Help! - Bob's Knobs installation disaster

[Gary M33]

I've had a disaster installing Bob's Knobs to my Meade LX90 10 inch.  I followed  the instructions, and all went well until the last screw.  The last one just would not find the thread, and whilst I played around with this, number 2 pinged out.  Now I have 2 of the screws, which just wont reach the thread.  To make matters worse, the original screws no longer reach either. 

Anybody got any clue what I need to do, because at this stage I feel I've just trashed my scope 

Edited August 20, 2022 by Gary M33

[knobby]

It's a bit worrying that the original screws won't go back in ?

Is the 1 screw that's in place still maybe wound in too far ?

[xtreemchaos]

you need to retap the holes to clean the threads.

[bosun21]

Have you tried pointing the scope towards the ground? This may allow the secondary to drop back into place. You could also remove the corrector plate from the front of your scope giving you direct access to the secondary mirror.

[Cleetus]

Assuming the threads are still ok, which seems to be what you are saying as the screws "cannot reach" threads then maybe two longer screws to bring secondary back towards you. Then try the process again.

[SthBohemia]

1 hour ago, Gary M33 said:

Anybody got any clue what I need to do,

You need to remove the front lens, then remove the secondary holder from the front lens, disassemble it and realign the assembly as it has fallen out of alignment (ie the screw holes where the Bobs knobs go are not aligned with the secondary screw holes. Take care at present as Meade secondaries dropout totally from the holder if all 3 adjusting screws come loose 😞 

Procedure-

Scope facing towards ceiling undo the outer ring (lens) retaining screws, remove retaining ring.

Remove any small spacers centralising the lens assembly, mark position for replacement. NOW-

Stick a paper sticker 10mm by 25mm on the lens AND where it fits into the tube, cut with a scalpel or similar. This is to allow you to replace the lens EXACTLY where it was. I put small file marks on edges of SCT lenses and the tube assembly to facilitate correctly aligning the lens after cleaning the internals of SCT's. Take out the lens with the secondary attached to it...

Remove the secondary assembly from the lens, note where the large washers are positioned. Undo all screws of the secondary assembly making sure that you don't drop the secondary mirror on the floor when removing your last screw holding it in!!

Align the outer screw holes where the knobs go with the inner holes that hold the secondary, feed the 3 screws into position and turn a few times so the unit can be adjusted with all 3 screws properly aligned- Done. 

Replacement of lens  etc etc opposite to disassembly.

May as well clean the main mirror while the SCT is partially apart 🙂 Maybe flock the tube as well??

P.S. Forgot to include- Sometimes the lens may become a little 'stuck' to its main tube fitting (the gasket that it sits on), in which case get an eyedropper and apply some isoprophy alcohol or similar around the outside diameter of the lens, let it soak in then remove the assembly.......

Edited August 20, 2022 by SthBohemia

[Gary M33]

Thanks for the replies, but seeing as I messed up the relatively simple installation of collimation screws, the putting it right part seems well beyond me.  Does anyone know of a telescope repair service in the Lincolnshire area that might be able to help?

 

[SthBohemia]

1 hour ago, Gary M33 said:

able to help?

If you do take it to a repair shop they should be able to do the whole job within 30 mins, that's with a 5 min tea break.

You are not the first to have the problem you have encountered, the operation as i described is not all that difficult 🙂 

If you place the scope on its side and gently roll it and then using some very fine wire it may be possible to centre another screw hole and insert  the screw, if you can do that the 3rd screw hole will be aligned... the only problem being if the screw holding the secondary is tight the assembly wont turn. Untightening the holding screw risks the assembly becoming totally detached...

[SteveWolves]

This happened to me with an 8" LX90 some years back but I only had 1 come out. I put the tube pointing down and gently slackened off the two other knobs till the third was able to get at the thread then had to gently screw all three in a few turns and find someone who helped me collimate.

[Peter-uk]

Quote

The last one just would not find the thread, and whilst I played around with this, number 2 pinged out.  Now I have 2 of the screws, which just wont reach the thread. 

buy two longer bolts to insert and pick up the threads pull the focuser back, then replace the bolts with ypur Bob's Knobs

[SthBohemia]

@Peter-uk the length of the screws has absolutely nothing to do with the problem...

[knobby]

2 hours ago, Gary M33 said:

Thanks for the replies, but seeing as I messed up the relatively simple installation of collimation screws, the putting it right part seems well beyond me.  Does anyone know of a telescope repair service in the Lincolnshire area that might be able to help?

 

Hi Gary, maybe see if you have a club near you 

http://www.astronomyclubs.co.uk/Clubs/Default.aspx?CountyId=49

They can probably help.

[catburglar]

3 hours ago, Gary M33 said:

Does anyone know of a telescope repair service in the Lincolnshire area that might be able to help?

I’m not sure where you are in Lincolnshire but Rother Valley Optics (based in Sheffield) might be able to sort this out for you….and they may be only an hour or two away from you…

[Davesellars]

1 hour ago, catburglar said:

I’m not sure where you are in Lincolnshire but Rother Valley Optics (based in Sheffield) might be able to sort this out for you….and they may be only an hour or two away from you…

I would definitely be doing this...  RVO are actually based in Rotherham (close to Sheffield though) but it's probably only an hour's drive from Lincoln.  Call them first and explain the situation to get an appointment to get it sorted out, install the Bobs Knobs and collimate.  I've never had to get anything serviced by them yet but they've always given great sales service.