GSO 200mm f/4 newtonian OTA

spec:

Primary mirror: 200 mm, coated 197mm, 1.9 kg， glass thickness 27mm

mirror with cell: 2.8 kg

primary mirror:

focal ratio: f/4

mirror to inner wall 13.5 mm

mirror face to back of tube : 50 mm

secondary: 63mm nom. (minor axis). Minimum required is 54 mm

tube 230 mm outer

OTA: 8.5 kg, including lock rings and dovetail, length 730mm nom.

as 100% illumination is around 9.3mm, this configuration is mainly for visual. of course won't stop you to go  for astrophoto, with appropriate sizing of secondary, eg 73mm(minor axis) 

 

The mirror has some minor polishing marks at 70% radius, at r =14 cm, width 1 cm

i guess those are left behind from figuring it to parabola

Slight hill at centre, radius 5 cm

coating is a bit opaque, guess it is over 20 years ago. 80 to 85% reflectivity

Focuser: JMI 2 inch, with motorfocus, jmi2

secondary holder:

 

collimation:

not easy, but do-able

first make alignment by visual, then use the laser collimator. btw it's a test of laser collimator too. the clearance of collimator and 1.25-to-2 inch adapter can throw the dot off the reticle

as always, alignment the secondary holder first. then primary cell.

a quarter turn of screw can throw red dot off the reticle

Repeat this procedures to dial in.

similar to this one. 

Agenaastro AD048, AD047

OCAL 

Yet another collimator github

Reference:

Another diy CF OTA is around 6.8 kg