[AZ-Observing] Re: MM date limits (again)

  • From: "Jones, Jack (AZ75)" <jack.jones@xxxxxxxxxxxxx>
  • To: "'az-observing@xxxxxxxxxxxxx'" <az-observing@xxxxxxxxxxxxx>
  • Date: Thu, 18 Mar 2004 12:45:22 -0700

Although I don't like the definitions much since they are "ground-oriented",
I like the references to the visibility of the horizon - civil: horizon is
clearly defined - nautical: horizon is indistinct. It's a continuum of
course, but I will try to memorize what the horizon looks like when a target
object goes invisible as a reference to warn how much time I have to play
with. (I'm also going to be running Starry Night on the notebook in real
time.) But usually I freak at the end of astron. twilight when first light
shows and I have 20 left.


> The 10 degrees was a sort of arbitrary choice, chosen as a 
> time when M30 
> would be several degrees above the horizon.  I do remember 
> looking at M30 
> in 2001 in very bright twilight.  I could see scopes and cars 
> clearly at 
> the other end of the field.  I would guess it was well past nautical 
> twilight when we saw it.
> In any event, I don't recall the distant mountains presenting 
> nearly as 
> much of a problem for seeing M30 as the horizon extinction and sky 
> brightness.
> Tom
See message header for info on list archives or unsubscribing, and please 
send personal replies to the author, not the list.

Other related posts: