We have been observing our vast universe for more than 3 centuries now, but it is not up until recently that we have started collecting well-grounded information about it. By information I mean photographs and yes taking pictures of stars, planets and distant galaxies can be done without the Hubble too. This is where an astrophotography telescope comes into play.
What is Astrophotography?
Astrophotography is the recording of astronomical objects using any camera from a DSLR to a basic point-and-shoot with the help of a telescope. Astrophotography telescopes are an all-in-one package that provides a clear and sharp shot of planets, stars, nebulae, galaxies etc.
How to Choose a Telescope for Astrophotography?
In order for a telescope to deliver a view of distant celestial bodies it needs magnification or what we know as zoom. Focal length is the distance from the objective lens to the focus point of your camera which is expressed in mm and the longer it is the better the magnification. This attribute affects another key factor – the focal ratio.
What makes astrophotography telescopes efficient is the speed of the scope. Focal ratio represents that in the form of an f-number and the lower the number the faster the ability of the scope to capture data. This also means shorter exposure.
The size of the opening of the telescope through which light comes in is measured in mm and is what we call an aperture. These numbers are also expressed in inches so a telescope with a 4 inch aperture has a 101.6mm opening. The bigger the aperture, the more light can come in, thus the photos come out brighter. Aperture directly affects focal length and ratio which means the bigger the opening, the heavier and bulkier the telescope.
These telescopes are the first ever to exist and they consist of a plano-convex objective lens and a plano-concave lens at the eye end. Refractor telescopes are easy to maintain and have colour fringing and glares. They are excellent when it comes to creating high contrast images for lunar, deep-sky and planetary astrophotography.
Unlike refractors, reflector astrophotography telescopes consist of mirrors which help reflect light at various angles eliminating colour fringing and they also give you an upside down preview. For this you need to align the scope’s finder with the objects you are going to observe. High-aperture viewing is something that’s done best with a reflector telescope, but you’ll need to adjust the reflector’s mirrors from time to time with a process called collimation.
Lenses and mirrors are both used in catadioptric astrophotography telescopes and combining them has resulted in a compact and portable device. You can get a smaller form factor catadioptric telescope with the same aperture as a refractor or reflector one. This is thanks to the corrector plate which helps fold the light path, together with the secondary mirror which magnifies the light internally. Since these telescopes work with mirrors they also require collimation but not as much as reflectors.
What is the Best Telescope to buy for Astrophotography?
Celestron CPC Deluxe 1100 HD
This telescope comes with a motorized forked mount made to improve tracking efficiency and you can control it from anywhere, thanks to its Wi-Fi module. Although quite compact, this unit has a big aperture which lets you see objects that are otherwise invisible at night. Together with the Starbright XL coating, the CPC Deluxe 1100 HD makes images look clear as day.
The GPS-powered mount and StarLock guider system allow this telescope to lock to up to 145,000 objects by pressing a couple of buttons. LX600’s lenses have ultra-high transmission coatings and this unit also comes with a coma-free optical system, which makes for less distorted images.
Orion SpaceProbe 130ST
The wide 5.1-inch aperture on the 130ST makes it perform great in low light when it comes to colour saturation and image clarity. Although it has a big opening, this telescope is relatively small (60cm) .
Celestron CPC 925 Deluxe HD
This may be a more low-end model than the CPC Deluxe 1100 HD, but despite that, it comes with a StarBright XLT coating and provides aberration-free images since it corrects from both coma and field curvature. With Celestron’s own Fastar compatible optical system, EdgeHD, you can attach a third-party lens to improve focal ratio.
What is a Good Starter Telescope for Astrophotography?
Orion 9024 Astroviewer
This 3.1-inch refractor telescope provides crisp images even at higher magnifications, allows for an excellent view of deep sky objects and the solar system and it also comes with Starry Night software, which is a great learning tool for beginners. The simplicity and solid equatorial mount of this telescope make it great for beginners.
Celestron Nexstar 130SLT
With the computerized mount on this device, you are able to choose from 40,000 different objects. The Nexstar 130 SLT automatically tracks the object, you just need to take your shot. The 130mm aperture on this device is more than enough to take some stunning shots.
This compact unit packs 400mm of aperture, a finderscope, two eyepieces, tripod and a mobile phone camera adaptor with a wireless Bluetooth remote trigger. This is a great first time telescope for taking photos of the open sky.
Celestrone Inspire AZ80
Although the AZ80 doesn’t have as wide an aperture as Gskyer’s AZ70400, it is still a great choice for aspiring astrophotographers. This device is very easy to set up, which makes it a good choice if you are on the go and it also comes with a built-in smartphone adaptor.
How to Set up an Equatorial Mount?
1. First adjust the tripod legs of the equatorial mount so that the top of it is level with your hips. Fit the central accessory tray if there is one.
2. Place the metal peg so it lines up on top of the tripod with the gap underneath the mount, sitting between the two bolts of the azimuth lock. Secure the head of the mount by tightening the big bolt hanging from the underside of the tripod top.
3. Take the safety screw off the bar and slide up the counter weights halfway through and tighten the screws on the weights to secure them. After that replace the safety screw on the end.
4. Next, you need to position the RA axis to face the the north celestial pole. Set the altitude setting on the mount to match your local latitude. Then release the front and back bolts and tilt the mount head so you have the pointer lined up with the right number on the altitude scale and then tighten the bolts back.
5. Afterwards, start fitting the slow motion cable on the small D-shaped shafts found on the RA and declination axis. Tighten the screws on the end of each cable to keep them in place. For reflector telescopes rotate the dec. axis so you have the cable at the top next to the eyepiece and for a refractor, fix the cable so that it extends to the bottom.
6. Mount the two tube rings onto the plate clamped to the mount head. Whilst the tube rings are open, place the tube in them and then screw down the locking bolts so the tube doesn’t slide out. You’ll need an extra pair of hands for this and if you have a reflector telescope, remember the eyepiece goes on top.
7. Screw the finder scope into the clamp on the telescope tube and align it by placing a low-mag eyepiece in the main scope focuser – try to find something similar to a pylon in the horizon. When you’ve done that, look through the finderscope and adjust the screws on its bracket until you have the pylon in the crosshair.
8. Start balancing your scope with the tube placed in a horizontal position and the dec. axis lock loose. Slide the tube back and forth until you see that the scope is resting flat. Put the counterweight shaft of the RA axis in a horizontal position, loosen the lock and adjust the counterweights so the scope can remain still when you let go.