melted plastic in the diagonal

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daslolo
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melted plastic in the diagonal

Post by daslolo » Tue Mar 10, 2020 12:51 am

Today I watched the sun. The setup was Orion 120mm - beloptic ir/uv cut filter - 2" diagonal - quark
To the touch the entire optical chain was cold, the quark was barely lukewarm - the altaz dec motor shaft is slipping so I was doing most of the tracking by hand.
The sun sets, I pull the scope back in and remove the quark for the night and look what I see!

Maybe that happened before I installed the beloptik and was using another ir/uv cut filter...
melty mirror lip.jpeg
melty mirror lip.jpeg (67.15 KiB) Viewed 1184 times
PST on its way to modding heaven
Quark + Orion 120mm + beloptik
LX65 8" ACF

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DeepSolar64
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Re: melted plastic in the diagonal

Post by DeepSolar64 » Tue Mar 10, 2020 5:17 am

Looks like the IR filter wasn't very effective. It's just figuring out which one it is, since you used two different ones. Did it totally ruin the diagonal?
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Orion 70mm Solar Telescope
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Lunt, Coronado, TeleVue, Orion and Celestron Eyepieces

christian viladrich
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Re: melted plastic in the diagonal

Post by christian viladrich » Tue Mar 10, 2020 7:41 pm

Just remember that the IR/UV cut Beloptik filter blocks UV et IR.
Still, there is a lot of energy passing in the 400-700 nm band, and ... black plastic aborbs light.
Image

In any case, it might be that the culprit is the other IR-block filter.
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daslolo
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Re: melted plastic in the diagonal

Post by daslolo » Wed Mar 11, 2020 7:25 am

How did the light even reach the black plastic? Is the telescope miscollimated you think?
PST on its way to modding heaven
Quark + Orion 120mm + beloptik
LX65 8" ACF

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Re: melted plastic in the diagonal

Post by marktownley » Thu Mar 12, 2020 9:22 pm

daslolo wrote:
Wed Mar 11, 2020 7:25 am
How did the light even reach the black plastic? Is the telescope miscollimated you think?
The sun wasn't centred in the field of view...
Image
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Re: melted plastic in the diagonal

Post by VitaminSun » Fri Mar 13, 2020 1:15 am

daslolo wrote:
Wed Mar 11, 2020 7:25 am
How did the light even reach the black plastic? Is the telescope miscollimated you think?
several things can cause this,

sag in the focuser.
cross threaded nosepieces,
too small of a mirror


The lesson to be learned is that you should never use anything plastic in your telescopes when it is pointed at a nuclear fire.

Even a fully ir/uv blocked and color filtered system can cause enough energy to activate the smoke point on many materials, even powder coatings.

Your telescope effectively becomes a high power laser when pointed at the sun, and the energy value is rated in watts / radiometric power.

https://en.wikipedia.org/wiki/Radiant_flux

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daslolo
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Re: melted plastic in the diagonal

Post by daslolo » Fri Mar 13, 2020 2:37 am

No, the lesson to be learned is : always open every part of the optical train to verify that they didn't cut corners
I'm saying that because I bought this diagonal due to its all metal construction, external construction.
Fortunately in the land of the free (return) these sort of cost cutting measures are met swiftly, shipped back to sender.

Sag in the focuser: I thought of that and replaced the rack and pinion with a crayford with no sag that I can see
cross threadede nosepieces : what is it?
mirror too small: does it look too small on the photo? Can you show me a diagonal with a large mirror, for reference.
sun not centered in the field of view : interesting that, I assumed that eyepieces mirrors were sized to bounce all the light that the diag baffles/tube let in.
PST on its way to modding heaven
Quark + Orion 120mm + beloptik
LX65 8" ACF

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Re: melted plastic in the diagonal

Post by VitaminSun » Fri Mar 13, 2020 2:58 am

A cross threaded nosepiece is not square to the optical axis, so the incoming light would be not centered on the mirror.

Ill have to check my diags and see if the two i have are full size. My old diag had no separation between the exit hole, the glass was end to edge.

The part you roasted could be a gasket to prevent chipping when it was mounted to the base. Can you unthread the eyepiece port, or is it cemented in.

What brand is it also?

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