General Observing Tips

General Observing Tips

Or how to see what you are looking at. This applies to Star Parties and Sidewalk sessions.

Eyeglasses and Focus

Try looking in the eyepiece both with your glasses and without them. Which looks better will depend on your prescription. (For the technical: if you’re astigmatic it’s usually better to keep glasses on. Otherwise its usually better to leave them off.) You may notice that the telescope owners tend to focus with their glasses on — this is so that we’re focusing for the corrected vision of our guests, not because we prefer to observe that way.

If the image is not sharp, ask the telescope owner if you may focus. Experienced observers refocus every time they look in the eyepiece. If you can’t reach focus, or want to annoy the telescope owner, say the magic phrase “Is this thing collimated?”.

Look through the eyepiece

We look through, not at the eyepiece. To look through the eyepiece, you should place your eye very close to it, about a half-inch, and then pretend you’re looking down a verrrry long tube. Optical guys call this “focusing on infinity”. It’s not like looking at your cellphone display.

Young children have trouble with this. There is no hard limit, but children younger than 6 to 8 years tend to look at the eyepiece (or at their parents) and not through the telescope. Your youngsters are welcome, but don’t be disappointed if they report they can’t see anything — looking through a telescope isn’t a simple concept and they may not be ready for it.

If you don’t see anything move your eye up and down and also look up, down, left and right. If that doesn’t work, the scope is probably off target.

Some telescopes will have several eyepieces mounted on them in different places. Only one will be for the main telescope, the others will be for finders. Only the main eyepiece will show full detail. It sounds silly, but it’s quite easy to look though the wrong eyepiece and be unimpressed with the view.

Dark adaption

Dark adaptation is critical at dark sites. It means allowing your eyes to see more in a low light environment. You do not need to do anything special, just turn off the lights and wait. Typically it will take about 1/2 hour for your eyes to fully adapt to the dark. (and after an hour it is even better). Any source of bright light will erase your adaptation immediately and your eyes will have to recharge for 1/2 hour again (dark adaptation involves biochemical changes that takes time for your eyes to process). Red light has the least effect in general, but even a red light if bright will still nullify your adaptation. In general, if you can perceive that the color of the light is red, it’s bright enough to effect your dark adaptation. This is why astronomers leave lights off completely and use only very dim red lights to find things and fuss with their equipment.

Relax and be comfortable, breath normally

(But be careful not to breath on the eyepiece). This includes wearing clothing appropriate to the conditions, ideally you want to be snugly warm (it gets cold out there even in the summer). OAFs will be happy to adjust the telescope for you so that you are in a comfortable position if they can, but usually you will need a stool or small ladder. There is physiology and psychology at play here. If you are contorted and uncomfortable your body is busy with other things so less blood and oxygen get to your eyes. For best seeing your eyes need lots of fresh oxygen, so holding your breath will not help that. Also if you are contorted and off balance, maintaining a white knuckle grip on that ladder high up to keep from falling, well you are probably more concerned about not breaking your neck than whats in the eyepiece. If that is the case just ask your friendly OAF if he/she can reposition the ladder or stool. We’d be happy to!

Take your time

There is looking, and then there is seeing. At Star parties with long lineups taking your time may be a luxury the people behind you may not appreciate, but do spend a minute or two at least, as opposed to 5 or 10 seconds.

The atmosphere is usually turbulent. At times you will not see much detail then suddenly a patch of steady air comes your way and ‘holy mackerel’ you can see stunning detail!! Astronomers pretty much always view objects for extended periods of time for this very reason. Sometimes with large objects you only see parts of it clearly at a time so over the course of an extended observation you eventually get to see most or all of it clearly as the ‘seeing’ (thats what we call it) comes and goes. Ask your OAF “how is the seeing tonight?”. Hopefully it is a good night and he /she will say it is pretty steady!

Another aspect of taking your time is that the initial glance at an object just registers with your brain that there is something there, the next few seconds classify it. If you stop there you only have gotten to the point where your brain says, “yup there is something there, looks like an ‘xyz'”. After 10 seconds or so you start to analyse detail, that is when you really start to see what is there and the longer you look the more detail you will discern. And if the “seeing” is good or it clears up momentarily for you it will be a sight that you will remember for a long time.

Sit if you can

This is part of relax and be comfortable, and an extension of take your time. At star parties or sidewalks this may not be practical. But if the crowds are thin, especially later in the evening, have a seat, get comfy and have a good long gawk!

Try not to close your other eye

This is a psychological thing mostly. You are more relaxed when both eyes are open. For many this is awkward and distracting. Try holding your hand over your other eye instead. Often astronomers will wear an eye patch over the other eye just for this purpose. Arrr Captain … ya big oaf!

Protect your eyes from glaring lights

This mostly applies to sidewalk sessions. Often OAFs will stand in front of any direct lights for you but sometimes we can’t so shield your eyes and you will get a better and more comfortable look. Please be careful not to touch the eyepiece though.

Use a technique called averted vision

This is simply not looking directly at the object but off to the side a bit.

The center of your eye is excellent for detecting detail and colour. But your peripheral vision is far more sensitive to light and it will pick up faint objects that a direct gaze will miss. Generally, all astronomers use direct and averted vision on a regular basis.

Different parts of our peripheral vision have different sensitivities. Look all around, you may find that by looking in a particular direction you will pick up fainter objects. Most people find these directions work:

  • if you’re right-eyed: look right;
  • if you’re left-eyed: look left;
  • If you’re using binoculars or a binocular telescope: look up.

Averted vision is not needed at sidewalk sessions, since the streetlights won’t let anyone dark-adapt. It’s also not necessary when looking at show-piece objects from a dark site with a large telescope. But averted vision is the way to see the dimmest, most challenging the the most distant objects. (For some, if it’s hard to see, it’s way cooler.) Many of these objects are not visible at all without averted vision, or a much larger scope. It is also useful when looking at bright objects, like star clusters, allowing you to see many more stars, or nebulae, allowing you to see more faint or low-contrast structure.

Look at the same object in different scopes

A large telescope will show fine detail, and reveal faint parts of an object. But it might not show all of it at once. A small telescope is more likely to show the whole object plus give you an impression of its surroundings. They’re complimentary views.

Also, some scopes will use filters and others will not. Filters always dim the object but also increase the contrast of certain features. Over a dozen different filters are commonly used in visual astronomy. They all reveal subtly different things about the same object.

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