Telescopes
Orion XT10i Optical Tube Assembly (OTA)
The XT10i is a Newtonian telescope. The Newtonian telescope is a type of reflecting telescope that was first successfully created by Sir Isaac Newton himself. These telescopes have two mirrors with a parabolic primary mirror and a flat diagonal secondary mirror. When light enters the tube, the light will travel down near the end of the telescope and reflect off the primary mirror. Once the light bounces off the primary mirror, it will travel back towards the opening and reflect off the secondary mirror. Finally, after reflecting off the second mirror, the light is directed out of the focuser from which it can be focused via an eyepiece or camera. The focal length of this OTA is 1200 mm and the diameter is 10 inches (254 mm). This means that the focal ratio (aka f-number or f-stop) is f/4.7 which is considered a fast scope. This Newtonian allows you to see objects with magnitude of about 15 (Magnitudes with human eyes: Little to no light pollution: 6.5, Urban Area: 3 or 4).
TPO 8″ Carbon Fiber f/8 Ritchey Chretien OTA
This TPO instrument is a Ritchey Chretien (RC) telescope. The RC telescope is a reflecting telescope similar to the Newtonian design due to using mirrors, but the design of the mirrors and of the telescope are completely different. The mirrors within the RC telescope are hyperbolic and this includes the primary mirror as well as the secondary mirror. Also, due to the compactness of this RC scope, the light traveling in the tube is folded twice. Basically, light enters the tube in the front, hits the primary mirror at the back, bounces towards the front center of the scope where the secondary mirror is located. Then, the light bounces off the secondary mirror to the center of the back of the telescope from which it can be focused via an eyepiece or camera. This compactness allows to have longer focal length telescopes in a smaller package. Telescopes designed in this way are referred to as Cassegrain telescopes. The purpose of the RC design is that it gets rid of some annoying astigmatism from the optics (i.e. coma). Many research based telescopes are RC designed. Probably the most famous RC telescope is the Hubble Telescope!
Orion ED80T Triplet Apochromatic Refractor
The ED80T is a refracting telescope commonly referred to as a refractor. A refractor is a telescope that uses a lens inside the telescope to form an image. Most people when thinking of telescopes probably think of a refractor. The way this telescope works is when light enters the objective lens, the light passing through is refracted towards the end of the telescope so the image can be projected through an eyepiece or camera. Though when light passes through a lens, each wavelength (color) of light is bent by a different amount. The light then becomes unfocused which is known as chromatic aberration. It is an issue because the colors of light focus at different locations that can cause halos around bright objects. Chromatic aberration can be minimized to the point where these colored halos cannot be seen by using a triplet refractor. The ED80T is a triplet refractor because it has three lenses. Each lens in the ED80T help correct the aberration ever so slightly to form a complete focused image. These color corrected lenses is known as an apochromat (APO).
Mounts
Dobsonian Mount
A Dobsonian is an alt-azimuth mount design popularized by John Dobson. These mounts are generally used with Newtonian telescopes. This Dobsonian came with the XT10i as the original mount for the OTA. A push-to system is integrated within this mount. When searching for an object in the night sky, the push-to system indicates the necessary altitude and azimuth adjustments needed to find the object. The name of this system is push-to because it requires the user to manually adjust or push the mount into position to find the desired object based on the information from the hand controller. This mount is simple in design and simple in setting up for that easy night where all you want to do is star gaze.
Atlas EQ-G Mount
The Atlas EQ-G is a German Equatorial Mount (GEM). This GEM is great for tracking objects in the night sky because it compensates by having one rotational axis parallel to the earth’s axis of rotation. For an alt-azimuth mount, tracking an object would require moving the scope in both axes (up/down and left/right). However for an equatorial mount, only one axis is necessary to change to successfully track an object. This mount comes with a go-to system where the mount will automatically slew the telescope to a desired object by using the hand controller. This mount will also track the objects keeping them in view of the eyepiece or camera. The tracking capabilities of this mount are essential for astrophotography. Tracking is essential, for example, when an object, like a galaxy, requires a longer exposure time in order to bring the details out more clearly.
Orion SkyView Pro Mount
The SkyView is also a GEM. This equatorial mount is great for traveling and taking pictures when on the road because of its light weight. Unlike the Atlas EQ-G, this mount does not have a go-to system. However, the SkyView Pro does have a motor to compensate for the rotation of the Earth for keeping objects within the field of view of the telescope.
Accessories
Finder Scope
A finder scope is a device used in astronomy for locating a desired object in the night sky. Typically a finder scope is composed of a small telescope mounted on the main telescope along the same line of sight. The finder scope usually has a smaller magnification but larger field of view than the main telescope. The less magnification and greater field of view makes the finder scope ideal for searching for particular objects in the night sky. This finder scope has a lens with a diameter of 50 mm and a magnification of 9x with a comfortable right-angle viewing orientation. Also, this finder has an internal correct-image prism which provides a corrected oriented view through the finder making it easier to find objects.
Guide Scope
A guide scope (the image above is a 60 mm scope) is a finder scope with a camera inserted through the viewport that continuously checks the tracking of the mount. The way that this works is a person would interface with the camera inserted into the guide scope, lock onto a star from the camera view, monitor the change in position of the star, and finally correct the mount’s direction to ensure the locked star remains in the same location within the view. This is necessary for long exposures which helps for taking pictures of faint objects in the night sky like some galaxies and nebulae. Though this process for guiding may seem overly complicated, there does exist software that simplifies these procedures ten-fold by essentially automating the whole process. The software is PHD which stands for “Push Here Dummy”. The name signifies the simplicity of the software and it is often used by many astrophotographers.
Eyepiece Collection
There are never enough eyepieces or accessories for a telescope. These two cases contain many accessories from color filters, tube extensions, barlows, camera adapters, finder scope, and eyepieces. Eyepieces are perhaps one of the most important accessories that one could own for their telescope. Each eyepiece has a measured focal length. The magnification that an eyepiece will have can be calculated by knowing the focal length of the eyepiece and the focal length of the telescope OTA. To determine the magnification of the eyepiece, divide the focal length of the OTA by the focal length of the eyepiece (i.e. eyepiece with 10 mm focal length for the XT10i OTA is 1200/10 = 120x). The smaller the focal length of the eyepiece then the more the magnification for a given telescope. For the best visual experience, it is best to have at least a few different eyepieces covering a wide range of focal lengths. Having multiple eyepieces will help balance the visual experience from low focal length eyepieces for high magnification (i.e. planets) to larger focal length eyepieces for less magnification but a greater field of view (i.e. large galaxies, moon, sun).
Cameras
Many different cameras can be used for astrophotography within a telescope. The Canon cameras (1200D/T5 and the 60D above) with the correct adapters and software (BackyardEOS) can be a terrific camera for astrophotography. The QHY 5-II camera is also great for astrophotography and is often used for guiding the telescope within a guide scope. There are a few different ways of taking photographs using a telescope. Two of the techniques for taking photographs are: prime focus and eyepiece projection. Prime focus is when the camera (with no lens nor eyepiece) is inserted straight into the focuser which uses the telescope itself as the lens. The prime focus technique is best for a wider field of view shot which can be used for capturing all or most of larger objects (i.e. Moon, Andromeda galaxy, etc). Eyepiece projection on the other hand is when the camera (with no lens) is attached to an eyepiece and the eyepiece is inserted into the focuser. This technique is best for taking higher magnification shots for capturing smaller objects (i.e. planets).
Upgrades
Focuser
The focuser that came with the XT10i is the Orion 2″ Crayford Focuser (image on the left). This Orion Focuser is a single speed focuser. Single speed focusers only have one rate or speed for turning the wheel knobs when lowering or raising the eyepiece holder. This focuser was upgraded with a Moonlite Focuser (image on the right) which is a dual speed focuser. The Moonlite has one knob for the standard rate and another knob that is more sensitive (8:1 rate ratio) to aid in finding focus. Also, the Moonlite Focuser is a lower profile than the Orion Focuser which helped with achieving prime focus for the XT10i OTA. A lower profile is when the eyepiece holder from a focuser may allow to be set at a lower position than another focuser. Some telescopes, many Newtonians in fact, need a lower profile focuser for using the prime focus technique because the focus plane is sometimes too low for a camera in a standard focuser to reach.
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