop when I popped in there last year. It was a real monster - they told me it took four of them to get the OTA onto the mount

This is going to be a great scope when it's up and running - hope you have ordered some dark skies to go with it

[Moonshane]

cheers John

I think you'd have to be some sort of he-man to use this equatorially. at the height the EP would be I think I'd sooner have a 16" f6-7 which would be about the same!

ladders ain't for me.

Looking forward to the first time I get to look through an eyepiece. will be at home to test but swiftly followed by a darker site - guaranteed!

[swamp thing]

You'll be driving to dark sites a lot more regularly.

My 16" has done plenty of miles in my van.

After you've used it from dark site you'll find it hard to use it at home.

I never set up at home now.

Regards Steve

[Gina]

WOW! What a beautiful monster

[spaceboy]

You'll be driving to dark sites a lot more regularly.

My 16" has done plenty of miles in my van.

After you've used it from dark site you'll find it hard to use it at home.

I never set up at home now.

Regards Steve

Is the 16" any good under LP skies or dose it suck in too much LP? Do you stop down the aperture at all? I had a 127 MAK last summer and found it was great under the light night skies due to the smaller aperture.

[nightfisher]

shane let me know when you are going for first light with this beauty.............i should be able to do some observing/imaging on same night as this beast of yours should suck all the clouds of the pennines!!!

looking good, might arrange a look through it, i would of course bring the jafa cakes:D

[Moonshane]

You'll be driving to dark sites a lot more regularly.

My 16" has done plenty of miles in my van.

After you've used it from dark site you'll find it hard to use it at home.

I never set up at home now.

Regards Steve

cheers Steve - I agree. already got a site near Hayfield, Derbyshire lined up.

WOW! What a beautiful monster

Thanks Gina. not as bad as it looks as I have some long arms on me - maybe they will be longer soon.

Is the 16" any good under LP skies or dose it suck in too much LP? Do you stop down the aperture at all? I had a 127 MAK last summer and found it was great under the light night skies due to the smaller aperture.

I don't believe in more aperture being bad with LP. I think it's an urban myth. I was using a 22" in bad LP the other night and we were picking out galaxies in Virgo for fun.

shane let me know when you are going for first light with this beauty.............i should be able to do some observing/imaging on same night as this beast of yours should suck all the clouds of the pennines!!!

looking good, might arrange a look through it, i would of course bring the jafa cakes:D

ha ha

not sure about first light (will be find the glitch night) but you and your jaffa cakes will be welcome anytime thereafter!