bern wrote:Hi everyone, I'm so happy with all of your help and I'm able to spot saturn.
Now have another question..
my telescope aperture is 4.5", focal lenght 1000mm and using 10mm lens to view saturn with a size of about 3mm. anyway for me to increase the size of the saturn?
Thanks
Congrats!!! You just own the telescope for 3 days and manage to learn how to use it and found the planet! Keep up the good work!
Assuming under perfect clear skies, there is a limit how much a telescope can magnify an object before it turns blurry and un-focusable. A very general rule of thumb is 50 times magnification (written as 50x) per inch of aperture for mass-produced average optics. So for your scope : 4.5 inch x 50 = 225x
Since it is very rare we have perfectly clear skies, so the practical useable is most probably lower than the theoretical 225x for your scope. So the smallest focal length eyepiece that is usable for your telescope is about 5mm. To make Saturn slightly bigger, you can use barlow as recommended or a smaller focal length eyepiece smaller than 10mm.
Do some reading up on these terms and factors (borrow Star Ware book from library or get hold of The Backyard Astronomer's Guide) and find out how they influence each other. This will help you understand how to choose a good eyepiece for a certain type of telescope for a certain type of celestal object:
(1) Eye relief
(2) Apparent Field-of-View (AFOV)
(3) True Field-of-View (TFOV)
(4) Eye relief
(5) Exit Pupil
(6) Coma
(7) Astigmatism
(8) Vignetting
(9) On-Axis, Off-Axis sharpness.
(10) Eyepiece Field Stop
(11) Kidney-Bean effect and black outs
(12) Eyepiece performance on fast and slow focal ratio telescopes
Do join some sidewalks/starparties with your scope. You can try out participant's eyepieces on your scope and observe the effects.