Electronic polar alignment has made setting up an equatorial mount easier than ever, but it isn't necessarily the best choice for every observer. If you spend most of your evenings looking through an eyepiece rather than taking photographs, bringing a laptop outside simply to align the telescope may be more trouble than you want. And if you've been using an optical polar finder for years, you may see little reason to change a procedure that already works well.
The iOptron AccuAlign Optical Polar Scope Kit lets you replace the iPolar electronic polar scope in your CEM26 with a traditional illuminated optical finder. Instead of connecting a computer and running alignment software, you look directly through the AccuAlign scope and position Polaris on its calibrated reticle. The mount's Go2Nova hand controller tells you where the star belongs for your location, date, and time. Once you've adjusted the mount to put Polaris in the indicated position, your polar alignment is complete.
This C2633 kit includes the AccuAlign optical polar scope, a separate LED illuminator with power cable, and a protective cover. It is designed to fit the CEM26's existing polar scope opening and draws illumination power directly from the mount, so there's no separate battery to replace.
Why Polaris Doesn't Belong in the Center
The purpose of polar alignment is to position an equatorial mount's right ascension axis parallel to the Earth's rotational axis. When that alignment is correct, the mount can follow the apparent movement of the stars by turning its right ascension axis at the appropriate tracking rate.
Polaris makes a convenient reference for observers in the Northern Hemisphere, but it isn't located exactly at the north celestial pole. It is approximately three-quarters of a degree away. Simply centering Polaris in an ordinary finder will get you reasonably close, but the remaining error can produce noticeable tracking drift, particularly during photographic exposures.
AccuAlign solves this problem with a calibrated reticle. The reticle has twelve-hour clock markings with ten-minute divisions and two groups of concentric circles. The inner circles, marked from 36 to 44 arcminutes, are used with Polaris in the Northern Hemisphere. The outer circles, marked from 60 to 70 arcminutes, are intended for alignment using Sigma Octantis in the Southern Hemisphere.
After entering your observing location and the correct date and time, select the pole star position display on the Go2Nova hand controller. It shows the appropriate clock position and distance from the pole. Look through the AccuAlign scope and adjust the mount's altitude and azimuth controls until the reference star is positioned where the controller indicates.
The reticle uses dark-field illumination, meaning its reference markings are illuminated against a dark background instead of flooding the entire field with light. This makes it easier to see the markings while preserving the visibility of Polaris and the surrounding stars.
The CEM26 has another advantage over some conventional German equatorial mounts: its declination shaft does not obstruct the polar scope's view. You don't have to rotate the declination axis to clear the optical path before aligning, and you can check the polar alignment while the mount is tracking.
Mount-Powered Illumination
The supplied LED illuminator threads onto the AccuAlign polar scope and connects to the CEM26's DC 12V OUT socket using the included cable. Power comes directly from the mount, eliminating the need for a separate coin-cell battery.
The brightness of the illuminator is fixed rather than electronically adjustable. If the reticle appears too bright under a very dark sky, iOptron recommends partially obstructing the LED to reduce its illumination. This is a simple way to make the markings less intrusive without changing the polar scope's operation.
Installing AccuAlign in Your CEM26
The kit is designed to replace the iPolar electronic polar scope already installed in a compatible CEM26 mount. The two systems occupy the same opening in the right ascension axis, so they cannot be used simultaneously.
Installation requires a set of metric Allen wrenches and a little care. The existing iPolar camera is removed by releasing its retaining screws, and the AccuAlign optical polar scope is inserted with one of its major reticle marks oriented toward the twelve o'clock position. The retaining screws are then tightened gently, the LED illuminator is threaded into place, and its cable is connected to the mount's 12V output.
iOptron specifically warns against overtightening the retaining screws. The polar scope also has three small reticle adjustment screws that allow its optical alignment to be checked and corrected. If necessary, this adjustment is performed using a distant stationary object and rotating the mount's right ascension axis to verify that the reticle remains properly centered. Once correctly aligned, the polar scope can be used for normal observing sessions without repeating this adjustment every night.
One mechanical consideration is worth knowing before installation: the added length of the optical polar scope prevents the CEM26's right ascension axis locking wrench from being used in the normal manner. This is noted in iOptron's installation instructions and should be considered if that wrench is part of your usual setup or maintenance procedure.
If you decide to return to electronic polar alignment later, retain the original iPolar camera and its associated hardware. The optical and electronic finders can be exchanged, although the appropriate installation and alignment checks should be performed whenever the equipment is changed.
What Owners Say on Cloudy Nights
Optical polar finders still have an enthusiastic following among experienced observers, and the AccuAlign system is no exception.
In a Cloudy Nights discussion about his first imaging experience with a CEM26, one owner described using the AccuAlign scope with a Sky-Watcher Esprit 80 refractor. He reported finding the polar scope particularly easy to use because Polaris was clearly visible, and he used a phone application to determine the star's exact position on the reticle.
His experience illustrates one reason optical finders remain popular. Once you understand the reticle, the procedure becomes familiar and repeatable. You don't have to configure another piece of software, establish a computer connection, or work through an electronic alignment routine every time you set up.
Under the Night Sky
For visual observing, a reasonably accurate polar alignment is often all you need to make an evening much more enjoyable. Once the mount is aligned and tracking, Jupiter can remain comfortably within the eyepiece while you examine its cloud belts, Saturn can be followed at high magnification, and close double stars can be studied without repeatedly repositioning the telescope.
The convenience is particularly noticeable during shorter observing sessions. If you've only got an hour before the clouds return, being able to set up and align without bringing out a laptop means more of that hour can be spent looking at the sky.
And should you later decide to try astrophotography, the AccuAlign scope remains useful. A careful optical polar alignment provides a good starting point, while drift alignment or other precision methods can be used when longer exposures demand greater accuracy.
Observing Tip: Begin Before the Sky Is Completely Dark
Polaris is bright enough to become visible relatively early in evening twilight. If you begin polar alignment while there's still some light in the sky, finding the star in the polar scope can be considerably easier than searching for it against a completely dark background.
Before observing, make sure the mount has the correct location, date, time, and time zone entered in its hand controller. Display the pole star position, orient the reticle correctly, and then place Polaris on the indicated circle and clock position using the mount's altitude and azimuth adjustments.
It's worth checking the optical alignment of a newly installed polar scope before your first nighttime session. iOptron's instructions describe how to use a distant stationary object to verify that the reticle remains centered as the right ascension axis rotates. Doing that work during daylight is much easier than trying to make fine mechanical adjustments after dark.
Supplied Accessories
- iOptron AccuAlign dark-field illuminated optical polar scope (#3330)
- Polar scope LED illuminator and power cable (#3334)
- Protective polar scope cover
FAQ
- Will this kit fit my CEM26?
- Yes. The C2633 kit is designed specifically for the CEM26 and fits in the mount's existing polar scope opening. It replaces the iPolar electronic polar scope if one is installed.
- Can I use AccuAlign and iPolar at the same time?
- No. Both use the same opening in the right ascension axis. You can retain your original iPolar camera if you wish to reinstall it later.
- Does the illuminator require batteries?
- No. The included LED illuminator is powered from the CEM26's DC 12V OUT connection.
- Can I polar align when Polaris is hidden?
- The AccuAlign optical method requires a view of the appropriate pole star. If Polaris is obstructed, the CEM26's Go2Nova hand controller also provides a star-based polar alignment routine that does not require looking directly toward the celestial pole.
Final Thoughts
There's nothing outdated about a good optical polar scope. Electronic alignment systems have made some things more convenient, particularly for astrophotographers who already operate their equipment from a computer, but plenty of observers still prefer the simplicity of looking through a finder and making the adjustments themselves.
The AccuAlign kit gives CEM26 owners that choice. It provides the illuminated reticle, mounting compatibility, and electrical connections needed to align the mount without another computer program or a separate battery-powered accessory. And once you've become familiar with the process, polar alignment can become a routine part of setting up the telescope rather than a separate project before the observing begins.
For visual observers who want to keep their nights uncomplicated, that's a worthwhile reason to consider the AccuAlign kit.
