[anthony2302749]

Originally Posted by davidpretorius

the c9.25 and c14 are apparently ideal setups for planetary in terms or mirror setups, but not the c11.

I not sure I understand fully why?

I was just pondering the above question. If we say that all things are equal then there would be no difference between any of the SCT on the market. But if you look at the specs of the competing scopes you may see some interesting stats.

Just working with Secondary Mirror obstruction by area (could not find relevant info on obstruction by diameter to I will leave in out of the equation) you will notice there is quite a variation in centre obstructions.

Celestron 9.25” @ f10 = 13%
Meade 10” @ f10 = 13.7%

Celestron 11” @ f10 = 12%
Meade 12” @ f10 = 11.1%

Celestron 14” @ f11 = 10%
Meade 14” @ f10 =12.4%

If a smaller centre obstruction will give you better contrast then you can infer the following.

• There is little difference between the C9.25” and the M10” and in the right hands should produce quality images if everything is equal e.g. collimation, camera, weather etc.
• When it comes to the C11” verse the M12” it looks that the M12” would be the better choice for planetary imaging due to the smaller central obstruction.
• And finally the big one, the C14” verse the M14” again the C14” is the better choice for planetary imaging again due to the smaller central obstruction.

So apart for the size of your bank account, if we go on the premise that a smaller centre obstruction will give you better contrast when imaging the planets then the C9.25”, M10” M12” or the C14” would be the scopes of choice. But remember technique makes up 90% of the imaging process.

Me may need to rethink my decision about my next scope for planetary imaging. Maybe a M12” or, yes you guessed it, a C14”.


Anthony