The collapsible dob - that wouldn't collapse...

[Sgt Pinback]

I had a fantastic first night observing experience (report on beginner's observing forum), but I had an issue when I was collapsing the telescope to come back inside.

Basically, it would not collapse - it was as if both rails were glued solid. The rails slide out until there is a click, I presume a spring loaded bearing clicking into a groove at full extension. But despite undoing the lock nuts, it would not budge. I made sure I was pressing centrally and not forcing one side only, but nothing. Then I gave it a slap with the palm of my hand, to shock it into movement, but thought 'Yikes - What am I doing - It's a blooming telescope!!'.

So I brought it inside still extended and let it warm up again indoors. I wonder if it was something to do with the temperature of the rails or sleeves? It really wasn't that cold. After about 15 minutes I tried again and it did start to move under pressure, but was very stiff. Maybe half an hour later It was all OK again.

Is this a common problem with collapsible dobs? Should I expect this often? Or is it because this one has two rails instead of three? The scope seems well made, better than I expected and I am usually careful with things. So a bit of a mystery...

Any ideas and tips welcome! Thanks

[cantab]

Does sound like thermal contraction making the thing sieze up. Can't help you on how to fix it, but I suspect unless you somehow have a lemon others will have encountered and addressed the issue.

[Guest]

Although the lock nuts are undone check the tensioning nuts at the bottom of the tubes themselves; black on an SW flex tube

[Pappy Nick]

Hi there fellow Heritage owner

I get this problem all the time with mine. Admittedly I can get it to collapse eventually, but with a bit more force than was needed to extend the damn thing. I have found though that this problem's getting better with time.

Hope this helps

[Sgt Pinback]

OK, thanks for the replies...

I will check the tensioning nuts, although indoors, the tube extends and retracts smoothly.

It must be that the rails and sleeves are a different material. I think the sleeves and frame are aluminium, but the smooth rails could be a different alloy. It sounds like I will have to live with it and resist the urge to give it a clout!

Thanks again

[Davidv]

Haven't got a clue about your Heritage as I haven't got one, but I see from your "sgt pinback" name you must be a fan of Dark Star - one of my all time favourite films.

[Sgt Pinback]

Yes Davidv,

Ah, Dark Star - it was one of those occasions when you find yourself watching a bizarre late film, wondering 'What the hell is this?'

It was 2001 meets Alien, with a sprinkling of Kelly's Heroes hippy. There are some great lines in there that are still pretty unique. "Sgt Pinback, it's time to feed the Alien" (a beachball) and "Hello, I'm Bomb number 20" are hard to forget, along with a spaceman surfing into re-entry burnup - to the tune of Benson Arizona...

.

As a postscript to the collapsible dob problem, I was out last night and the same thing happened again. Easy to extend, but the devil to collapse again. Hey ho.