Modification of a budget Bresser Messier 10" Newtonian

[Vroobel]

In 2017 I bought a Bresser Messier 10" Newtonian OTA with a Dobsonian mount. I built my ATM Opus Magnum EQ fork mount with hope that it will hold the Newtonian. When I finish building the fork mount I realised that a weight of the OTA causes big problem for guiding (inertia). Earlier I found that three clips holding its main mirror and a part of focuser tube staing inside the OTA make annoying shadows on bright star images ( https://www.cloudynights.com/topic/572839-how-to-remove-clips-shadows-in-a-newtonian ). Another problem was that a spider holding a secondary mirror wasn't a perfect cross, so the spikes became blurry. Also, the secondary mirror wasn't in a middle. And finally, a quite heavy Canon 6D and Baader MPCC were causing that the focuser didn't keep the optical axis. It caused that the position of the camera was changing within the night and flats were unable to counteract the vignetting properly. Everything together made that I stopped using it. I found that replacing a steel tube with a carbon one should eliminate problems of the load and stiffness of the focuser. But what about the rest? As it cost nothing, I made some alterations using my love to the 3D creations, but not only about that. It was to check, whether spending money makes sens.
 

1. A 10 mm thick arched supporting plate providing a bigger stiffness for the focuser thanks to its area. As it's 10mm thick, the focuser tube goes outside 10mm less.
   
   
   
    
2. A collar reducing slightly an aperture of the main mirror, but hiding the clips causing shadows.
   
   
   
   
   
    
3.  The focuser tube is shorter now that eliminated another shadow, bigger than the ones caused by the clips.
   
   
   
    
4.  The secondary mirror is equipped with a home-made horse-shoe-style dew heater and PTC sensor that allows connecting it to my Smart Dew Heaters Controller based on the Arduino.
   
   
   
   
   
    
5.  And as last the ZWO EAF is attached to the focuser.
   
   
   
   

This way the old budget Newtonian became a quite nice OTA, especially that it's F/5. It's still hard to guide with 17kg + accesories, but the results are satisfactory for me (please take into account that it's 1270mm FL driven by fully ATM EQ fork mount). I can consider the carbon tube now, if I found any cheap. The guiding will be easier, if I reduce the weight around twice.

 

Edited April 4, 2023 by Vroobel