Just another Dark Star Restoration.

[Johns22]

About 18 months ago I was asked to collect an 'old' telescope locally which was taking up room in someone's garage. I did so one dark and miserable winter evening finding a blue dobsonian flavour scope which had been stored very badly, without any dust covers. The primary mirror looked in dreadful condition and the OTA was randomly wrapped in old plastic bags. Due to the weather and not knowing the person, I loaded it into the car and brought it home. It then stood in my workshop till now.

Knowing very little about telescopes, I didn't fully understand what I had until very recently when I started searching the interweb for more information. I also (incorrectly!) assumed at the time that the telescope was of the 8 inch variety but having started to dig into it over the past couple of weeks, it's actually a Dark Star 10" dobsonian. I found threads on this group where people have done similar restoration projects to these scopes and I was sold on trying to save it. It'll be fine... 🤑

Earlier this week, I dug it out and removed the primary mirror which I soaked in warm soapy water for a time but it quickly become obvious it was not going to be saved. Unfortunately I didn't take any photo's of how the mirror was initially but you can see from the attached it is very bad even after some cleansing. Next I removed the secondary mirror which looked better but instantly separated from the holder in my hand. I'm surprised that hasn't got intimate with the primary before! 😳 After attacking the primary mirror silicon fixing with a wood saw, both mirrors have now been delivered to Orion Optics for recoating. Roll on 7-10 days when we'll then enjoy cloudy nights for several weeks!

I was also puzzled as to why someone had bothered to wrap the bottom of the OTA in duck tape. Upon removal of said tape it became apparent that the OTA is split from the bottom up for a few inches. I have carefully removed the tape (and subsequently the old sticky residue left over) and it looks like it will repair. 🥴 So I'm going to do the right thing and replicate a hack I've seen on FaceSpace whereby using paper clips and a soldering iron, you can repair most plastic splits. I just can't find any paper clips right now - I'm sure the office will assist here!

I've also purchased a Skywatcher single speed focuser from a friendly chap over on Astrobuy&sell which has turned up this weekend. I must admit I didn't really think about the size of it but it's huge! Much bigger than the existing Dark Star focuser but seeing similar stories on this forum, I'm going to make it fit! I just need a 58mm or 60mm holesaw and some timber to allow me to central the hole and drill out.

Today I have taken the base apart as it tended to move the as one unit when swiveled, rather than the required 2 pieces. I see again from similar threads that some new teflon furniture pads should fix that issue. I'm already browsing the Jungleweb store for said replacements.

I am considering respraying inside the OTA with the matt black paint mentioned elsewhere just to give it that brand new rebuilt look. I'm also impressed with some photos I've seen of others who have repainted the outside of the OTA but that looks like a big job - maybe too big for me. Plus, I'm feeling the 'patina' vibe with this telescope at the moment. Anything can change though right?

I hope to have the OTA repaired and the Skywatcher focuser installed this week. I will post updates as I go.

Any help/guidance/constructive criticism welcome!

 

 

 

[The60mmKid]

Very cool! Thanks for sharing!

[John]

That looks a full on job but worth the effort I'm sure 🙂

I think I've got an old brochure for Dark Star telescopes somewhere - I'll have to look it out !

 

[JeremyS]

Given the condition of that Chevy, restoring the Dark Star newt should be a piece of cake for you 👍🏻

Looking forward to seeing how you get on.

[bosun21]

If I were you I would definitely flock the inside of the tube while you have it completely disassembled. It’s a felt like material that adheres to the inner tube and comes in broad strips. First light optics stock the material required. You said at the start that you know little about telescopes. Do you know how to collimate the mirrors? On their return from Orion optics they will have to be aligned with each other and the new focuser tube. There’s a multitude of videos on YouTube explaining how to collimate a reflector. I would also replace the Teflon pads with a lazy Susan bearing. I’ll be following your restoration  with interest. Thanks for posting.

Edited July 18, 2023 by bosun21

[neil phillips]

I had the 8.3/4 Darkstar many years ago great scopes. Can you see any initials on the primary anywhere ? David Hinds made the mirrors for some of them. A very respected mirror maker. I met the guy who made them when i was down in wales many moons ago. A nice bloke loved hes astronomy. I second the flocking advice. When you finally test the scope let it cool outside for a hour or longer to give its best. Some of us have fans on the bottom to speed up the cooling process.

Will watch this thread, nice find

[Johns22]

Thanks all! It sounds like flocking is the best choice then. I have seen people flocking scopes in the past but I didn't appreciate it's the preferred option. 

I didn't see any markings on the mirror before I took it to Orion - they guy there did also speak positively of it though when I mentioned it was out of a Dark star.

On collimation, I have done this in the past. But not believing in my own skills, I took that scope to my local astronomy club where a helpful chap re-did it. He told me that I did have it collimated but not in the way he would have done it. I was then baffled in a subsequent discussion in the same room whereby some opinions were lasers were the best and others believed a simple collimation cap was always perfect. Do I buy a laser (which also needs collimating?) or a cap?

I haven't ordered the teflon pads yet so will take a look at that Lazy Susan bearing this evening.  Update: Just had a quick look and this appears to be a great piece of advice thank you @bosun21 - it even got a guy wondering if these could replace the yellow plastic rings on the scope (I really dislike the look of those)!

Thanks again - I always appreciate advice or challenges on what I think is right!

Edited July 19, 2023 by Johns22

[PeterStudz]

This looks great! I restored an 8” Dob as a beginner and I really enjoyed the experience. I’d definitely go for flocking. It was easier than I thought (I did the while OTA and things like the focuser  draw tube) taking about 1/2 a day.

Personally I’m not a fan of a lazy suzan bearing. After some experimenting I used Teflon sheet like this fro eBay…

https://www.ebay.co.uk/itm/123981266447?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=4pKUCQI7T5S&sssrc=4429486&ssuid=I8jCpZsmREe&var=&widget_ver=artemis&media=COPY

That would be enough to get it working and see how things are. But it looks like the top surface is smooth? Which isn’t ideal. I found this to be ideal. Cheap and easy to cut too. But of course its up to you…

 

Edited July 19, 2023 by PeterStudz

[Johns22]

2 hours ago, PeterStudz said:

This looks great! I restored an 8” Dob as a beginner and I really enjoyed the experience. I’d definitely go for flocking. It was easier than I thought (I did the while OTA and things like the focuser  draw tube) taking about 1/2 a day.

Personally I’m not a fan of a lazy suzan bearing. After some experimenting I used Teflon sheet like this fro eBay…

https://www.ebay.co.uk/itm/123981266447?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=4pKUCQI7T5S&sssrc=4429486&ssuid=I8jCpZsmREe&var=&widget_ver=artemis&media=COPY

That would be enough to get it working and see how things are. But it looks like the top surface is smooth? Which isn’t ideal. I found this to be ideal. Cheap and easy to cut too. But of course its up to you…

 

Thanks for this option. Just to be clear, you have a sheet of 4mm Teflon on the base and then the textured aluminum on the top surface?

I understand what you're saying in regard to the bearing - I guess a low friction bearing could become frustrating when you're on target and a small breeze or sneeze causes unwanted rotation. I guess if the base wasn't perfectly level either, you would have to hold on to the OTA whilst viewing to stop rotation?

[bosun21]

If you have no central screw on the base which is a tension adjustment screw then the Teflon method will be better suited for your scope. 

[PeterStudz]

5 hours ago, Johns22 said:

Thanks for this option. Just to be clear, you have a sheet of 4mm Teflon on the base and then the textured aluminum on the top surface?

I understand what you're saying in regard to the bearing - I guess a low friction bearing could become frustrating when you're on target and a small breeze or sneeze causes unwanted rotation. I guess if the base wasn't perfectly level either, you would have to hold on to the OTA whilst viewing to stop rotation?

The Teflon sheet that I bought was a relatively small rectangle. I cut into squares with a hacksaw and drilled a hole in the middle to make pads (see picture). It would basically be a replacement for what you have. The textured aluminium is on the top surface and just tacked on with a few very small wood screws. Just enough to keep it flat and keep it fixed to the base. Personally I’d just clean it up and replace the pads. Then see how it performs - you might find it perfectly satisfactory.

Many of the commercial Dobs with Teflon pads just have them running on some sort of smooth surface. This can be a bit ‘sticky’, especially at high powers. Eg when trying to move a target into the middle of the FOV it’ll jerk and overshoot. Ideally you want enough of what’s called ‘stiction’ (the holding force that must be overcome before the bearing can begin to move) to change eyepieces etc without risk of the OTA moving, but at the same time will move off smoothly without jerking and without overshooting. I tested mine by having Mars at a silly magnification of around x400 and I could still center it smoothly. And when stopped it stayed where it was left. 

The lazy suzan that I tried (could have just been too cheap) was too free running. And there was some unevenness at higher power. To increase tension I needed to tighten and fiddle with the centre bolt, but it was never as good as the Teflon pads plus textured aluminium. Again, it could have just been the lazy susan that I bought off the internet. 

[Johns22]

I've managed to spare some time this evening trying to move forward with the project. My fix for the split in the OTA failed unfortunately. It seems the OTA is made from some sort of fibreboard rather than plastic. So I've cleaned up the surface around the split and used Gorilla glue to try and secure it and stop it spreading any further up the OTA. I've also measured up for flocking material - it does seem like a good time to do this. I've been cleaning up and measuring the teflon on the base ready to order that too.

I had an email this morning from Orion Optics to say my mirrors are ready to collect. Very impressed with that quick turnaround - they will be collected in the morning.

Collimator is on the way!

I'm not sure now whether to stick with the original focuser or change to the Skywatcher. The reason for my doubt is that the Skywatcher focuser tube sits a long way into the OTA compared to the Dark Star original (see pictures). I'm also concerned that I won't achieve focus without altering where the mirror mounts. Any thoughts?

 

[bosun21]

I would definitely fit the new focuser as the drawtube protruding into the tube will be retracted to reach focus. The old one looks worse for wear. I would also fit some sort of strap around the tube where the crack is for extra support.

[PeterStudz]

If you haven’t already it’s worth having a good search on this forum. I found a wealth of info on here when I worked on my telescope. Sometimes I had to try and search multiple times before I found what I was looking for. Here are a couple of examples I found which might help. The first obviously has an upgrade to the focuser which might be reassuring…

 

You could try and contact the post authors. Some people don’t come to the forum often or won’t see a post. There must be others on here who have some Dark Star knowledge.

It would be interesting to know what the tube is actually made of. This would help with selecting glue, flocking, drilling holes etc. the paint is certainly Hammerite, which of course is still available although the formula has changed (more environmentally friendly) over the years. 

I’d certainly at last cover that crack and do something to stop it spreading. My DIY experience of cracks is that however much filler/sanding/painting  I undertake the crack is always still somewhat visible. As suggested some sort of strap would work. You could even make it look part of the design. I made a dew shield out of very thin veneer. Go around with some of that plus glue and it works out very thin and stiff. And it’s easy to work, sand and paint with just about anything. 

 

Edited July 21, 2023 by PeterStudz

[Johns22]

I've made a little more progress today - and have collected the mirrors from Orion Optics on Friday. A 4 day turnaround was pretty impressive and the mirrors look excellent!

I have mounted the Telrad finder properly, rather than it being stuck on with sellotape! I have also purchased some matt black spray paint and painted the spider and other secondary mirror fixings. The flocking material for inside the OTA has arrived from FLO but I want to drill out the hole for the new focuser before I fit that. Hopefully I can get the correct holesaw and some bathroom silicone sealant to attach the mirrors early this coming week so I can keep the project moving. Once the focuser is mounted, I will give it all a good clean, remove all the nuts and bolts into the OTA and get flocking!

I'm trying to find something suitable to act as a band around the bottom of the OTA where it has previously split. The resin I have used has made a great job of repairing the split but it would be nice to have something additional. I have thought about a duct clamp which could also act as somewhere for magnetic weights to be attached for balance once it's all together.

 

 

 

[bosun21]

Be careful when siliconing the mirrors in place that you position them properly. I would use a good double sided tape to check that collimation is achievable and once ascertained mark the position with a marker and silicone them in that position.

[Astrobits]

Cracks are very difficult to fill to the very point of propagation. So they are likely to continue after you think that you have dealt with them. The best way to stop a crack is to drill a hole, centered at the furthest point of the crack, and then fill and finish as you want.

Nigel

[doublevodka]

On 23/07/2023 at 15:27, Johns22 said:

Hopefully I can get the correct holesaw

@Johns22 if you get a set of holesaws there might be an easier way to centralise the hole.

Get one that matches the current hole and put that inside the larger one, this video explains it a bit better than me

 

Good luck with the rest of the rebuild, I suspect it'll be a very nice scope once completed 👍

[Johns22]

I've finally managed to spare some more time on the Darkstar scope this evening. I think I now have everything here to complete the project, it's just a matter of time...

Tonight I finally put my brave pants on and drilled the OTA for the new focuser fitment. I really wanted to follow the video above but I didn't have the right sized holesaw to use as the guide unfortunately. Therefore I had to revert back to mounting a piece of wood and finding centre with lots of measuring and double checking. Thankfully all went smoothly and the focuser fitted perfectly. I've since dismantled the OTA completely to give it a good clean down. I know I said I didn't want to paint it and I still don't want too but I have found a potential cool alternative. I have purchased some vinyl wrap from eBay and I intend to wrap the OTA to make it look a little different - and make it mine I suppose. This means I will be painting the mounting box and the swivel base just to smarten the whole thing up.

I'm not sure how much further I'm going to get over the next week as I have my daughters birthday followed by a long family holiday but I would at least like to get it wrapped before I go - to see if I like it! 😁

Thanks again to those who follow this project!

[Marvin Jenkins]

Can’t take my eyes off the Chevy. Are you proposing to wrap that classic scope in some kind of pixel urban camo?

Can you not find a wrap that is like the original finish. I still think the best finish for anything metallic is Parkerisation.

That weird micro crinkly dull olive that was used on camera bodies in the fifties.

I f you wrap the scope in that then you have to wrap the Chevy to match.

M