URGENT ADVICE NEEDED!

[daz]

Have been working on my scope this morning, and I have dropped a screwdriver bit-head straight onto the primary and taken a great chunk out of the mirror.

To say I am annoyed is an understatement!!!!

Best place to go for a replacement??????

[OXO]

http://www.beaconhilltelescopes.mcmail.com/

Try these Daz they do all sorts of stuff like Mirror's etc etc...

Sorry about the Bad news Daz thats a real Bummer , were is the chunk missing from? the centre or the outter edges of the mirror?..

James

[daz]

It's on the outer edge, so it may not be too bad.

I am gutted - absolutley gutted.

Found BH - £42ish for a new one, dunno if it's parabolic though....

[OXO]

It's on the outer edge, so it may not be too bad.

You may get away with that Daz or at least until you get a New Mirror that is. I would imagine the Mirror you have seen for 42quid is Parabolic maybe ask them matey..

James

[tom.yates]

DAZ , This may sound strange but why dont you just mask the mirror with tape just enough to cover the chip people also do this if they have either turned down edge when figuring a mirror so they only use the part of the mirror that is ok.

Tom.

[daz]

Cheers All

Will check it out ASAP and let you know the damage.

God, I could cry :tearyeyed: :tearyeyed: :tearyeyed: :tearyeyed:

[Astroman]

Daz: Tom's idea is a good one, depending on what size scope you start with.  You may not notice anything at all, even with the chunk missing.  Sometimes, manufacturers use an undersized secondary, which means you're not using the edge of the mirror anyway.  I'd recommend doing a star test on it and see if you can detect the defect.  I'll write up a procedure later, if you don't know how, ok?

Remember,

Don't Panic!

[daz]

Thanks buddy

Sitting here all dejected and forlorn

Even if it turns out OK, that chip is going to eat away at me - same as the scratch on the tube (which will be painted new year), it's my pride and joy and I am furious with myself for not taking simple precautions!! It's a question of how long I can live with the knowledge that it's there!!

Well, won't be testing tonight as there are snow clouds on the horizon. Bad in one way, good in another. I love the snow - something magical about it! Plus I get to play snowballs with the kids

[Astroman]

Plus I get to play snowballs with the kids

Oooh, I'm jealous! I moved to Arizona from Chicago when my daughter was only 3. (She's 27 now.) We only made one snowman before the move, and she doesn't remember it much. That would have been fun!

[Jamie]

Sorry to hear of your misfortune mate.

I would go down the Tom/Astroman route till you find the best

mirror that suits you. (price/quality)

If Astroman says he can talk you through it then you should try it for now.

I know exactly how you feel cos i smashed up an 8" SCT about 3 years ago

and i was devistated.

Just remember there WILL be light at the end of this tunnel.

[daz]

I managed to bring myself to inspect the damage a little closer. The chip is about 3mm long and is approx 3/4 inch from the edge.

Just hope it's far enough towards the edge.

Astroman - a procedure would be great if you don't mind

[FLO]

Daz,

Don't worry

First: A chip that size will only show if it scatters light (if that happens then cover the chip with matt black paint).  

Second: You don't need to change the mirror but if you do...  Your scope is fitted with an 8" f5 parabolic mirror. An f5 light cone is an f5 light cone so any 8" f5 mirror will work, parabolic or spherical.  

(If you'd like me to supply a replacement, PM me).  

Steve 8)

[daz]

Thanks Steve, much appreciated!

Will be testing at the next clear sky - hopefully tomorrow!!

[The Warthog]

DAZ , This may sound strange but why dont you just mask the mirror with tape just enough to cover the chip people also do this if they have either turned down edge when figuring a mirror so they only use the part of the mirror that is ok.

Tom.

Yeah, that! The chip is probably much smaller in area than it looks, and won't affect your mirror's performance that much. A lot of people don't know that, in addition to being incorrectly figured, Hubble's telescope had to have a chunk taken out of it with a circular saw because it had some awful flaw. It didn't affect the performance at all. Even if your chip is 10% of the mirror (a hell of a chip) you won't lose all that much. Use duct tape. My daughter works for 3M.

[Astroman]

The black paint would work, but find out if it's a problem first. JMHO. Here's the procedure. If you have any questions, PM me or do it here. Either way, it's not difficult.

Star test:

Locate a bright star using a high power eyepiece. After allowing the scope to reach ambient temperature, defocus the image until a few diffraction rings are apparent. If the scope is a Newtonian, the center will be a dark circle, which is the reflection of the secondary obstruction. (This is also a great way to check collimation-the secondary shadow should be perfectly centered within the diffraction rings.) The light and dark alternating rings should be perfectly concentric and round. It is possible to see distortions in your mirror by the distortions in the circles, if you ignore seeing effects like turbulence and tube currents. Check for persistent defects in the circles. Once you establish if there are any defects, rack the focuser to the opposite side of focus and recheck. The rings should appear the same. If not, it points to other optical problems, like astigmatism or pinched optics or aberrations within the mirror or mirror cell.

Be sure the scope is at temperature before evaluating the mirror’s performance. Tube currents can easily appear to show problems that don’t exist, so it’s important that any perceived defects are persistent.

[Nightowl]

Can understand how you feel Daz Oooooch!!! Many years ago I remember grinding my own 6inch mirror and flat Turned out perfect ...Mounted the main mirror in my tube set up the spider and fitted the flat. Set about Colming ......screwdriver dissapeared down the tube and SMASHED the main mirror.....Contemplated throwing my self in the Mersey back then .... Chin up mate all things fade with time and either a new mirror or re-worked one. :sunny:

Best Regards AJ.

[daz]

Astroman - Thanks buddy

Thanks to everyone with your encouraging comments - everything is now geared up for a clear sky, you know, like the ones we usually get!!

[daz]

And just to finish off this sorry tale....

I slipped outside yesterday with mount in hands and bashed into the wall. Now I've cracked the side-panel. It's removeable though, so it's no great shakes, but it's bleddy typical...

[tom.yates]

Keep your chin up mate.

Tom.