Celestron RASA 6″: A Fast & Portable Powerhouse for Astrophotographers? Preview

Introduction

RASA Performance for Everyone

Celestron’s Rowe-Ackermann Schmidt Astrographs (RASA) are engineered for astrophotographers who prioritize speed, precision, and portability. Weighing just 5.7 kg (12.5 lbs) and featuring an f/2.2 optical design, the RASA 6 dramatically shortens exposure times. This makes it easier to capture crisp, detailed images of faint deep-sky objects by reducing the need for extended tracking times.

The RASA 6 delivers similar high-end performance to its larger siblings but at a more affordable price point ($1.699 at the time of writing). Thanks to its fast optics, the RASA 6 collects light faster and provides higher resolution (i.e., has a bigger aperture) than most other telescopes in its price range. This makes the RASA 6″ an excellent choice for capturing fine details in galaxies, nebulae, and star clusters. Notably, this same optical system is already used in Celestron’s Origin smart home observatory, but the standalone RASA 6″ now makes this telescope available to astrophotographers who want to pair it with their own equipment.

The Celestron RASA 6″ telescope is available from High Point Scientific (USA/WW) and Agena Astro (USA/WW).

Wide Field of View

With its 335mm focal length and 6″ aperture, the RASA 6 delivers a 3.8° field of view for camera sensors up to 22mm diagonal, making it ideal for capturing wide-field images of emission nebulae, star clusters, and some of the larger galaxies. Depending on pairing the telescope with different astro-cameras, the field of view and resolution will vary. I did some calculations you can expect for popular sensor sizes. For example, the RASA 6 should give you the following views:

ASI678MC (IMX678, 2.0µm pixels):
1.23 arcseconds/pixel, 0.87° x 0.65° field of view
(Similar QHY model: QHY5III678C – same IMX678 sensor)

ASI533MC Pro (IMX533, 3.76µm pixels):
2.32 arcseconds/pixel, 1.54° x 1.54° field of view
(Similar QHY model: QHY533C – same IMX533 sensor)

ASI2600MC Pro (IMX571, 3.76µm pixels):
2.32 arcseconds/pixel, 4.02° x 2.69° field of view
(Similar QHY model: QHY268C – same IMX571 sensor)

One popular rule of thumb that I ascribe to is that 1 to 2 arcseconds per pixel is optimal for deep-sky imaging from your backyard, and this is slightly out of reach with the larger sensor cameras. However, it is perfect for the smaller pixel-sized cameras like the ASI678 (or QHY5III678C equivalent) that are often used for planetary imaging and in smart telescope setups. On the other hand, the larger field of view that bigger camera sensors provide is a must for capturing larger nebulae and galaxies such as the Andromeda galaxy, the Veil Nebula, and the Heart Nebula that all span several degrees in the night sky in a single picture – without having to create mosaics. Note that APS-C format IMX 571 sensor is 28mm, so you will probably suffer from some vignetting at the edges of the view when pairing it with the RASA 6″.

User Feedback: What the Community Says

Early feedback from the amateur astrophotography community suggests that this compact powerhouse is generating a lot of excitement. On popular social media platforms and astrophotography websites, users have praised the new 6-inch RASA for striking a great balance between portability and performance. Many have noted its impressive speed, allowing for detailed captures with shorter exposures, and its ease of use—even without autoguiding in some setups. There’s also growing interest in its potential as a lightweight, mobile option for both backyard and on-the-go astrophotography.

Pros of the RASA 6″

Ultra-Fast Optics (f/2.2)
The RASA 6″ features an incredibly fast f/2.2 focal ratio, allowing for extremely short exposure times. This means you can capture detailed images of faint deep-sky objects without needing long exposures, which may even eliminate the need for autoguiding (i.e., an extra guide scope and guide camera) — perfect for maximizing imaging time under variable skies.

Wide Field of View
As mentioned, with a focal length of 335mm and a 6″ (150mm) aperture, the RASA 6 delivers a 3.8° field of view with camera sensors up to a 22mm diagonal. This makes the RASA 6 ideal for imaging (parts of) larger emission nebulae, star clusters, and galaxies. However, you’ll need a longer focal length telescopes for high-quality planetary imaging, or similar tiny objects like distant galaxies in the night sky.

Portable and Lightweight
Weighing just 5.7 kg (12.5 lbs), the RASA 6 is the most compact and portable member of the RASA family. Its lightweight design allows it to be mounted on more mid-range GOTO telescope mounts like a ZWO AM3, a SkyWatcher (H)EQ5, or Celestron’s own AVX mount.

Sharp Across the Field
The flat-field optical design, combined with Celestron’s StarBright XLT coatings, results in crisp stars all the way to the corners—even with large sensors. Users have noted that the level of sharpness produced by RASA telescopes is tough to match at this price point.

Cons of the RASA 6″

Limited Camera Compatibility
Due to the front-mounted design and specific back-focus requirements, RASA telescopes are incompatible with DSLRs and some larger cameras. Also, the 3″ diameter of typical astro-cameras like the 533MC-Pro will contribute to central obstruction, affecting its light-gathering capabilities.

No Visual Observation
RASA telescopes are designed exclusively for astrophotography and cannot be used for visual observing, as the camera occupies the prime focus position.

Sensitivity to Backfocus and Tilt
The fast optics make RASA telescopes particularly sensitive to backfocus errors and sensor tilt, requiring precise setup to achieve optimal image quality. While I do not have personal experience testing this, many RASA owners in the past argue that the extremely shallow critical focus zone makes RASA telescopes extremely sensitive to small amounts of tilt. It will be interesting to find out if that issue is resolved with the RASA 6 integrated filter drawer design.

Front-Mounted Camera Can Be Awkward
Some users have indicated that the front-facing camera position can be a bit awkward to work with—especially for cable management. Also, adding large electronic filter wheels are out of the question. Some users also worry about dew and exposure to the elements when the imaging train is out in front. So I’d recommend using an extra dew shield.

Additional Technical Details

Some other technical details of the Celestron RASA 6 include:

• Integrated filter drawer accepts both 1.25″ and 2″ filters without compromising optical performance
• 12V MagLev cooling fan maintains optimal temperature while keeping dust out
• Standard M42 camera adapter for easy attachment of astronomy cameras

Conclusion: A New Era in Astrophotography?

The RASA 6″ offers an exciting new option for astrophotographers seeking speed, precision, and portability in a compact package. With its fast f/2.2 optics, wide field of view, and advanced features, it promises to be a game-changer in the world of astrophotography.

That said, the RASA 6 is a brand-new release, and as with any new telescope, we’ll need to wait for more in-field feedback from users to fully assess its performance and reliability over time. While the specs and features look promising, a closer look at real-world usage will be key to determining how it stands up to expectations. Let’s wait and see how this exciting new telescope holds up!

The Celestron RASA 6″ telescope is available from High Point Scientific (USA/WW) and Agena Astro (USA/WW).

Clear skies!

Wido (@Wido’s Astroforum)

I’m thankful for any thoughts or real-life experiences you can share about the RASA 6 in the comments below—your insights could really help out fellow astrophotographers!