I just got a 20 inch telescope. I’m trying to figure out what it can achieve vs my 12 inch telescope. Is it possible to actually see the disc of Saturn’s moon Titan? Or is that going to depend on the seeing conditions more than anything?
I just got a 20 inch telescope. I’m trying to figure out what it can achieve vs my 12 inch telescope. Is it possible to actually see the disc of Saturn’s moon Titan? Or is that going to depend on the seeing conditions more than anything?
Titan’s angular diameter is about 0.85 arcsec. The Dawes limit for a 20" instrument is 0.23 arcsec.
So, technically the answer is yes. But you only get 3 Dawes limits across the diameter, so you will not be able to see any substantial detail - not that it has much detail to begin with, anyway. But yes, you will be able to tell it’s not a star, and it has an actual apparent diameter.
Keep in mind that 0.23 arcsec seeing is rare. Keep an eye on the seeing forecast for your area, and test the seeing when you begin observations.
The scope must be in perfect collimation, and must be at thermal equilibrium with the environment (a hot scope brought out of the house will underperform for an hour or so).
You will need fairly substantial magnification, several hundred for sure, maybe approaching the 1000x limit of your aperture. Seeing will be the major limiting factor most of the time.
The Dawes limit for the 12" is 0.39 arcsec. Titan would look like a fat star. Again, perfect everything is the requirement here.