A few (perhaps idiotic) questions.

[chrissara]

Sorry if these questions appear inane, but they are ones that have been bugging me for awhile.

1. A few years ago a professional astromer told me that you can observe stars and planets during the day via a telescope. I just grinned at him. He noted my surprise and muttered something about filters. Can anyone confirm or deny that during the day it is possible to observe stars via a telescope and filters? This leads into my next question on radio telescopes (and whether he may have been referring to those)

2. How do radio telescopes work? I understand generally that they work on a radar type principle. Is it possible for an amatuer to build a small one or is that useless (i.e. you need the larger type ones such as Parkes) or is it that the cost is porhibitive or there are licencing requirements.

3. Binoculars. Is there any way one can determine the theoretical maximum magnitude observational limits of binoculars? There are a few websites that do telescope limits I am aware of. Also, how do the larger binoculars go compared to say a 6" SGC or 8"-10" Dob - the ones I refer to such as the ones for sale at Andrews:
http://www.andrewscom.com.au/site-co...11-andrews.htm
The ones I am looking at are the $449, $329 or $229 ones.

Thanks in advance.

[[1ponders] (Paul)]

Yes you can view brighter stars by day, as well as the planets Mercury (when it's at a greatest elongation is safest and brightest), Venus, Mars, Jupiter and Saturn. Not sure about Uranus, it mightn't be bright enough.

You can build radio telescopes in your back yard. As for the theory and technical stuff

The faintest star you can see with a 50mm objective in excellent conditions is between 9.5 and 10.3 (depending on which book I look in). This also depends on the quality of the lenses and your own eyesight. For a 100mm objective around mag 11 (again depending on the book) Doubling the objectives as in binocular may allow you to see more because of how the eyes work in stereo mode, but don't quote me on that.

[janoskiss (Steve H)]

1. Yes, but finding them is tricky.
2. Radio telescopes work the same way as optical ones, it's just that the wavelength is a lot longer (about a million times). Of course you cannot look through an eyepiece at the image, but need a detector in the focal plane to record it.
3. All else being equal, limiting magnitude goes like log(aperture sqared)/log(2.5), or about 0.5 magnitude increase with every 25% increase in aperture. Trouble with binoculars is that all else is not equal, because the magnification is fixed. I can easily pick up mag 9-10 galaxies with my 20x90. The reason to get binos is the wide true field of view. just on aperture, a 6" or 8" scope will show you a lot more, and when you consider higher magnifications attainable with the scope, more still.

[wraithe]

I cant answer any of your questions regarding optical astronomy...
but i can point you towards radio astronomy...The concept with radio astronomy is to recieve a radio wave and (damm too early in the morning to think).. turn it into a signal that can be displayed on your pc..you dont necassarily need to use a pc but being able to record and log what is going on is a huge advantage...
the easiest star to watch and get readings from is the sun...you can do that every day..no late nights..
The static you hear on a radio between signals, is basically what you are looking for(but at different frequencies of course)..
here is a link that will show you how simple a radio telescope can be...from here you could get as elaborate as your pockets allow...
http://my.integritynet.com.au/purdic...-telescope.htm

[ving (David)]

in theory, binos light gathering capabilities are the same as a telescopes... ie, a 8" reflector will probably kill a bino woth a 80mm objective.... in theory. I dont have any binos to try this on. you know, aperture rules...

you could get 2 8" dobs and make a pair of binos with them... that'd be interesting

as mentioned, bright planets and stars can be see with a telescope during the day... just last year we had jupiter up next to the moon during the day and it was clearly visible...

[[1ponders] (Paul)]

Speaking of 8" binos....I had the pleasure of looking through Binofied's binoviewer in NZ last year. 2 8" newts, . Eta Carina was mindblowing. What I really want to do though is have a look through his "Retina Wrecker" 2 16" newts. http://www.binoscope.co.nz/

[fringe_dweller]

Originally Posted by janoskiss

The reason to get binos is the wide true field of view. just on aperture, a 6" or 8" scope will show you a lot more, and when you consider higher magnifications attainable with the scope, more still.

I would just add to Steve's reply, the standout quality of binoc's (and binoc viewers), to me, is that when you are use both eyes, you get an increase in contrast by 1.4X and with faint extended diffuse objects like galaxies and comets, thats a good thing