I don't plan to make my own :) - but would like to take a look skyward these clear Winter evenings. Patrick Moore used to say " a good pair of bins is preferable to a telescope for the "casual" viewer". Thing is I've forgotten what spec. he said would be preferable for astro. use. Can someone pls advise me? (X x Y) Also is there a reasonable good make available for £50-100? I know this is not going to be super quality for that price but want to avoid buying complete no-no's. I guess it'll be an ebay thing. (!) thx
Standard Navy issue was 7x50 - that's a good balance of aperture and magnification for spotting submarines at night. I'd suspect that 10x50 or 15x70 won't gather quite as much light.
This is what I recall from when I bought my bins for night viewing over 20 yrs ago.
A major consideration for viewing at night is, what is known as, the binoculars exit pupil.
In prolonged darkness most peoples pupils adjust to around 5.5 mm IIRC.
The formula for calculating the bins exit pupil is object lens diameter (mm)/magnification. So a 10 x 50 pair of bins has an exit pupil of 5mm and an exit pupil of that size doesn't quite take full advantage of your pupils light gathering abilities but is close enough.
Similarly a 8 x 22 pair would have an exit pupil of 2.75mm and would perform poorly at night.
Another thing to consider is the magnification and whether you will be using a tripod.
Lying back in a deckchair in the garden looking skyward at night using hand held bins with just 8 x magnification for any length of time will cause the steadiness of your hold to deteriorate and the greater the magnification the more pronounced the effect will be on what you see. The larger the object lens will also mean the weight is greater increasing your shakiness.
So without a tripod it's a trade off of one thing against the others.
Reworking the above formula means you can determine the object lens size if you know what magnification you are looking for. Of course you will be stuck with whatever sizes manufacturers make.
If, just as an example, you want 15 times mag your object lens should be minimum 15 x 5.5 mm diameter to make full use of your eyes. That would mean an object lens of 82 mm. These would perform very badly hand held due to the weight & magnification problem but well on a tripod.
By the way, taking into account all the above, I bought 8 x 40 for handheld use with en EP of 5mm.
I do some astronomy when I have the time (and the clear skies). So far as binoculars go, there are some things you should know. First of all, it's very difficult to eyeball anything just by holding the binoculars in your hands. It's not too bad for terrestrial viewing, when you're looking horizontally. However, when pointing upwards, the amount of wobble increases with the magnification, plus they'll get heavy after a very short time. It rapidly gets boring just loking at fields of stars, so objects like the moon are a natural target. To see detail, you will need some way to support them. Either "sandbagging" on a convenient wall/fence or a stand/tripod. Next, don't think you'll see any detail on the planets through binoculars. They're just too damn small - you _will_ need a telescope to see detail on Jupiter or the rings of Saturn.
Here's where my views diverge from the accepted (i.e. P.M's) views. The advice about starting with binoculars was prevalent in the 60's (I still have The Observer's Book of Astronomy from that time.) when telescopes were _not_ mass produced and binoculars were readily available as WW2 surplus. That made the costs of entry much cheaper with bino's than with a specialty telescope. However, when you think about it, a pair of binoculars has twice as much optics as a telescope and therefore the amount of high- precision glass is double what you'd get in a telescope (plus the extra stuff to make the view "upright" which astronomical telescopes don't have).
You can pick up a reasonably crappy telescope on eBay. They're pretty much all made in China these days - including the "names" such as Meade or Celestron, Plus they come with a rudimentary tripod, which you wouldn't get with a pair of binoculars. Reflectors are cheaper than refractors for the same aperture and their apertures are much greater than you'd ever get with binoculars. Also, with a telescope you can change the eyepieces, to get different magnification (high for planets, lower for the moon) which you can't do with any but the most expensive binoculars.
Plus of course, if you decide it's not for you, you can always unload your gear on eBay again.
If you're a casual observer you may find that the suggested 15 x 70's are a bit heavy for extended hand holding use, but if you are prepared to get a tripod as well you can get a lot of enjoyment from them. Some brands come with a tripod mount that allows easy mounting, so it's worth checking before you buy.
I have seen M101 as a faint (but distinct) blur using a pair of these.
You can get Celestrons or Strathspeys for about £75 online from reputable dealers.
uk.sci.astronomy and sci.astro.amateur are probably as good places as any to ask (or search the archives for them).
It does - thanks all. I thought there'd be special considerations for night viewing. Many (many) years ago I bought a "Scout" telescope. A good instrument in itself (brass in leather case). It worked well with the standard 25x lens. At the same time I suckered myself into buying a 75x lens (not the same manufacture quality). It was laughable when I came to use it. Terrestial use on a tripod was ... just... about possible but handheld ay night was *im*possible :-) Apart from the fact that the amount of light entering the "big" end was insufficent, the 75 x made the scene skate all over the place. Live and learn eh. ps I asked on this group because of the folk here that *do* stuff for real.
The 50's will gather the same amopunt of light the 70's more but the higher magnification makes holding them still enough very difficult.
The only bins I have had have been 10x with various apertures and star gazing hand held is not really practical. 7x would better but a support of some sort really is required.
I go along with pete's post, indeed this is an opertune thread as The Lad has expressed an interest in a telescope for his birthday, 9 in Feb. So any more useful tips on choosing a decent and not to expensive telescope would be very much appreciated. Along with how easy they are to setup and guide without the motor drives and computer gizmos as I doubt the budget will stretch to that. I'd rather have good optics than handy "toys".
We are located in the middle of North Pennines so have really good dark skies, I suspect probably the darkest in England.
The other year i paid £85 inc postage for a meade EXT70 telescope, off ebay from one of the big telescope shops,
this is one of the scopes with an electronic handset and motorized base, so once you've pointed it in the right direction, it tracks what ever your looking at, and you just select which star/planet/satelite pass you want to look at, and it points the scope at it for you, all you have to do is select the magnifcation you want from the eyepiece and focus it.
taught me a lot about the sky, can even manually point it at an object and ask the handset what your looking at, and it'll tell you, as well as ask it to give you a tour of the interesting things that can be seen on that night... it has a database of all the events... comet passes, staelites turning where you get the flash off the solar panels, which plannets are best viewed etc.
i sold it because i'd outgrown it's small objective lense, which was 70mm, and i wanted to see more, but as is usual with me, once i had the cash from selling it (for a tenner more than i bought it for) i bought something else (actually went round europe and spent the telescope cash on a tank of fuel in my motorhome :)
One day i'm going to get one of the larger lensed tracking telescopes, and a half decent camera for it, fit an electric focuser, and plonk the whole lot on the flat roof of my dormer bungalow, and control the scope and see the results from the warmth of my bed.
i know people will say meade is chinese now, and there are better scopes out there, sure, but they cost a lot more too, if you can get a tracking scope for about 100 quid, then it'd make a great first scope, and if you get bored you can be guarenteed to make your money back on it,
These days objective lenses are moulded plastic, frequently aspheric, and all the better for it. I'd look at 70mm objectives and regard 50 as a bare minimum.
My best Moon-viewing binoculars are Navy surplus, the tracking sight from a Seacat missile launcher. Very heavy and need a tripod though. Those huge old East German border guard jobs are pretty good too.
Hate to puncture the dream but putting a telescope on the roof of a heated building would wreck the stability of the image - all those thermals would not go un-noticed.
My experience is that the weight is the most important thing. You end up with arm ache very fast. Also, to avoid neck ache you find yourself lying on your back most of the time.
In fact probably the ideal 'support' would be a bracket that takes the weight on your forehead while you lie back on a cushion.
To state the obvious, a tripod is indeed important -- but you need a pan and tilt head on it. A ball and socket head is near useless, especially if you try to watch the sky.
The tricky thing about the tripod is its height. When you are using one for terrestrial viewing, it only has to come up to eye height (whatever observing position you assume: standing, sitting etc.). However, if you want to use one to view stuff overhead, well that's where the top of the tripod has to be - over your head. Also, you need to add on to that height the distance from the bino's mount point tothe eyepice - another good
6 inches or so. You also get into a very uncomfortable position which is difficult to hold for any length of time.
The upshot being, that you could end up with the need for a very tall tripod. This will have a fair bit of weight on the top and therefore will swing around and oscillate badly when touched. Some observers perfer a parallelogram arrangement (google for it). This has the advantage of maintaining binocular pointing direction even when they're moved up or down. Making some is within the abilities of a DIYer, and this newsgroup being ....
True. Some of us have tripods costing several hundred pounds for photographic use anyway. Good tripods tend to come much higher than cheap ones. But point taken, absolutely.
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