Buying a Telescope

This usually comes down to Visual or Imaging. The first is using eyepieces to look at objects. The second is usually where a camera replaces the eyepiece for long exposures. Telescopes referred to as Astrographs should be able to be used for astrophotography out of the box. For visual use you likely will want a large aperture Dobsonian to focus as many of the ancient photons to the eyepiece as possible. Unlike a camera your eye only retains the photons for a short period.

For imaging a quality tracking mount and an Apochromatic (APO) refractor is the gold standard. As a beginner you likely don't need the gold standard. Expect the mount to cost as much as the telescope.

There are large Dobsonian telescopes that track. The issue is that their Alt/Az (up/down and left/right) mount motion causes an issue called field rotation if used for long exposures. It's possible to put a 8" Newtonian reflector on a large German Equatorial Mount (GEM) but the eyepiece is often at an uncomfortable visual position and any wind may vibrate the large tube for imaging.

The local astronomy club's members often offer public observing nights that allows visitors to enjoy views through the telescopes.

Looking through a telescope is where most of us get started and many of us stay. The aperture of the telescope, the light gathering part, plays a major factor in what you can see. The next component is how dark your skies are. Generally, you want to use the largest aperture that you are comfortable purchasing, storing and moving around so that you can see fainter and more detail in objects.
If you want to keep the cost down look at Dobsonian telescopes. For a nice upgrade add digital setting circles that help you locate objects, even in the city.
For a go-to scope that usually has a longer focal length (more power with the same eyepiece) for the same aperture look into a SCT. This could be on a Alt-Az (up/down-left/right) mount or a German Equatorial (GEM) or Strain Wave mount. On the GEM or Strain Wave mounts this could be used for astrophotography also.
Refractors are usually the image quality leader and are often used for planetary and double star viewing. They are weak when used looking ar Deep Sky Objects (DSOs) due to their smaller aperture.

Many astronomers find great pleasure sharing views of the sky with the general public. Usually the views are limited to bright objects with the Moon, Saturn and Jupiter topping the list. Weather permitting, I set up a telescope most Halloween nights (the parents like it as much as the kids) and often join members of the St. Petersburg Astronomy Club (SPAC) during public outreach nights. Visit your local public outreach events even if you do not yet have a telescope. Contact your local astronomy club for the dates, times (some may be daytime solar events) and locations. Sky & Telescope, a magazine for amateur astronomers, has an excellent astronomy club finder.

The Andromeda Galaxy taken from a bright suburb in Florida.

Astrophotography may be as easy as a camera on a tripod and capturing a dark landscape with the moon or star trails. It also may be as taxing as tracking stars for dozens of hours and taking hundreds of photos to combine the best shots into one good image. Using a wide-angle lens with a camera on a tripod you can usually take up a 30 second exposure without any noticeable blur to the stars. If you increase the exposure time stars will become streaks due to the rotation of the Earth.

While there are some inexpensive options to help extend the time, such as a home-made barn door tracker or move shoot move. The real solution is a tracking mount. More specifically a polar aligned tracking mount. The most popular of these is the German Equatorial Mount (GEM). If you plan on taking quality deep sky images you will need a quality mount that's capable of handling the weight of your equipment and allows accurate polar alignment and autoguiding. The mount really matters - maybe more than the telescope. Think of it this way: telescopes may come and go but a quality mount, like eyepieces, usually stick around.

Astrophotography takes practice and there is a lot to learn. Go to your local club's dark sky nights. Show up early and talk to people that have set up for photography. Do not touch any equipment unless the owner ask you to. This may be carefully polar aligned and a small bump, even stepping next to a tripod leg, may change the alignment.

Below breaks down a few of the astrophotography methods.

Travel astronomy is a special niche. I don't mean the usual trip of taking your telescope from the house to a dark sky site and back. Travel usually means flying to distant locations to observe. The easy solution is to ask someone on CloudyNights.com or StargazersLounge.com, or the astronomy club where you are going, if they would be willing share their telescope with you for an evening or two. If you are going to travel with a scope as checked luggage look into a solid hard-sided case like the Pelican Air cases. There are a few companies that make travel friendly scopes like collapsible Dobsonians (Sky-Watcher) and refractors that unscrew into shorter lengths (Astro-Physics) to fit in carry-on luggage.

The latest entries are smart telescopes that fit into a back pack, like the ZWO Seestar. This type of telescope may soon become the best option for travelers where astronomy isn't the primary purpose of the trip.

If you happen to be going somewhere that has a professional telescope check about getting a tour. Sometimes they are the classic observatories, like the Lowell Observatory in Arizona, and sometimes, like the Very Large Array (VLA) in New Mexico, it is group of outdoor radio telescopes.

A small, wide angle telescope is often attached to the main telescope to help you locate objects. It must be aligned to point at the same location as the main telescope. Locating objects visually with only the main telescope is much more difficult than you would think.

Sometimes the small finder telescope is replaced with a zero magnification finder. The Telrad is the most popular of these, although there are others. Some have lit-up bullseye and others have single red dots. You may have both eyes open and the display works like a heads-up display superimposing the dimly glowing circles or dot on where you are looking and, the main telescope is pointed, at the sky.

If you have a go-to telescope that is using a camera and it offers plate solving then when it is slews (moves) to an object it will take a brief photo of the stars and compare it to a database to make any adjustments and perfectly center the object. Plate solving is a somewhat new feature and it works amazingly well. I don't even attach the hand controller to my mount and allow the ASIAir to handled all telescope control.

High Power Lasers

High powered, usually green, lasers have become popular in amateur astronomy. Initially, they were used for pointing out objects at public events. Pointing at Saturn with your finger in the dark to 300 cub scouts doesn't work, but a green laser drawing a line to Saturn was a winner. Most of the cub scouts were more interested in the laser than in seeing Saturn. The lasers also were mounted on telescopes to be used to aim the main scope. This all works well. The issue is that the laser's beam may ruin someone's astro photo. Also, be careful not to point the beam at planes, helicopters or people. The brightest lasers could blind someone.

Solar filters are an usual beast. They attach to the front of the telescope to block most of the light to protect your eyes. The unusual part is that they attach to the front of the telescope instead of screwing into the bottom of the eyepiece. This is because blocking the light at the eyepiece would create a very hot filter possibly capable of cracking the filter and allowing light through to your eye. This would be bad. Make sure that your solar filter is appropriate for visual use and covers the front of the telescope while attaching firmly to it. Finally, make sure that there are no cracks or tears in the filter every time that you use it. Generally, solar filters allow you to see sun spots and major solar flares.

There are a few manufacturers that make dedicated (and expensive) solar telescopes. These have the advantage of having special filters built into them that allow you to see much more solar detail. This includes the boiling surface of the sun and detail on solar flares and arches. If you have a chance to look through one of these telescopes during a daytime event I highly recommend it.

Most filters screw into the bottom of the eyepiece. Filters can only block various wavelengths of light. That's it. The magic is to block the undesirable wavelengths and leave the good wavelengths. The goal is to make the background black and what you are looking for stand out more. If you have a 2" focuser and use a 2" to 1-1/4" adapter see if your adapter is threaded on the bottom. That will allow you to buy all 2" filters and use them on both sized eyepieces. The 2" filters do cost more than the 1-1/4" but not as much as buying both sizes.

A light pollution filter or Light Pollution Reduction (LPR) filter are, in my opinion, one of the more useful filters, at least in the city. They attempt to block artificial lights, such as street lights, billboard lighting and other outdoor lights. This leaves the natural light that galaxies, stars and nebulas light through. This increases the contrast often allowing you to see things that would otherwise be washed out. These filters have had a new challenge with outdoor LED lighting that has new wavelengths that need blocking. The manufacturers are aware of this and working on the problem.

Color filters are also common and they are often used to help being out details on planets. Using a red or orange filter to look at Mars is one of the more common usages.

There are dozens of other specialty visual filters: Ultra High Contrast (UHC), O-III, H-Beta, etc. Some of these filters pass through very narrow bandwidths so you need to know what bandwidths that your target emits. I use UHC for faint nebula like the Owl (M97) or Thor's Helmet (NGC2359). An O-III filter makes the cloud of the Great Orion Nebula (M42) stand out. An H-Beta filter is supposed to help with the Horsehead nebula (Barnard 33). I still haven't seen the Horsehead visually. I recommend skipping the H-Beta filter and attempting the Horsehead unless you are in a very dark location with a big telescope.

Astrophotography Filter Bandpass Charts

LPR filter

Narrow band filter

Very narrow band filter

Astrophotography has it's own set of filters, some for emission nebula, others for broad spectrum galaxies. A few are really specialized for very low focal ratio telescopes, like f/2, and allowing gray scale astro cameras to collect data that can be combined into a color image. Photographic filters are usually not for visual use.

Here are dew heater straps (dark objects) on the primary telescope and the guide scope. I often need to run them at 90-100% to keep the dew off. I doubt that a 5v USB dew heater would generate enough heat to do the job.

If you live in a moderate to high humidity area you will encounter issues with dew. It loves to form on exposed glass - front telescope elements, eyepieces and sometimes mirrors. The good news is that there are ways to defend against it. The goal is to prevent new high humidity air from getting to the front elements and keeping the element slightly above the dew point.

For telescopes that have a front lens element like refractors and SCTs a combination of lens hood or an add-on dew shield along with a dew heater are usually the best option. A dew shield is an extended lens hood that extends out the front of the telescope's optical tube and it passively blocks dew and helps hold in a small amount of heat. A add-on dew shield is a requirement for most SCTs.

The dew heater slightly warms the front element to prevent dew from forming. This is usually in the form of a heated strap that goes around the tube where the outer lens element is located. On SCTs it also may be a replacement front retainer ring that holds the front element in. In both cases the dew heater will connect to a power source. Some are USB powered and the more advanced strips connect to a dew heater controller with multiple outputs that has variable heat and may even monitor the dew point and keep the heat at exactly the minimum needed temperature.

Eyepieces and finder scopes also have issues with dew. Usually a dew heater on both solves the problem.

In a pinch I have use a Hot Hands hand warmer and a rubber band around an eyepiece to stop the dew. There's not much temperature control with this option, but it worked. I used a microfiber cloth to occasionally wipe the dew from the Telrad's plastic heads-up display.

Newtonian telescopes often only need an eyepiece and finder dew heater. The primary mirror retains enough heat for most observing sessions. Some Newtonian telescopes have dew heater elements built in behind the secondary mirror. You will know it when you need it.

The old school fix of last resort is to bring along a small hair drier to warm things off and remove the dew. Fortunately the dew heaters are getting better and this option isn't needed as much. It's much easier to stay ahead of dew than try to reverse it once the glass is wet.

There are a lot of really great dew heaters and dew strips available. I use Dew Not, Kendrick and Astro Zap strips and can recommend all of them. Some year ago I decided to design my own microprocessor controlled dew heater controller. I built three and members of the SPAC club built another 20. They are basic two channel dew heater controllers that are all, to the best of my knowledge, still in use from Florida to Wyoming. Buying the commercial dew strips was easier than making my own (I don't sew).

The latest twist to dew heater control is that dew heater controllers are built into ASIAir, Pegasus and other third party telescope controllers and power centers. You still need the dew strips and they plug into the telescope controller. Sometimes that might require an adapter to get to a female RCA jack that the heater strips like to plug into.

With a standard Dobsonian scope you don't need much, if any power. A little eyepiece dew control and, maybe, digital setting circles. If you are at a location with electricity you will likely plug in and be happy. In the field you may not have that option. The eyepiece issue could be handled by the previously mentioned hand warmer, a USB 5v power with a USB dew strap or a 12v dew controller. If the eyepiece is an inexpensive one you may opt just to use clean micro fiber cloth and wipe the dew off. Digital setting circles, if you have that, usually have the option to run from an internal battery or external power.

Powering a more power hungry telescope - like one with go-to scope, astrophotography cameras, telescope controller that is also a wi-fi hub and dew heaters may require 12v and 3-7 amps per hour (each set-up varies). I have a separate page for telescope power. Bounce over to it and then come back here.

Red Lights and Seeing in the Dark

When you go from a well lit area to a dark location a couple of things happen to your eyes. Your pupils get larger quickly. Over the next about 20 minutes your body also releases chemicals that assist your night vision. The takeaway is that if you stay in the dark for about 30 minutes you will see better in the dark regardless of your age. Younger people's pupils open more and the opening decreases a bit as you get older. That's about going from a maximum diameter of around 7mm to 5mm. Another reason to start astronomy when you are young.

Averted vision may also help you see really dim objects. Instead of looking directly at the object, instead look slightly to the side of it. This will allow more of the incoming photons to hit the light sensing cells (mostly rods) in your eyes allowing you to make out the image better.

For dark adapted eyes we want to keep them that way. A dim or variable brightness red light is the answer. You can take a standard flashlight and stretch one or more red balloons over the end, tape red plastic over the lens or purchase a red astronomy flashlight. Ideally this light should be small enough to go on a lanyard. Most astronomers wear one around their neck since it may be difficult to find a flashlight in the dark. Red headlamp lights are often too bright and blind other astronomers although they may work if you are observing alone. I haven't made many specific recommendations here but I will for Rigel Systems astro flashlights. They are designed for astronomers. Some models, like the SkyLite have a switch to go between red and white light, which can be handy at times. I believe that they all have dimmer dials on them.

After the Moon and bright planets you'll need to come up with a list of things to look at. Usually the best starting point are the Messier Objects. These are some of the brightest objects in the sky. A great set of charts to locate them, especially if you are using a Telrad finder, is on the Los Angeles Astronomical Society's site.

Beyond the Messier objects there are Caldwell Objects and many other observing lists. Just do a web search for 'observing list'. There are hundreds of lists to pick from. Wikipedia has an awesome list of Astronomical catalogs, many specializing in particular types of objects, like the Abell catalog of planetary nebulae or the like the Arp Atlas of Peculiar Galaxies. There are also many observing lists online for various times of the year.

In addition to pre-made lists there are dedicated observing list programs like Sky Tools, Deep Sky Planner and AstroPlanner. You likely don't need one of these unless you are getting serious about your time under the stars. These allow you to easily make custom lists to match your observing interests.

The Tarus (the Bull) Constellation showing where Messier 1 (M1) is located next to the tip of the horn (bottom left). M1 is the glowing gas left over after a star went supernova (exploded leaving a neutron star). The explosion was seen from Earth in the year 1054.

There are thousands of objects that you can see with a moderately sized telescope in a dark location. Start with the Messier Catalog, then the Caldwell or brighter NGC catalog objects. In star catalogs the lower the magnitude value is the brighter the object is. Some objects, like nebulas, have their magnitude values as if they were a point light source and not disbursed gas so don't expect them to appear as bright as their value suggests. Each whole number change between magnitudes is a change of about 2.5 times in brightness, up or down.

Don't expect to see much color visually in a telescope. With the exception of really bright objects, like planets and some stars there isn't enough light energy to activate the cones (color) in our eyes leaving the rods (B&W) to see the objects.

Locate what you want to find on a star chart and using bright stars 'hop' from one to the next triangulate your object and locate it in the eyepiece. This works best in dark skies with a knowledgeable telescope operator.

Many mounts have Right ascension (RA) and Declination (DEC) markers on them. If you know the current coordinates of your object and set the RA dial correctly you should be angle to locate an object by the numbers. It's easier said than done but it does work.

Life is getting much easier now. Digital Setting Circles are a small special purpose computer that connect to two encoders on the telescope's mount that keeps track of the telescope's movement. Once the date is entered and it's aligned on a couple of bright stars, it knows where everything in its databases is located. You enter the catalog, like Messier, and object ID, like 31 (Andromeda galaxy), and manually move the telescope while watching the numbers on the display. When both numbers are zero you should be on your target. This has low electrical power needs and many have an internal 9v or rechargeable battery. It is also silent. I highly recommend Digital Setting Circles for manual telescope mounts.

After an initial alignment the motors on the mount move the telescope to your selected object. This requires the most power and the motors are a bit nosier when slewing (quickly moving the telescope). With a wireless setup you can control the telescope from a computer with a wi-fi or, in come cases, bluetooth connection. This control is common for astrophotography and allows the telescope operator to stay inside while hours of photographs are made in the cold.

There are many phone, tablet and desktop computer programs that will show you a representation of the night sky. They will use your location (city or longitude and latitude) as well as the current date and time to display what is overhead. The phone and tablet apps alow you to move the device around to see the section of the sky that fits on their screen. You may also zoom in for more detail as well as turn on and off various labels. Some allow you to change the date, time and location. Like most apps, some of these have a small charge if you want more features.

The desktop programs often have a larger database, photos of many of the objects. They also have the ability to change the location, date and time and change the clock speed. This later item allows you to see things like precession, which takes 26,000 years to make a complete loop. This changes which star is our North star. Past and future events, like Halley's Comet and eclipses may be viewed by the armchair astronomer. While many of these are commercial programs, like The Sky or Redshift. Others are free and quite good, like Stellarium, Cartes du Ciel or C2A (Computer Aided Astronomy).

Many of these programs have the ability to connect to digital setting circles and go-to telescopes so that the program or app controls the telescope Most also have Moon phases and a list of what's up tonight and many other filters and features.

There are phone apps and online dark sky maps that show where the bright and dark areas are located. They will allow you to see the relative brightness of your location to other locations near and far. Africa looks pretty good for observing.

To measure a location's brightness there are Sky Quality Meters and a scale named the Bortle Scale. The Bortle Scale assigns a number between '1', very dark location, to '10', in a bright inner city. The Bortle number is what is commonly used to describe how dark a location is. I live in a Bortle 8-9 location and the photos on my astrophotography page were taken there, with the help of previously discussed artificial light blocking filters.

There's an organization called DarkSky International (previously called the International Dark-Sky Association or IDA) that is dedicated to reducing light pollution (man-made artificial light) and bring back a darker night sky. Most astronomy clubs support and may have liaisons communicating with DarkSky and working to educate the local governments about the value of well directed lighting. Most amateur astronomers still refer to DarkSky as the IDA.

About the only thing more important than dark skies are clear skies. Clouds, with or without rain, will prevent most astronomy. With thin clouds you may still be able to look at the Moon, Jupiter and Saturn, but that will be about it. I use a phone app called Clear Outside that does a really great job predicting the percentage of cloud cover at your location. It even breaks down the cloud cover different elevations. I plan my observing and astrophotography days using this app. This is, at least when I wrote this, a free app.