Friday, June 18, 2010

Finally! Clear Skies!

We had clear skies last night, so I rolled out Big Bertha.  I need to work on rebalancing the telescope and mount.  A German equatorial mount relies on a very nearly perfect balance so that a relatively small motor can make it track across the sky--and if you aren't properly balanced, you either have to clamp down the clutch locks, or it doesn't track well.

Nonetheless, I was able to get the optical system reasonably well collimated.  Still, I think the structure is still not quite stiff enough, and collimated in one position meant that it wasn't so well collimated in another position.  Unfortunately, stiffer would mean heavier, and it is already pushing the upper limits of the CI-700 mount.  This expensive beast is about what it needs to properly support it.

Short (f/4.5) focal ratio mirrors tend to not do so well at high power compared to longer focal length mirrors, and it does show.  There wasn't much point in going up above 160x on the Moon (although some of this was the burbling of the atmosphere).  Still, the resolution is pretty amazing, even at 160x.  (Telescope resolution improves inversely with diameter of the objective, so a 17.5" telescope at the same magnification will show at least twice the detail of an optically comparable 8" telescope.)

Saturn was a bit disappointing--and at least partly because of the collimation issues.  Where Big Bertha really shines is on faint, deep sky objects, where magnification is far less important than the amount of light it gathers.  I could not quite get the telescope pointed at M51, partly because of the odd angle required from my ladder.  The Ring Nebula, however, was quite satisfying.


  1. And I thought I had too many expensive hobbies :)

  2. The good news is that telescope mounts pretty much never wear out. The bad news is that they aren't so good at overthrowing governments. The good news is that high end optics, like those made by Astro-Physics, are in such high demand that if you get on the waiting list, by the time your order is ready, you can usually resell it for 15% more than you paid.