My dumbest question yet

[Hzadbhat]

Greetings from somewhere that is not where you are. (told you this would be dumb)

I've got 2 reflectors and they both have dust caps. On my 8" there is one cap and it has two removable coverlets on it.

My 10", being collapsable, there are two covers, and both seem to have the same feature.

But what is their purpose (if any)?

Thanks

(already trying to phrase the next dumb question. I build stuff for a living, if you want to know some tips on how to build something. that's what I do, you nice folk do astronomy ((as do I)) and that is why I ask)

Cheers

[glowjet]

I think this stems from the old manufacturing days and really was a function intended to reduce glare from such as the Moon but never, never try it on the Sun

John.

[Peter Drew]

It's probably a focusing aid for photography. When a star or planet is viewed with the cap on but the small caps removed, if the focus is wrong then you will see two circles, when correct the circles will coincide.

[michael.h.f.wilkinson]

It's probably a focusing aid for photography. When a star or planet is viewed with the cap on but the small caps removed, if the focus is wrong then you will see two circles, when correct the circles will coincide.

That sounds right. A single reduced aperture was often meant for lunar (OK) and solar (NOT AT ALL OK!!!! ) observing. Dual apertures are suitable for focusing.

[Hzadbhat]

Never fear about me using anything but a top solar filter when I finally do, but thanks for the tip.

The majority would be aware of this, but there's always someone.

[rwilkey]

It's used t reduce the aperture of the scope when viewing bright objects like the Moon or some planets. For solar you can just use Baader solar film and just cover the small hole (safely), saves you covering a large full aperture. I prefer not to reduce the aperture for any dark sky viewing.