Post your home made scope
Posted 23 January 2013 - 02:36 PM
Collimating the ballscope using the trusses is fairly easy, but a little different than a 'regular' Newtonian. On the plus side, there is no running back and forth since everything is done at the top end. If I get set up before dark, I use a regular Cheshire collimating tool to collimate the secondary and then the primary in the usual way, and that gets me pretty close. Then I look at a star to zero out the coma by adjusting the truss. I look at the star out of focus, and stick my hand into the beam and move it around until the shadow of my hand is on the 'thin' side of the donut (out of focus image of the star). I then know which way I need to move the truss. After a few iterations, the coma has been taken care of. Overall, I'd say that it's no harder than collimating a 'regular' f/4 Newtonian. The collimation seems to hold well throughout a night.
The reason I put the collimation at the top was to allow me to put the mirror farther back into the ball, thus helping balance. The hardware, plus room to allow for the adjustment, would have taken up about 1" of space back there. Also, since the mirror doesn't move relative to the ball, the mirror edge supports are glued to the inside of the ball, and aren't attached to the part of the mirror cell with the triangles and bars. So, from a certain point of view, the ball is also the frame for the mirror cell.
Posted 23 January 2013 - 03:10 PM
Posted 23 January 2013 - 03:11 PM
Posted 23 January 2013 - 11:35 PM
Posted 23 January 2013 - 11:55 PM
Posted 23 January 2013 - 11:59 PM
Posted 24 January 2013 - 12:07 AM
As one critical observer noted "that the CA for an 4" f/12 was about as good as it gets. The rings were concentric and perfectly shaped" and " this looks lens like it was turned on a lathe, perfect star test images and as good as a 4" achromat can be. He was even speculating that maybe the glass was special and that this wasn't a Fraunhofer design to get such good correction."
It doesn't get better in a 4" than what this scope puts up. I built up a 6" f/12 Istar and I say the same thing.
Posted 24 January 2013 - 03:36 AM
- mdowns likes this
Posted 24 January 2013 - 04:03 PM
Six inch refractor made from cat food tins and plastic drain pipes, used for solar imaging.
Friskies, Fancy Feast - or Tender Vittles?
Posted 25 January 2013 - 04:16 AM
Posted 25 January 2013 - 05:24 AM
- mdowns likes this
Posted 25 January 2013 - 07:03 AM
Looks like what I'd call a B&Q scope!
Posted 25 January 2013 - 09:57 AM
Looks a touch like Steampunk which I like.
is it hard to collimate?
Posted 25 January 2013 - 10:01 AM
Posted 25 January 2013 - 12:17 PM
Posted 25 January 2013 - 04:09 PM
my scope with two 635mm mirrors is called "Hexy" (the tubes are 16 sided=Hexadecagon shapes ) -it is F4.7--has fourteen, motors to control all aspects of Hexy's movement's ,pushbutton control box in eyepiece area , it has motorised sliding focusers/diagonal's ,-both tubes are pivoted to swing in 90 degree opposing direction,s to allow merging at the eyepiece,s
The alt/az is controlled by motors and special setting circles --the colour scheme is Black blue & Gold
(martian skies blue)
Have melted and polished my own mirror's The whole shebang including the aluminised mirrors has cost £1500.00.
Hexy is roughly equivalent to a 36 inch mirror due to the binocular format .
Collimation is a snip=very easy.
this is an old pic. but the eyepiece/ tertiaries are where the 50mm tube is coming out of the cages . Hexy is so well balanced on big bearings-I can literally move Her round and up and down with one finger .
Hope you all like her.
Posted 25 January 2013 - 04:37 PM
Posted 25 January 2013 - 06:47 PM
Posted 25 January 2013 - 06:50 PM
This is my little pair of binocular's--the mirror,s are 635mm
Posted 26 January 2013 - 03:20 AM
Here's my my build using a Carton 100mm f/13 lens.
Scope parts are made from M.D.F. board and plastic soil pipe.