New Scope - Darkstar 10" - Restoration Project

[Stub Mandrel]

19 minutes ago, Bruce Leeroy said:

have the 8.75" copper colour version,

Great, thanks Bruce. The link I gave earlier says they can recoat your primary for £54 plus postage.

[Stub Mandrel]

20 minutes ago, AndyH said:

Note the extremely strong springs. Once collimated it stays there. Also, where the name sticker is, that's a piece of steel from a length of round bar, for balance. I can see the tooth marks where it was cut! The board is 19mm(3/4") thick.

I think it will be easy to modify my lens cell to match that just by adding clips. They look like car valve springs!

[Bruce Leeroy]

26 minutes ago, Stub Mandrel said:

The link I gave earlier says they can recoat your primary for £54 plus postage.

That sounds tempting, I can't seem to spot your link?

[AndyH]

 

Valve springs? Heh, maybe not quite but not far away. Incredibly difficult to compress between the fingers

That's a good price for aluminising. I've been out of the loop regarding that stuff. Can you or anyone else recommend places to use??

 

Cheers, Andy

 

[Bruce Leeroy]

59 minutes ago, AndyH said:

I've been out of the loop regarding that stuff. Can you or anyone else recommend places to use??

https://www.galvoptics.co.uk/optical-components/telescope-products-andamp-services/telescope-mirror-coating---primary/

http://www.orionoptics.co.uk/OPTICS/mirrorrecoating.html

I found these 2 links some time ago but have never used their services.

[AndyH]

I think i may have used Galvoptics about 10 years ago?

[Stub Mandrel]

1 hour ago, Bruce Leeroy said:

That sounds tempting, I can't seem to spot your link?

http://www.scientificmirrors.co.uk/Aluminising.html

 

[sloz1664]

7 hours ago, Stub Mandrel said:

http://www.scientificmirrors.co.uk/Aluminising.html

 

That's good to know Niel. As and when I need to re-coat the ol'Tal. BTW great purchase on the DarkStar Dob. I'm sure you will fettle it back to it's best... and beyond. Lots of photos on your progress.

Steve

[Stub Mandrel]

Rats, a clear night but I can't try the scope out.

The Lens cell is made of MDF and has split where each of the three screws go in. As a temporary fix I have filled the deep cracks with most excellent "Super 'Phatic" glue which is watery soaks in and is very strong and sticky, then clamped the cracks closed. This should restore the strength enough to take firm (and slightly longer) screws. It will dry overnight.

I've also taken the opportunity to drill two new mounting holes so they are now evenly spaced at 33.1mm. This should better centralise the mirror in the tube.

The base wouldn't rotate smoothly. the MDF of the bottom of the upper part of the base (if that makes sense) has swollen with water absorption over the years making it convex by enough to rub and stop more than two teflon pads working at a time. I tried to peel off the formica on this surface, went well until right at centre, when it split ?

I will need to remove the base and fit a square of ply instead, or maybe just a 1/4" thick ring of something hard to replace the formica.

I've measured up the holes for the finder mount, I should be able to 3D print a nice dovetail socket to fit neatly in the same place that will take one of my guidescope finders.

[Stub Mandrel]

The temporary repair to the mirror cell has gone well. It refitted it using the new holes with just a little persuasion as the tube had taken a minor set out of round. A peep down the end showed the mirror with an even gap all round instead of slightly offset ?

The focuser is fitted with a washer for packing. I suspect this may not bee needed with the mirror in the right place, but I won't fiddle with its alignment until I have the recoated mirror assembled into a new cell, especially as I may build a new focuser or at the least do a hefty tuning of the existing one as it is a bit worn.

Collimation was way off, but took hardly any time at all to sort with my home made laser collimator. The three brass hex screws on the secondary moved easily, and it appears to be sprung which made adjustment straightforward, although as I can see no point in putting a centre spot on the mirror in its present state I had to estimate the centre. It's not far off now compared to about 2" off before. Adjusting the primary literally took 30 seconds to get the beam straight back up the pipe from not even hitting the secondary.

If I can sort the az bearing I will hopefully get some clear sky tonight for a tryout before I remove the mirror from the cell ready for recoating.

[NGC 1502]

 

Hi Niel, one of the great things about basic Dobs is the way simple DIY fixes work so well. About the only thing we can’t do is re-aluminise the mirrors. I’m really fortunate to have Galvoptics just 10 miles away, a family firm I’ve used several times with no problems.

You could use furniture sliders as a temporary substitute for Teflon, would get you up and running. Yet another simple low tech fix........?

Ed.

Edited August 1, 2018 by NGC 1502

[Stub Mandrel]

12 minutes ago, NGC 1502 said:

 

Hi Niel, one of the great things about basic Dobs is the way simple DIY fixes work so well. About the only thing we can’t do is re-aluminise the mirrors. I’m really fortunate to have Galvoptics just 10 miles away, a family firm I’ve used several times with no problems.

You could use furniture sliders as a temporary substitute for Teflon, would get you up and running. Yet another simple low tech fix........?

Ed.

I ordered some teflon furniture sliders just in case, but they are OK, its the sheet of formica they slide on I broke ?

Battling with my VAT return or I would head out to B&Q...

[Stub Mandrel]

Result!

My steplad just got in. he used to fit kitchens and he's found me a door with super smooth and flat laminate on both sides. Cut to size and soon to replace the base of the upper unit ?

[AndyH]

1 minute ago, Stub Mandrel said:

Result!

My steplad just got in. he used to fit kitchens and he's found me a door with super smooth and flat laminate on both sides. Cut to size and soon to replace the base of the upper unit ?

[sloz1664]

14 minutes ago, Stub Mandrel said:

Result!

My steplad just got in. he used to fit kitchens and he's found me a door with super smooth and flat laminate on both sides. Cut to size and soon to replace the base of the upper unit ?

Project's on it's way then.. I saw your thread on the fabulous manufacture of your Focuser, as yet to be aluminised. Now there's a project....Focuser for the DarkStar. It would look quite fetching in Cobalt blue.

Steve

[Stub Mandrel]

1 minute ago, sloz1664 said:

Project's on it's way then.. I saw your thread on the fabulous manufacture of your Focuser, as yet to be aluminised. Now there's a project....Focuser for the DarkStar. It would look quite fetching in Cobalt blue.

Steve

I got a pair of Vixen rings for £13 off Ebay (including postage!) to fit the little scope. I've stocked up on distilled water so all I need to do is cast some lead electrodes and dive in!

[sloz1664]

I looked at dabbling with aluminising, but since retiring as an Engineering Manager I've lost my access to a toolroom and all the goodies I could manufacture. So it would have been a wasted exercise. Still I have kept in contact with all the Engineering and Tooling firms I have dealt with over the years.

Steve

[NGC 1502]

2 hours ago, sloz1664 said:

I looked at dabbling with aluminising, but since retiring as an Engineering Manager I've lost my access to a toolroom and all the goodies I could manufacture. So it would have been a wasted exercise. Still I have kept in contact with all the Engineering and Tooling firms I have dealt with over the years.

Steve

 

It’s possible to aluminise, but you probably know the kit is very expensive, and specialised. An astronomy venue I used to visit ( Fieldview astronomy B&B ) had the kit, but they had issues with uneven coatings, and the pump took hours to produce the required vacuum in the coating chamber. Not sure, but I think they gave up on the idea. They also changed the business to cater for the birding community when the starcamp moved from Thetford to Kelling Heath and greatly reduced the numbers of astronomy visitors.

Ed.

[Stub Mandrel]

First light! Only half an hour at twilight.

The base isn't very smooth, probably the battered old pads. I will replace with the teflon glider pads when they arrive.

Finding targets with no finder is 'interesting' so I had to use low power 32 and 40mm plossl most of the time. Jupiter looked great at about 55x with the moons as sharp points in a blue sky, although so bright I could see no detail. cloud came in so I found Vega and tried to get the double double. Lots of faint stars almost everywhere I looked even in blue sky. The focuser has tight spots and although I found a pair of stars I couldn't split them again in the 10mm EP, but simulating the view in Stellarium they were much to close together to be the double double.

Saturn then appeared as it was getting darkish and looked tiny but perfect, even though far from properly dark Titan stood out really clearly! Saturn hid behind a roof before I could focus the 10mm ep on it. The ability to drag the scope around the garden to keep a low planet visible contrasts with the GEQ - but when aimed so low down it's tough finding planets above roofs!

I tried the 18mm ortho EP that came with the scope on the stars left behind by saturn. I didn't find eye relief an issue even with my glasses on. I'm no expert but my impression was like looking at stars through a hole or window, they seemed tiny but dead sharp.

Then it just got too cloudy before it was even properly dark.

Main impressions:

• Focuser is rough as a badger's bottom at the moment, not helped by rack being loose!
• If I can get AZ as smooth as ALT it will be very easy to point.
• I need an EP rack hung on the base!
• A mirror can look absolutely shot and still deliver good views. I suspect it's going to be ace when recoated.
• Decent finder is essential. I'm printing a new finder bracket now!

 

[sloz1664]

13 hours ago, NGC 1502 said:

 

It’s possible to aluminise, but you probably know the kit is very expensive, and specialised. An astronomy venue I used to visit ( Fieldview astronomy B&B ) had the kit, but they had issues with uneven coatings, and the pump took hours to produce the required vacuum in the coating chamber. Not sure, but I think they gave up on the idea. They also changed the business to cater for the birding community when the starcamp moved from Thetford to Kelling Heath and greatly reduced the numbers of astronomy visitors.

Ed.

Hi Ed

It must be my age. What I meant to describe was anodising and not aluminising. Being involved in Engineering for 49 years, you think I should know better.

Steve

[John]

Sounds very promising Neil

I've found my old Dark Star catalogue now - it's mostly photocopied paper but for the 1980's that was as good as it got !

I'll scan the relevent pages when I get a moment and PM them to you as you might be interested. Dark Star were based in Shropshire at the time of my catalogue - I don't know if that was earlier or later than their Welsh address ?

 

[Stub Mandrel]

Thanks John.

I've just stripped the focuser and cleaned out the gunk and readjusted it. It's nothing exceptional;, but is now quite smooth.

Edited August 2, 2018 by Stub Mandrel

[AndyH]

Excellent !

 One step at a time and you'll have a cracking scope. I've never really heard a bad thing about the mirrors on the Dark Star scopes of this era.

I reckon most folk opted for the higher grade optics, as I've noticed, there wasn't a huge difference in price from std(1/4pv) to higher(1/8pv) back then.

Keep up the good work

[John]

10 hours ago, Stub Mandrel said:

Thanks John.

I've just stripped the focuser and cleaned out the gunk and readjusted it. It's nothing exceptional;, but is now quite smooth.

PM sent

[Doc]

Nice buy Neil.

A darkstar dob was the first dob I ever had way back in 1984 I think. It was a great dob, 8" I think. I changed it for a 10" Hardin dob.