Seeing versus Transparency - a simple explanation

Introduction

When you first get started in astronomy you might hear terms like seeing and transparency.   The lingo is often confusing until you finally "get it" and it clicks in your head.  I'll try and give a simple explanation to explain the differences between the two.  Other sites are already out there that go into the details.

Seeing

Seeing is a term that describes how stable the air is.  The more stable the air, the finer details you can see in your telescope.   Have you ever seen a mirage?   The shimmering air over a hot road causes the road behind it to blur.  This is the same thing that happens in your telescope, but since it is magnified many many times, it doesn't take as much of a difference in temperature to show.   Differences in air temperature in the different layers of the atmosphere cause small "mirages".  Even looking over a warm rooftop can greatly affect your seeing!

Viewing the planets are where seeing is the most critical.   To get the fine details on Jupiter's belt or Mar's surface or the rings of Saturn you need the nice stable air.  

Splitting double stars and resolving stars in globular clusters are other areas that need good seeing.   Looking at galaxies, nebula and other objects are less critical, so on nights of "bad seeing" those are better targets of interest.

If the stars are twinkling a lot, that is an indication of poor seeing.   Often they twinkle near the horizon, but are steady overhead.  You are looking through more air when going near the horizon, so there's more opportunities for the air to deflect the light.  If the stars are clear and steady near the horizon, it's a night of excellent seeing.  Get out the scope and look at whatever planets are up!

When you are looking through the telescope and the seeing is bad, keep looking.  Often you'll get little patches of good seeing and the view will clear up for a couple seconds.  Be patient and you'll be rewarded.   Even on nights of good seeing, you'll get small patches of excellent seeing!

Transparency

Transparency is a little more obvious as it is a measure of how much light makes it through the atmosphere.   The worst days of transparency are cloudy days!  Many things affect transparency like dust, humidity and pollution.  On bright objects like Jupiter transparency won't affect your view much (unless it is really horrible).  In fact even a little bit of fine haze can help on the planets.   

But on other objects like galaxies and nebula transparency can be the difference between find an object or not even seeing it all!  Some nebula from my home (with moderate light pollution) disappear completely when the transparency is bad.

An Analogy 

Imagine you are the bottom of a pool looking up at the blue diving board.  The water is crisp, clear and still.  Both the seeing and transparency are excellent.  The diving board is clear and it's easy to see the color.

One child jumps in the pool and makes waves all over the pool.   The seeing has just gotten much worse and the view of the diving board shakes back and forth.  It's hard to make out the edges of the diving board and it looks more like a shifting blob.   This is the same thing that will happen to the view in the telescope.  The air is shifting slightly and causing the light to bend back and forth just like the waves in the pool.

Another child who was in the sandpit and covered with sand now jumps in to wash off, then gets out.   The sand goes everywhere and is suspended in the water.  The water gets murky and hard to see through.  Now the diving board is shaking back and forth like above, but it's also dim and hard to see. You may not even know what color it is.  Both the seeing and the transparency are bad.  

Once the water has settled down (seeing improved again) you can make out the shape of the diving board again, but it's still very dim.   All the sand in the water is blocking some of the light.  Now the seeing is good, but the transparency is poor.

Telescope "seeing"

If you don't let your scope cool long enough, then your telescope itself can affect your seeing.   Basically you have warm air coming off your lens/mirror which is making a localized air current in the scope causing the light to shimmer and shake.  The effect is usually much worse than atmospheric seeing, so it's important to let your scope cool to the air temperature by leaving it out for a while before you use it (at least for planetary or other high magnification work).

Generally the larger the scope, the longer it needs to cool.  Many of the bigger scopes actually have cooling fans for just that reason.  If you can, set out the telescope as soon as the sun sets.  If you set it out while the sun is still up, then you'll heat up the scope, which is counter-productive!

Smaller scopes ( less than 4") take less than half an hour to cool.  Many you can use right away with very little degradation.  

Medium sized scope (4" to 10" or so) take about an hour to cool.   

Larger scopes (over 10") can take 2 hours or more depending on the scope type.   Some larger scopes never fully cool, especially when the air temperature keeps dropping as the night goes one.  They "chase" the ambient temperature.

You can use a larger scope before it's fully cooled, but just use it for lower magnification work.  I take out my large 18" scope and start using it immediately, but only at 60x magnification.  Sometimes it's neat to look at Jupiter at the beginning of the session to see how bad it looks, then I have another look a couple hours later before I put the scope away.  The difference is astonishing in how much detail you see.

Astronomy Beginner's Frustrations (and how to avoid them)

It seems every beginner is going to suffer some frustration on their first few/many times out under the stars with their carefully selected first telescope. What frustrations they have start with their choice of telescope.

Goto/Push-To: 

The first time you take the scope out and you set everything up (as you've read in the manual many times before going out - hopefully!) and go to do the alignment procedure. The first few times you mess up with one of the steps and have to start all over, sometimes resetting the whole scope. Then finally, you (supposedly) get it aligned and select one of the famous objects. The scope whirs or you push it to where you need to go, then you look in the eyepiece and...... nothing but stars. You scratch your head and wonder why it's not working? Did my scope miss? Is the object not visible in my scope from my location?

Often times your first night out you end up seeing.... nothing! A big fat zero. You might be lucky and have a planet up that's easy to spot and just use the hand controller to put it there without using the computer. Other times you're stuck with just a view of a few stars that look just like the stars you see with your eyes.

Then you finally get it aligned successfully (for real and absolute positive, but maybe not on your first night out) and you slew to some of the big name objects and actually see them! Result! Then you do the tour of the best objects and many you can't see. Did your goto miss? Can you not see it? Often it's just a case of the wrong eyepiece used. M57 looks like a slightly fuzzy star if your magnification is too low. Some get washed out in light polution. Maybe the transparency is horrid. But you're new and you have no clue.

Time and experience heal both the alignment woes and the object selection/eyepiece selection woes. But often their is a rough start, especially if you didn't find Cloudy Nights (or a similar forum) before purchasing and trying the scope out.

My personal goto problem was the Orion XT12i. Besides being a monster to haul in and out, when I first got it the computer was in equatorial mode (for some awful reason). A call to Orion support finally fixed it so I could have some success on my 3rd night out. The first 2 were total busts as I was unprepared for manually moving/aiming the scope.

Some people never get their goto right. Sometimes the scope itself is defective. Sometimes it's a PEBTAO (Problem Exists Between Telescope and Operator). Either way it's frustrating.

But usually after the first few tries it becomes easier and after several uses it becomes second nature.  Once the Goto scope is aligned, you can view objects quickly and easily.   Generally the kinks are worked out with goto much sooner than you can learn the manual method (starhopping).  And the ability to track objects automatically once you've found them is very valuable (and almost priceless with children who want to view as well).

Manual

You did it... you got the bigger scope that you have to manually point so you could get more aperture to pull things in. You'll definitely be able to see more, better things more-better than those that chose a similarly priced GOTO scope.

So you go out and your setup is pretty easy and straightforward. If it's a dobsonian, you just plop it down. If it's an EQ scope, it's a bit tougher, but for your first night getting the axis pointed roughly north is close enough.

Update 12/2022

I wrote an app to help teach the skill of star hopping!

IOS:
Standard: https://apps.apple.com/us/app/star-hop-trainer/id1659902403
Pro: https://apps.apple.com/us/app/star-hop-pro/id1660056372

Android:
Standard: https://play.google.com/store/apps/details?id=com.starhop.free
Pro: https://play.google.com/store/apps/details?id=com.starhop.pro

Now what? If you're lucky, one of the big planets (Jupiter and Saturn really) are up and you know about where they are in the sky. They're pretty easy to find being bright. You align it in your finder scope and put an eyepiece in.... and.... all you see are stars! Wait, this was supposed to be easier than the GOTO option at least for something like the planets. You scratch your head and pan around a bit and hopefully find the planet. Looking back in the finder, you realize it wasn't aligned properly! You spend some time getting the finder and scope to agree with each other and now you're in business. The planet looks great and a big smile of satisfaction sets in.

So now you want to see something else. Where do you start? Starhopping is not too hard, but the first few times it is tricky getting oriented and then moving the scope in the correct direction. If you're using paper charts, you have to twist them around until the match the sky at that time of night. And then if you look through the finder and it's not a RACI (Right Angle, Correct Image), you're confused as the star patterns don't match the chart. If you haven't read that the finder or even the scope changes how the stars are flipped/mirrored it can be very confusing. And if using paper charts you have to do the mental gymnastics to try and get the two to match. Plus depending on the chart there may be more or less stars visible, so you have to try and filter out the ones that don't match. Finding some of the objects that aren't right near a bright(ish) star make your head hurt quickly!

Electronic charts (like Sky Safari) can help a lot if you know how to set them up. You can flip the view to match what you see (either for finder or for through the scope) and you can also change how many stars are visible to better match up. This helps a lot as the view you see with your eye matches what is on your chart and your mind only has to deal with trying to figure out where to go next to get to the object you are looking for.

Still, many of the first nights are spent searching rather than viewing. My first night with the dob I spent 1.5 hrs searching and about 20 mins viewing. And of course the most frustrating thing is not finding what you are looking for. You seem soooooo close, and don't want to give up, yet after 40 mins you're done for.

Solutions? 

The absolute best thing to do is try and find someone experienced to help show you want to do. Nothing beats it.

Second best is reading a lot before going out. Know how your scope works, how the views will look and what you might expect from each bit of your equipment.

If using a manual telescope, get out with binoculars first. Even 7x35s or 10x50s will let you learn star patterns and match them to charts and see some of the brighter faint fuzzies while using the forgiving wide field of view of the binocs. Even cheap ones will have a much larger field of view (FOV) versus the telescope and will be similar to the view through the finder scope on the telescope.

Give yourself time your first night. Get out before the sun sets to get everything set up while you can see. Try out the alignment of goto scopes (even indoors just to learn how the software works). Get your finder aligned. All these things can be done before it gets dark. Then take your time and understand each step.

Books like Turn Left at Orion, Nightwatch and The Backyard Astronomer's Guide can really help explain many of the nuances of using a telescope and finding/viewing objects in the night sky.

Rewards!

After it is all said and done, most people get to see the objects that wow them.... and the first few sights through a telescope never leave you. My wife and I will never forget our first view of Saturn through our cheap Meade 4.5" reflector. Even the views today through my 18" dob cannot replace that first tiny view of the ringed planet. 

And it only gets better and much much easier as you go on!

Christmas and Telescopes - How to avoid a bad experience

Buying a First Telescope

Many children develop a curiosity for space and that usually leads to wanting a telescope to look up "there".  And here's where one of the biggest tragedies occurs.... a scope that is too cheap!   No, I am not advocating very expensive telescopes for children.   But there is a breaking point between getting a "junk" scope and getting something actually useful.

When I was 9, I was reading everything I could about space, the planets, galaxies, etc.  I couldn't get enough.  And for Christmas I got a telescope.   A little refractor.   Unfortunately it was so shaky and the eyepieces were so bad that it was hard to get even a decent view of the moon.  I thought telescopes were not for me and it was 30 years before I got another one.

And here is the biggest point of this blog.  If you get a telescope that is too cheap, it's worse than getting no telescope at all!   Really!  A pair of binoculars would be better (10x50, 8x42 or even 7x35's).  A wobbly telescope that is very hard to use will discourage budding astronomers.

The easiest bit of advice is do not buy a telescope from a department store or toy store.  They build them to a price point just to sell them.  On the box they will tout very high magnifications like 600x which are not practical in a scope that size.  The optics are horrible, the mount is not good enough.  If you look on craiglist, you will see tons of these scopes recycled back into the market.

What will you see?

The second big bit of advise is to set your expectations accordingly.   All of the objects to look at in a telescope are very far away.  Even the planets, our closest neighbors, are far away.  Only the moon is somewhat close.  Most any telescope will give good "wow" views of the moon.

The Hubble Telescope images available on the web have set people's expectations high.  No amateur telescope comes close to what you will find.  For example, the Orion Nebula:

Orion Nebula - Hubble Telescope

Orion Nebula - Amateur Telescope

The Orion Nebula is one of the most stunning objects in the sky besides the planets.   But if you think you will see the left picture in a telescope then you will be sorely disappointed.

The planets are similar.  Size is important in telescopes.  Distance is also important.   Here's 3 different images of Jupiter:

Jupiter taken from orbit around the planet (showing the shadow of a moon as well)

Jupiter in a smaller telescope (also showing the 4 moons)

Jupiter in a large amateur telescope

It's a striking difference!   Saturn is very similar:

Saturn from the Voyager 2 spacecraft

Saturn through an average amateur telescope

So what is the point?   That's often the question that arises.
 Even though the view is not as spectacular, there's something about seeing things with your own eyes that no photo, no matter how stunning, can replace.  My wife and I first looked at Saturn in a little Meade 4.5" reflector telescope.   It looked just like the picture I posted above.   But yet it didn't seem real.  It felt like someone had just pasted a picture on the end of the scope.  Seeing it for real was just something you can't quite put into words.  Even now, in both our 11" telescope and even now in our 18" telescope, nothing beats the awe of that first look!

The other part of looking through a telescope is not only viewing what you are looking at, but imaging and thinking about what you are actually seeing.  Learn about the objects and imagine what is actually out there.   Billions of stars in the galaxies, millions of stars in the clusters, new stars being born in the nebula, and the remains of dead stars in the planetary nebula.  Engaging the rest of the brain seems to be key in enjoying astronomy.

On many of the galaxies you will see, the light that is hitting your eye was generated when the dinosaurs were still walking on the earth.  And if you look up some Quasars you can see light that was formed around the same time as our own solar system was formed.

What to buy?

So if you made it this far, then you still want to buy something.  So what do you buy?  There are 2 main routes you can go, either with a computerized telescope (it finds objects for you) or a manual telescope (where you learn to point it).  Both have strengths and weaknesses and there is a trade-off with going one for the other.

For the most part, aperture (the size of the telescope's main lens or mirror) is king.  The bigger the aperture, the more detail and the brighter things will appear.  Of course the scope also gets heavier and more expensive, so finding a balance that works for you is key.

Computerized Telescope

This is a subcategory of telescope where you do some initial setup of the telescope to align the scope's computer with the night sky.  After doing the alignment you can punch in desired objects into a controller and the scope will move to the object itself and then you can just look.

Pros

• Once aligned, it's easy to find objects via the computer.  You can see a lot of objects in one night and most provide a "tour" of the best objects for that night.
• Will track the object once you find it, so it stays in the eyepiece view until you move to the next object, which also helps when using it with multiple people as you don't have to keep realigning the scope for the next person
• Can easier use higher magnifications (due to tracking above)

Cons

• Less aperture for the same money (you have to pay for the computer as well as the telescope)
• Needs batteries or power cords
• Initial alignment can be frustrating.  First several nights you will need a lot of time just to align it.  Plan on 30-90 minutes.  If using with children, then you should do the first alignment on your own and only bring them out when it is aligned (or at least have something else for them to do while you are aligning).  Once you get it down, complete setup and alignment will probably only take under 10 mins.
• If you go too cheap, the tracking motors will "wobble" so the view shakes a bit
• You don't learn the sky as much.  Beyond learning the first few alignment stars, you'll probably just punch stuff into the computer and watch it "do it's thing" and then look through the eyepiece.

Manual Telescope

For this subcategory of telescopes, the user is responsible for pointing the scope and keeping it aligned on the object.  The telescope and mount are usually fairly simple and robust and have very little to break.   You can either get the same size scope cheaper, or get a larger telescope for the same money.

Pros

• Larger aperture for the same money spent, or cheaper for the same aperture vs computerized scope
• No power needed, so can take anywhere (camping is great!)
• Less complex, so less to go wrong (they last decades)
• You learn the night sky very well by navigating to objects on your own

Cons

• Finding objects is up to you.   So the first few nights you can spend most of your time not seeing anything.  There are a few things that are very easy to find for new people (Moon, Venus, Jupiter, Orion Nebula) but beyond that it'll take a bit of knowledge and time.  Finding stuff you haven't seen before will take longer than some you visit often.
• No tracking -  you just got it lined up and you see it!   Now the next person wants to see it, but wait, it's already slipping out of view.  You have to adjust it again and then hand it back over.   And if someone bumps the scope significantly, you have to start all over!

Recommendations (as of Feb 2015)

Under $200

Choices here are very limited.  If you want a computerized scope you are probably out of luck.   At Christmas Costco in the past has had a Celestron 102mm  (4") scope on a marginal go-to mount for $199.   I'm not sure if they still do or not.  It works well enough to be usable.

For a manual scope you can get the Astronomers Without Borders scope for $199.  It is a 130mm (5") scope on a table-top mount.  If you don't have a sturdy table to put it on, you'll need a tripod as well.

Most others you don't want to touch.  They will provide more frustration than anything else.

Craigslist - Often you can pick up one of the scopes in the next category for under $200.   There are many Christmas presents that are left unused after the first few uses and later go up to be sold.  It can save you a lot of money if you know what you are looking for.  But you need to check them over and make sure the optics (lenses and mirrors) look good and that the computer (if it has one) works properly.

$200-$500

Celestron Nexstar 4SE - this one just squeezes under the $500 mark.  It has the computer and is small and portable.   

Orion XT6 - manual scope but with 6" aperture.  Small and portable and a great size for children too.  At around $300 leaves more room for eyepieces (more on that later).

Orion Starblast 6i - tabletop scope with a "push to" computer.  This helps you push the scope to the right place, but you actually move the scope yourself.  This also means no tracking.  But 6" of aperture with computer help just squeezes in under $500.

Orion XT8 - manual scope with 8" of aperture.   Still small enough to move around easily for most adults.  You can see a LOT with this telescope and it's still well under the $500 mark.

Apertura AD8 - Similar to the XT8 above, but with better mechanical workings.   At just over $500 it's really in the next category, but I'll squeeze it in here.  Many prefer this to the Orion XT8.  The Orion XT8 Plus is similar in upgrades and also similar in price.

$500-$1000

Celestron Nexstar 6SE - bigger brother to the 4SE above.   It grabs double the light of the 4SE so you can see a lot more.   A great little scope and a common family scope.

Orion XT8i - push to computerized version of the XT8 above.   For many a great compromise between aperture and computer help.  At under $700 it's a lot of scope for the money.

Orion XT8g - A goto version of the XT8i.  This one is full goto and has tracking as well.   At just over $1000 it too is just out of this category, but is a better fit here.  This scope is bigger and heavier than the Nexstar 8SE (below) but cheaper as well.

Orion XT10, XT10i, Apertura AD10, AD12 - Larger dobson telescopes that can go even deeper.  They start getting heavier as they get bigger though!

$1000+

Celestron Nexstar 8SE - the biggest of the SE series and at $1200 it's a serious scope.  For many this is a "lifetime" scope as you can see a lot, yet it's still fairly portable and easy to carry/set up.

Celestron Evolution Series (6, 8 or 9.25" sizes) - newer cousins to the SE series, this adds some neat features like built-in battery, wifi control (so you can control it with your smartphone!) and more robust motors/tracking.

Orion XT12i, XT10g, XT12g,  -   These dobsonian telescopes get big and they can see lots of detail and "go deep" (see dimmer objects).  But they also get heavy and more expensive.  If you're really serious about viewing things it can be very worthwhile, but probably not good as a starter scope.  Often times people use a dolly or other wheeled setups to move them in and out.

Wait!   Leave some money in your budget!

There are always a few things that people forget about when they buy just the scope and then later have more expenses they didn't plan on.

Eyepieces

The biggest upgrade after getting a scope is getting a better eyepiece.  The eyepieces that come with some scopes range from downright horrible to just usable.  Some of the eyepiece designs still sold with telescopes were invented in the 1600's (yes, when telescopes were first pointed at the stars!).

There are many factors and stats to look into on eyepieces.  And if you search you will find tons of information about them.   But one of the easiest ways to show the difference in a cheap eyepiece vs an upgrade one is with some pictures:

Now look at the size of this lens!

Look where your eye goes!

These are both 9mm eyepieces.  But the one on the left has a tiny opening for your eye.   It is a struggle to get lined up in just the right spot to see through it.   But the one on the right has a nice large area to get your eye lined up with and an eyecup that helps guide you to the same spot.   One other thing less obvious is that you have to have your eye really close to the eyepiece on the left and that can be very uncomfortable.

An eyepiece kit may look handy and at around $125 they are a decent value.  But I rarely see anyone who stays happy with the kit and usually moves on.  It's usually better to buy 1 or 2 "better" eyepieces for the same price.  For example 2 of the Agena Starguider eyepieces is about the same price as a kit, but they are much higher quality and will probably stick around in your eyepiece set for a long time.

Other things to buy

Batteries/Power - If you have a computerized telescope, you may need to buy batteries, a rechargeable battery pack, or a power cord you can plug in to the wall.

A Planisphere -  this is an easy way to see what stars and constellations are up for the time of year.  Useful for aligning a computerized telescope or orienting yourself on star charts if using a manual telescope.

A Star Atlas - If manually moving your telescope, or even for knowing what to look at with a computerized scope, a star atlas gives you a more detailed view of the sky.  The Pocket Sky Atlas is a relatively cheap atlas that is detailed enough for the new astronomer without being too detailed to be overwhelming.  Also these days you can get a great sky atlas for your smart phone.   Sky Safari is a great tool and comes in 3 "sizes".  I'd recommend the Plus version ($15) as it has plenty to keep you busy for a long time.  It's available for both iPhone and Android.

Red Light - a little red light is used for reading star charts, changing eyepieces, setting up, etc to help preserve your night vision.  You want all "white lights" turned off so your eyes adjust to the night sky.  They become much much more sensitive after about 30 mins, but even a second of bright light can destroy that and you have to start all over again waiting 30 mins.

Finders Scopes - If manually moving your telescope you may want a better finder scope.  This is a small scope which helps you point the bigger scope where you want it.   A Telrad is a pointing device that is very handy.   You may also want a RACI finderscope, which basically means when you look through it the view will match the same pattern as when you look directly at it with your eyes and when you look in the star charts.

Observing chair - If you are comfortable, it is easier to see in the eyepiece.  Bending over or contorting to reach the eyepiece means your eye won't be steady, which makes it harder to get a clear view.   Using a chair to steady yourself helps a lot.  You need an adjustable chair for most scopes as the eyepiece moves as the scope moves.   Choice range from the simple "drummer's throne" to a dedicated astronomy chair, with prices in a wide range as well.  There are also plans for making your own if you have a decent DIY streak.

Books - You can read a lot on the web these days, but sometimes it's easier to read through a book.  There are several good books for newbies:

• Turn Left at Orion
• NightWatch
• The Backyard Astronomer's Guide

Final Thoughts

Buying a telescope is a big decision and a lot of thought can go into getting the best scope that works for you.   Cloudy Nights is a website with a beginner forum that can help answer any of your questions and help you choose the right scope for you and your family.  Hopefully this helped you make a better decision (even if that is not to buy a telescope yet!) and prevents some of the frustration new buyers face.