SingAstro

Hi WT,

With a 5 inch (127mm) Newtonian, you should use magnifications up to a maximum of about 250x as Airconvent says. A rule of thumb is 50x per inch of aperture. However, even with large telescopes, the practical maximum for viewing planets and most other objects is about 300x-400x due to atmospheric disturbance.

Also, at a high magnification (more than 100x), a telescope's optics would have to be properly collimated (aligned). Do ensure that this has been done, otherwise the image will be soft/blur.

Further, what 4mm eyepiece are you using? With such a short focal length eyepiece, it would be best to use one of the upper-end types which have good eye relief (around 15mm+) and a sufficiently wide apparent field of view (50 degrees+). Otherwise it would be difficult to view the objects properly. It may be better to use the 20mm eyepiece with the 3x barlow than the 4mm eyepiece alone.

I have often viewed Jupiter previously with my 5" Celestron C-5 Schmidt Cassegrain telescope, and the views were quite good, i.e. could see two belts and the Great Red Spot when present (which is actually quite subtle). Therefore, you should be able to get similar views too.

From Singapore's urban skies, I think the following types of objects are suitable for viewing through telescopes:

(1) The Moon with its great wealth of detail (craters, ridges, rays, etc)

(2) The bright planets: Saturn, Jupiter, Venus, Mars, in that order.

(3) Bright open star clusters (e.g. NGC 3532 in Carina; NGC 6231, M6, M7 in Scorpius; the Beehive Cluster M44 in Cancer, etc.)

(4) Double and multiple stars (e.g. Albireo in Cygnus).

(5) The Great Orion Nebula (M42 in Orion).


Do try to view Saturn next. It is high up in the sky nowadays at about 8pm, in the East, in the constellation Leo. Saturn would be a good sight in your scope, better than Jupiter and certainly much better than Mars.


Most other fainter objects can't be seen well in Singapore, esp. galaxies, most diffuse and planetary nebula, most globular clusters, the Milky Way.
You have to go to a dark sky rural location in order to see these objects well. And remember to get a pair of binoculars too (e.g. 7x50mm, 8x50mm, 10x50mm).

As Airconvent says, do try to join up with others during observing sessions to find out more.

starfinder wrote:Hi WT,

With a 5 inch (127mm) Newtonian, you should use magnifications up to a maximum of about 250x as Airconvent says. A rule of thumb is 50x per inch of aperture. However, even with large telescopes, the practical maximum for viewing planets and most other objects is about 300x-400x due to atmospheric disturbance.

Also, at a high magnification (more than 100x), a telescope's optics would have to be properly collimated (aligned). Do ensure that this has been done, otherwise the image will be soft/blur.

Further, what 4mm eyepiece are you using? With such a short focal length eyepiece, it would be best to use one of the upper-end types which have good eye relief (around 15mm+) and a sufficiently wide apparent field of view (50 degrees+). Otherwise it would be difficult to view the objects properly. It may be better to use the 20mm eyepiece with the 3x barlow than the 4mm eyepiece alone.

I have often viewed Jupiter previously with my 5" Celestron C-5 Schmidt Cassegrain telescope, and the views were quite good, i.e. could see two belts and the Great Red Spot when present (which is actually quite subtle). Therefore, you should be able to get similar views too.

From Singapore's urban skies, I think the following types of objects are suitable for viewing through telescopes:

(1) The Moon with its great wealth of detail (craters, ridges, rays, etc)

(2) The bright planets: Saturn, Jupiter, Venus, Mars, in that order.

(3) Bright open star clusters (e.g. NGC 3532 in Carina; NGC 6231, M6, M7 in Scorpius; the Beehive Cluster M44 in Cancer, etc.)

(4) Double and multiple stars (e.g. Albireo in Cygnus).

(5) The Great Orion Nebula (M42 in Orion).


Do try to view Saturn next. It is high up in the sky nowadays at about 8pm, in the East, in the constellation Leo. Saturn would be a good sight in your scope, better than Jupiter and certainly much better than Mars.


Most other fainter objects can't be seen well in Singapore, esp. galaxies, most diffuse and planetary nebula, most globular clusters, the Milky Way.
You have to go to a dark sky rural location in order to see these objects well. And remember to get a pair of binoculars too (e.g. 7x50mm, 8x50mm, 10x50mm).

As Airconvent says, do try to join up with others during observing sessions to find out more.

Thank for sharing yr information. By the way how do i know whether my scope is properly collimated ????. Beacsue it's a new scope so i guess the collimation should be no problem
I cant get the similar View of the Jupiter as what u enable to see ????
are u sure about that.. i can see two belts and the Great Red Spot with my scope ????

WT wrote:
Thank for sharing yr information. By the way how do i know whether my scope is properly collimated ????. Beacsue it's a new scope so i guess the collimation should be no problem
I cant get the similar View of the Jupiter as what u enable to see ????
are u sure about that.. i can see two belts and the Great Red Spot with my scope ????

Hi, your scope might already have been miscollimated when you got it, or it may have gone out of collimation when you shifted it about (e.g. transported it in your car). Miscollimated optics in Newtonians and SCTs are quite common and no cause for alarm.

I don't have much experience in collimating Newtonians, especially the classical type. This article might help:
http://www.skyandtelescope.com/howto/diy/3306876.html
(I wouldn't open up the telescope though)

See also this entertaining how-to video:
http://www.andysshotglass.com/Collimating.html

And your scope's manual might have a section on collimation.


Yes, you should be able to see Jupiter's two main belts and the Great Red Spot in your 5 inch Newtonian at a magnification of over 200x, provided it is well collimated and good eyepieces are used.