Subsequent to my thread on " how do you estimate focal reduction" i am still unsure whether its possible to get F2 out of an LX90 without the image deteriorating very much.
regards philip
There exists also a 'Hyperstar' system for some Meade OTAs. I think it is only available for 10" & 12" and requires a secondaru holder having 6 screws instead of three, which I believe the later models have. Google 'hyperstar'
Phillip I assume you are using a GstarEX.
For any focal reducer there is an optimum distance from the sensor to get the flattest field. For full frame or even c size sensors you are basically limited to a reduction of 0.85 to at best 0.70. The field of any simple optic is curved concave towards the optic and if you go for too much reduction it then curves the other way ie away from the optic.
As the GstarEX is at most 8mm (diagonal) so even a highly curved field for a large sensor will be approximately flat for the centre part of the image plane.
So a reduction of 0.2 is quite feasible as long as the focal length of the FR is many times the size of the imaging sensor diagonal.
Phillip I assume you are using a GstarEX.
For any focal reducer there is an optimum distance from the sensor to get the flattest field. For full frame or even c size sensors you are basically limited to a reduction of 0.85 to at best 0.70. The field of any simple optic is curved concave towards the optic and if you go for too much reduction it then curves the other way ie away from the optic.
As the GstarEX is at most 8mm (diagonal) so even a highly curved field for a large sensor will be approximately flat for the centre part of the image plane.
So a reduction of 0.2 is quite feasible as long as the focal length of the FR is many times the size of the imaging sensor diagonal.
Bert
Thanks for the info bert i was a bit perplexed at F2 but the images i posted seemed to indicate that. regards philip