15 replies to this topic

[cyberduck]

Hi,

 

I screwed up. In a litteral kind of sense.

 

While trying to figure out if I could put a focus motor on the macro focus side of my focuser, I screwed a screw too far mindlessly assuming it would stop when it reached the axis. It didn’t, instead it got loose inside the focuser.

• While I can manage to get the screw aligned with the whole and get the right allen key in inside the head of the screw, it seems impossible to screw the screw back up through the hole.
• The macro focuser knob does not come off when pulling hard and it does not seem to be locked by any screws, and except for three screws on the micro focus side, there are no more screws to unscrew on the thing.
• Loosening the three screws on the micro focuser side does not seem to make a difference. I still can’t get the macro focus knob loose from the the main body.

 

Next steps I can think of are…

 

• Use force to try to pry off the macro focus knob in the hope of getting to the lost screw.
• Align the screw in the hole, put super glue at the tip of the allen wrench and try to screw it back up.
• Contact the vendor and hope they know how to deal with a situation like this.
• Give up and just buy a new focuser.

Before I doing something rash or expensive, any suggestions what to do?

 

I have no idea what brand the micro focuser is, but it is a 2.5” rack and pinion focuser that came with the TecnoSky AG70 Quadruplet APO bought in Switzerland.

 

/Chris

[scopewizard]

That screw is a cap screw to cover the hole in case of dirt.

If you rotate the knob slowly, you should see inside same hole the other screw holding the knob.

If you can loosen it and the knob will come off.

 

Good luck and don't force anything.

Edited by scopewizard, 18 May 2025 - 10:50 AM.

[GalaxyPiper]

DOAH....

 

I can relate to the frustration. Just take it slow, and don't force anything. 

My first thought is to turn the hole upside down, lay on my back and use a bright head lamp and a sewing needle and try to get the grub screw alighted and maybe started again.

 

After a couple of hours of that, I would go to Cloudy Nights and ask for help...er, so here you are...

 

Like Scopelizard said above, rotating the knob while looking down the hole you will see another grub screw come into view. Use another Allan wrench and Loosen the screw and the knob should come loose. Then the first grub screw will also come tumbling out.

 

Make sure you do this in tall grass or deep piled carpeting in the house. That will make it more fun and challenging to look for the tiny grub screw. Using magnets would be cheating, so no points given.

Edited by GalaxyPiper, 18 May 2025 - 11:12 AM.

[cyberduck]

Waiting for anybody replying to my cry for help, I went for the thing with superglue - and surprisingly it worked!

 

When I came back here, I see that it was not one of the recommended options...  :-)

 

I guess getting the macro knob off is the right thing to do. Next time...

 

Thanks for the help!

[rainycityastro]

It appears to be a focuser made by Kasai trading. Am I right? I had the EXACT same issue with that focuser. But there is an easy way to fix it. The knob is affixed with an internal screw, You can disassemble the focuser pretty easily once you know how. I would not have recommended the superglue approach. You risk gumming up the inside of the precision mechanism.  Reach out to me with your email by PM and I will send you the document. I am unable to attach it here.

I would open it up and clean it with acetone and regrease it gently. It is a beautiful focuser. IME, every bit as good as feathertouch. 

Edited by rainycityastro, 20 May 2025 - 04:32 PM.

[rainycityastro]

Managed to attach the image. Here is how you disassemble that focuser.

Attached Thumbnails

• 

Edited by rainycityastro, 20 May 2025 - 07:17 PM.

[K-night]

Here's a great tutorial created by Polyphemos.

[Procyon]

You guys feel like helping another victim of "small hex screw falling inside focuser disease"?

 

I bought a used scope and heard the shaking of a tiny screw within the focuser. I read this thread and helped me understand more. I looked at all the hex screws and noticed one had been replaced by a regular tiny straight line screw type instead of the hex types around and near it. I'm guessing the previous owner accidently dropped it the same way as the OP and who knows what he might have gone threw to take it out, in the end he probably just replaced it. Honestly, I don't really care much if it remains in there, pestering me every time I lift the scope, but if you guys have any sound ideas, I'll gladly try them. 

 

The focuser is a 2" Stellarvue Crayford type. I could be wrong about that screw being added though, I'm lost to be honest lol.

 

 

 

 

 

 

Edited by Procyon, 21 May 2025 - 11:43 AM.

[rainycityastro]

Almost all focusers use this elegant trick to keep outside screws to a minimum. There is an outside screw to protect the overall mechanism. But the screw conceals an inside screw that passes through the outside threaded hole to operate the inside screw. 

It will take a bit of figuring out for your specific focuser. See the photograph I attached above to get an idea of how this mechanism works.

 

All these focusers are made in the far east so they are all metric Allen head screws. Which simplifies things a bit.

Edited by rainycityastro, 21 May 2025 - 12:17 PM.

[K-night]

I would follow the procedure outlined in post #7 link. 

 

A Crayford has larger gaps between shaft and body. You may only need to remove the focuser from the scope, the drawtube from the focuser, and then tap the focuser around to see if the screw will fall out the opening. If the screw is blocked by a bearing or cup race, follow the disassembly procedure in the how-to. It appears from your images the Stellarvue screws are even easier to access.

Edited by K-night, 21 May 2025 - 12:21 PM.

[GalaxyPiper]

These Crayford Focusers are actually easy to dissemble. If you haven't done it before it can be intimidating, with mental alarm bells ringing and red lights flashing.  

 

But relax. Like anything. take it slow, and make notes, even to the point of counting the number of turns it took to take the screw out or make it "release".

 

Compartmentalize everything with tags. you can use a egg crate for this job and write right on the crate where it came from.

 

Slow and thorough clock makers, engine mechanics, and bomb disposal techs know this.

 

Then when it comes time to reassemble, just do everything in reverse.

 

Just convince yourself that you are the Doctor of your domain, be organized and clean, and quiet please.

 

No cats allowed, as they have a tendency to do gravity checks on anything loose on maintenance benches, tabletops, and counter tops.

 

Do not take anything apart that may have spring tension or hydraulic tension behind it, as it will be launched across the room and roll under refrigerators, dishwashers, washing machines, dryers and benches...oh, and under any vehicles.

 

Always wear safety glasses for the same reason, unless you like playing the pirate every Halloween, or weekends and weekdays...for a very long time.

 

A cow magnet on the end of a stick does wonders locating and retrieving metal items...like grub screws.

 

Ace Hardware sells a aluminum pole with a flat magnet on the end for things like this. it saves the knees.

 

Remember, experience is the best teacher...

Edited by GalaxyPiper, 21 May 2025 - 02:01 PM.

[Procyon]

These Crayford Focusers are actually easy to dissemble. If you haven't done it before it can be intimidating, with mental alarm bells ringing and red lights flashing.  

 

But relax. Like anything. take it slow, and make notes, even to the point of counting the number of turns it took to take the screw out or make it "release".

 

Compartmentalize everything with tags. you can use a egg crate for this job and write right on the crate where it came from.

 

Slow and thorough clock makers, engine mechanics, and bomb disposal techs know this.

 

Then when it comes time to reassemble, just do everything in reverse.

 

Just convince yourself that you are the Doctor of your domain, be organized and clean, and quiet please.

 

No cats allowed, as they have a tendency to do gravity checks on anything loose on maintenance benches, tabletops, and counter tops.

 

Do not take anything apart that may have spring tension or hydraulic tension behind it, as it will be launched across the room and roll under refrigerators, dishwashers, washing machines, dryers and benches...oh, and under any vehicles.

 

Always were safety glasses for the same reason, unless you like playing the pirate every Halloween, or weekends and weekdays...for a very long time.

 

A cow magnet on the end of a stick does wonders locating and retrieving metal items...like grub screws.

 

Ace Hardware sells a aluminum pole with a flat magnet on the end for things like this. it saves the knees.

 

Remember, experience is the best teacher...

Should I do all this out on the lawn? lol The grass might help the screw stay assembled when it falls.

 

I'm not sure where, I think it was inside some Stellarvue manual, that might have said messing around with this screw on the focuser may misalign the objective, or something. Or did I see this in a bad dream? There's no way right?

Edited by Procyon, 21 May 2025 - 12:49 PM.

[Procyon]

Wow, I took out the focuser, and no matter how much I shook the thing I could no longer hear that screw flying around in there. Looked at ever crack and couldn't see anything. Maybe it's a sign to just leave it alone for now. Crazy... Thanks all, I'll look at post 7 better when the time comes also. 

Edited by Procyon, 21 May 2025 - 12:57 PM.

[GalaxyPiper]

Sure, messing with anything can mess with alignment. 

 

That's why you go "S L O W...."

 

I wouldn't mess with anything that is still under warranty, but after that, anything is game.

 

My philosophy is that I can't break it any more than it is already... I guess that gives me false courage on trying to fix it myself. Besides, I have always liked puzzles, and this is just another puzzle to me.

 

But, if one is carful enough, particular enough, **** enough, and has OCD...like counting the number of turns on each screw like a safe cracker...then the world is your oyster, and the pearls will be presented for the taking.

 

Playing "Mission Impossible" music can be helpful too! Just don't suspend yourself from the ceiling, the misses will not approve of the cracked plaster and bent Chandelier...

Edited by GalaxyPiper, 21 May 2025 - 01:06 PM.

[rainycityastro]

These Crayford Focusers are actually easy to dissemble. If you haven't done it before it can be intimidating, with mental alarm bells ringing and red lights flashing.  

 

But relax. Like anything. take it slow, and make notes, even to the point of counting the number of turns it took to take the screw out or make it "release".

 

Compartmentalize everything with tags. you can use a egg crate for this job and write right on the crate where it came from.

 

Slow and thorough clock makers, engine mechanics, and bomb disposal techs know this.

 

Then when it comes time to reassemble, just do everything in reverse.

 

Just convince yourself that you are the Doctor of your domain, be organized and clean, and quiet please.

 

No cats allowed, as they have a tendency to do gravity checks on anything loose on maintenance benches, tabletops, and counter tops.

 

Do not take anything apart that may have spring tension or hydraulic tension behind it, as it will be launched across the room and roll under refrigerators, dishwashers, washing machines, dryers and benches...oh, and under any vehicles.

 

Always were safety glasses for the same reason, unless you like playing the pirate every Halloween, or weekends and weekdays...for a very long time.

 

A cow magnet on the end of a stick does wonders locating and retrieving metal items...like grub screws.

 

Ace Hardware sells a aluminum pole with a flat magnet on the end for things like this. it saves the knees.

 

Remember, experience is the best teacher...

    But very correct. 

Edited by rainycityastro, 21 May 2025 - 01:20 PM.

[cyberduck]

It appears to be a focuser made by Kasai trading. Am I right? I had the EXACT same issue with that focuser. But there is an easy way to fix it. The knob is affixed with an internal screw, You can disassemble the focuser pretty easily once you know how. I would not have recommended the superglue approach. You risk gumming up the inside of the precision mechanism.  Reach out to me with your email by PM and I will send you the document. I am unable to attach it here.

I would open it up and clean it with acetone and regrease it gently. It is a beautiful focuser. IME, every bit as good as feathertouch. 

I have no idea who made the Focuser, only know it came with the TecnoSky AG70 APO (an Italian brand), but it sure looks the same as the picture you posted. Thanks for the offer of sending it offline.

 

Can't really compare with any other focuser, but I certainly agree it is nice!

 

Regarding the superglue, I only use a tiny amount on the tip of the allen key and I don't think I messed anything up. But I agree, dismantling the focuser is way better.