Your eyepieces are the first accessories you should have and use with your telescope. Since they are interchangeable, a telescope can be used at a variety of powers.
Look through the eyepiece by placing your eye just behind it to take advantage of its eye relief, the spacing between the lens and your eye. This should be at least 15 mm for the best comfort, maybe more if you wear eyeglasses. You’ll lose field of view if you place your eye farther away and may even move your eye out of the beam of light from the eyepiece. Viewing too close to the eyepiece will prevent you from blinking and may also cause a black ring to appear around the field of view.
Now turn the focus knob of the telescope, first one way then the other until the object is in focus.
Always start with the lowest power eyepiece (i.e., the one with the highest number in millimeters printed on it). It is much easier to focus and has a wider field of view, making it easier to aim the telescope at a distant target.
As power increases, the sharpness and detail seen will be diminished. The higher powers are mainly used for lunar, planetary, and binary star observations.
Most of your observations will be done with lower powers. With these lower powers, the images will be much brighter and crisper, providing more enjoyment and satisfaction with the wider fields of view.
A good way to increase magnification is to use a Barlow lens. A Barlow lens rated at 2x can be used with your existing eyepiece and it will double the magnification of any existing eyepiece. Since longer-focal-length eyepieces generally have longer eye relief, using a Barlow to increase magnification will allow more comfortable high-power viewing.
A basic set of eyepieces would be 32 mm, 20mm (or 26mm), and 10mm (or 16mm), plus a Barlow (2x or 3x power).
Saturday, 15 February 2014
Why don't the images I see through my telescope look the same as photos taken with the same telescope?
The reason photos sometimes look better than what you see with the unaided eye is due to the camera’s ability to store light continuously as long as the shutter is open. The human eye doesn’t do that. Instead, it captures a scene moment to moment.
Many pictures you see in magazines and catalogs are time exposures. The camera shutter is kept open for several minutes or even hours while the telescope tracks the object across the sky. This allows the camera to record fainter detail and colors that cannot be seen with the naked eye.
Many pictures you see in magazines and catalogs are time exposures. The camera shutter is kept open for several minutes or even hours while the telescope tracks the object across the sky. This allows the camera to record fainter detail and colors that cannot be seen with the naked eye.
I have a refractor telescope with 900mm focal length and 60mm objective lens. Why can't I get a clear image when I try to use a 2x Barlow lens with a 6mm eyepiece?
This is because you’ve exceeded the practical limits of magnification for your telescope. The practical limits of magnification of a telescope are determined by the laws of optics and the nature of the human eye.
As a rule of thumb, the maximum usable power is equal to 50x-60x the aperture of the telescope (in inches) under ideal conditions. Powers higher than this usually give you a dim, lower contrast image. For example, the maximum power on a 60 mm telescope (2.4 in aperture) is in the range 120x-142x. The higher powers are mainly used for lunar, planetary, and binary star observations. As power increases, the sharpness and detail seen will be diminished.
The combination of the 6 mm eyepiece, 2x Barlow, and 900 mm focal length gives 300x. This is well beyond the maximum usable power of the scope.
The Earth's atmosphere also plays an important part in limiting the maximum magnification you can use. Instabilities in the atmosphere such as heat radiating from the ground and surrounding buildings, high altitude winds, and other weather conditions can cause the image to blur. This "bad seeing" can drastically distort your image. This also explains why bright stars appear to twinkle. The best time to use high magnification is on nights when the stars do not appear to twinkle very much.
As a rule of thumb, the maximum usable power is equal to 50x-60x the aperture of the telescope (in inches) under ideal conditions. Powers higher than this usually give you a dim, lower contrast image. For example, the maximum power on a 60 mm telescope (2.4 in aperture) is in the range 120x-142x. The higher powers are mainly used for lunar, planetary, and binary star observations. As power increases, the sharpness and detail seen will be diminished.
The combination of the 6 mm eyepiece, 2x Barlow, and 900 mm focal length gives 300x. This is well beyond the maximum usable power of the scope.
The Earth's atmosphere also plays an important part in limiting the maximum magnification you can use. Instabilities in the atmosphere such as heat radiating from the ground and surrounding buildings, high altitude winds, and other weather conditions can cause the image to blur. This "bad seeing" can drastically distort your image. This also explains why bright stars appear to twinkle. The best time to use high magnification is on nights when the stars do not appear to twinkle very much.
Everything I see through my refractor telescope is an inverted upside down image. How can I correct this?
To correct an inverted image, you will need a 90° diagonal lens. When a 90° diagonal is used, the mirror flips the image over, giving a right side up but reversed left to right image. You can achieve a fully corrected image using an erect image prism diagonal.
These image converters are available from Nipon Scope online store.
These image converters are available from Nipon Scope online store.
How to determine a telescope's magnification?
The magnification of a telescope changes as the eyepiece is changed. Magnification can be calculated by dividing the focal length of your telescope by the focal length of the eyepiece.
Calculating magnification = Telescope's focal length / Eyepiece focal length
Always start with your lowest magnification eyepiece (longest focal length) and work upwards from there.
A 2x Barlow lens will double the magnification of whatever eyepiece you use with it while preserving its eye relief. For example: using a telescope with a 800 mm focal length with a 16 mm eyepiece will give you 50x magnification. Using the same telescope and eyepiece with a 2x Barlow lens will give 100x magnification. This would be the same magnification as a 800 mm telescope with a 8 mm eyepiece.
Calculating magnification = Telescope's focal length / Eyepiece focal length
Always start with your lowest magnification eyepiece (longest focal length) and work upwards from there.
A 2x Barlow lens will double the magnification of whatever eyepiece you use with it while preserving its eye relief. For example: using a telescope with a 800 mm focal length with a 16 mm eyepiece will give you 50x magnification. Using the same telescope and eyepiece with a 2x Barlow lens will give 100x magnification. This would be the same magnification as a 800 mm telescope with a 8 mm eyepiece.
How far can I see with a telescope?
The farthest you can see in the sky with your telescope will depend on its ability to gather light and where you observe.
The most distant objects visible with amateur-sized telescopes are faint galaxies and the brightest quasars. They will be brighter and easier to see in a telescope that gathers more light and has a greater magnitude limit. Here bigger is better and a larger aperture scope will see more remote objects.
Location is also important. Even with a big telescope, you’ll see fainter, deeper and farther out into the universe from an isolated dark-sky site than from the heart of a megalopolis. For example: quasars are all very faint as seen from the earth. The brightest one is 3C 273 in Virgo. It is magnitude 12.9. A good 4-inch scope is capable of seeing it in dark-sky conditions. You’ll need a larger scope to be able to see it at all from a city.
The most distant objects visible with amateur-sized telescopes are faint galaxies and the brightest quasars. They will be brighter and easier to see in a telescope that gathers more light and has a greater magnitude limit. Here bigger is better and a larger aperture scope will see more remote objects.
Location is also important. Even with a big telescope, you’ll see fainter, deeper and farther out into the universe from an isolated dark-sky site than from the heart of a megalopolis. For example: quasars are all very faint as seen from the earth. The brightest one is 3C 273 in Virgo. It is magnitude 12.9. A good 4-inch scope is capable of seeing it in dark-sky conditions. You’ll need a larger scope to be able to see it at all from a city.
Sunday, 15 July 2012
When using an adaptor direct from camera body to scope, is it possible to shoot in auto focus or do you use manuel (i.e. F stops)? I would appreciate some advice (question from JE)
Hi, thanks for your enquiry. You would need to set the camera to manual mode when the camera lens is removed, as part of the auto focus function is achieved through the lens system.
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