Altair Astro has added two cameras to its GPCAM3 range: the colour 678C and the 678M, its monochromatic sibling.
Both are fitted with the Sony IMX678 Starvis 2 CMOS sensor that promises to deliver excellent ‘lucky imaging’ capability – perfect for the planetary imaging game.
With an array of planets peppering the early 2025 skies, it was the ideal time to put the Altair 678C through its paces.
Unboxing the Altair 678C
Unpacking the Altair 678C, we found a small yet striking camera in Altair’s signature purple colour.
Weighing in at 70g and only 72mm in length, the body is barely larger or heavier than a 1.25-inch Plössl eyepiece, allowing it to be used successfully with lightweight telescopes and mounts.
Included in the box is a 1.25-inch nosepiece extension, 1.5-metre USB 3.0 cable, ST4 guide cable and an installation CD.
Given that many laptops and PCs today don’t include a CD or DVD drive, it’s helpful that the software and drivers can also be found in the downloads section of Altair’s website.
Installing the camera drivers was simple, as Altair has bundled them into a single download.
Altair’s AltairCapture software can also be downloaded from this location if you aren’t already running any astronomy capture software.
Once installed, we plugged in the 678C, which was instantly recognised with no additional configuration required.
How the Altair 678C performs
With a waxing Moon in the sky, we popped the Altair 678C onto our 8-inch Newtonian reflector.
At 1,000mm focal length, the 2µm pixels gave a 0.41 arcseconds/pixel resolution, slightly short of the 0.25 arcseconds/pixel resolution commonly considered optimal for average seeing conditions.
However, by adding our own 2x Barlow lens we increased the resolution to 0.21 arcseconds/pixel.
Once attached, the Barlow and 1.25-inch extension gave us enough back focus to bring the Moon to a crisp appearance.
The first thing we noticed was a green tint to the live view, confirmed by our software histogram.
Checking the settings in AltairCapture, we were able to control the white balance and correct this.
However, using different software (FireCapture) at a later session, we unfortunately didn’t have the individual colour channel control allowed by some other cameras, so weren’t able to balance the colour channels mid-operation.
However, this could be easily corrected in post-processing, so wasn’t detrimental to our images.
With the camera set to 8-bit mode and with the resolution set to maximum, we were easily able to achieve the advertised 47 frames per second (fps) with a balance of the exposure time/gain settings (gain 182, exposure 13.44ms).
During a two-minute capture, zero frames were dropped and the capture speed was maintained throughout.
Finished with the Moon, we slewed over to Jupiter.
With the planet in the centre of the field, we applied a tighter ‘Region of Interest’ setting focused on an area 350 x 350 pixels in size.
This area was filled by Jupiter, with just enough black space around the edge to ensure we weren’t clipping the planet.
With the gain set to 245 and exposure time at 9.85ms, we were achieving an impressive 148fps on this smaller image.
Once we were happy with our captured videos, we proceeded to process our files.
We started with AutoStakkert! but immediately hit an issue with the longer captures, in that our PC ran out of memory.
This was overcome by adding an initial step of using PIPP (Planetary Imaging PreProcessor) to review the video, reorder it by quality and discard the worst frames.
This reduced the file size sufficiently for AutoStakkert! to successfully process and stack the resulting video into a single image, ready for final processing and wavelets application in RegiStax.
Summary review
It quickly became apparent that the new Altair GPCAM 678C is a very capable and user-friendly camera.
Simple enough for beginners, it also returns images that will satisfy intermediate planetary imagers.
From its straightforward setup to delivering consistently high frame rates at low gain settings, it was a pleasure to use and returned some excellent planetary images.
High resolution, low amp glow
This GPCAM from Altair Astro features the new IMX678 Starvis 2 CMOS sensor from Sony.
This 8.3MP colour sensor features 2µm pixels in a 3,840 x 2,160 array and promises capture speeds of up to 47fps at full resolution in 8-bit mode and more than 71fps when cropped to 1,920 x 1,080 resolution.
As this is a high-resolution sensor, it returns large file sizes: a two-minute capture at full resolution resulted in a 30GB file size, so hard drive space may be an issue.
In fact, on a later session, we managed to fill our 500GB hard drive within a couple of hours.
Another area where the IMX678 excels is its ability to handle amp glow.
With the cap still on our telescope, we tested this by running a series of dark calibration frames and pushing the exposure length up.
Given that this camera is only passively cooled, we were still getting perfect amp-glow-free images at five-minute exposures.
5 best features
1.25-inch nosepiece
Despite the camera itself being 1.25 inches wide and therefore compatible with most focusers, Altair
has also included a 1.25-inch nosepiece extension. This comes in very handy when additional back focus is required; this was always needed, so it remained attached to the camera throughout our imaging sessions.
Passive cooling
The Altair 678C is a passively cooled camera, so does not include any fans or Peltier coolers, but instead uses heat sinks to disperse generated heat. To help disperse the heat, the body of the camera is ridged, increasing the surface area and allowing for quicker cooling mid-operation.
1.25-inch filter thread
The inside of the black removable filter is threaded for 1.25-inch filters, allowing the use of aftermarket IR/UV cut filters or other specialist filters like a quad-band for deep-sky use. Planetary imaging filters like IR pass or coloured filters can also be used when paired with a clear optical window.
Connectivity
Located on the back of the camera is a USB 3.0 port which, when combined with the supplied 1.5-metre cable, allows full PC control. Alongside this is a guide port that allows the Altair 678C to be connected to
a mount and used instead as a guide camera.
Removable UV/IR filter
Secured within the nosepiece of the 678C version is a removable infrared and ultraviolet block filter. This allows us to change to a clear filter should our image needs require it. This also allows us to clean the sensor as and when needed.
Vital stats
- Price: £259
- Sensor: Sony IMX678 Starvis 2 CMOS
- Resolution: 8.3MP, 3,840 x 2,160
- Exposure range: 0.1ms–1,000 seconds
- Connectivity: USB 3.0, USB 2.0
- Size: 37mm x 72.4mm
- Weight: 70g
- Supplier: Altair Astro
- Tel: 01603 721946
- www.altairastro.com
This review appeared in the May 2025 issue of BBC Sky at Night Magazine
