Astronomy Gadgets
Reviews of some of the astronomy equipment that I have used, including photographs.
- Telrad Red Dot Finder
- Skywatcher Red Dot Finder
- SkyWatcher Night Vision Torch
- SkyWatcher "Auto" Focuser
- Antares Laser Collimator
- T-Mount Adaptor
- Afoccal Adaptor
- 45° Erecting Prism
Telrad Reflex Dot Finder
The first gadgets I acquired is my Telrad reflex dot finder. I was experiencing difficulty locating objects in the sky, mainly because I haven't learned every star visible yet. I know the general position of the objects and can star hop between bright stars, but looking through the finder scope dramatically increases the number of stars visible and the finder scope projects an inverted view to your eye - up is down and left is right. I rapidly got confused, lost my way and lost my patience.
The "Red Dot" finder works by superimposing an electronic crosshair over the sky (which is not magnified, you just look through a small piece of glass) and it makes star hopping that much easier by limiting to eye-visible stars only. The crosshair has the added feature of being able to measure distance between stars. The inner circle has a diameter of 1/2 degree, middle of 2 degrees and the outer circle has a diameter of 4 degrees. A regular finder scope can still be used to pinpoint accuracy even further with its magnification.
The red dot finder attaches with its own base which can be stuck to the telescope tube with some double sided sticky tape. When not in use it can be removed from the base for safe storage. It needs to be aligned to the telescope, the same as any other finder scope, and is very easy to do by adjusting three set screws near the view finder.
The device works brilliantly and the crosshair has a variable brightness control, however I feel the unit is a bit bulky and could have been made a lot smaller, given that there is a lot of unused empty space inside (as shown in final picture).
Skywatcher Red Dot Finder
This red dot finder was part of the package when I bought my StarTravel 102 refractor. Its much smaller than the Telrad finder and I find it much easier to use as well. It mounts onto the finderscope bracket, unlike the Telrad which has its own base, so you can't use a 9x50 finder scope as well. It features adjustable brightness control as well as two alignment screws.
SkyWatcher Night Vision Torch
In low light and darkness our eyes pupil expands to a larger aperture to allow as much light as possible to enter the eye. The process can take up to 20 minutes for your eye to become accustomed to the low light levels. While this is good for viewing the sky as many more stars will be visible, it simply does not allow you to read any text or star maps. A conventional torch will ruin your "night vision" in a fraction of a second as the intensity of the light will cause the pupil to contact back to normal. It will take another 20 minutes to become accustomed to the low light again.
This is a simple tool that makes a big difference at night. This is nothing more than an led torch, but it has dual functionality as it emits red and white light. Red light at night will preserve night vision because it offers enough light to see by, but not at an intensity to cause your pupil to contract. This is also why red light is used in dark rooms, as the intensity is not great enough to spoil the film. Many star maps are specially designed to be viewed under red light. The white light function will illuminate a further distance and brighter, useful for clearing up when night vision is not required any more.
SkyWatcher "Auto" Focuser
My SkyWatcher came with a 2" rack and pinion focuser and like most focusers it features two small wheels to turn. For low power focusing this is adequate, but difficult to make very small adjustments needed to obtain perfect focus. At high magnifications the vibrations caused by even touching the focuser make the image un-viewable and the target rapidly moves out of the field of vision. Focusing is near impossible.
Motor focusers use a small stepper motor to control focus wheels. These, when activated, can turn the focus dial smoothly without causing any vibrations and allow for the target to remain in view. The also allow for very small adjustments to be made, which cannot be done with an unmodified focuser.
I have purchased and installed the SkyWatcher Auto focuser. Despite being called "Auto", this does not mean that it automatically focuses but instead is motorised. The package consists of the motor, control unit, brackets and screws. The installation was very easy, taking only 3 minutes and only requiring a screwdriver. The control box, although large, functions perfectly with two buttons for in and out focus and a variable speed control. Even at high magnification (100X) there is no visible vibration caused by focusing.
Antares Laser Collimator
Accurate collimation is vital for image quality in Newtonian optics, and this laser collimator makes the job easy. Once the focuser is perfectly aligned with the secondary, it is simply a case of adjusting the secondary to point the holographic laser dot inside the central marking on the primary, then to adjust the primary so that the return beam is back in the collimator. The process is described further in my collimation article.
I had been struggling to collimate manually for a while now, but since I have had a laser collimator, the process only too a few minutes!
This collimator is solid, machined out of aluminium with a pewter finish. Instead of a target screen to be viewed end on, it features a plate cut at 45 degrees so the return beam is visible from the primary mirror end of the telescope. This allows you to see what your adjustments are doing.
T-Mount Adaptor
A T-Mount adaptor is essential if you wish to connect your dSLR camera to a telescope. This circular bracket attaches to the camera body via the standard lens socket, while the other end accepts the screw thread of the focuser or barlow lens. This allows you to use your SLR camera in "prime focus" mode. Photographed below is a Canon EOS T-Mount adaptor, although they are available for pretty much any SLR make.
Afoccal Adaptor
The another method of connecting a dSLR camera to a telescope is afocally. In this arrangement an eyepiece is used inside the adaptor to allow greater magnification. These adaptors come in a variety of shapes and sizes, for 1.25" and 2".
The adaptor typically splits into to sections, the inner and outer tubes. When split in two an eyepiece will fit inside the inner tube and secured in place, then the outer tube slides over the top and is again secured with screws. One end of the adaptor fits into the focuser eyepiece slot, while the other end attaches to the T-Mount and camera.
So far I haven't had much success with my adaptor. I found it near impossible to focus as their just isn't enough travel in the mechanism, or the fully extended focuser and fully extended adaptor and camera put a huge strain on the mount and focuser base.
45° Erecting Prism
This clever little apparatus serves two purposes for me. 1) It allows a more comfortable viewing angle for visual observations and 2) It corrects the orientation of the sky. I was always having problems with the reversed view you get, and often getting lost by moving in the wrong direction!
