25 replies to this topic

[humma kavula]

houston i have a problem. 

 

so im removing the mirror from the cell and one of the screws snapped with the remaining of the screw still inside. im in a world of poop right now. can i still get away without one screw? i need advice. i know i can somehow remove that bit thats in there and just make a trip to ace hardware but i dont have the tools to remove that. see pics below. the mirror came out clean it was a success (i will post a pic of the clean mirror shortly) but im worried about this screw. 

Attached Thumbnails

• 
• 
• 

Edited by humma kavula, 25 October 2020 - 12:38 PM.

[Starman1]

The removal of the screw requires one of three methods:

1) a drill drills a small hole in the bolt.  An Easy-Out is tightened into the hole, backing the remnant of the screw out of the hole.

2) A Dremel tool with a high speed disc cuts a slot in the bolt.  Then, a flat blade screwdriver removes the screw.

3) a small left-handed drill bit is used in a drill and, as the screw is drilled, the friction backs the bolt out until you can grab it with pliers and remove it.

 

Personally, from my experience in drilling holes in small hardened bolts, I'd use method #2.

 

Of course, you also have the option of simply using one screw to hold the clip in place.  You only need an infinitesimally small amount of pressure to hold the mirror (not even

enough to cause any compression of the rubber), and one screw would suffice.

[humma kavula]

starman your advice is solid. thank you. i managed to put everything back together and its all hunky dory. i tested the scope outside on a distant pole and all looks well. i will eventually take it to a shop and have a pro extract it for me but for now it works. thanks for your advice. 

 

chris

Edited by humma kavula, 26 October 2020 - 10:37 AM.

[bblamo]

I broke one bolt holding the mirror clips yesterday, dang it!

3 out of 6 felt like they were stuck for some reason.  I wanted to remove the mirror for cleaning.

 

I decided to not mess with the stuck bolts and cleaned the mirror whilst in the cell.  For now the one mirror clip will have one bolt.  I didn’t like the Phillips head bolts either.  Holding down pressure on a screwdriver next to the mirror is just asking for cuss words.  I see these are the same size bolts that I used to add a fan on the back and I used Allen hex for those.  When I get by the hardware store I’ll pick up some more Allen hex bolt and replace them all.

bblamo

[humma kavula]

funny, i went to ace today to get the bolts needed to attach the fan and they were hex too. yes they are the same size bolts. same length too. when i have that remaining bolt extracted im going to upgrade the weak bolts. those things are like bubble gum. are they made in china? 

 

also i think there was thread lock applied to these bolts because as you mentioned they were a PITA to remove and using force next to the mirror was making me feel very uneasy. if you asked me, i'd prefer some kind of quick release clamping system to remove the mirror from its cell. guess you and i are in this together lol as long as it holds we should be fine. 

 

waiting on the clouds to  move out of the way Grrr! 

[stubeeef]

Remove a Stripped or Broken Screw

 

https://www.lowes.co...or-broken-screw

Edited by stubeeef, 25 October 2020 - 09:42 PM.

[cuzimthedad]

 

also i think there was thread lock applied to these bolts because as you mentioned they were a PITA to remove and using force next to the mirror was making me feel very uneasy. if you asked me, i'd prefer some kind of quick release clamping system to remove the mirror from its cell. guess you and i are in this together lol as long as it holds we should be fine. 

From what I saw in your photos, it did look like there was some thread lock on the bolts.

[Jon Isaacs]

I'd just leave it.

 

Make sure the clips don't touch the mirror.

 

Jon

[humma kavula]

yeah it seems to work great. got to see the moon so awesome last night. jupiter, saturn and also mars. im waiting on my sv305 camera.

[NC Startrekker]

funny, i went to ace today to get the bolts needed to attach the fan and they were hex too. yes they are the same size bolts. same length too. when i have that remaining bolt extracted im going to upgrade the weak bolts. those things are like bubble gum. are they made in china? 

 

also i think there was thread lock applied to these bolts because as you mentioned they were a PITA to remove and using force next to the mirror was making me feel very uneasy. if you asked me, i'd prefer some kind of quick release clamping system to remove the mirror from its cell. guess you and i are in this together lol as long as it holds we should be fine. 

 

waiting on the clouds to  move out of the way Grrr! 

One tip FWIW - make sure to use"stainless steel" cap head screws or bolts on all things astro.  The more common ones are usually Zinc plated and will eventually rust.  You would want to avoid them rusting tight in place.  Both the big box chains and local hardware stores will carry stainless steel; although they probably will not have as wide a range of lengths, diameters and thread counts.

[humma kavula]

yup... when i take the cell to the shop to have that extracted im replacing all screws wit SS screws. 

[SteveG]

I would not fix it. You don’t need all 6 screws to keep the mirror from falling out. Make sure you are not tight against the mirror with the clips. You should be able to slide a business card underneath.

[bblamo]

I would not fix it. You don’t need all 6 screws to keep the mirror from falling out. Make sure you are not tight against the mirror with the clips. You should be able to slide a business card underneath.

I wonder how tight the clip screws should be.  I tried leaving them loose but I noticed that when I did a laser collimation I could watch the laser spot actually move on the target as I tilted the scope from horizontal to vertical.

In my scope the clips are rubber so I have them tight enough that nothing is moving when I change alt.

One would think that there should be a proper torque value published.

bblamo

[Jon Isaacs]

I wonder how tight the clip screws should be.  I tried leaving them loose but I noticed that when I did a laser collimation I could watch the laser spot actually move on the target as I tilted the scope from horizontal to vertical.

In my scope the clips are rubber so I have them tight enough that nothing is moving when I change alt.

One would think that there should be a proper torque value published.

bblamo

 

The clips are not meant to keep the mirror from moving.  In a Dob, gravity should keep the mirror in one place, once it's set.  

 

If the clips are keeping the mirror from moving, they are probably causing some astigmatism.  

 

What happens is that the clips actually deform the mirror ever so slightly.  In terms of a fraction of wave length of light, it's significant.

 

A common scenario in the forum:

 

Post 1:  I took my Dob apart to clean the mirror and when I put it back together, the images are not good at all.  

 

Post 2:  Did you tighten the mirror clips so they're actually touching the mirror?  If so, loosen them.

 

Post 3:  Yes.  I loosened them and now all is good. Thanks.

 

Jon

[bblamo]

Ok, today I will take the mirror cell out and adjust the clips so that they are slightly off of the mirror.

I found this CN thread from 2018. https://www.cloudyni...y-mirror-clips/
This topic with the exact same issue I was concerned with has already been discussed in detail.  There is just so much information on here it’s hard to find it all.

Thanks for the tip.

bblamo

[Old Rookie]

Just back them out to about .040" - .060" or about the width of a credit card.  As mentioned above, they don't need to touch and should not touch the mirror.  

[humma kavula]

jon that makes sense. 2 nights ago i was looking at the moon and it "seemed" very nice and clear but when i tried looking at the planets i found it very difficult to focus them. i was confused thinking it may have been my 10mm plossl because when i would switch to a lower power (25mm) the planet looked a little better but still had a blur to it. i did a star collimation test and my secondary mirror was dead on in the middle so i knew i was collimated. im going to remove the cell and loosen the screws because in all honesty i did synch them down pretty good. hope this helps my issue. 

 

 

chris

[humma kavula]

ok i was able to loosen the screws a great amount without feeling any play from the mirror. hopefully this will help with the difficulty in focusing on planets. however, i did accidentally touch the mirror with a finger and a small smudge can be seen. should i clean the mirror again? im sure itll be fine but figured i ask. 

 

also, i just got this scope second hand. i noticed one of the alt knobs is missing a a nylon washer (assuming its nylon) is this normal?

 

thanks people i really mean it!

 

chris

Attached Thumbnails

• 
• 

[bblamo]

Chris is that an Orion scope?

that other knob should pull the inside alt bearing up tight to the inside of the Dob frame.  There is a plastic bushing inserted through a hole that’s a knob tightens against.

there is not a washer on that knob.

 

bblamo

Edited by bblamo, 27 October 2020 - 11:41 AM.

[humma kavula]

okay great to hear thank you bblamo

[bblamo]

Fixing the broken bolt was a 10 minute fix.  It's true that both bolts would not be needed to hold the mirror clip I decided that since I was going to take the mirror cell out to adjust the clips I would fix the broken one.

It took a 3.2 mm drill bit and a 4mm thread tap.  I put it on the drill press and the started drilling from the back side.  That actually unscrewed the broken piece from the cell.  Then I hand threaded the 4mm tap in just to clean it up.

The phillips bolts are now all replaced with SS hex allen bolts and I have the clips adjusted so that they are just off of the mirror.

 

All I need now are temps warmer than the teens and the smoke to stay north.

 

Clear skies everyone!

bblamo

[humma kavula]

and i forgot to mention that yes its an orion xt8 plus. 

 

just out of curiosity, when you said smoke stay north, are you talking about the fires in california? is that affecting you in colorado?

[bblamo]

We have 4 big fires in Colorado, two of them are largest ever,  just northwest of me.  I can see smoke today that is flowing east but it is north of where I am.  At times I get ash falling on the yard.  We had a good snow Sunday night that is helping them get the fires controlled.   I have had the California smoke overhead but it is high and effects transparency. 

[SteveG]

 however, i did accidentally touch the mirror with a finger and a small smudge can be seen. should i clean the mirror again? im sure itll be fine but figured i ask. 

 

 

 

chris

No! That tiny smudge won't do a thing, and you're likely to cause more damage by overcleaning. I know it's hard, but resist the urge and just forget about it until next year.

[humma kavula]

roger that steve. i just had a solar session and woooooow lol first time seeing the sun. unbelievable. no pics yet im waiting on my sv305 cam