I've always been intrested in everything science, especially Zoology, Paleontology, and I've just started out as an amateur astronomer. I've tried to be part of some other science forums, but a lot of them are not worth joining, I just hope I can actully learn something here.

I've started by reading many diffrent magazines and books on the subject, as well as reading on the internet about diffrent topics having to do with astronomy. I'm intrested in anything having to do with astronomy, especially the advancements in technology enabling us to see further into the cosmos. I'm also interested in star evolution, how they are born, and how they die.

I have a Celestron Advanced Series GT Telescope, because of the temperature and bad weather, I've only had it out three times, and only seen the moon. I hope to get it out during warmer weather this spring and summer to look at more distant objects.

A book I'm reading right now is "Chasing Hubble's Shadows: The Search for Galaxies at the Edge of Time" by Jeff Kanipe, It's a book I whould recommend to anyone intrested in the subject. I'm also reading Astronomy Magazine, which I will also recommend to anyone intrested in Astronomy. I plan on reading "Lives of the Planets" by Richard Corfield.

I hope to learn a lot while I'm here.
~Elizabeth~:)

Have you bought your first telescope yet ?

Have you bought your first telescope yet ?

Yep, I have a Celestron Advanced Series GT reflector Telescope. Because of weather and the cold I've only had it out three times, and only seen decent images of the moon. I identfied only one feature, Sinus Iridum, its a plain of basaltic-lava, not a crater like I thought it was at first. I tried to bring in Mars, but then the clouds came.

Yep, I have a Celestron Advanced Series GT reflector Telescope. Because of weather and the cold I've only had it out three times, and only seen decent images of the moon. I identfied only one feature, Sinus Iridum, its a plain of basaltic-lava, not a crater like I thought it was at first. I tried to bring in Mars, but then the clouds came.

I have an ancient Russian 6" refractor which is good for detail on the planets. Sadly, seeing conditions are only suitable on occasional nights during the year. I also have a pair of 15x100 mm binoculars which I use more frequently than the telescope. On a good night I can get breathtaking views of galaxies.

Are you into deep sky or planet viewing ?

I have an ancient Russian 6" refractor which is good for detail on the planets. Sadly, seeing conditions are only suitable on occasional nights during the year. I also have a pair of 15x100 mm binoculars which I use more frequently than the telescope. On a good night I can get breathtaking views of galaxies.

Are you into deep sky or planet viewing ?

Eventually I'd like to be familiar with both. I'm just starting with objects closer to home first. I hope to get a good veiw of mars soon, because I know exactly where it will rise. I know where to find the Andromeda Galaxy, and would love to simply see it with the naked eye. Most clear nights, I don't bother with the telescope, I just look at and name off all the stars I know. I guess after some planets, the Orion Nebula whould be the best object to veiw, because its easy to find, unless you have any other suggestions.

Eventually I'd like to be familiar with both. I'm just starting with objects closer to home first. I hope to get a good veiw of mars soon, because I know exactly where it will rise. I know where to find the Andromeda Galaxy, and would love to simply see it with the naked eye. Most clear nights, I don't bother with the telescope, I just look at and name off all the stars I know. I guess after some planets, the Orion Nebula whould be the best object to veiw, because its easy to find, unless you have any other suggestions.

Some telescopes are more suitable for deep sky, others for planets. Do you know the focal ratio of yours?

If you use a low power, say 25x, to look at galaxies you will be astounded. You will get virtually all of the galaxy into your field of view and the lower magnification gives a bright image. Are you aware the many beginners use magnifications which are too high. This results in an image which darker than need be plus atmospheric distortion is more of a nuisance. As a rule of thumb try not to exceed 50X per inch of aperture . So, for an 8" telescope about 400X would be the maximum useable magnification. This only applies when seeing conditions are really good. You will often find that a lower magnification will give you a sharper image which means you will see more detail even though the image is smaller.

I can recommend a book or two on fiding one's way round the galaxies, if youare interested.

I live in the UK where clear nights are few and far between. I imagine it's better where you are

This is good timing.

I have just bought a telescope myself - my first one. It's an 8 inch reflector on a Dobsonian mount. No fancy GOTO function or motor tracking - I chose to prioritise aperture over technology, given how much I wanted to spend on it.

How big is your telescope, Star-gazer?

I'm in the Southern hemisphere (southern Australia), and it's summer here. We've had some good nights for viewing.

I've looked at Mars, which even at high magnification is pretty featureless, although clearly a disc rather than a point. I also saw Saturn, which was impressive to see first-hand. The rings are clearly visible. I didn't look for the moons at the time.

I've also found quite a few impressive nebulae. The Orion nebula is one of the best, and easy to find. One of my favorite objects so far has been the Globular Cluster 47 Tucanae, which is just on the edge of the Small Magellanic Cloud.

The southern hemisphere has rich pickings for small telescopes, since much of the Milky Way is visible. I'm still trying to find my way around the Carina constellation. There is so much there!

On the other hand, one of the books I have talks about lots of interesting northern-hemisphere constellations that I either can never see or which are always close to my local horizon.

At the time I bought the scope, it was a new moon. Also, at the moment, the moon is quite close to the sun, which makes viewing it difficult. One of the things I'm looking forward to is getting a long hard look at the Moon close-up.

Myles:

Do you know how the focal ratio affects things? I'm still a little puzzled about that. (My own telescope has a ratio of about f/6.)

Hum,
my small scope has a focal length of 6.3 - i choose such a low focal length it because i wanted a short portable tube and i wanted a large field of view (ie nice views).
The bad thing is that the optics usually perform better at longer focal lengths (better for planets and splitting double stars etc)

http://en.wikipedia.org/wiki/F-number

Myles:

Do you know how the focal ratio affects things? I'm still a little puzzled about that. (My own telescope has a ratio of about f/6.)

As a general rule the smaller the focal ratio the better for deep sky and vice versa for planets. Your f/6 is fine for deep sky but should also yield good views of planets. If you have a camera, the principle is easy to understand. If you are taking a pic in low light then you open the aperture to gather the maximum amount of light and do the opposite for bright conditions.

With your camera you might have a range from 1.4 to 32. The smaller the f number the more light that is admitted for a given shutter speed. You cannot change the f number on your telescope but it is easy to see that f/6 will capture more light than f/10. F/6 will perform better for deep sky objects, which are faint. You will still get good views of the planets but they would be sharper at f/10.

One important point to remember is not to use too high a magnification, As I mentioned to Elizabeth, about 50X per inch is the maximum . And that applies only under good conditions. You will frequently get a sharper but smaller image if you use a lower magnification,

One final thing is that you have to get your eye in, that is used to viewing. Often the longer you look the more detail you will see. You should certainly be able to see the polar caps on mars as well as some other surface features. It's a question of sticking at it. A practised observer will see more than a newcomer. Keep viewing and good luck.

Thanks, Myles.

Myles,
With your camera you might have a range from 1.4 to 32. The smaller the f number the more light that is admitted for a given shutter speed. You cannot change the f number on your telescope but it is easy to see that f/6 will capture more light than f/10.
You are confusing a camera with an astronomical telescope. The focal length of a telescope has no direct effect on its light-gathering ability. Light-gathering ability is a function of effective aperature minus losses due to imperfections in the mirror finish (as I am certain James R knows, no mirror is a perfect reflector) and the quality of the coatings used on the optical surfaces. Other losses come from internal reflections in the tube and eyepieces. The reason I said no direct effect is because of the secondary mirror used in reflecting telescopes. The shorter the focal length of a reflecting telescope, the larger the secondary mirror has to be, which blocks a larger percentage of the incoming light gathered by your telescope. The main advantage of a shorter focal length is portability. The tube lengths are shorter, which makes them lighter and require a less massive mount to hold them steady.

Congrats on your telescope James, I'm sure you will get pleasure from it. And don't forget to get a neutral-density filter (moon filter) to look at the moon when it is over half-full. Though I don't think it is dangerous, an 8-inch scope can gather enough light to be uncomfortably bright when viewing the moon for any extended length of time.

Myles,

You are confusing a camera with an astronomical telescope. The focal length of a telescope has no direct effect on its light-gathering ability. Light-gathering ability is a function of effective aperature minus losses due to imperfections in the mirror finish (as I am certain James R knows, no mirror is a perfect reflector) and the quality of the coatings used on the optical surfaces. Other losses come from internal reflections in the tube and eyepieces. The reason I said no direct effect is because of the secondary mirror used in reflecting telescopes. The shorter the focal length of a reflecting telescope, the larger the secondary mirror has to be, which blocks a larger percentage of the incoming light gathered by your telescope. The main advantage of a shorter focal length is portability. The tube lengths are shorter, which makes them lighter and require a less massive mount to hold them steady.

Congrats on your telescope James, I'm sure you will get pleasure from it. And don't forget to get a neutral-density filter (moon filter) to look at the moon when it is over half-full. Though I don't think it is dangerous, an 8-inch scope can gather enough light to be uncomfortably bright when viewing the moon for any extended length of time.


You are quite right. I was trying to avoid getting into apertures, focal lengths and focal ratios. The point I was really trying to get across is that a small focal ratio is generally regarded as being better than a large one for deep sky viewing because it is easier to obtain lower power and hence a wider field of view. A larger focal ratio is generally regarded as better for planets because itis easier to obtain higher powers. I also wished to avoid talking about Barlow lenses which would have further complicated matters.

But in the end , I made hash of it. My only excuse is that it was about 4 am and I should have been in bed. Apologies for causing confusion.