Always check first before any observing session

That the lens cap on your telescope is fully removed.

I bought my scope about 3 weeks ago. I've only used it twice since then because of bad weather and stuff. When i looked at the front of the scope there is a small lens cap in the middle of the lens with a couple of grooves in it to make for easy removal.

No worries.Had a look at the moon and stuff.Great.

TODAY when i removed the lens cap....................i noticed that the whole "front" end of the scope comes off (not just the little lens cap in the middle with the grooves) to reveal the lens underneath. Up until now i had been viewing with only a fraction of the light available reaching the lens because of the "2 part" cap. I had been taking out just the middle of the cap and not the complete cap.

I looked at the moon a few mins ago with the cap FULLY removed and i was nearly blinded. BRILLIANT. ASTRONOMY WILL NEVER BE THE SAME.

WHY would a lens cap be made in this way? (large removable disk with a smaller internal removable disk).

Its done for solar projection, so that the full aperture inst used for projecting the sun, but to be honest on such a size aperture stopping it down is not the done thing really.

Thanks Dave i had a sneaky feeling that's what it was for.

Stopping down my Celestron 6" achromat refractor to 4.5 inch aperture by leaving the lens cap on turns it into a virtually flawless 4.5" long-focal-length planetary apochromat.

Without the expenditure.

(Not that there is much wrong with the scope at 6" aperture!)

Peter.

Peter,

I'm sure I read somewhere that you can get some kind of chromatic corrector for that work very well with those 6" achros which vastly improves the colour correction. Just thinking that with one you could maybe use the whole 6" for planetary viewing!

I think you are referring to "Minus Violet" filters Dave.

Deliberately designed to block frequencies of light most responsible for Chromatic Abberation in achromat scopes.
And cameras.

See:

www.lumicon.com/cat_description/cat_desc...olet-chart-906lg.jpg


Peter.