A stupid question?

[Starlord19]

I am still very new to this so please don't laugh! I have just bought a newt and was wondering what the small opening in the main lens cover was for? It has its own little lens cap, but is not mentioned in the instructions . Thanks, Mark. 

[Putaendo Patrick]

Essentially it is to reduce the aperture - some people use it for example to observe the Moon when it is very bright.

[RT65CB-SWL]

Some amateurs stick Baader safety solar film [on the inside of the 'main' cap] so they can observe sunspots in white light. If you do decide to do this, then make a full aperture solar filter for your finder scope too! - and if you have enough left over, how about a full aperture filter for the OTA.

If your 'scope has an RDF remove it from the OTA and use the shadow to align it. 

[Alien 13]

As previously said, what it also does is increase the effective F ratio of the scope which can sometimes make a cheap eyepiece perform better.

Alan 

[Starlord19]

Thanks everyone. I thought it might be to do with reducing the aperture but it makes such a small opening that It didn't seem to make sense. 

[LukeSkywatcher]

With my first ever telescope (a 90mm refractor), i didnt know that the whole front dust cap came off. I didnt want to mess with it and break the scope. I spent 6 months observing through the small 1" central hole at the front of the scope. When i eventually realised that the whole cover came off and there was a 90mm glass lens underneath i was amazed and even looking at the Moon felt like i was burning my eyeball. I wasnt though.

So this is not a stupid question. As we say here on SGL: "The only stupid question is the one you dont ask".

[Louis D]

I'm assuming the small opening is off-center, correct?  If you align that hole between your spider vanes, you'll have an unobstructed telescope with no dark spot in the center of defocussed images and no star spikes due to diffraction around the vanes.  It will behave much more "refractor"-like in this mode.  You should have higher contrast despite the lower ultimate resolution and decreased image brightness.