Thursday, December 26, 2019

80mm f/15 first light

After what seems like a month of cloudy and rainy weather, we had a pocket of clear skies tonight.  It wasn't especially good -- transparency still poor and seeing worse -- but it was my first opportunity to look through the 80mm f/15 Jaegers refractor I acquired.  I intend it for a H-alpha solar scope, but I've discovered it's a very pleasing nighttime instrument as well.

When the scope arrived the focuser was jolted out of square with the tube, and I was surprised to find no set screws for the focuser.  So during the day today I affixed the focuser to the tube by drilling holes and using thread forming screws.  I accidentally broke off one drill bit into the hole I was drilling, but it serves the purpose to set the focuser!  I also made a make-shift dew shield with some black foam and Velcro.  I set up my tripod with simple alt-az mount to its tallest setting, and find that it is still not tall enough to comfortably view with the scope at zenith.  It's a shaky mount too and not able to handle the 20 pounds this 80mm weighs.

The first target was M42, and I was able to sight up the scope tube and find it pretty quickly with a 40mm plossl eyepiece.  Nebulosity looked really good, especially the dark nebula, which was a surprise and indicates the scope has very good contrast (it is baffled by I think three or maybe four disks inside the tube).  I steadily increased magnification, first a 26mm plossl then a 13mm Ethos -- and yet I could not find the E or F stars in the trapezium.  The Ethos gave a stunning view, as it usually does.  Stars were nice and pin point and a rough star test showed round on both sides of focus (though seeing was not nearly good enough).

Next was M45, which was at zenith, and I needed to sit on the ground to reach the eyepiece.  So, a taller mount is called for.  A telrad at the objective end of the tube would be very helpful.  But the main issue is the height and steadiness of the mount.

I tried Rigel next, and could not find its B star.  M35 showed a pleasing spray of stars.  No question but refractors show the prettiest sky images.

So now I can move with confidence to make a cell for the energy rejection filter, and to go ahead with the solar scope.  My only worry is if there is enough in focus.  And of course the mount.

During the day I had a quick look at the sun with the PST, and it showed one large faint fan like prominence on one end of the limb and a small bright spike on the other side.  Looking forward to more views.

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