MLAstro SHG700 Review: A Practical Solar Spectroheliograph for Refractor Owners

Introduction

Solar photography usually means investing in a dedicated solar telescope or a specialized eyepiece, both of which can be expensive and finicky to tune. The MLAstro SHG700 takes a different approach. It is a spectroheliograph, a device that scans the Sun and reconstructs an image from the spectral data it collects. Instead of capturing the Sun all at once like a camera, it records a narrow slice of light and builds the full picture through software.

What makes this interesting is that it works with a standard refractor telescope. If you already own a refractor for deep-sky astrophotography, you can repurpose it for solar imaging with this unit. The results, particularly in hydrogen alpha, are surprisingly detailed for the effort involved.

What Is the MLAstro SHG700?

The MLAstro SHG700 is a high-spec spectroheliograph designed for solar photography only. It is not intended for visual observation, and looking through it directly could harm your eyes. Instead, it attaches to a camera and a telescope, and the imaging happens entirely through the capture and processing workflow.

At the front of the unit sits a small slit assembly. This is not a mirror, despite its appearance. It is a precision diffraction grating with a tiny slit at the center. Incoming light passes through that slit and is spread into a spectrum. The spectrum is then projected onto a camera sensor installed at the rear of the unit. Because the grating is very precise, the spectrum spreads across a wide field of view, which allows you to zoom into specific wavelengths with good resolution.

A selector dial on the side lets you move the field of view so the wavelength you are interested in, such as hydrogen alpha, falls onto the camera sensor. This is the core adjustment you make before and during a capture session.

The SHG700 is based on an open-source design called the Solex, which you can 3D print and build yourself. The MLAstro version is a more complete implementation with full metal parts, proper micrometer-style adjustments, and better optics. It also does not require energy rejection filters, which simplifies the setup compared to some other solar imaging methods.

How the SHG700 Works

The imaging process is different from what most astrophotographers are used to. Instead of taking a single frame of the Sun, you scan across it. The telescope mount moves the Sun through the slit while the camera records the spectral data. Each frame captures a slightly different portion of the Sun, and the software stitches those frames back together into a full image.

This sounds complicated, but in practice it is straightforward. You point the telescope at the Sun, center the hydrogen alpha line on the sensor, and then move the mount in right ascension while recording. A single scan takes only a few seconds. The resulting video file, which looks like a dark line with flickering detail, is then processed using free open-source software to reconstruct the solar image.

The unit has three focus points that need to be adjusted: the camera focus, the internal optics, and the telescope focus. Each one is a simple step, and the process is well documented. The initial setup takes some patience, but once you understand the sequence, it becomes routine.

One important note is that the declination axis of the mount and the slit need to be as parallel as possible. If they are not, your scan may be truncated, missing part of the solar disc. This is one of the few things that takes practice to get right.

Capturing a Solar Scan

To capture a scan, you first need to prepare the unit before attaching it to the telescope. This can be done in daylight, even on a cloudy day. You point the unit at the sky, connect a camera, and adjust the focus so the spectral lines are sharp. You also rotate the camera so the lines are horizontal, and center the hydrogen alpha line on the sensor.

Once the unit is prepared, you attach it to the telescope. The telescope should be a refractor, and you should check the documentation to confirm compatibility. The unit works well with a 102 mm aperture refractor at f/7, which is a common size for deep-sky imaging rigs.

When everything is connected, you reduce the exposure and gain on the camera, then center the Sun in the spectrograph. You will see a shimmering effect around the hydrogen alpha line, which indicates you are on the right track. From there, you move the mount away from the Sun, start the capture, and scan through the Sun at a steady rate. The whole process takes less than a minute per scan.

The biggest challenge during capture is wind. Because the image is built from many frames taken over time, any vibration between frames shows up as vertical banding in the final image. Imaging from a sheltered location or on a calm day makes a significant difference.

Processing and Results

After the scan, you open the video file in a free program called Solex. The software processes the spectral data and reconstructs the solar image automatically. It also generates additional outputs, including a white light version, a Doppler map showing which parts of the Sun are moving toward or away from you, and a colorized hydrogen alpha image with prominences.

The Doppler map is particularly interesting. It shows the rotation of the Sun, with one side appearing blue and the other red. Active regions and prominences are also detected automatically, giving you a wealth of scientific data without extra effort.

In practice, you can go from unboxing the unit to a usable solar image in under an hour, assuming you already know how to use your mount, camera, and capture software. Stacking multiple scans improves the result further, reducing the banding artifacts caused by wind and seeing conditions.

Buying Advice

The MLAstro SHG700 is priced at around $800. That is not cheap, but it is less than many dedicated solar telescopes or hydrogen alpha eyepieces. Compared to building your own Solex from a kit, which costs roughly $500 to $600 including optics, the SHG700 costs about $200 to $300 more. That premium buys you a fully assembled, metal-bodied unit with precise adjustments that work out of the box.

This device is best suited to astrophotographers who already own a refractor and a solid mount. You will also need a monochrome camera with small pixels, such as the recommended model with two-micron pixels, and a few adapters. The camera adapter is not included, so you will need to provide an M42 to 1.25 inch adapter yourself.

If you are interested in solar photography and want detailed hydrogen alpha images without the cost and complexity of a dedicated solar telescope, the SHG700 is a compelling option. It is also a great way to keep imaging during the day when nighttime skies are cloudy, especially during periods of high solar activity when the Sun changes noticeably from day to day.

Conclusion

The MLAstro SHG700 is an impressive piece of equipment that makes solar spectroheliography accessible to anyone with a compatible refractor. The scanning process takes a little getting used to, and wind can be a real nuisance, but the results speak for themselves. Detailed hydrogen alpha images, Doppler maps, and prominence data are all achievable with free software and a modest amount of practice.

For the price, it is hard to argue with what this unit delivers. If you have been curious about solar imaging but were put off by the cost of dedicated solar telescopes, the SHG700 is worth a serious look.