| Basic Telescope DesignsThe job of a | | | | maintenance, such as collimation |
| telescope is to collect light, not to | | | | (discussed in another article) which is |
| magnify an image (the eyepiece does that | | | | vital for great results in your |
| job). The larger the objective (the part | | | | astrophotography, although you will |
| that collects the light) whether it be a | | | | learn how to do this quickly with |
| lens, in refractors, or a mirror, in | | | | practice.Schmidt-Cassegrain |
| reflectors, the more light the telescope | | | | TelescopesThis is a very popular design, |
| will collect. The more light you can | | | | with a high tech look. Also known as a |
| collect, the more detail you will be | | | | CAT (Catadrioptics). They use a |
| able to capture, and also important for | | | | combination of lenses and mirrors to |
| astrophotography, the shorter your | | | | collect and focus the light onto the |
| exposures will need to be to capture | | | | eyepiece or camera. The light enters the |
| this detail.Refractor TelescopesThe type | | | | telescope through a thin 'lens' called a |
| of telescope most people visualize when | | | | schmidt corrector plate, goes to the |
| they hear the word telescope is the | | | | back of the scope to a spherical primary |
| 'Refractor'. This is what Galileo used | | | | mirror which reflects the light back |
| for his break-thru discoveries. A | | | | towards the front. Here the light |
| refractor has an objective lens at the | | | | strikes another mirror, the secondary |
| front which passes the light straight | | | | mirror which is mounted on the corrector |
| through to the back of the tube, | | | | plate. This secondary mirror then |
| focusing this light at an eyepiece or | | | | reflects the light back towards the back |
| for astrophotography a | | | | where it is focused onto a hole in the |
| camera.Advantages:-No central | | | | primary mirror where the light is |
| obstruction (see more in the reflecting | | | | collected by an eyepiece or your |
| scopes), giving higher contrast.-Due to | | | | astrophotography |
| the simple design they require little | | | | camera.Advantages:-Compact and |
| maintenance.-Excellent for planetary and | | | | portable.-Low maintenance although once |
| lunar viewing and photography.-Excellent | | | | again collimation is required for top |
| for wide field viewing and | | | | performance.-Many, many astrophotography |
| astrophotography especially in shorter | | | | accessories available.-Cheaper per inch |
| focal lengths (more on this | | | | of aperture as compared with |
| later).-Because the objective is | | | | refractors.-Excellent all-round |
| permanently mounted and aligned there is | | | | telescope, good to very good for both |
| no need for collimation (again more on | | | | visual and astrophography.-Very good for |
| this in another article).-Excellent | | | | planetary and lunar viewing and |
| color in apochromatic and ED (Extra | | | | astrophotography.-Very good to excellent |
| Dispersion) | | | | for DSO (Deep Space Object) |
| designs.Disadvantages:-Costlier per inch | | | | astrophotography with a caveat (see the |
| of aperture (objective) than reflectors | | | | disadvantages).-Very good to excellent |
| and catadioptric telescopes.-Can become | | | | optics, both Meade and Celestron are |
| bulky and difficult to manage, | | | | putting out excellent optics on a |
| especially in larger lens | | | | consistant basis.Disadvantages:-Costlier |
| designs.Newtonian TelescopesThis design | | | | per inch of aperture as compared with |
| was invented by Sir Isaac Newton (he of | | | | Newtonian telescopes.-Loss of contrast |
| the apple on the head fame). Instead of | | | | due to the central obstruction which is |
| a lens at the front of the tube this | | | | even larger than that in the Newtonian |
| telescope design uses a concave, | | | | scopes.-Due to their longer focal |
| parabolic mirror to collect light | | | | lengths the field of view is smaller and |
| reflecting it back towards the front of | | | | longer exposures are required for |
| the tube to a flat diagonal mirror which | | | | astrophotography, although a lens known |
| reflects the light out the side of the | | | | as a focal reducer is available which |
| telescope to the eyepiece or camera for | | | | minimizes or removes this problem. The |
| astrophotography.Advantages:-Lowest cost | | | | longer focal length is actually an |
| per inch of all the telescope | | | | advantage in planetary and lunar |
| designs.-More light gathering power per | | | | photography.Maksutov-CassegrainThe |
| dollar because of the lower cost | | | | Maksutov-Cassegrain telescope design is |
| design.-Absolutely perfect color | | | | basically the same as the |
| rendition.-More compact design compared | | | | Schmidt-Cassegrain design except it uses |
| to a refractor of similar light | | | | a meniscus lens at the front instead of |
| gathering ability.-Excellent contrast | | | | a Schmidt corrector plate. The main |
| for planetary and lunar astrophotography | | | | advantage to the Mak telescope design is |
| and viewing in longer focal lengths.-Can | | | | you will get sharper higher contrast |
| get excellent wide-field astrophotos and | | | | planetary and lunar images when compared |
| short exposures in shorter focal | | | | with the Schmidt design.Carl Gilbertson |
| lengths.Disadvantages:-Slight loss of | | | | has been involved in amatuer astronomy |
| contrast due to the central obstruction | | | | for over 30 years and astrophotography |
| (the flat secondary mirror) as compared | | | | for over twenty-five years. |
| to a refractor.-Requires more | | | | |