Binoculars - A good start

As I have mentioned before a great place to begin your astronomical hobby is with binoculars, but do you actually know what it is you are looking at when the nice salesman is telling you about them being nitrogen filled and that they have a zoom ya de ya de ya, total discombobulation (thanks to K for the word of the day).

So lets start with a nice basic thing that you'll want to know, what is the magnification of the binoculars that I'm looking at, what does it all mean? Binoculars are commonly described by using a pair of numbers that just look like a maths sum on the side, it's the number you look at and go "oh yes", like you know. You'll see it represented like this; 7x50 or 25x50 or any other kind s of numbers. This is really incredibly simple, the first number represents the amount of magnification that the binoculars offer so in the case of the 7x50's the 7 means that whatever you look at through the eyepieces will appear 7 times closer than they would to the naked eye. See told you it was simple, the next bit is just as easy to understand so don't worry.

The 50 in the 7x50's relates to the size of the lens, or the big bit of the binoculars, the objective lens as it's commonly called, so the 50 stands for 50mm,

The objective lens is very important to you if you want to use the binoculars astronomically, as the bigger the lens at the end, the more light that you can catch, the better you will see in dim light. One important thing to remember is that everything through binoculars is magnified, which includes your own movements, so any shakes or wobbles will also be very noticable, so the higher the power the harder it is to hold them steady, and if you are using 50mm or above the binoculars will also be slightly heavier than smaller ones, this again adds to the problems of holding them steady.

So now you know the magnification and the objective lens diameter you can do a a calculation that will tell you the exit pupil, why is this important you ask, well it's a bit to do with how old you are, no I have not gone totally nuts, as you get older your pupils shrink and so getting a pair of binos with a huge exit pupil may not be worth it to you if you cant take advantage of them, with this in mind the formula is this. Divide the objective lens size by the magnification and this will tell you the exit pupil size so with our 7x50's you get approx 7.1mm of exit pupil, so 7.1mm of light is transmitted to you pupil. A bit techy but maybe important to you.

The next thing that you will probably come up against is the lens's themselves, you turn the len's towards you and are greeted by a lovely coloured lens and you think "ooooooogh, pretty", but beware, amber and red coatings are an astronomical no-no, they seem to be a bit of a gimmick to hide poor optics, but are said to be to reduce light glare.

The prism will be your next area of attention, the prism is what lets you see a correctly oriented image when you look through the binoculars. Typically there are two types of prism, Porro prisms and roof prisms, what's the difference though?

Porro prism can be identified by their offset tubes, so the objective lens is not in line with the ocular lens, or eye piece. The eyepieces are usually closer together than the rear lens's, but the reverse can be true in compact models. Porro prism are usually much better quality than roof prism another benefit is that they have a single pivot between the two halves of the binocular, making then easier to adjust to your eyes. Porro prism are also described as Bak4 or Bak7, with Bak4 actually being the better quality, and therefore the ones to go for if possible.

Roof prisms are essentially in line inside the optical tubes, and therefore can make for a more compact set. Roof prisms usually have two pivot pints between the two halves of the binoculars, and are more difficult to adjust to your face. Roof prisms can give an optical image equal to Porro prisms.

Another thing to think about is dewing of your lens's, when your outside and the night is cold, and you bring out your lovely warm binoculars from their brand new bag, the difference in temperature between the outside air temp, and the binocular temp is likely to cause one thing, dewing, this will end your observations very quickly, so consider getting nitrogen filled binos as they will not suffer from this problem at all, my own binoculars (15 x 50 in case your wondering) are nitrogen filled and I have never known them to mist, they are also waterproof.

So what to do to choose, well heres a few things you can do to test them in the shop;

• Steer away from zoom binos, there has not been a decent zoom made EVER (yet)
• Steer away from Red or amber coatings
• Give them a bloody good shake, if they rattle, don't buy them
• Check the focussing through its entire range, reject any with loose spots or that bind whilst focussing
• Do the same check with the focussing for the right eyepiece adjustment
• and check the hinge is also smooth
• If you re going to use your new binoculars with spectacles then make sure you can see properly through them with the eyecups folded down and the binocular at spectacle distance, so about 25mm
• If you have a big nose make sure it fits between the binoculars
• Check what prism you are buying, remember Bak-4 are best in my opinion

To see just what can be achieved with a monster set of binos, the look no further than Space Jocky he uses a set of Strathspey 25 x 100's (see pic at top of post)

Now these are some big binos, and will only be used on some form of tripod or support, but the results that you can get with them speak for themselves, check Space Jockys site for cracking images.

Follow Space Jockey on his blog or on Twitter, he really is an expert when it comes to using binoculars.

So I hope that helps a bit and good luck with any purchase you may make, and if you do, tell us about it.

Craig

Beginning Astronomy

So you've seen a shiny new telescope in a shop, borrowed a set of binoculars and looked at the moon, and now you think that you're ready to take the plunge and get that scope. Well firstly STOP!!!!!! my advice is to truly understand what it is that you are about to undertake, and stick with the binoculars for a bit, Space Jockey uses a set of 25 x 100's and is able to view just as much as a lot of people with a scope, why? because he knows how to use them and what to look for, he sees nebula as well as star formations, check out his blog here.

If your still hooked after a little binocular dabbling (and you will be) then if you want to, plump for a scope, but, which one? Reflector? Refractor? Dobsonian? Matsukov? Schmitt Cassegrain? the list is endless with each scope being good at something, but not good at all things. One thing to remember is that the bigger the aperture the more light you can gather, the better you may see, with this in mind Reflectors are good value for money, they provide the biggest aperture for your money. But they can be big and difficult to move about, bear in mind the bigger it is and the more it does, the more likely it is to stay put away, as it's so much hassle to get out and set up. Reflectors are relatively inexpensive and can be bought for around the £100 mark.

Mount is another consideration as the one you buy could be critical to your enjoyment, up and down, side to side (Alt Az) or Equatorial? What a decision to be faced with, equatorial follow the arc of the sky and can be very accurate and easy to use, once you find out just how to use them, Alt Az is in my opinion easier, but not what you want in my opinion if you want to advance in the field of astronomy.

So what did I buy when I first began this obsession? Well as I mentioned I got a pair of binoculars first a pair of 15 x 50 and I was hooked. I looked at the Moon and saw so much detail, I had a bit of a moment you might say, I then purchased a book that I would recommend to anyone starting out, it's called "Turn left at Orion" and will teach you the sky and how to star hop, so as to know where you are, and more importantly, what you are seeing. Once I had the hang of that, something which took a time I might add I began the trawl, you know the one where you read everything and talk to everyone about telescopes, but still are unable to make up your mind as to which one to get.

Everyone was more than happy to explain to me their personal preferences and as to why they had made that purchase. I first leant towards a Dobsonian, I like the simplicity and the sheer size of the scope, but I new that I wanted to image the sky and that a Dobsonian would not suit the way in which I wanted to do it, I then thought I'd go straight to the reflector good scopes with plenty of punch and more portable than the Dobsonian. But I still could not make up my mind, all the scopes had their pros and cons.

Finally I turned to what I already know, photography. This led me to take a closer look at the Maksutov style of scope as they are basically to me a large telephoto lens on an equatorial mount. But which one again, so many to choose from so little money. I then spoke to the good folk at David Hinds I explained what I would like to do and they steered me towards an offer they had on at the time. I am now the very proud owner of a Celestron C6 XLT Schmitt Cassegrain, and as you can see in the picture at the top of this blog it resembles a big DSLR lens. I bought it because it was an excellent price and is kind of a jack of all trades if there is such a thing in the telescope world, it produces me superb images of planets and nebula, and Im over the Moon with it, if you excuse the pun.

So to conclude, my advice, check around, but speak to the experts, it's a lot of money to be disappointed about spending, and look through as many scopes as you possibly can, each one is different in it's capabilities. Get the best mount you can afford, it's very important to have a steady base for your scope, and a good mount will be able to take all those upgrades and new tubes you no doubt will eventually get.

Also remember that whenever you buy anything that looks at the sky, after you have bought it and are eager to get out and use it, the sky will automatically cloud over for the following weeks.

Good luck, and clear skies.