Sky-Watcher Skyliner 200p Restoration Project

[PeterStudz]

Many thanks to @Grumpy Martian for arranging to meet me at a motorway service station near my home and giving me this telescope for free. There are some “dimples” on the primary mirror so it might require recoating. But I’ve already done a rough collimation, propped it up against a garden chair and looked at a random bit and of sky. It seems to focus OK.

It hasn’t got a base so I’ll need to make one out of ply. Will probably take a while for me to get going although my daughter wants to use it now. 

[Guest]

Wish you well with the project Peter. Great to meet you, socially/anti socially distancing ofcourse. Lol.

Oh I wish that I had a telescope when I was a child.

[PeterStudz]

3 hours ago, Grumpy Martian said:

Wish you well with the project Peter. Great to meet you, socially/anti socially distancing ofcourse. Lol.

Oh I wish that I had a telescope when I was a child.

Many thanks Martin. I’ll let you know how I get on, good or bad. But I’m confident I can make something from it. And it was great to meet you too. 
 

All of this brings back memories of my first telescope as a child. And back then something like this would have been my dream telescope. 

[PeterStudz]

It now has a ground board. Manage to get some time over the Bank Holiday weekend to knock this up. Two bits of 18mm ply. Bottom an octagon, top a circle 520mm in diameter. Decided to try Teflon pads over a lazy suzan, although I’ve made it so it can be easily fiddled with and modified if required. There’s a sheet of 2mm textured ABS in an attempt to get the required “sticktion”. Seems to work well, although I’ll only find out for sure when using the telescope. To keep costs down I went for a sheet that doesn’t quite cover the base. Anything larger would have been twice the price and I wasn’t sure if it would work. Finished off with anti-vibration washing machine feet. 

 

Obviously now need to do the rocker box. That’s when I can get a free day!

[Guest]

Progress is looking good.

[PeterStudz]

On 11/05/2021 at 16:21, Grumpy Martian said:

Progress is looking good.

The rocker box is coming along. I haven’t as yet attached it to the ground board and it needs trimming up, bracing along the bottom and finishing off. Easier to line up when square and trim up later. But even just resting it on the ground board the weight alone means it’s actually useable. Smooth too and doesn’t seem to be sticky when it matters.

I decided to keep the original altitude side bearings. This meant that the left/right sides of the rocker box hand to be accurate within a millimetre or two. To do this I used the OTA itself as a jig for the rocker box sides. Making sure that the sides and front edges were all dead square (I haven’t got a power saw so cut by hand) meant that the whole thing went together with just a quick check over with a set square - no clamping necessary. 

I’ve used some PTFE and wood blocks for the altitude bearings to rest on. The holes for the tension knobs being oversized. I also managed to replicate the “patented tension control handles” with an M10 knob and a simple thrust bearing. Works really well.

[Guest]

I am really pleased that you have been able to make the mount for the Newtonian. 

[PeterStudz]

I’ll post an update when it’s finished. Making this has been fun and by doing so you really appreciate what a fantastic design this is. Mr Dobson was a cleaver guy! It’s downhill from here, although “finishing off” can take as long as building. 

I also took the mirror cell out as I wanted to remove the altitude bearings as part of the build. It’s not too bad. Rather dirty and it’ll need a careful clean. I thought it might be a little stiff to remove but it was far harder to get back in! After that I’ll get everything working and if necessary consider getting it recoated. 

[NGC 1502]

Well done and great to see DIY telescope making is alive and giving good results.

Regarding a mirror recoat, depending on how bad it currently is you may find it gives excellent views as it is. Of course I do get the desire to make it the best you can.

An 8” Dob can be a lifetime scope, please let us know further when you can.

Cheers from another ATM (amateur telescope maker) in Essex. I’m currently rebuilding a 6” Dob I first made in 1994. I’ve never made a mirror, the 6” mirror & secondary was made by David Hinds. It splits very difficult double stars because David was a master of his craft.

Ed.

[PeterStudz]

Good advise about the mirror. I had kind of come to that conclusion too. And of course I need some sort of mount in order to properly test it out.

I’ll let you know how I get on. It’s annoying that work is getting in the way of my construction fun but will get there!

[PeterStudz]

@Grumpy Martian

It’s getting there, slowly. The “moon” is functional as it serves as a handle. The azimuth bearing works well. Had some stiction at high magnification on the altitude bearings although friction is fine. Some PTFE tape that I had at home has improved things significantly but will experiment some more. 

Still need to fix the rocker box to the base board. Seal the ends of the plywood, sand smooth and paint. But I’ve had it out to test. First the moon (I have a picture of that), then M13 and the Ring Nebula which was a first for me. Not bad given the primary mirror. There might be an issue at magnification above 200x, but hard to tell for obvious reasons.

Edited June 8, 2021 by PeterStudz
Spelling

[Guest]

Looks excellent skillful work Peter. You might be receiving orders soon. Lol

[Swoop1]

Very nice Peter. I really like the detail of The Plough and Orion being added to the mount, a classy touch.

[johninderby]

Nice job 👍🏻 Well worth making a proper base to replace the mdf one that comes with most dobs.

Best thing I’ve found to finish the ply is Osmo Polyx satin oil. Harder than polyurethane when hardened but so easy to get a perfect finish. Just brush on then wipe off the excess with a lint free cloth. Takes two or three coats. 

https://osmouk.com/product/polyx-oil-original/

You can stain the ply first if you wish but also looks good in a natural finish.

 

Edited June 8, 2021 by johninderby

[200pman]

Nice.looks good workmanship.

[PeterStudz]

At last, the base is finished! Took a while for me to paint as during the summer and early autumn my daughter (me too) got into observing Jupiter and Saturn. And it was at every opportunity. From camping in the garden to late nights, whenever it wasn’t cloudy. Somewhat fortunately most of this was during the school holidays, although it did tire me out! Work also got in the way too.

Painting would mean at least a week off as I would need to allow the paint to fully cure. Unpainted It also allowed me to fiddle with the setup. I’m really pleased with the textured ABS sheet on Teflon/PTFE pads for the azimuth bearing. Hardly any stiction even at high magnification. Tried some other possibilities but nothing that I tried was better than this. 

The altitude bearings took a bit more effort. Just running on PTFE pads there was too much stiction for my liking. Some dehydrator sheets (basically PTFE paper) which I had at home and stuck to the sides of the trunnions with PTFE tape worked perfectly. The last picture shows what I mean. Initially this was just a temporary installation but it’s lasted so well that I’ve kept is as is. 

I’ve also made the rocker box easy to remove from the ground boards without tools. I thought it might be easier to transport via car this way and  if necessary, it allows possible future modifications. 

Just got to give the OTA some more attention. I intend to take it apart, give it a good clean and flock. Probably add a handle. However, I already have a primary mirror solution. More on this later. 

[200pman]

Nice job.

[wookie1965]

I'm so jealous of your woodworking skills I'm hopeless with it. 

The base looks absolutely fantastic the constellations on the sides really sets it off. 

[Andy ES]

Skilful professional job, looks fantastic! The constellations are very clever.

i would be very proud of this effort.

[PeterStudz]

Thanks for the nice comments. 

Just as I thought I’d have a little free time to finishing the OTA a load of work came in. Don’t you just hate it when that happens! I just need a couple of free days maximum - I think! Will probably be early in the New Year.

I’ll try and post some pictures as I strip the OTA down and flock etc. I’ve got most of the bits I need together now. I have a feeling that there are pits where the secondary adjustment screws meet the holder. At the moment the secondary is a pain to adjust. Eg as soon as I get it bang on and tighten the screws it slips out of position again. Will probably do the milk bottle mod but will see when I take it apart. 

And happy Christmas!

 

[Pixies]

On 23/12/2021 at 11:25, PeterStudz said:

Thanks for the nice comments. 

Just as I thought I’d have a little free time to finishing the OTA a load of work came in. Don’t you just hate it when that happens! I just need a couple of free days maximum - I think! Will probably be early in the New Year.

I’ll try and post some pictures as I strip the OTA down and flock etc. I’ve got most of the bits I need together now. I have a feeling that there are pits where the secondary adjustment screws meet the holder. At the moment the secondary is a pain to adjust. Eg as soon as I get it bang on and tighten the screws it slips out of position again. Will probably do the milk bottle mod but will see when I take it apart. 

And happy Christmas!

 

I found a steel washer and milk-bottle plastic fixed the same problem I had with my Bresser. If you are taking the secondary assembly apart, you can use the opportunity to replace the 3 adjusting screws with some thumbscrews - it's makes adjustment so much easier.

 

[PeterStudz]

I’ve been meaning to finish writing this up for months but life got in the way, so here goes…

I managed to get a second hand Skyliner primary with mirror cell (plus secondary & spider) for £50 from a forum member back at the end of last October. Thanks again @CraigT82! As soon as I received it I couldn’t wait and (going against my advice of being patient) immediately installed it into my mirror cell and OTA. To my surprise I only needed to adjust one primary adjustment screw in order to get it collimated.

You can see the state of the old mirror. It’s not just dirt, but also about half a dozen spots with corrosion plus scratches. Hard to get a picture with my phone camera but if you looked at the back light was getting through in these areas. Surprisingly I got decent views of Jupiter and Saturn with this. The secondary is fine and just needed a quick wash in order to remove dust and cobwebs. Quite how it got like this I haven’t a clue. Someone had obviously removed the mirror cell before as it had been forced back incorrectly - there’s a notch in the cell to accommodate the OTA tube seam. It also looked like someone had tried to remove a corrosion spot or two and in the process scratched the surface.

I’ve included some pictures of the old and “new” mirror in its cell. Now I also have a spare secondary + spider assemblers, primary + cell. Hmmm… at some time in the future I might try and get the primary recoated and make a compact “folds into a case” travel Dob. How hard can it be?  

[PeterStudz]

In the middle of January I had some spare time (I took a day off) to strip down the OTA. The plan was to flock the OTA, do the milk bottle mod to the secondary, blacken the edges & back of the secondary, remove the focuser & give it a clean, blacken the draw tube and add a handle to the OTA.

I stripped down the OTA the afternoon/night before. I’d already had the secondary assembly out several times before so I could get dimensions for the milk bottle washers etc. Just a year before collimation was some sort of mysterious, frightening dark art. Now I could happily take the mirrors out, fiddle with them, replace everything and collimate without looking up instructions - like riding a bike. 

The secondary and draw tube were  blackened with blackboard paint and left to dry overnight. Milk bottle washers installed, Bobs knobs added. Interestingly I was going to include a metal washer with the milk bottle washers but the gap was too small. Maybe more about that later. I had got a small sample of Black 3.0 paint (blackest and mattest acrylic paint on the planet - apparently) but adhesion is pants. Sneeze on it and it flakes off. I wouldn’t have it anywhere near optics. Once cured the blackboard paint stuck down hard. Amazing how much gunk, dead bits of spider and detritus that there was in the focuser. These telescopes are great in that everything comes apart with ease. Unusual for this day and age.

The OTA was now just a metal tube. Scary stuff! Could I get it all back together without screwing up and/or breaking something? I’d got a handle from the ever useful WDS Components. Curved brackets to fit the inside of the OTA made earlier and blacked with blackboard paint. I drilled holes in the OTA using a step drill after drilling a pilot hole. Far easier to do than I thought, the step drill cutting through the thin steel like butter all in one go. 

If you look down the OTA you can see why I decided to flock the whole OTA. There are some white marks that I just could not remove. Even after cleaning and scrubbing. And the more I cleaned the more shinny the inside of the tube became. What made these white stains I haven’t a clue.

[PeterStudz]

The next day I flocked the OTA with flocking material from FLO. This was done in 3 sections using 2 rolls. Top and bottom then finally the middle section. I got this method from another forum member - @Spile - thanks for that! I went slowly but it was easier than I expected. And the flocking material wasn’t as sticky as I imagined. I found a head torch useful as looking down the tube is just so dark. After I’d finished I cut holes for the focuser, bolts etc using a very sharp surgical knife. Then finally vacuumed  the inside of the tube in order to remove any loose fibres. Hopefully you can see the improvement. 

For good measure I also flocked the inside of the focuser drawtube. It was only a 5 minute job.

I had also planned to give the primary a wash. But it wasn’t that dirty and in the end a chickened out and just gave it a quick rinse. More than it needed anyway.

Putting everything back together went well apart from one issue. The night was going be clear and I wanted, if possible and to ease my mind, test the telescope out ASAP. The only issue I had was that the mirror clips weren’t quite tight enough and I spent a good half hour chasing the donut around before it clicked. So out with the primary mirror cell once again. It’s not removing the cell that I find tricky it’s getting it back in again. This time I got it right. 

Testing the telescope on the moon revealed that all was well. And I love the handle - no more slippery “fish” - every Dob should include at least one handle! 

[PeterStudz]

Just a few more finishing touches. I like to use a simple RDF with a RACI finder scope. Out of scraps (metal bracket & ply) I made a bracket for a little RDF. Painted and bolted to the RACI bracket. It’s simple, light, tight together and quick to swap from one to the other.

I also added an eyecup to the finder. It’s a DK-19 rubber eyecup for NIKON DSLR viewfinder. Tight fit but then it’s better that way. Why oh why these can’t be included, or even offered as an extra, I have no idea. It’s so much more comfortable. But more than that I often, not always, observe wearing glasses. My daughter always does. My glasses cost £220 and for obvious I really don’t want a solid hard tube rubbing up against the lenses.