Is A Full-Frame Camera for Astrophotography Worth It?

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A full-frame camera has a larger image sensor, which means you can capture a wider field of view through your telescope or lens. This can help you create larger astrophotos, (in terms of both image resolution in pixels, and file size).

While it might seem like upgrading from a crop-sensor camera to a full-frame model is a no-brainer, there are some drawbacks to consider. This includes everything from the added cost of the camera to incompatibility issues with your current gear. 

full frame vs. crop sensor camera

There is a big difference in the field of view captured with a crop sensor camera compared to a full-frame.

A larger sensor allows you to take advantage of the native focal length of your telescope or lens without cropping any of the image away. However, to fully utilize a large image sensor your optics (including optical filters) must be up to the task.  

For most amateur astrophotographers, a crop sensor camera makes a lot more sense in terms of cost and compatibility with their existing equipment. Large filters and a telescope with a full-frame image circle are necessary to fully utilize a full-frame astrophotography camera.

Modified DSLR cameraModified DSLR camera

Crop sensor CMOS sensors are found in most entry-level DSLR and Mirrorless cameras. (Canon EOS Rebel XSi).

Upgrading to Full-Frame

If you are looking to buy a new astrophotography camera, you may be wondering whether it is worth it to invest in one with a full-frame camera sensor. While it may seem like an obvious choice for those who can afford it, the decision to upgrade to a larger sensor comes with several new challenges. 

As with any big upgrade to your astrophotography equipment, compatibility, and desired user experience must be factored in before taking the plunge. The necessity for larger filters, a telescope with a large image circle, and an unforgiving sensor plane (tilt) are just a few of the potential issues that may arise. 

William Optics RedCat 51William Optics RedCat 51

Ashley using a full-frame ZWO ASI2400MC Pro color camera on the William Optics RedCat 51.

When these issues are addressed, you can enjoy the native focal length of your telescope or lens, and capture beautiful, massive images. As someone who has tested countless cameras to capture the night sky, I am in the unique position to offer you some sound advice based on experience, not theory. 

With that being said, I have some advice for those thinking about upgrading to a full-frame camera for astrophotography. For a complete overview of the gear I use to capture deep-sky images, please visit the astrophotography equipment page. 

Astrophotography Camera Sensor Sizes

Over the last 10 years, I have used many cameras for astrophotography, from tiny planetary imaging cameras to several full-frame CMOS cameras (mono, one-shot-color, mirrorless).

These days, I bounce around between a full-frame ZWO ASI2400MC Pro (color), and a ZWO ASI2600MM Pro (mono) for almost every astrophotography project I take on.  

full-frame astrophotographyfull-frame astrophotography

The difference in sensor size between a crop sensor and a full-frame astrophotography camera.

While a larger image sensor may seem like an obvious advantage, remember that this camera will be much more unforgiving to the optics you pair with it. Only the best astrophotography telescopes will deliver a sharp, flat field with a full-frame camera attached. 

You also need to think about the larger filters you will need to use with a full-frame sensor, which can increase your overall cost of upgrading even more. As you can see, this decision involves a lot more than just the price of the camera itself. 

Whether you are looking into buying a full-frame astrophotography camera like the Canon EOS Ra, or even a cooled monochrome dedicated astronomy camera, I think this article will help you make a decision. 

My Canon EOS Ra astrophotography camera uses an astro-modified full-frame sensor.

Astrophotography Camera Sensor Sizes

If you began your astrophotography journey with a DSLR or mirrorless camera, chances are it was either an affordable crop-sensor (APS-C) camera body. If you were serious about photography, maybe you even started out with a full-frame DSLR.

These are the 2 primary sensor sizes in today’s professional photography cameras, and they are now quite typical in astrophotography cameras as well. Not too long ago, dedicated astronomy cameras used much smaller sensors. 

In the dedicated astronomy camera world, an APS-C sensor is still considered to be quite large. They cover a large field of view, yet do not require extra large astronomical filters and full-frame compatible telescopes.

Crop Sensor Cameras

A great example of a camera in this category the crop sensor format is the popular ZWO ASI2600MM Pro. It features a sensitive monochrome CMOS sensor in a cooled camera body. 

If the field of view is too narrow for you, you could always capture a high-resolution mosaic image of a particular target to cover the whole thing. This will require a little more work, but it can provide some incredible results. 

If you’re more into astrophotography with a camera lens, a Canon EOS Rebel T8i is a great choice for a beginner. 

Full Frame Cameras

The full-frame astrophotography cameras I use most are currently the Canon EOS Ra, and the ZWO ASI2400MC Pro. The Canon EOS Ra is an astro-modified mirrorless camera body, while the ASI2400MC Pro is a one-shot-color camera.

Both of these cameras can capture images at the native focal length of my telescopes without cropping the field of view. When shooting Nightscapes or the Milky Way with a camera lens, I always use the mirrorless Canon EOS Ra rather than using an adapter with the astronomy camera.

Images captured using a full-frame camera are larger than ones using a crop-sensor, which increases file size, and image stacking time. The larger ASI6200MM Pro is used less, because I do not own filters large enough to fully utilize the sensor. 

I currently use 2 dedicated astronomy cameras, the ZWO ASI2400MC Pro (color), and the ZWO ASI6200MM Pro (mono).

Using a Full-Frame Camera for Deep-Sky Objects

If you have decided to go with a full-frame camera for astrophotography, and you have sorted out any potential issues, you can enjoy a massive field of view from your telescope.

This is especially beneficial when capturing large deep-sky objects such as hydrogen emission regions in the night sky. Certain objects (the North America Nebula, for example) are massive in size in terms of arc seconds (120 x 100 arcminutes). 

The image below shows the Heart and Soul Nebulae captured using a full-frame astrophotography camera (Canon EOS Ra) and a 61mm refractor telescope with a focal length of 275mm. 

heart and soul nebula radian raptor 61heart and soul nebula radian raptor 61

The Heart and Soul Nebulae. Canon EOS Ra, Radian 61 APO. 

The Andromeda Galaxy. ZWO ASI2400MC Pro, William Optics FLT 132.

Certain telescopes perform better than others with a full-frame camera. To increase your chances of compatibility, make sure that the telescope has an image circle of 46mm or larger, and that you are using the dedicated field flattener if it needs one. 

Things to Consider:

  • Price of filters and performance
  • Price of a filter wheel
  • Telescopes with a full-frame image circle
  • Image tilt, flexure (focuser stability)
  • Vignetting
  • Increased File Size

Nightscapes and the Milky Way

A full-frame camera is also great for Nightscapes and Milky Way Photography, especially when paired with a fast camera lens. The wider field of view (when paired with a wide-angle lens) is a little more forgiving in terms of star trailing when using a stationary tripod. 

If you’re mostly interested in landscape astrophotography images using a camera lens, I highly recommend using a mirrorless camera over a dedicated astronomy camera. These camera bodies have the features and control you need to make the most of your dark sky excursions. 

The following image was captured using a Sigma 24mm F/1.4 art series lens on a star tracker. 

Milky Way AstrophotographyMilky Way Astrophotography

The Milky Way using a full-frame mirrorless camera and 24mm lens.  

If you are familiar with daytime landscape photography, you’ll know how beneficial a camera with a large image sensor can be. You can capture more of the scene at once, and have more options in terms of composition and framing. 

The same benefits apply when you are taking pictures at night. While you can always create a mosaic using a crop sensor camera, this requires more work and can be tricky to get right. 

nightscape photography examplenightscape photography example

Understanding Image Scale

The image scale of your image refers to the relation between the pixel size of your camera sensor, and the focal length of your telescope. It provides a value in arc seconds per pixel, which is essentially the area of sky each pixel collects at a time. 

The ideal image scale range is about 1.0-2.0 arcseconds per pixel. This image scale range produces images with pleasing star shapes (round), and an image that is not too sharp or soft. Just right. 

You can use the simple formula below to calculate the image scale of your camera and telescope combination. Pixel size divided by focal length, multiplied by 206.

For example, let’s say I am using the ZWO ASI2400MC Pro camera with pixels that are 5.76 um in size, and I have it attached to my Sky-Watcher Esprit 100 Telescope with a focal length of 500mm.

This system has an image scale of 2.1. Of course, this is just a starting point for your image data, as you may choose to sharpen/soften the details in your image substantially in post-processing. 

The Orion NebulaThe Orion Nebula

The Orion Nebula captured using an image scale of 1.0 arc seconds per pixel. 

Is a Full-Frame Camera Worth It?

If you own a high-quality astrophotography telescope with a full-frame image circle (at least 46mm), you can enjoy incredibly large format images that use your telescope’s native focal length. However, most telescopes that advertise being ‘full-frame’ compatible will still not look perfect to the edge of the field. 

This seems to be the case even when the dedicated field flattener is used. As mentioned earlier, even minor issues in tilt may become worse, and vignetting will come into play. 

If you are okay with cropping the image by up to 10%, this shouldn’t be an issue for you. However, many people will want to maximize the entire full-frame sensor from edge to edge, and this may lead to expensive equipment upgrades. 

A 2″ (48mm) round-mounted filter will cover most of a full-frame sensor, but you will likely see substantial vignetting around the edges of the frame. To fully cover a large full-frame sensor, you may need to invest in larger (50mm) astronomical filters which can be very expensive. 

Aberration inspectorAberration inspector

Use Aberration Inspector in PixInsight to diagnose issues such as tilt and vignetting. (Redcat 61 + Full-Frame Camera).

All telescopes are not created equal, and some will be up to the task of a full-frame camera, while others are not. Upgrading to a full-frame astrophotography camera is the ultimate test of your telescope or lens’s optical performance, so be ready to deal with the results!


 

Trevor Jones is a deep-sky astrophotographer and a valued member of the RASC. His passion is to inspire others to start their astrophotography journey on his YouTube Channel, so they can appreciate the night sky as much as he does. His images have been featured in astronomy books, and online publications including the NASA Astronomy Picture of the Day (APOD).

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