Manual polar

With these rules, you can have a guesstimation for the longest exposure you can make before stars begin trailing noticeably.

As a rule of thumb, the shorter the focal length and the larger the pixel size , the more tolerant you can be on the quality of the PA. If you are curious and want to calculate the optical resolution for your setup, this is a nice calculator , providing also some more info. As a final side note, if you like to print your images, you should know that prints are more forgiving than screens : the resolution is lower, and you usually look at prints from farther away.

The Crop Factor affects the field of view, but not the optical resolution. If you were to image with a full-frame camera, providing the optical resolution stays the same, you will not have smaller trails than those you get with your crop sensor camera. With a full-frame, you have just to zoom in more into the image to see them. For this reason only, you may want to have a better alignment when working with micro four-thirds and APS-C sensor cameras.

If you are interested in knowing how the different sensor types affect your astrophotography, you can read our recent guide on this. While PA plays a significant role in avoiding trailing stars and getting pinpoint sharp images, there are other factors to consider that will degrade your image quality and introduce star trailing.

These are the periodic error of the mount, the stability of the tripod and wedge, and the balancing of the payload on the mount itself.

We have always used stars to help us identify the cardinal points N, E, S, W and the celestial pole. Because of the precession of Earth Axis of Rotation, the celestial poles change in time. Polaris, the bright North Star, has been used since ancient times as a navigation beacon, helping sailors and wanderers travel North and orient themselves at night. Polaris is one of the brightest stars in the Northern sky, located in the relatively faint Ursa Minor constellation.

Luckily, you can easily locate it by extending 5 times the distance between Merak and Dubhe in the famous, and readily visible, Ursa Major constellations also known as the Big Dipper. People living in the Southern Hemisphere are not as lucky as those in the Northern Hemisphere, as they do not have a bright star to indicate where the SCP is.

Instead, they have to look for a relatively faint star Sigma-Octans in the faint Octans constellation. It seems like to PA your mount, you must be able to see either Polaris or Sigma-Octans, depending on the hemisphere you are in. This would be the ideal situation, but it is relatively easy to PA your equatorial mount even if you cannot see the celestial pole. This is a coarse PA you can do if you are imaging bright targets with short exposures or if you are doing starry landscapes and star fields with wide-angle lenses.

This method requires you to know the latitude and magnetic declination the offset between the magnetic North Pole and the celestial pole for your location. Remember to level your mount to the ground as best as you can and use the wedge to inclinate the mount upwards and to move it left and right. For Brussels, this is 1. Next, I use a compass or my phone to point the mount in the proper direction: for me 1.

The reason why this gives a coarse alignment is the reduced precision of the scale and the fact that the metal of the mount can affect the accuracy of the compass.

Modern phones are often shielded by interferences from metal and electronics, thus being more precise than a classic compass. Polar Scope Align Pro offers a neat Daylight Polar Alignment tool you can use to align the mount in the day time or at night if you cannot see the celestial pole.

But why would you need to polar align in daylight? One reason would be you want to image the Sun or the early evening Moon with your long focal telescope. All drift methods rely on nulling the drifting of stars in the frame observed during long exposures tests shot. As a personal note, I found it difficult to apply this method on a star tracker, but if you have a full-grown computerized equatorial mount, then you should be fine.

While very accurate in theory, in practice, the accuracy of the method can be reduced by large periodic errors of the mount, as you cannot know how much of the drift you see is due to bad PA or to periodic error. Yet, you can use this method for long exposure deep-sky astrophotography with fairly long telephoto lenses and scopes. This is a method I came up with, and it is based on the ability to measure differences in declination and right ascension between stars.

Declination DEC and Right Ascension RA are universal coordinates for stars, referred to as the celestial equator and the celestial pole. If you chose stars that are rather close, you can use the motor of the mount to hop, thus reducing the risk of bumping the mount and improving the precision of the method. The accuracy of the method also strongly depends on the accuracy of the DEC and RA scales and on how well you can eyeball the stars positions on the LCD screen.

Having the celestial pole in sight allows you to get the best possible polar alignment. Here are some of the most common methods used. If you are living in the Southern Hemisphere, this is by far the most simple and precise way to polar align. And even if you are in the Northern Hemisphere and can use the bright Polaris to PA, this method is the one that will ensure you the best precision. Confirmed astrophotographers with pro-graded equipment, all do electronically assisted polar alignment , but it requires some extra pieces of equipment and a computer.

In short, a camera such as the Polemaster or a similar device or a planetary camera , is mounted on the mount in such a way that the camera is pointing in the same direction of the mount. The computer software will analyze the images from the camera and guide you to manipulate the mount so as to get it perfectly aligned. We have already mentioned some software for electronically assisted astrophotography in this guide , some of which, like PHD2, have some polar alignment functions. SharpCap is another great software for lunar and planetary imaging.

Easy and quick. Note that some of those software does not even require to have the celestial pole visible in the frame.

Some GoTo mounts can also use a star alignment procedure to polar align your mount if you cannot see Polaris or Sigma-Octans. Manually polar align the mount essentially requires to frame the star of reference Polaris or Sigma-Octans with a polar scope finder connected to the mount. And this is the most common type of polar alignment, particularly if you use a star tracker. The polar scope finder can be a simple plastic tube, like that of the Omegon Minitrack LX2 , or a more sophisticated optical scope with an alignment reticle inside it.

For all practical purposes, the location of the polar scope finder does not matter, as long as it is parallel with the axis of rotation of the mount. With the simple polar finder tube, you look inside the tube and aim to place Polaris at the center of the field of view. These polar scopes offer you a certain amount of magnification and a built-in alignment reticle to help you place Polaris in a precise position so that the mount is precisely aligned to the true celestial pole.

For quick polar alignment, or to help you identify Polaris, some people prefer to use a green laser. The precision of the alignment is not better than that you can obtain using a simple polar finder tube, but the process will be much more comfortable.

On the other hand, you better check if the use of such a laser is forbidden by law and, in any case, check for passing aircrafts and never point the laser at an aircraft. Particularly in the beginning, polar aligning your mount is a daunting and stressful task, as all your results depend on achieving a good PA.

If you ask in groups and forums on how to improve your polar alignment, you will get a multitude of answers:. In principle, all those answers are correct. The difficulty is to know the ones that are correct for the method you intend to use. There is a lot of skepticism about this. In this post , I explain in detail why the Star Adventurer must be leveled. Other reticles define the position of Polaris with respect to the position of other stars, so one does not need to bother to set the proper date, time and location, nor to level the mount.

Yet, if you rely on other stars to PA, you need to be able to see those stars: they may be occulted by trees or buildings or be washed out in light pollution. The most challenging task of manual polar alignment is to efficiently look inside the polar finder.

Since the mount will point upwards, chances are you will need to kneel before your mount and do a bit of contortionism. This makes it difficult to look along the axes with the polar scope , a requirement for placing Polaris in the right position in the reticle. If you are not looking along the axes of the polar scope, you cannot precisely place Polaris on the reticle. If finding Polaris is easy peasy to the naked eye, at times, I struggle to identify it among the many stars visible in through polar scope, particularly if I am under a dark sky.

Then look for the brightest star: that should be Polaris. One trick is to increase the illumination of the polar scope illuminator or shine your red flashlight in the polar scope. And if you are early at your location, you can polar align as soon as Polaris is visible: this way, you will probably see only it in the polar scope.

Remember: tracking is different from PA. Since Sigma-Octans are fairly faint, these tips will probably not help you if you are imaging in the Southern Hemisphere. Particularly with lightweight mounts, manipulating and moving the payload to frame your target can make you lose the PA. Cooling Vest with Four 4 Strip Packs. Cooling Vest Manual - PC. Cooling Vest with Multiple 4.

Cooling Vest Manual - KM. Cooling Vest Fitted Fashion Vest. Fashion Vest for Men or Women. Cool Fit Kit. Deluxe Neck Tie Insert. Fashion Cooling Scarves Insert. Deluxe Cooling Wrist Wrap Insert. Deluxe Ankle Wrap Insert. Breast and Chest Cooling Therapy Insert. Deluxe Cooling Hats Insert.

Cooling Wraps and Accessories Insert. Evaporative Vest Instructions. Industrial Care and Use Manual. Industrial Vest Description and Fabric Options. Roller Ice.