Since the introduction of ZWO’s harmonic mount AM3 and ASI2600MC Duo camera, I have had a thought in mind: I want to create a portable astrophotography system with them.

Now that the equipment is in place, let’s get started.

First, let’s take a look at the equipment:

1.AM3: The external packaging box is beautifully designed.

The suitcase inside the package is made of EPP high-density foam material, molded in one piece with excellent compression resistance and shock absorption performance, making it convenient for transportation. Upon opening, you can see that all accessories are placed compactly.

The weight of the AM3 is 3.9kg, which is much lighter compared to the AM5, which weighs 5.5kg. The size has also been significantly reduced. This reduction in size and weight is the basis of a portable system. The tripod is the TC40, which weighs 2.3kg.

The load capacity of the AM3 is 8kg without counterweight and 13kg with counterweight. Due to the characteristics of the harmonic mount, it is not necessary to balance the equipment before shooting. This provides a solid foundation for quick-starting astrophotography.

2. ASI2600MC Duo: Integrated Guiding and Imaging Camera

The significant innovation of ASI2600MC Duo is it integrates a main sensor and a guide sensor into one camera body, whilst the external dimensions remain the same, allowing for a more convenient and portable astrophotography system.

A larger APS-C format sensor, IMX571, works as the main sensor. A smaller guide sensor, SC2210, works as the guide sensor. A focus knob on the side of the camera can be used to focus the guide sensor.

When we compare the specification of the Duo camera with the Pro, we will easily find that the Duo camera has achieved some great improvements, such as frame rate, full well capacity and DDR cache, just as shown in the table below.

Now, here comes the crucial part. As a combined camera with two sensors, the total photosensitive area has increased. When connecting to telescopes, does the photosensitive area cover the light cone at the back end of the telescope? In other words, does the camera have any requirements for the interface diameter of the telescopes?

The manufacturer recommends using the M54 interface, as shown in the figure below, it is undoubtedly the most perfect option.

I plan to use the Canon’s 135/2L lens. Can it work with this camera? Let’s take a closer look at the camera’s mechanical structure diagram: There is a 44mm diameter circle that can simultaneously cover both sensors.

Fortunately, the diameter of the light cone entering the camera sensor increases slightly with the distance from the lens (objective), which means it is possible to use a slightly smaller M42 interface (of course not too small). The expanded light cone can also cover both camera sensors. This assumption was later confirmed after actual installation, but we will discuss this later.

Regarding the optical design of the lens, having an M42 interface at the front end of the ASI2600MC Duo should not affect the light intensity on the camera’s photosensitive area. However, in the case of APO + field flattener optical design, it has been observed that having an M42 interface at the front end may obstruct the light path.

3. Now that we have introduced the key equipment, let’s proceed with assembling the portable photography system.

1) Since we no longer need a separate guide scope, the assembly process becomes much easier. The most “troublesome” part is the black filter drawer as shown in the middle of the picture below – It has a Canon interface on the front, and an M42 interface on the rear end. The bottom of the filter drawer has screw holes, that can be screwed to the dovetail plate. The rear end can be connected to the ASI2600MC Duo using the M42-M48-M54 adapter ring, and the front end can be connected to the Canon 135/2L lens. Actually this part is not that “troublesome”.

2) The installation of other components is also easy. By adding a short dovetail plate with a cross-shaped pattern at the front end of the long dovetail plate, the EAF and ASIAIR can be installed on either side.

3) After all the components are installed, it looks as shown in the picture below.

4) After disassembled, the equatorial mount, lens, camera, ASIAIR and power supply can be comfortably placed inside a photography bag. There still is some space to accommodate some small accessories.

5) Finally, hang up the tripod on my photography bag. One portable astrophotography setup pack is ready to start his adventure with me.

As for the weight, equatorial mount and tripod weigh 3.9 + 2.3kg. The equipment weighs 2.9kg. The photography bag weighs about 2kg, and the lithium battery weighs 3.5kg. So the total weight is 14.6kg. Leaving the tripod alone, it occupies a space of about 50x35x22cm.

This system is much lighter and more portable compared to conventional astrophotography systems.

6) To verify if the M42 interface matching the ASI2600 Duo camera can fully cover both the guiding and imaging camera sensors, a test shoot was conducted. The weather conditions were not good so the total shooting time was not too long, but the results were visible.

In the guiding frames, the stars appeared round without any vignetting, indicating that the M42 filter interface is compatible with the ASI2600MC Duo when the 135mm lens is mounted.

Using the above equipment to capture M31, the guiding error was between 0.5-0.7. The stars appeared solid, without any distortion or trailing in the corners.

This portable astrophotography setup excites me. I can imagine how convenient it will be for an old man like me to carry it each time I want to go night sky site, and I cannot wait to do so.

Discussion:

The portable photography setup described above is suitable for situations where DSLR lenses are used. For users who were originally engaged in DSLR photography, they may have 3-5 lenses. These lenses can be readily utilized by simply swapping them onto the filter drawer interface. They can be used for both daily photography and astrophotography, making it very convenient.

For enthusiasts using 60/80/90/102mm aperture telescopes, the installation of the telescope, EAF, filter wheel, and other components can be done using conventional methods. However, they can still benefit from the lightweight and portable nature of the AM3 setup, along with the impact design of the ASI2600MC Duo camera. By eliminating the need for guide scope, the calibration issue associated with aligning the guide scope and the main telescope is also eliminated. I believe the guiding performance should be better in this case. What do you think?

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