Hi,
I read from internet articles and other people that the bigger the primary or the objective lens, the more powerful the scope is. Other things like the focal length also affects the performance of the scope. And lets not talk about external equipment like the eye pieces.
How is it that some model such as Meade ETX-70AT Astro Telescope w/Autostar Controller and Tripod have only a 70mm objective lens and 350mm of focal length be able to see nebulas and galaxies as described by binoculars.com? I saw some pictures taken by this particular scope and I must say it is simply amazing for a scope of this price. With only a 70mm primary mirror and a 350mm focal length, how is that possible to surpass a scope like the celestron newtonian reflector 114 eq short?
This celestron reflector has a objective lens of 114mm and a focal length of 1000mm but yet it costs only a half of the Meade scope mentioned here.
Lastly, does that means that there are other factors affecting the power of the scope and the objective lens and the focal length is not so important? I am really confused and hope I cAN be enlightened on this. Thanks
Confused
Ok, Lets start off with the binoculars.com. First of all, dont believe what others see, believe what your eyes see. Moreover, these are more of a sales gimmick than what the telescope can perform.
The visual performance of a telescope really depends on alot of factors. But mainly: Your aperture (the big-ness of your primary) and location.
Like the iris of your eyes, telescopes have the same logic. The bigger your iris are, the more light can gather into your eye, so you can see darker objects. And thats why our iris are bigger at night. Effectively, the bigger the aperture, the more light-gathering power you have, thus, having an 8"er will certainly be a big replacement to our puny 7mm iris - go figure.
Although you can see much with a 4"er, but why are things brighter and have more contrast in a 8"er? Simple maths will show you that although the 8"er is twice the aperture, its light gathering power is alot more that the 4"er. But of course, the mirror that you use, its lambda wave, coatings etc etc, will all contribute to its overall visual performance.
For Astrophotography, a short focal ratio will cut down on exposure times. But then again, thats another matter altogther.
Next, location. The darker the site, the less light pollution, the more your eyes are readily dark-adapted = the more you will see. Its that simple.
I hope i answer your qns!
Charlie
The visual performance of a telescope really depends on alot of factors. But mainly: Your aperture (the big-ness of your primary) and location.
Like the iris of your eyes, telescopes have the same logic. The bigger your iris are, the more light can gather into your eye, so you can see darker objects. And thats why our iris are bigger at night. Effectively, the bigger the aperture, the more light-gathering power you have, thus, having an 8"er will certainly be a big replacement to our puny 7mm iris - go figure.
Although you can see much with a 4"er, but why are things brighter and have more contrast in a 8"er? Simple maths will show you that although the 8"er is twice the aperture, its light gathering power is alot more that the 4"er. But of course, the mirror that you use, its lambda wave, coatings etc etc, will all contribute to its overall visual performance.
For Astrophotography, a short focal ratio will cut down on exposure times. But then again, thats another matter altogther.
Next, location. The darker the site, the less light pollution, the more your eyes are readily dark-adapted = the more you will see. Its that simple.
I hope i answer your qns!
Charlie
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weixing
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Hi,
Visual and astrophotography are totally different. In astrophotography, you don't need a very big scope to get very nice images. What you need is a very dark site, good seeing, clear weather, a very good mount, and very long exposure. This will allow you to reach magnitude beyond the visual magnitude limit of your telescope.
Also, if your site is very dark, you can actually see a lots of DSO using a small scope. Some DSOs are not as dim as you think... it is just that the light pollution in singapore is just too bad. I know an amatuer astronomer in US who tell me that he is able to see his shadow being cast by Milky Way... WOW :O
Overall, sky, site and weather condition affect the performance of your scope.
By the way, I think what binoculars.com mean is that you will be able to see all these objects under perfect conditions... Give me a 70mm scope and I can see even more DSO if I observe from the Moon...
Know what I mean..
Hope the above information helps.
Visual and astrophotography are totally different. In astrophotography, you don't need a very big scope to get very nice images. What you need is a very dark site, good seeing, clear weather, a very good mount, and very long exposure. This will allow you to reach magnitude beyond the visual magnitude limit of your telescope.
Also, if your site is very dark, you can actually see a lots of DSO using a small scope. Some DSOs are not as dim as you think... it is just that the light pollution in singapore is just too bad. I know an amatuer astronomer in US who tell me that he is able to see his shadow being cast by Milky Way... WOW :O
Overall, sky, site and weather condition affect the performance of your scope.
By the way, I think what binoculars.com mean is that you will be able to see all these objects under perfect conditions... Give me a 70mm scope and I can see even more DSO if I observe from the Moon...
Know what I mean.. Hope the above information helps.
Yang Weixing
"The universe is composed mainly of hydrogen and ignorance."
"The universe is composed mainly of hydrogen and ignorance."