Orion Optics 8” f8 - the repair job

[Stu]

I plucked up the courage to start checking over my poor 8” f8 today after its nasty little accident described here.

Well, I’m quite optimistic now that the scope can be recovered relatively easily. When I removed the front ring, the whole tube naturally sprang back into a more normal shape with no creases at all. It was as if the impact had caused a deformation in the ring which was forcing the tube out of shape.

I have removed the secondary spider, which will straighten up with no problem, and have been able to work the tube back into a pretty good shape now. I have a spare front ring from an old 8” f6 tube which fits in, and brings the tube back into good shape when it is fitted.

I am having a think about fitting a Baader SteelTrack focuser which I bought for another project so that I have dual speed focusing, something I think the scope would really benefit from as it is all about high power and sharp focus.

So, all looking positive so far. I may well remove and wash the primary whilst I’m at it, but will report back on this thread as I progress.

[DaveL59]

Result! It looks way better than when first seen I bet  

Figured the outer ring would be holding the deformed shape as the tube itself is pretty thin material. Had that been my TAL-1 it'd either have just dented whatever surface it hit or be some serious metalwork to reform it back to round. You might find a couple extra screws at the locations where it still deforms will pull it out to the new ring and that'll be that. 

Edited May 24, 2020 by DaveL59

[R26 oldtimer]

That's great news Stu! You're almost there!

[Second Time Around]

You must be so relieved, Stu.  I can only imagine how you must have felt! Hope it's sorted soon.

[AdeKing]

Fantastic news Stu, doesn't look nearly as bad now you've got the front ring off.

You must be very relieved.

Hopefully it won't need too much more work to get it back into commission now.

[CraigT82]

What a result! Looks pretty good to me... I mean theres no real reason a scope tube should be round anyway! 

[markse68]

Great news Stu!   Lucky in a way that the tube is so thin and flexible. My car used to attract drunken louts and a few times I came out to find the roof and bonnet caved in 😢 Like your tube though it only took an equal and opposite shove and they popped out with minimal evidence of damage 👍

Did the spider adjusters come like that or did you fit the brass screws and thumb nuts?

[Nigella Bryant]

Great news, glad it's been fixable, great to see. Well done.

[Stu]

15 minutes ago, markse68 said:

Did the spider adjusters come like that or did you fit the brass screws and thumb nuts?

That’s how it came Mark, seems quite a good setup.

[markse68]

9 minutes ago, Stu said:

That’s how it came Mark, seems quite a good setup.

Nice! Now you’ve got it out I found on my one which is quite similar that adding half nuts gently tightened against the ends of the vanes dramatically stiffened the whole structure- not sure if it makes much difference in use and of course an additional obstruction/source of diffraction 🤔 but at edge and I’ve not noticed detrimental effect

Edited May 24, 2020 by markse68

[Stu]

Well the spider straightened out very easily 👍👍

[andrew s]

Going well, hope it continues well.

Regards Andrew 

[Gina]

Just seen this!!  PHEW bet that was a gut-wrenching experience!!  Glad it isn't as bad as it first looked.  Lucky you had a spare front ring. 

Good luck with the repairs.

[MarkAR]

OMG, that has really surprised me at how well the tube rounded up. Glad there were no creases.

[JeremyS]

Looking good, Stu.

Maybe a side line in panel beating beckons?

🙂

 

[Alan White]

Great job Stu, lucky you had the other ring.
That makes you realise how distorted it was with the two rings alongside each other.
Great job, I am relieved for you.

 

[Stu]

I’ve just taken the primary cell out of the scope, with the aim of giving it a clean. It has insulating tape around the cell attached to the mirror. Not sure what purpose this could serve? Will have to remove it to get the mirror out anyway.

More importantly, the clips are touching the mirror quite tightly so it would seem to make sense to drop the mirror a fraction to give a little space. Would people agree? The mirror is supported on threaded plastic rods of some sort so if I back these off evenly then the mirror should drop back from the clips.

[markse68]

The tape is to stop the mirror rotating- losing collimation Stu- good idea- I put gaffa on the back of mine but my cell is open at the back. Gaffa is stickier than insulating tape which tends to suffer the dissolving adhesive syndrome from plasticisers in the PVC- May be worth an upgrade

yea back those screws off a little so the mirror is free to breath- sounds like you didn’t have an issue but pinched optics aren’t a good thing! Although it looks like there are felt pads in between the retaining tabs and the glass so it’s probably not applying much pressure at all

Edited May 30, 2020 by markse68

[Stu]

1 hour ago, markse68 said:

The tape is to stop the mirror rotating- losing collimation Stu- good idea- I put gaffa on the back of mine but my cell is open at the back. Gaffa is stickier than insulating tape which tends to suffer the dissolving adhesive syndrome from plasticisers in the PVC- May be worth an upgrade

yea back those screws off a little so the mirror is free to breath- sounds like you didn’t have an issue but pinched optics aren’t a good thing! Although it looks like there are felt pads in between the retaining tabs and the glass so it’s probably not applying much pressure at all

Thanks Mark. The cell also has gripping plastic grub screws from the side, would they not stop any rotation? Will put small bits of gaffs tape on if it needs it.

The mirror cleaned up very well without any need for cotton wool. I would always rather leave untouched if possible and the four chunks of funk came off quite easily under running water and with a bit of a jiggle under water after a good soak.

[markse68]

Hi Stu, from what I’ve read on other forums where they can get quite obsessive about these things (😉) the mirror should be absolutely free of any even minute strain- eg even ptfe pads supporting the underside are frowned upon as being soft they might deform into surface irregularities in the glass and cause strain on the mirror when changing altitude! So your lateral screws shouldn’t be tight enough to grip the mirror and therefore won’t prevent rotation. Whether or not this would create observable real world issues is 🤷‍♂️ Probably more an issue with the gargantuan thin mirrors they tend to use! I’ve got my mirror rattling loose in there with just the gaffa tape loosely applied to stop rotation- my mirror is far from parallel/perpendicular with the back side so it really makes a difference. I rarely have to tweak collimation which I check every time I use the scope and my issues with astigmatism I had last year have vanished, though that was more likely the secondary

 

[R26 oldtimer]

13 minutes ago, Stu said:

The mirror cleaned up very well without any need for cotton wool.

At first glance, I misread that as "steel wool" 🤔😱

[Chriske]

The mirror should be able to move in its holder, just a fraction of a mm. The mirror should, depending on its size, rest on 3, 6, 9,18 or 27 soft pads.
Small clips on top will prevent the mirror from tilting.
We never use glue or whatever to secure the mirror in it's cell either.

[Stu]

45 minutes ago, Chriske said:

The mirror should be able to move in its holder, just a fraction of a mm. The mirror should, depending on its size, rest on 3, 6, 9,18 or 27 soft pads.
Small clips on top will prevent the mirror from tilting.
We never use glue or whatever to secure the mirror in it's cell either.

Thanks very much for that info.

This one rests on three plastic (Delrin?) screws which I assume if fine for an 8”? I have not seen any issues with astigmatism when using it before so hopefully ok.

[Stu]

Gosh, can’t believe it has been so long since I looked at this! Life getting in the way.

Anyway, remembering that another Jupiter opposition is slipping away, I ordered some flocking (5m roll) which arrived today. The f8 tube is quite long and narrow, so a little challenging to flock! I ended up cutting lengths of roughly half the tube length, halving them down the length so they were more manageable, and then hanging them somewhat like wallpaper with the tube upright. This worked very well and I got the whole OTA done this evening. No wastage either, I was expecting at least one piece to go wrong and end up in a sticky heap, but managed to avoid it.

Looks quite dark down the tube, second picture with flash, not too many bubbles I hope.

Anyway, I can now get the scope back together fairly quickly I hope. I plan to upgrade the focuser at some point, I have a Feathertouch I will put on it but need a base plate making up I think, so will use the original until I get that sorted. The only only thing I need to do is spray the replacement top ring black, as it is currently green.

More to follow soon, followed by some views of Jupiter hopefully.

[Moonshane]

Just saw this mate. Ouch. Although I did think it looked like it would be ok with a new end ring.

All looking great to me 👍👍