Scope lense cover why 2 holes???

[freelander86]

Hi,

My Celestron 130 scope has a plastic dust cap/cover. But on this there are two smaller holes/caps...

Anyone know what they are for?

To let air into the tube perhaps for cooling?

Freelander86

[FrankieValley]

Hi,

My Celestron 130 scope has a plastic dust cap/cover. But on this there are two smaller holes/caps...

Anyone know what they are for?

To let air into the tube perhaps for cooling?

Freelander86

I've wondered the same, but I use the smaller hole on my reflector end cap for solar observation. NOTE: NEVER LOOK THROUGH AN EYEPIECE DIRECTLY AT THE SUN, etc!!!!!!!!!!!

I cover the hole with BAADER AstroSolar™ Safety Film (ND 5.0) so that I can then look through an eyepiece NOTE: MAKE SURE IT CANNOT FALL OFF!!!..... or image the sun with a webcam.

An alternative is to leave the hole uncovered (see first warning) and PROJECT the image of the sun TOWARDS THE GROUND onto a sheet of paper/card.

My thought is that the latter is why the smaller hole is there, because if you simply removed the entire end-cap you will quickly heat the secondary mirror and it may warp, explode, crack, etc. After all the reflector is basically one big magnifying glass!

[rowan46]

one is an of axis hole for looking at the moon the idea being that less light coming through make it easier to see. the other bit is to store the bit that comes out so it doesn't get lost, you put the detatchable cap over the stub.

[Tiddles]

one is an of axis hole for looking at the moon the idea being that less light coming through make it easier to see. the other bit is to store the bit that comes out so it doesn't get lost, you put the detatchable cap over the stub.

Thank you.

[Chris H]

So many people ask this question, why don't Skywatcher put it in the instructions?

[freelander86]

Thanks for the replies!

Thought it would be something simple.

Not tried it but youd think looking at anything through the first smaller cap would be too small to use... will have to try it on the moon tonight

Freelander86

[Adwonas]

haha I was wondering the same thing!

[Capricorn]

Obvious: One for each eye.