Aperture-Masking

I've read over and over that larger-aperture telescopes are better on nights where the seeing is good or better, and that most of the times the smaller scope (up to 6") beats the larger scope in fine detail/contrast/etc. when seeing is just average.

If that is the case, does aperture masking solve this problem? Let's say the seeing isn't good enough to use a 10" - would masking it down to 5" (or so) be a good idea? Is that the whole point of aperture masking?

-Mike

Mike,

there is a lot of myth, opinion, and nonsense floating around about aperture masking.

It cuts down the amount of light, everybody concedes that. This may be useful for extremely bright objects.

It may enable you to overcome defects in your mirror. If you shield off a significant portion of your mirror, you shield off some of its defects, and make for a longer F ratio--which is generally easier on the optical system.

It might help on nights of bad seeing--although there is a lot of folklore and disagreement on this. If the size of the hole is smaller than the sixe of the disturbed cell, the theory goes, you will have a more stable view. This has not been my experience.

Anyway. I would not be surprised if you got lots of contradictory responses.

Alex

At a recent star party a fellow member had both his scopes setup, a 15" Obsession f/4.5 and a Astro Physics 130 f/5. We put both scopes on Jupiter and got the image sizes close to the same size with Pentax XL eyepieces. The 15" was the best every time at full aperature. The seeing was good but definitely not what it can be here in FL. Even my 8" f/6 newt gave images that were sharper albeit a tiny bit less contrast than the AP. There is an old saying among drag racers, " There is only one thing better than cubic inches - and that's more of them!!" Aperature always rules if the quality of the optics will allow.

Walt