In this lesson, I will share my thoughts on these functions and accessories with hobby photographers looking to photograph starry skies (rather than with experts and specialists of astrophotography) and explain why I think PENTAX is the best photographic gear available in this field.

The PENTAX O-GPS1 GPS Unit, launched in 2011, simplified celestial-tracking photography through the use of the ASTROTRACER function in combination with a PENTAX digital SLR camera. Of course, I purchased the O-GPS1 as soon as it was released, and took off with my two cameras — a PENTAX K-5 and a PENTAX K-r — for photoshoots at Mt. Fuji, in the mountainous Okuchichibu region north of Tokyo, and Yuzawa in Niigata Prefecture, looking for a clear sky during the rainy season.

My astrophotography changed dramatically with the introduction of the PENTAX O-GPS1 and its ASTROTRACER function. In the old days, if we wanted to follow the movement of stars and capture beautiful images of celestial bodies, we had to shift the camera’s position. This meant using heavy, cumbersome equipment such as equatorial devices.

My name is Takaki Kasahara. I’m an astrophotography equipment engineer; my friends call me Hoshi Otoko , or Star Man.

Photo at right: This setup is all you need!

Thinking about astrophotography, most people who are familiar with photographic gear probably have an image of elaborate and cumbersome equipment. The ASTROTRACER function, however, cuts the required equipment to a minimum.

Note: PENTAX cameras featuring the GPS function, such as the PENTAX K-1 Mark II, K-1 and K-3, provide the ASTROTRACER function without the need of the O-GPS1.

By accurately tracking the movement of the stars, the ASTROTRACER function captures them as point images even with extended exposures.

It has been seven years since the ASTROTRACER function made its debut, so many people are familiar with it. Simply told, this function shifts the camera’s image sensor in synchronization with the movement of celestial bodies, capturing images in which stars and planets appear to be stationary.

ASTROTRACER’s advantages over equatorial devices

The camera can be placed on the ground if necessary. The size and weight of your photographic equipment can be greatly reduced.

ASTROTRACER provides several advantages unavailable with equatorial devices:

The first is simplified, easy-to-understand operations. Just make a high-precision calibration to properly set up the camera, then expose the image for 30 to 90 seconds, depending on the focal length of the lens being used. This captures stars as point images, and also lets you easily photograph the Milky Way and nebulas, objects difficult to even see with the naked eye.

The second advantage is that, unlike when using equatorial equipment, you don’t need special skills or astrophotographic knowledge. Equatorial equipment requires a polar alignment based on the position of the North Star. On the other hand, ASTROTRACER’s high-precision calibration can be made even in the southern hemisphere, where the North Star does not appear. Once you have the camera set up based on the high-precision calibration, the camera memorizes the setup — even when the power is turned off, or when the tripod-mounted camera is repositioned to recompose the image. This is a very helpful feature in the field photography.

Since the O-GPS1 system is lightweight, you can use a compact tripod. When you are in a rush, you can even place the camera on the ground. This free repositioning of the camera is simply not possible with equatorial devices, so this is an extremely important advantage.

Especially with the compact photographic equipment such as portable equatorial devices, image composition is crucial. Even a slight movement of the equipment while composing an image can cause an error in polar alignment. Or if you try to force a difficult composition and throw the equipment off balance, the entire photographic system may be out of line. Either way, the result is streaks, not sharp pinpoint stars, in the image.

The final and most important advantage is the reasonable cost for a full-scale astrophotography system. Equatorial equipment can easily cost JPY100,000 or more; the O-GPS1 retails at about JPY20,000.

Let me list up these advantages:

ASTROTRACER:

A 60-second exposure time, for example, can capture a celestial image with stars as point images along with drifting clouds;

Telephoto photography is available up to a focal length of 135mm;

High-precision calibration data is retained as long as the battery remains in the camera body: Late-model PENTAX lenses can be exchanged while the power of the camera and the O-GPS1 is turned off; Manual lenses without lens information contacts require the input of focal length data; This is a very useful feature when you are waiting for the sky to clear in a car or tent; When you move to a completely new location, you may have to repeat the high-precision calibration.

You can reposition the tripod-mounted camera to recompose the image. This is an extremely important benefit in astrophotography;

You can place the camera on the ground;

High-precision calibration can be made in locations where the North Star does not appear;

ASTROTRACER comes in handy in the southern hemisphere;

ASTROTRACER provides immediacy: When you come across a beautiful starry sky on the road, you can complete your astrophotography in just 10 minutes.



Equatorial devices: