Thanks for the replies Andy and Nick, I appreciate it.
I am trying to minimise the length of the optical path once the light cone exits the Mewlon tube at the rear cell, so I can remain faithful to the 105 – 118 mm back focus range as recommended by Takahashi.
- 105mm = optimal
- 118mm = maximum recommended
I read that the image circle at the Mewlon 210 native FL is 18mm and using the Tak x0.8 Reducer increases this to 39mm. To benefit from this, I assume you would need to place the sensor in the recommended 105 – 118 mm range.
If I install a motorised focuser at the rear cell, it would eat up over 60mm (even based on a relatively low-profile unit like the JMI Event Horizon) of back focus. Therefore, I am looking at the Robofocus unit that operates on the Tak focus knob and doesn’t introduce any additional components into the optical path.
I occasionally image with my Tak Reducer, Filter Wheel and Atik 414 EX camera and using this combo with a motorised focuser fitted in the optical path at the rear of the mirror cell, would push the imaging chip plane well beyond the 105-118 mm range that Tak advises. (I maintain a 56mm distance between the rear of the Tak Reducer and the Atik imager chip).
Cheers
Dennis
PS - Beren: thanks for the PM re Pegasus.