The Mapstar Scope build

[mapstar]

You really are teasing us with this thread :-)

Ian

Not sure about teasing, but it's tormented me for 10months and I really wish it had come together as quickly as the thread has.

Hope the next two come together a lot quicker a

Although I'll not be going through them all like this one just the major bits.

I think the box, what with work and home life, took me 3 week's to complete.

Hopefully its a good read though shame my photography skills aren't up to much!

Damian

[mapstar]

my 16" sumerian will be up for sale if all these big dob builds carry on

I doubt that very much and it was the Sumerian scope's that inspired me to build one.

Great scope's although I've not seen one in the wood.

[wookie1965]

That mirror box is a work of art

[mapstar]

That mirror box is a work of art

Cheers Paul

[swamp thing]

Are you going to anodise the cell Damien? I didn't do mine as I built it ,but I am now going to strip it and get the ally anodised a racy blue to match the shroud. I'm such a tart

Coming on nicely matey 

[mapstar]

Are you going to anodise the cell Damien? I didn't do mine as I built it ,but I am now going to strip it and get the ally anodised a racy blue to match the shroud. I'm such a tart

Coming on nicely matey

Thanks Steve

I'd not planned on it, although did think about it. The welds probably wouldn't colour as I didn't specify to the welder, they use a different grade of ally to tig with that take's a colour.

It may get done

[SimonfromSussex]

Looking great so far Damien! Loving the mix of aluminium and wood.

[mapstar]

At this stage it was around June and next up was the alt bearings and cross brace.

First up the alt bearings which I made from 1" thick ply.The bearings took quite some time to do and the size was worked out using the Albert Highe calculations for the weight distribution in the full tube assembly. The size came out to be just over 17.5" radius so airing on the side of caution I actually cut them 18".  These were cut out using the router and then a hole saw for the individual holes.

After chamfering the edges of the holes I then jigged up and cut the 5 bolt holes for attaching using a 10mm router bit. I cut them this size so I could bush the holes with stainless tube (10mm OD 1mm thick wall) to prevent wear when fitting/removing the attachment bolts.The bearings could then be fitted to either side

There is in the end actually 6 holes in each.The last hole was cut in after when the bearings were bolted onto the mirror box and I could get a correct measurement so the allen key could be inserted to tighten the truss tube lower fixing (later pic)

I'd bought some formica which was then glued on with contact adhesive then trimmed with the router. I then fitted the end stops to complete the bearings.

Pic below shows the chamfered holes and the bushes fitted 

Next up I made a cross brace for the upper part of the alt bearings for when the scope was at low elevations. Again this was made from 1" thick ply.

I then fitted 2 insert nuts either side and as this needed to be kept square I fitted some aluminium plates to the ends to keep them from getting transport knocks.

The rocker box was next on the agenda so onwards and upwards but first I'd drown another teabag!!

Damian

[mapstar]

Looking great so far Damien! Loving the mix of aluminium and wood.

Thanks Simon. Hows your scope doing? 

[SimonfromSussex]

Thanks Simon. Hows your scope doing? 

Sadly the weather has been dreadful here since wales (apart from one night with a full moon typically) so no chance to get out 

I'm desperate for some clear sky!!

[wookie1965]

Oh i wish i was good a woodwork i cant even saw straight.

[mapstar]

Oh i wish i was good a woodwork i cant even saw straight.

It's all about practice (and having a table saw he he!) Work today guys. Didn't even get around to mirror polishing today.

Damian

[mapstar]

Morning all,

Last part of the build is the ground board and rocker box. Design wise I considered the sumerian style round base as they look elegant and different. When I worked it all out with materials and size it was getting close to a 900mm wide base and would've meant ordering more ply. Maybe this will be for the 22" scopes in future? 

So I settled on a square base as it was more compact thus easier to store, transport and make as time was becoming an issue.

First off the ground board. This was constructed from 30mm thick ply and a triangle made up of a 12mm piece and 18mm piece laminated together. Here it is glueing up

The central hole was to fit the pivot assembly in which was in a previous post. Pic shows the pivot and central teflon pad fitted with 5mm stainless countersunk allen cap screws and again finished off with several coats of varnish.

It would also have the three teflon pads above each foot at roughly 50mm square (rouglhy 14psi on each bearing). The size of this was a radius equal to the central point of the alt bearing vertical mounts of the rocker box. Roughly 380mm

The rocker box was constructed from 18mm and 24mm ply.Unusually this took only a week to construct mainly due to lots of time off work!

The initial dry run just so I could see what it was like is shown below. Again it would be biscuit jointed

 

Before glueing I angled the front/rear edge's of the alt bearing runners and also added more chamfered holes to match the ones on the alt bearings. Here it is after I had glued everything together.

I then added a centre bush for the Azimuth pivot point. Epoxy was used to glue it in.

After everything was varnished and blackboard painted I set about fitting the formica to the bottom which I then trimmed with the router for a neat finish.

The box just needed the teflon alt bearing runners and side guides fitting to be completed. Each teflon runner was 75mm long although with slight clearance for the box the bearing would only run on about 60mm of this (again calculated at 14psi) Pic below also shows the central pivot top screw in the back ground

The ground board I glued on some  3mm 1/8" rubber  to each foot

Finally completed it was early September and the scope was more or less ready for putting together and first light and testing  .I didn't really get a shot of it on its own? so here it is with the cross brace laid inside just requiring the side guide teflon pads fitting

Another new box of tea bags first!!

Damian 

[faulksy]

i like this a lot

[jamespels]

I think a budget review is needed, though. Just how much of it really went on tea bags??!

[mapstar]

I think a budget review is needed, though. Just how much of it really went on tea bags??!

It wasn't much James as we now have part share's in said tea company ;-)

[Rustysplit]

Enough of this talk of tea. More pics fella. Beautifully built project, looking forward to seeing the complete assembled 'scope.

[mapstar]

Enough of this talk of tea. More pics fella. Beautifully built project, looking forward to seeing the complete assembled 'scope.

Cheers Alan

More pic's later on when I get home from work and finally put it all together.

Damian

[faulksy]

Cheers Alan

More pic's later on when I get home from work and finally put it all together.

Damian

the moment we have all been waiting for. yehaaa

[mapstar]

]And finally after much posting about the build (Its been 10 months for me) onto the last bit

After all the build up the scope needed to be finished for a star party in September (its amazing how you run out of time) and so the guy who I was building it for would be picking it up on the Tuesday night. As mentioned in a previous post the secondary was the last thing to actually go on after the finder brackets were all fitted and the truss assembly screws finished.

So off I went and bought some Dow Corning glazing adhesive and bonded the Kendrick dew pad to the back of the secondary on Sunday morning, the plan being to bond the secondary to the holder on Monday evening. As it happened to my horror when I checked Monday afternoon the dew pad just peeled off!!

Cursing and running out of time we had to bond the whole thing in one go and hope for the best Monday evening. Tuesday I assembled the scope and waited for the owner to bring the primary. I've not yet got a photo with the scope and primary together.

Everything was set up and the primary was put in for the first time, to be honest at first we thought the primary was not fully on the cell as it was really soft at going in the bearings doing a great job of flexing and distributing the weight.

Anyway here she is in all here glory minus the primary mirror

[faulksy]

Fair play mapstar, that's a thing of beauty. I bet your well proud. That uta looks nice and slim, will he have to use a light guard. Well done mate :-) :-)

sent from my fone using fingers

[Rustysplit]

  Beautiful. Really nice looking dob. Really like the lightweight look of this build. The thinner than usual truss tubes make it look so much sleeker. I bet you are proud of this Damian? You should be.

[Rustysplit]

Any pics of someone next to it for scale?

[Rustysplit]

Interesting use of bricks as a secondary too

[mapstar]

More photos guys

Its first star ha ha!!!!!!

Anyway, and just in case anyone needs to really get a scale of a 24" dob here's me with it! (worst luck!!) 

The star test we didn't manage due to clouds!!!!!  but the balance was great even with a 21 ethos in the focuser. The alt bearings were smooth and the whole assembly once locked up with the 4mm allen key was solid with no vibration. The collimation worked really well and as planned which was a huge relief, the cell moving up and down smoothly. 

Few more pics to follow.

Damian