MIrror in LED torch (flashlight) shocker

[Macavity]

OK, I know that they claim only 90-something % reflectivity, but I was a bit worried when I casually shone my white LED torch through my MAK127. You could see "straight through" the secondary mirror.

I calmed down a bit, when I found you could just about see it through a Density 5 solar filter too. But, pause for thought - <impressed>!

[The Warthog]

Did you shine it through the front or the back? Of course, that 'mirror' is only a thin aluminium coating on the back of the corrector lens. I'll have to try that!

[brianb]

The "flashlight test" always shows "defects" of absolutely no practical consequence, that's why it's a Bad Idea to do it.

The only reason I ever shine a flashlight at the front end is to check for dew on the front surface, an issue which does have a very real impact on performance.

[Macavity]

Did you shine it through the front or the back? Of course, that 'mirror' is only a thin aluminium coating on the back of the corrector lens. I'll have to try that!

Shone it throught the back... for a change - So it was the plated-on secondary.

IIRC, I did (vaguely) learn something. That probably the secondary mirror was about the right size - even a tad oversized. Not totally insignificant, when folks claim the MAK127 has a "narrow field of view", and/or is vignetted by the exit orifice. I suspect the ultimate source of the HARD vignetting is the far end of the mirror transit tube... Which may indeed usefully function as internal baffling.

The outside of the corrector plate was (once) significantly smeary - and from new! But a drop of Smirnoff works wonders! And no, I'm NOT advocating such things - At least for cleaning optics.