projecting the sun?

[Jarrod]

hi all,

i was just outside roughly collimating my reflector, and thought i might try projecting the suns image onto paper, but im not sure of the risks to the eyepieces or telescope. id only be using the cheap eyepieces that came with the telescope, but thier the only eyepieces i have, so i don't want to risk dameging them. my telescope is a celestron powerseeker 127mm newtonian. it also has a lens in the foccuser to reduce it's length f/length, so im thinking that it wouldnt be exactly the same as projecting the sun through a normal newtonian.

can anyone reccomend a safe method, or any precautions i need to take,
or even tell me that i shouldnt bother because i'll wreck the telescope?

thanks,

jarrod.

[Astroman]

Personally I wouldn't do it. The lenses that are in the focuser will be pretty close to a focal point so the suns intensity will be very high and could damage them, making your telescope unusable. Also if they are a cheap lens made of plastic you could set your telescope on fire. So my recommendation would be to get a quality solar filter designed to go at the front of the scope.

[ballaratdragons]

Andrew is spot-on.

I melted an EP doing projection! The glass actually has bubbles in it now!

That's scarey :scared:

[CoombellKid]

spend $40 and buy some solar film.

I melted an ep doing the same thing during the last Venus transit.

even better buy a PST and freak yourself out : )

regards,CS

[Jarrod]

i didnt think it would be a good idea. i melted the inside of a 50mm refractor once before (thats why i had second thoughts about trying it this time). althogh it was made of plastic, and i was tracking the sun with it for nearly an hour before i could smell it :whistle:.

jarrod.

[ballaratdragons]

Here's one way you can try.

Take the EP out and let the sun project out onto a piece of white cardboard. Move the card back and forward for focus.
That way works for me :thumbsup:

But I still prefer using my full apature solar filter for looking at the Sun.

[leon]

I wouldn't let the Sun anywhere near my optical stuff, from lenses to scopes.

Leon

[Glenhuon]

I have done eyepiece projection a few times with my 60mm, the main ones that come to mind are the transit of Venus and of Mercury, but the eyepiece was a front lense from an 8mm cine projector turned down to fit the 1" focusser (expendable). Best advice has already been given, invest in some Baader film and make a full aperture filter if you want to do the occasional bit of solar viewing.

[Geoff45]

The days of eyepiece projection date back to the time that a 6" reflector or 4" refractor were big sizes for an amateur scope. You could probably get away with it for sizes like this. For my 4" reflector eyepiece projection works just fine. (But I use an expendable eyepiece just in case!) Also, there is no way I'm letting the sun near my apo.
You could also use an off centre aperture mask to bring the effective size of your scope down to 3 or 4". Geoff