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Is there danger in observing the Sun through a Flextube scope?

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Hello everybody!

As you all know, the transit of Mercury is coming up, and I'd like to get a solar filter and mount it on one of the cover's caps.

However, I have the Skywatcher 250px Flextube, and I was wondering if there is danger in observing the Sun through such an open tube (with a filter on the end-cap).

I know that sun rays are pretty much parallel to each other.. so in theory, no stray rays should enter from the side (correct me if I'm wrong here),
but what about a passing vehicle that reflects the sunlight or something on that lines? Can any damage be done that way?

Just to be on the safe side, I'm gonna cover the tube anyways...
but I was wondering about this, and I also would like to raise these questions for other people with open scopes that might be viewing the transit. 


Edit: I'm assuming here that I should move the plastic cover to the front of the telescope for solar viewing. Is that the case?

Edited by soundwave

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That's an interesting question but dont do it.  ive seen a lightbridge iwith an open tube and front solar film being used for eclipse viewing but I wouldnt recommend it. I have a lightbridge too and I have had wisps of smoke from my flocking in the past when pointed away from the sun as the light can hit the mirror at an angle between the trusses and although it wont focus to a point it will concentrate the ligjt which can be a safety issue.



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you definitely need a shroud for the open bit



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A plastic cover could have a tendency to melt onto to you mirror..... I have a metal front cap and it got really hot, so I put a towel on it.

Secondly, finding the Sun in a finderscope or a Tetrad is definitely not recommended. I would remove them from the scope.

If you are going to put Solar Film over the smaller hole in the front cap. make sure that the front cap can not come off, a gaffer tape job!

It only takes a second of sunlight to damage your precious eyes.

Agree with your safety concerns, good luck on the day.



PS I will be using my Altair Astro 115 APO with a Baader Hershel Wedge.... so no need for a finder scope...


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Covering the front cap other than the foiled aperture hole with white paper would reduce heat on the cap.  not really necessary though if you have an adequate shroud.

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1 hour ago, Dave In Vermont said:

Other than the stated concerns over the use of open-tube telescopes, finding the Sun in any scope can be safely and easily accomplished with these - bought or home-made:


I've had one for many years. Utterly simple.


ST80 Helio-Pod Series g.JPG


These are also dead easy to make. You just need a pinhole at one end and a translucent screen behind it. The trick is not  to mark up the translucent screen with the sun's position in advance. Make the gadget, put it on the scope, find the sun and then mark the solar dot on the translucent screen.


Edited by ollypenrice
Translucent usually has a L in it!

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Excuse to show off my home-made one again :-) Fits in a standard finder holder. But anything that combines a hole and a screen will work.

Solar Finder 4.jpg

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