16" f4 Orion Optics UK Dobsonian Project

[Glasspusher]

Well done Shane, nice to see a project come to completion..you have done a lot of research which has clearly paid off. Looking forward to your first light report.

John

[Moonshane]

cheers John

very kind words indeed. I agree with all you say too. at the minute I am trying to stifle the pride as I will get very frustrated with the clouds around and the fact it still needs a tweak here and there to get it spot on.

[Moonshane]

Well done Shane, nice to see a project come to completion..you have done a lot of research which has clearly paid off. Looking forward to your first light report.

John

cheers John

funny you should say that as analysis paralysis was setting in a bit. so I figured, just get on with it, slowly, take your time and anything can be sorted as you go along. learned a lot ad next time I'll be doing more myself I reckon. the time after that I may even make my own primary.

[astroeddie]

Wow Shane,

Looks a real MOONSTER now.

The spoked bearings make the OT assembly look like a canon, and a big one at that.

Glad your project has been completed as such.

Now for those reports etc.

Congrats Eddie

[Glen]

Top work Shane, its been a pleasure to read/ follow this thread and to see it very nearly completed is great.

Definitely a project to be proud of!

[Moonshane]

cheers Glen. Really need to get the mirror raised up the tube so I can actually use the thing! I tried last night but clouded over again.

[life on mars?]

My first post, really impressed with the quality of your work. May I asked some questions please about the tube rings. I am going to make my old 8.75" Fullerscopes into a dob as it has a really heavy stand and I need to make it more portable to get away from light pollution. I read that yours came with the tube do you know anything about them, also the thickness and width of the steel as I am considering making them myself. Mine are going have to be 250 mm dia or another alternative is to bite the bullet and buy the tube Rings & Trunnion from oo for £60 then make the base. Your advice would be much appreciated.

[Moonshane]

hi there

thanks and welcome to the group!

if you are making your own base and around a 10" tube then I'd personally try and find some used Skywatcher rings as they would be a decent fit and also they have a flat on then to replace the need for trunnions. see here which uses the almost identical Celestron ones. http://stargazerslounge.com/diy-astronomer/144997-home-made-dobsonian-base.html page 2 has the finished pics.

my rings are the standard OO ones with 5mm thick by 50mm wide aluminium. probably easier to work with than steel. line with thin cork as this slips less than felt although with your scope might be OK with felt.

I have an 8.5" f8 mirror that I'll be making into a scope sometime (probably a truss) so I'll be interested in your progress!

[Moonshane]

still awaiting a gap in the clouds to enable me to gauge the real focus point with the paracorr in place plus my closest focusing eyepiece (18mm BGO) so I can move the mirror up the tube to the required point. I can then make the rear baffle and fit the fan but in the interim I made an off axis aperture mask today from some 3mm hardboard that was in the box where I had stored the primary mirror until just recently.

I routered a circle of an appropriate size and then created two more holes with the jigsaw by hand. the smaller one is for the central secondary support and the other larger one will sit nicely between two vanes and create a 170mm (6.7") f11 apo scope. given the good figure of the mirror (1/8 PV 0.984 strehl) I am hoping this will give good results on planets and doubles and prevent the need to try and squeeze in the 6" f11 when attending field events. if not, nothing ventured nothing gained. just need to add some matt black paint and it's done.

[tom33pr]

What an amazing job you did there!!!

Looking class! I love that black base nicely contrasting with the OTA! Very elegant looking scope!

You should set up a company and do this for living! I'm sure there would be a serious demand on those!

Regards and looking forward to the first report.

P.S. It'd be cool if you took a pic standing next to it, just to show the real scale of the monster!

[spaceboy]

P.S. It'd be cool if you took a pic standing next to it, just to show the real scale of the monster!

Even then you wouldn't get a great idea of scale. Shane is a larger than life fella.... 6' 6" is it ?

[tom33pr]

Even then you wouldn't get a great idea of scale. Shane is a larger than life fella.... 6' 6" is it ?

LOL! Squat beside it then

regards.

[spaceboy]

[life on mars?]

Thanks for advice Moonshane I did consider aluminium, thought it might not be sturdy

enough, but perhaps it will. I did built an 8' dome out of steel and aluminium years ago before I moved, still have it, but it would take a lot of work to rebuild it. Tried to post some photos of building the dome, but does not seem to work at the moment. Have to have a play around to see if I can get it to work.

Thanks again

[Moonshane]

no worries matey.

to add pics to a thread you have to 'go advanced' (i.e. the button below) and then click the paper click. it then brings up an upload file.

managed with some jiggery pokery to ascertain the focus point last night with the 16" and the end result is that the mirror needs to move up the tube by 40mm. I did this by taking off the focuser body and then hand holding the paracorr with the 18mm BGO inserted. my father in law then measured the height of the 1.25" adapter in the paracorr and this was 40mm less than the height in the fixed focuser so hence the focal point needs pushing out by 40mm.

as luck would have it, this is almost the exact distance by which the collimation bolts / feet extend out of the tube and also the height up the tube of the current fixings. given the above, I should be able to easily temporarily fit the cell at what I think is the correct height and then mark the position once I am sure all the eyepieces (and filters) I have will focus.

[spaceboy]

Sounds like your onto a winner there Shane. loving the off axis aperture mask. I purchased another dust cover for my 8" fleck in the hope to cut a larger hole and use it while viewing the moon but in the end there wouldn't have been much improvement over the stock 2" hole in the dust cover anyway. Certainly no where near 6.7"

[SniffTheGlove]

My first post, really impressed with the quality of your work. May I asked some questions please about the tube rings. I am going to make my old 8.75" Fullerscopes into a dob as it has a really heavy stand and I need to make it more portable to get away from light pollution. I read that yours came with the tube do you know anything about them, also the thickness and width of the steel as I am considering making them myself. Mine are going have to be 250 mm dia or another alternative is to bite the bullet and buy the tube Rings & Trunnion from oo for £60 then make the base. Your advice would be much appreciated.

Look on Astroboot regularly as they appear from time to time.

AstroBoot

There are a pair there (255mm) right now for £25

[life on mars?]

DSCN3307.jpg DSCN3306.jpg DSCN3308.jpg

Moonshane I hope this is going to work!

[Moonshane]

wow! if that's a home made dome it's really excellent and I cannot see you having any problems with making your dob base or anything else, come to think of it!

[Moonshane]

yesterday I decided that I had prevaricated enough and it was time to bite the bullet and drill my new holes to bring my focus point out enough for the focuser, paracorr and my eyepieces.

I had measure the approximate point to be around 40mm the other night and though that if I erred on the cautious side, that 50mm would be a nice round number and would ensure the most important point was covered - that the focus point was far enough OUT. a good thing about using a paracorr of course is that like a 2" barlow, it can be pulled out slightly if the focus point is a bit far out and not enough out focus is always easier to deal with than not enough in focus.

so after removing the primary of course, and using a set square with a dotted white sticker on (and stickers on the tube where the holes would be drilled) as a template I measured up 50mm from the existing holes and put a dot in the appropriate spot. I remeasured the marks to ensure they were all consistent and then drilled 7.5mm holes for my M6 bolts.

all went very smoothly and after tidying up the holes and cleaning out the swarf I reinstalled the primary. with a bit of persuasion it eventually went in perfectly. stage one completed.

at the same time I took the opportunity to address the tube slippage problem. a few days' thought had led to to realise that all I needed to do was move the cork lined 'holding ring' to the bottom and above the lower tube ring proper. this would then prevent and slippage and also still allow the tube to be moved if required for balancing. worked a treat. with everything on (finder, telrad, paracorr, dew shield, 26mm Nagler) I balanced the scope and it was all set for collimation.

I collimated the scope and waited with bated breath for a surprisingly clear night. as Vega popped out of the dusk sky, I could not wait any longer. I put in my 26mm Nagler and focused - yes! pin sharp focus. but something was missing on the stars in the outer field. hang on there was no coma......the Paracorr does an amazing job really superb. I then tried the other end of the scale, my 18mm BGO which requires the most in focus and yes! also spot on focus, sharp stars edge to edge. I am really delighted.

I made the most of the night and had a quick look around and although the moon spoiled things a little everything worked really well. cannot wait to get to a dark site.

I say the moon spoiled things a little but it did give me the chance to try my (unpainted and bare hardboard) aperture mask. I was completely shocked when I looked through the eyepiece with the mask in place. The sharpness and contrast was truly remarkable and I think even better than my 6" f11 and this without any filtration. with my 6-3mm Nagler zoom at 6mm (so 300x approx) the moon detail was fabulous e.g. Hadley crater and much of the rille quite easily seen despite being in full illumination. double stars were also easily better with the mask and Delta Cygni and Epsilon Lyrae were easily and clearly split.

the moon without the mask was also still very good and in moments of clarity I think just edged the view with the mask but not by much, and all this with the moon at a low elevation. I did have a quick look at Jupiter too and again despite very low elevation I could see the signs that this scope will be a brilliant planetary scope too. not even fitted the fan yet either.

A few have asked for some size context photos. here's me (grudgingly) beside my creation. I am 6'3" tall so you can see that the eyepiece is in reach of most people at most times with feet on the ground - my wife is 5'8" and is about 3" shot of zenith viewing.

really chuffed and looking forward to a moon free night or a dark site. next, fitting a fan and end baffles before the snow comes to reflect light up the tube!

[spaceboy]

Glad to see the focusing issue has been resolved painlessly and with out any broken primaries. The scope is not as large as I would have thought and looks within reason to be fairly manageable. Certainly looks the part anyway. Given you are 6'3" I think that focuser as it stands would be a perfect height for me at 5'10". A job very well done I would say Shane hats off to you on a successful project. Fingers crossed skies are clear for PSP

[Moonshane]

cheers mate

will be great to meet and hopefully you'll be as impressed as I was when I first looked through it!

[spaceboy]

hopefully you'll be as impressed as I was when I first looked through it!

No doubt there mate

[MjrTom]

Looking great Shane

Glad the project is coming to fruition

It looks a lot smaller than the Meade lightbridge 16 inch I was using last night.

[Astro Imp]

Hi Shane,

I have followed this project from the beginning and am pleased to see that all your hard work has worked out so well. You really deserve the greatest credit for this outstanding piece of work.

Well done and enjoy your new scope.

Clear skies.