A silly question

[lukeyboy]

Hi there i have just got my first scope for christmas and i have a stupid question.

The front cap which goes on the front to protect the mirror when its not in use has a smaller cap which comes off leaving a small hole, can someone tell me the reason for this?

Hope this question does not make your eyes roll too much and merry christmas

p.s cant wait for the skies to clear and get using this scope.

[plasma.d00d]

AFAIK its for collimationg your 'scope (helping make sure the mirrors are in the correct position).

From one new starter to another

[barkis]

Hi. Lukeboy,

The smaller cap is used as an aperture for solar viewing. The large one is left in place, and the small one is removed.

DO NOT VIEW THE SUN WITHOUT A DEDICATED SOLAR FILTER IN PLACE. EVEN USING THE SMALLER HOLE IN THE MAIN CAP IS NOT SUFFICIENT TO PROTECT YOUR EYES AND YOUR SIGHT WILL BE DAMAGED IF YOU DO. A PROPER FILTER IS USUALLY PLACED AT THE FRONT END OF THE TELESCOPE AND NOT IN THE EYEPIECE, ALTHOUGH THERE ARE EYEPIECE SOLAR FILTERS I DO NOT RECOMMEND THEIR USE A FRONT FILTER IS BEST SO SEEK ADVICE WHEN BUYING ONE.

Ron.

[steppenwolf]

With just the small cap removed, you have essentially 'stopped' down the telescope which means that you will have reduced the amount of light it collects (useful for looking at the Moon which is surprisingly bright through a telescope!) . *** HOWEVER AS ALREADY REPORTED, THIS DOES NOT CUT DOWN THE LIGHT ENOUGH TO ALLOW YOU TO LOOK AT THE SUN!! ***

[lukeyboy]

ahh that makes sense i dont feel so stupid now cheers :sunny:

The first clear night i hope to come back with some good reports.

[Casus belli]

The only stupid questions are the ones you dont ask. Welcome to sgl.

[Brinders]

I've put a piece of Baader Solar film behind the hole in my cap. I fitted it to view the transit of Venus across the sun's face a couple of years back. The film acts as a filter stopping (I think) around 99% of the sun's light but still allowing you to view it as a white disk without any danger to you eyes. That way when the sun is particularly active (it goes in cycles of about 4 years) you can observe sun spot activity. Good to know that not all observing has to be done in the dark!

Looking at the sun without any protection, even through a stopped down telelscope, (i.e. one where the aperture has been made effectively smaller) will lead to permanent eye damage and very likely blindness in the observing eye. Make sure that if you do use solar film that it is light proof and check it for pin pricks before use each session.

Enjoy your astronomy. This is a great forum and a wonderful hobby - welcome to SGL :reindeer:

[barkis]

You a right about the Solar Cycle Brinders, but the duration lasts 11 years. 22 years actually, as the there is reversal of polarity at the end of 11 years. So the total cycle time is 22 years.

Ron.

[geoff_k]

Welcome to the forum and happy hunting with the new scope.

If your scope is a refractor (you don't say which ) stopping down the aperture as described can also counter the affects of chromatic aberration found in some models of refractor. This manifests itself as false colour around brighter objects.

If you have any other type of scope just ignore me and enjoy!

Geoff

[Brinders]

You a right about the Solar Cycle Brinders, but the duration lasts 11 years. 22 years actually, as the there is reversal of polarity at the end of 11 years. So the total cycle time is 22 years.

Ron.

I stand corrected. Thank-you Ron.