SingAstro

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

The way a telescope work. One way To increase the power you would need to use a shorter eyepiece (ep)
X Mag power = focal length / ep length

E.g.
Your setup with a 10mm ep
1000mm / 10mm = 100x

So if you use a 5mm ep
1000mm / 5mm = 200x

Second way is to use what we call a Barlow

A 2x Barlow with a 10mm ep give you the same as a 5mm ep.

Hope this helps and your able to understand.

Clifford60 wrote:Use a 2x barlow to get it to 6mm in size or get a 5x tele extender and you have have a 15mm Saturn.

thanks, where can I get these stuff and what the damage like?

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.

Gary wrote:

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) 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) Kidney-Bean effect and black outs
(11) 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.

wow too chim... so can I use a 5mm EP and a 2x barlow together or 10mm with a 3x barlow? which is better?

Hi All, I intent to get this kit set any comment?

http://www.astro.com.sg/astro/display_i ... c=59378134

Hi bern,
Dont rush into making a purchase.
Go for more star parties abd sidewalk session. By then you would know what eps to be going for.

Davegn wrote:Hi bern,
Dont rush into making a purchase.
Go for more star parties abd sidewalk session. By then you would know what eps to be going for.

cos if just buy a 2x barlow will cost me at least 140 and this whole set at just 140 with gst. so think kind of good buy lor.

http://agenaastro.com/gso-1-25-2x-achro ... -lens.html

I'm using this barlow and it seems fine enough. I actually use it in preference over a Televue Big Barlow. Free shipping to the USA or $6.70 to Singapore (if you have a forwarding address)

bern wrote:cos if just buy a 2x barlow will cost me at least 140 and this whole set at just 140 with gst. so think kind of good buy lor.

Research more into the specifications of the $140 barlow (e.g is it using better multi-coated ED lens? body mainly plastic?...etc) vs the barlow in the whole set. Else you will not be able to objectively conclude whether which is a good or better buy. Best, look through a few of them during sidewalks and see if your eyes can see a difference.

cloud_cover wrote:http://agenaastro.com/gso-1-25-2x-achro ... -lens.html

I'm using this barlow and it seems fine enough. I actually use it in preference over a Televue Big Barlow. Free shipping to the USA or $6.70 to Singapore (if you have a forwarding address)

thanks will look around what poison to add later.

you get all your items here? cheap, good, safe?