Re: Plossl ??

On or about Mon, 28 Apr 2008 03:57:53 GMT did "Mark F." <res049nn@xxxxxxx>
dribble thusly:

Thanks for your help with my question about my new scope.

So I have played with my 10" hardin now for a few nights.
I have a few obserations.
1. The X2 barlow may work on the moon but make mars look blury.

If anything looks blurry, you're overmagnifying. The ceiling magnification
for a 10" scope is about 600x, but it's quite unlikely viewing conditions will
ever be good enough to support that. More reasonably, you're better off
staying at 300x or less. Assuming 1250mm as the focal length, that means you
shouldn't use less than a 4mm EP, or an 8mm EP with a 2x barlow.

It may look OK with the moon simply because it's a lot bigger, and there's
plenty of large-scale detail. Mars, however, is tiny.

2. It looks like there is a light coating or haze on the primary mirror 10"
and none on my old 4.5 does the 10" need cleaning?

Unlikely. I'm assuming it's not something as obvious as dew. In general,
don't clean the mirror. As someone else pointed out, they can get quite
apparently filthy before you notice any impact on performance.

4. Does a 2" plossl do more for viewing then a 1.25. Is it worth the upgrade
for a backyard duffus like me.

In general, a 2" EP barrel simply allows a larger focal length without
reducing the apparent FOV. For a Plossl, that means if it's about 40mm or
higher, you'll want a 2" barrel, so the AFOV can stay around 50-60 degrees.

PS this is the kit the scope came with -- Celestron #94304. It is OK or
junk?

Probably OK or better. Very doubtful that it's junk.

If that 12.5mm EP is what you're trying with the barlow, that should give you
about 200x magnification. If that's blurry, the most likely culprit is bad
seeing.
.

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