Amateur Astronomy


#1

Some folks on the Urban vs. Rural thread seem to have mistaken my moth collecting hobby for amateur astronomy. Never one to miss a chance to pontificate on something I know nothing about, here’s the thread as requested. Anyway, wasn’t moth collecting the accidental pastime of two very famous amateur astronomers who went on to win a Nobel prize? According to legend, moths and pigeons were among the sources of extraneous infrared noise that Penzias and Wilson had to eliminate from their horn antenna on the way to discovering the Cosmic Microwave Background radiation in 1965.

Any other trivia I can bore yiz with? :mrgreen:


#2

Recently there was an image published of the lights across Europe, taken from space, like the one below. What was surprising was how one of the darkest parts of the map was just below the Dublin conurbation, probably coinciding roughly with Wicklow.
In light terms could almost be described as a black hole.
So what TF is going on in Wicklow, or not going on, that makes it so dark??

https://www.savethenight.eu/Lights%20in%20Europe_files/luciw-filtered.png


#3

First things first. Common question for budding amateurs is what sort of equipment is needed.

Number one piece of equipment is your eyes. That was my main equipment for the first thirty years of astronomy interest. There’s a lot to be said for getting to know your way around the sky with the unaided eye. Also, certain events such as meteor showers are pretty much naked eye phenomena, as is satellite watching (heavens-above.com).

The second piece of equipment is a five quid piece of paper called a planisphere. Nowadays you can replace many, but not all, of its functions with amazing phone and tablet apps like StarWalk. The point is not to have the right gadget, but to understand how the sky moves during the night, and how it changes over the course of the year. There is some abstruse terminology associated with celestial position finding, but basically it’s all about the celestial equivalents of latitude and longitude, combined with the effects of the earths rotational peculiarities. You don’t need to know all (or even any) of the details to enjoy a spectacular night sky. But it adds to your appreciation if you know what’s going on.

Next up, a pair of binoculars. You want the lowest magnification and the largest objective lens size. Regular 10 x 50s are fine. That’s 10x magnification with a 50 mm (5 cm/ 2 in) objective lens. But you would be better with 9 x 70s if you can find them. Magnification counts for nothing – stars are too far away to be anything but points. Objective lens size determines how much light you collect, and therefore what the dimmest stars you can see are. This is true of telescopes too. Don’t splash out too much. I bought an expensive pair of 9 x 70s only to find that they had an annoying internal reflection, visible only in dim light (such as star gazing, duh!), which produced a faint double image of bright objects like planets. The biggest limitation of binoculars as astronomical instruments is the difficulty of steadying them.

If you are into photography, you may be able to do more than you thought with just your current equipment. Have a look at this guy’s photos (and follow the links on the right hand side). Two things to note – long exposure photography needs an (expensive) tracking mount to follow the motion of the sky. Modern DSLRs have infrared filters over the sensor which cut out some of the interesting frequencies from extended objects like nebulae.

Light pollution is your enemy. Unfortunately, the larger towns and cities are not good places to view from. Any artificial lighting threatens to either blind you directly, or can reflect off clouds or haze in the atmosphere, which can severely impact the view. Unfortunately, in Ireland, the sky is rarely as transparent as you might get in a dryer climate, so there is always some haze to reflect city lighting. With haze or broken cloud in a city, you’ll probably only be able to see the very brightest objects in the night sky. Even on a cloudless night, my experience from about six miles south of Dublin city centre is that the dimmest visible stars are up to six times brighter than the dimmest you will see from a dark rural location. If in doubt, look up your location in this light pollution guide (scroll down to the night sky simulator and zoom in on the map). A limiting visual magnitude of 6.0 is an almost perfectly dark location. Anything below 4.5 is dodgy.

This may sound sacrilegous, but unless the moon is specifically the target of your observations, it can be considered as light pollution too. A full moon will wipe out your view of the sky just as effectively as terrestrial pollution. Keep track of the moon’s phase using a plethora of web sites, such as timeanddate.com. It is worth mentioning sunlight too. There’s no sunlight at night, you may say, but it’s not true. At our latitude, there is some sunlight in the sky all night for the months of June and July. From an astronomer’s POV, there is no end to “astronomical twilight” for most of that period, as the sun is never more than 20 degrees below the horizon all night. Fortunately, this mostly affects the view to the north, which is the less interesting part of the sky.

Some people have never seen the night sky from a truly dark location. If you’re one of those, you owe it to yourself to make a point of it. Why not make a plan for the August Perseid meteor shower. It peaks on August 12th which is a Sunday, but you could try one of the other weekend nights too. The moon is reasonably favourable this year too, so if you’ve never watched a meteor shower, this is a good time. (However, if you’re like one of those people who’ve come back to me in the past and said “I saw a few feckin’ shootin’ stars … WAS THAT IT??”, then you don’t have the romantic spirit for amateur astronomy and you should try trainspotting or moth collecting).


#4

That’s a very pretty image!

What’s going on in Wicklow is mountains. Most of Wicklow is very sparsely populated. Unfortunately, this does NOT make Wicklow the greatest place for skywatching, the reason being that the hills make their own weather and you have dramatically more cloudy nights there, especially on the leeward side on the east coast. Anyone driving regularly from Dublin to Wexford will remark on how often the sky can be cloudy in south Dublin and Wicklow, but miraculously clears somewhere around the Arklow bypass.

For a truly dark (and clearer) east coast location, look on the east coast just level with the bottom of your black Wicklow blob. You will see a bright pixel which is Arklow, and just below it a not-so-bright pixel for Gorey. South again to Wexford town (with Rosslare jutting out into the sea), and back up north west to Enniscorthy. Inside the Gorey-Wexford-Enniscorthy triangle there are some of the darkest places in the British Isles, with the cloudlessness of the sunny south east, and not too far for Jackeens to travel. Of course, there are many very dark places in Ireland, and though the south east has the least cloud on average, we are quite blessed in general, with our sparse population. Compare, for instance, the south east of England, or the cities of the Ruhr valley. You won’t be seeing many stars from those locations.


#5

One more word on light interference. Even if you are in the darkest place on the planet, do not expect to jump up off the sofa from watching TV, and run out to see an amazing night sky. Your eyes are an amazingly sensitive piece of equipment and need time to adjust. If you go from a brightly lit area to a dark sky, you will likely see nothing at all for several minutes. You may conclude that it’s overcast. Give yourself time. Full dark adjustment can take half an hour. In the meantime, don’t look straight into bright lights, such as your cigarette lighter, your phone, or your neighbour’s security light. Turn out your own indoor lights if feasible, and shield your eyes with your hand from any lights you can’t remove.

Some amazing human eye facts:

The eye has an incredible range of sensitivities. At its most sensitive, the eye responds to individual photons. In practice you need half a dozen photons arriving within a 100 millisecond interval to create a neural signal that you could consciously register.

Your eyes adjust the contrast to suit the situation. When you read a book, the print looks like black on white, no matter what the conditions. But if you read the book outdoors in sunlight the black print is actually brighter than the white page as seen indoors in artificial light. No wonder you need time to adjust your eyes to near total darkness.

A sunny day is a hundred thousand times brighter than a night with a full moon. And that in turn is ten thousand times brighter than a moonless, star lit sky. From sunny day to starry night is a factor of a billion difference in illuminance.

You use different receptors for black and white vision, as opposed to colour vision. Your black and white vision is ten thousand times more sensitive than your colour vision. When you look at stars, only the brightest have any obvious colour. You’ll see a few red ones and maybe the odd bluish one. But even through the biggest telescopes astronomers see most things in black and white. Those glorious colour illustrations you see can only be captured photographically… so adjust your expectations accordingly when buying a telescope.


#6

Hi ps200603,

Many thanks for taking on this project. i have a lot of questions and its difficult to know where to begin. I had a huge interest in Astronomy in my teens, but didn’t have the money to get any decent equipment. Also any telescopes for sale in Ireland seemed to be underpowered and overpriced.

Reading through astronomy magazines and seeing all the ads gave me a sense that there was a bewildering range of telescopes, lenses, mountings, motors, cameras etc. There was an even wider rande of opinions as to which design or brand was any good. There was the chance that if you bought different equipment from different manufacturers they might not be compatible. Plus, I wasn’t sure if shipping a telescope through the postal system was a good idea. There was also the whole reflector/refractor deep space/solar system debate to consider.

To summarise some initial questions

  1. How does equipment react to being constantly shifted around/transported?

  2. Does the use of colour filters for photography produce “artificial” or “false” images, as beautiful as they might look. What would the colours of Juipter look like to the human eye from the window of a fictional spacecraft?

  3. How has the use of laptops/software impacted on the users experience?

  4. Is film still used for the best results or has everything gone digital?

  5. Are telescope designs such as the Schmidt-Cassegrain an excellent compromise in the reflector/refractor dilema or do they just give you the worst of both worlds?

  6. If all your current equipment were destroyed, what would you buy to start from scratch, using a budget of €1000, €2000 and €5000?

Please address these at your leisure. I’ve been waiting twenty years already to get serious about this.


#7

PmbF, I’ll see how many of those questions I can take on. First thing to bear in mind is I am not an expert. Like you, I have a long time casual interest, and a latter day desire to take it further. Apart from the practical side, I also started studying astronomy formally some time back. But I am a total novice. Take nothing here as gospel.


#8

I recommend
stellarium.org/

and/or

shatters.net/celestia/download.html

Currently in one of the best places in the world for astronomy/astrophotography yet I have no telescope or camera!!
Hoping to soon get an dslr with either an equatorial telescope or a pentax dslr with an astrotracer

I`ll post some results when I get the gear! But am a complete noob so very interested in what ppl have to say in this thread!


#9

+1. Stellarium is an absolutely indispensable tool. And it’s completely free!


#10

>> 1. How does equipment react to being constantly shifted around/transported?

It goes without saying that some astronomical equipment is fairly sensitive. Apart from the risk of breakage, or scratching optical surfaces, you can knock things out of alignment. In some instruments that can happen just through normal use, not to mention transportation. For instance, mirrors – especially the bigger, heavier ones – can move in their seatings. You can get a phenomenon called “mirror flop” whereby the mirror shifts slightly even depending on which direction the telescope is pointed.

The problem of alignment is greater with reflecting telescopes. Refractors are a generally simpler design. Also, for a given budget, a reflector will be bigger than a refractor. That said, larger reflecting telescopes are usually designed to be user serviceable, depending on type. The process of making sure your optics are correctly aligned is called “collimation”, and can be done with anything from zero equipment to fancy schmancy laser beam thingies.

Needless to say, unless you are building your own observatory you have to transport your equipment at least as far as the garden every time you want to observe. The stuff is built to be fairly robust. You’ll find that lenses and other small equipment are shipped in ridiculous amounts of foam padding, and you probably want to keep them that way when not in use.


#11

ps200306 is more knowledgeable but I’ll give some of these a go, but really, to get you the best info you should say what you are interested in doing, do you want to move the telescope a lot?, are you mostly interested in astro photography?, do you wanty to bring the scope on holidays?

  1. How does equipment react to being constantly shifted around/transported?
    That depends, the smaller scopes are designed to be shifted around, for example the Meade ETX-70 which is a refractor, about €150 but comes with a back pack cary case, had one of these for bringing on holidays etc. Great for looking at the planets, rings of Saturn and the bands around Jupiter. Where as if you go for something like this, Celestron C11, then it’s not going to like being moved around, the mirrors could loose allignment etc and your shagged.

  2. Does the use of colour filters for photography produce “artificial” or “false” images. As beautiful as they might look, what would the colours of juipter look like to the human eye from the window of a fictional spacecraft?
    What are the real colours of the planets?

  3. How has the use of laptops/software impacted on the users experience?
    That depends, if you are going to connect a camera to your scope then you can send the image to your laptop/tv, you can also download software to control your telescope from your laptop. You could also use your laptop to process images that you are taking, the cheapest way to astro photography is to just use a webcam that takes multiple images and software that alligns and stacks the images for you, as opposed to a camera were the shutter stays open gathering more light, but for this you need a very stable mount, a german equatorial like in the Celestron C11 I posted above, very heavy and a real pain to transport.

  4. Is film still used for the best results or has everything gone digital?
    Persoanlly I’ve never come accross film, only digital.

  5. Are telescope designs such as the Schmidt-Cassegrain an excellent compromise in the reflector/refractor dilema or do they just give you the worst of both worlds?
    Again is depends on what you want to do, if you want to move a lot with the scope, then you should go for a nice refractor, they are smaller and easier to transport, if you want midsize, maybe shift it the odd time, you could go for a medium size Schmidt-Cassegrain 5-8", as the light comes in from the top of the scope it is bounced of the bottom to a small mirror at the top and the back again to the lens at the bottom, this gives you a telescope with a focal length twice as long as the next scope I am going to suggest, but is half the size, if size isn’t a problem and you don’t want to move the scope then you can go for something like this, a Dobsonian, very cheap, best bang for the buck as they say, if you like you can make one yourself, captures lots of light but is pretty immobile.

  6. If all your current equipment were destroyed, what would you buy to start from scratch, using a budget of €1000, €2000 and €5000?
    That really depends on what you want to achieve.

If you want to learn the the constellations and the movement of the sky, you shouldn’t buy a goto telescope, which is why ps200306 is rightfully suggesting binoculars, you can see if you like the hobby and learn the sky while you are at it, then, once you know your way around the sky and have decided you have a real passion for the hobby, you can upgrade to a goto scope, astro photography is much easier with a goto also. The biggest mistake you can make is to go out and buy a €5000 scope when you are only starting in the hobby. Any real enthusiast will tell you not to go that way, as opposed to the guy who runs astronomy Ireland, I’ve been to some of their planet watches in the Phoenix park and there are these middle age guys standing proudly beside their €10,000 scopes that he sold them and they have no clue how to use them, it’s a disgrace. For astronomy in Ireland go to irishastronomy.org/


#12

Completely not true. Your answers make a lot of sense. Ta.


#13

Here’s my attempt on the colour question …

2. Does the use of colour filters for photography produce “artificial” or “false” images. As beautiful as they might look, what would the colours of juipter look like to the human eye from the window of a fictional spacecraft?

Well, you can look out the windows of spacecraft earth and see Jupiter at any appropriate time. So you know that Jupiter looks overall yellow-white in high contrast. A photograph will always be some kind of compromise, even without any additional filters at all, since the sensitivity of the camera optics will never be identical to those of the eye. Any professional image will tell you what filters were used, so a visual or “V-band” image is taken in a band of wavelengths that match the central part of the spectrum to which your eyes are sensitive. If you want to see something close to “real”, look for V-band imagery:

Colour filters are used for various purposes, to enhance contrast or highlight certain features, just like in regular photography. However, you’re probably aware that astronomical imagery is also done in different wavelengths for scientific reasons, rather than aesthetic ones. Different stuff is going on at different wavelengths, and an image is not “false” just because it shows things that you couldn’t see with the naked eye. The sun is a classic example – it’s visible surface is merely the region where it first becomes transparent to visible light. In different wavelengths the surface may be higher or lower than in the visible, and you can see different aspects of the convective and magnetic features of the “surface” and interior. (NEVER EVER look at the sun directly through a telescope or binoculars, of course).

https://www.tumblr.com/photo/1280/unknownskywalker/2499651330/1/tumblr_le5g6ojgye1qzyhb5

Colour has a different purpose again in the imagery of stars. Because it is a good approximation to a black body, a stars colour tells you its temperature (as well as indirectly about its size, mass and age). A common technique is to compute a “colour index” which is the difference in luminosity at two different wavelengths, which will be characteristic of a particular stellar temperature.

Anyway, to cut a long story short, if you get to the stage where you are buying colour filters, be aware of their uses. Hobby astronomy suppliers may sell you a filter that is, say, “great for high contrast images of planets” whereas if you are planning on doing stellar photometry you need filters with exact passbands in the UBV photometric system (which is just a fancy way of saying they pass light in the ultra-violet, blue, and visual, i.e. green-yellow parts of the spectrum. Sometimes it’s called UBVRI to add red and infrared. And sometimes it’s called the Johnson or Johnson-Cousins system).


#14

It was beautiful here last night, the sky was almost overcrowded. I went for a walk with the dog at around 11.30/12am - just around the farm - and it was glorious. I don’t bother with a flashlight. I seem to see less with it.

But it seemed - maybe I’m going a bit crazy here, that the sun was only setting, a livid red disc at about 11.30ish. I noticed it when I went out the back door, but when I looked again a few minutes later, it was gone.


#15

The moon was setting at precisely that time last last night, and would’ve had a red tint as you are looking at it through a lot of atmosphere, that said, it was a half moon. Could that have been it?


#16

Tip - Bring a red bulb flashlight or switch the bulb in your current flashlight with a red one!
Red light doesnt affect human night vision as much


#17

Saw that too, I reckon it a half-moon. Perhaps the sunburnt arse of a one-legged man?

Spectacular colour, though - really, really vivid red/orange. I reckon I was about ten minutes too late to go and get the camera and the tripod :frowning:


#18

*Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. *

Astronomy picture of the day

Time lapse movie of images taken from the ISS at night:

Absolutely stunning

The scale of the Universe:

Takes a few minutes to load


#19

+1. Would have been a half disc, with the illuminated half pointing northward (to the right) along the horizon as it set. If there was some cloud it could have seemed like a partly obscured solar disc. Would also have been large and bloated due to the moon illusion. It’s not that hard to be fooled. If you eyes are extremely dark adjusted a rising/setting moon can seem pretty bright.


#20

The scale of the universe thing is just mind boggling! Isn’t there a nebula you can see with very basic equipment? I can’t remember the name but it’s supposed to be very impressive.