ToupTek SkyEye 24AC – 1/2 – The purchase decision

Almost two years ago I added the ToupTek SkyEye 62AM to my setup – a full‑frame monochrome camera. Going full‑frame was an easy call at the time: both of my scopes – the Vixen VC200L and the Baader APO 95/580 CaF2 Travel Companion – deliver cleanly all the way into the corners of a full‑frame sensor, and it would have been a waste not to make use of that. I’ve been thoroughly happy with the 62AM ever since. It produces reliably excellent data in my setup, and for what I’m after it is simply the right camera.

Even so, I’ve known for a while that I wanted to complement the main sensor with a second, one‑shot‑color camera. In this post I want to walk through how I arrived at that decision, why the choice of manufacturer once again fell on ToupTek, and why the camera I ended up with is the SkyEye 24AC rather than the more obvious SkyEye 62AC.

Why a color camera at all?

The appeal of a mono camera is flexibility: luminance, RGB, narrowband in H‑alpha, OIII and SII – all captured separately, cleanly isolated, and freely combinable in post. But that flexibility comes at a price that is easy to underestimate at the scope: time and planning.

Every channel has to be planned, exposed and calibrated individually. Flats are needed per filter, the night has to be split up sensibly, and conditions should remain roughly comparable across multiple sessions. If, like me, you shoot with a filter drawer rather than a motorized filter wheel, there are also a few extra manual steps on the checklist.

Alongside the 62AM I’ve always kept an astro‑modified Canon EOS R in the rotation – also full‑frame. Especially on nights where I knew I’d only get a single session on a given target, I’ve happily reached for the Canon. One evening, one object, one image – done. If the weather closes in earlier than forecast or the night turns out shorter than planned, I still have a complete image across all channels and can start processing the next day, instead of waiting for “the second half of my data”.

The textbook example of this use case, for me, is comets. With a bit of luck you get 20 or 30 minutes in which comet and surroundings really line up. Spending that window changing filters kills the fun. What I want there is simple: point the scope at the comet, press go, shoot.

So the basic decision was made: I wanted a cooled one‑shot‑color camera – as a complement to the SkyEye 62AM, not as a replacement.

Why ToupTek again?

The manufacturer question was, honestly, answered quickly. I’ve been thoroughly happy with the SkyEye 62AM for a year and a half now: solid mechanics, clean sensor, reliable drivers, sensible price. ToupTek is, even if the name doesn’t always roll off the tongue in the German‑speaking market, one of the largest astro‑camera manufacturers out there. A substantial share of the cameras sold under other brand names – Lacerta, Omegon, and many more – ultimately come out of the same factory. Whatever convinced me about my mono camera speaks equally in favor of a second camera from the same house. Working from that premise, the shortlist narrowed down to two models from the same SkyEye family.

Two candidates: SkyEye 62AC or SkyEye 24AC

At first glance, the SkyEye 62AC would have been the logical pick: the color counterpart to my mono camera, same sensor, same 3.76 µm pixel pitch, same mechanical behavior, identical workflow. You can’t get more symmetrical than that.

The second option was the SkyEye 24AC: also full‑frame, but with significantly larger pixels and correspondingly lower resolution. 14 bit instead of the 16 bit of the 62. On paper, that sounds a bit like a step down – fewer pixels, less bit depth. In practice the calculation looks different.

Why the SkyEye 24AC won

In the end I went with the SkyEye 24AC. Several points drove that decision, and they all push in the same direction: time, light gathering per pixel, and complementarity with the existing setup.

Larger pixels mean more light per pixel. That’s the key difference with the 62AC. Every pixel sees noticeably more photon flux, the signal‑to‑noise ratio per exposure is higher, and especially on targets that need to be captured in a single evening you simply get to a solid result faster. What the 24AC loses in resolution it gains in efficiency – and efficiency is exactly what this use case calls for.

Smaller files, faster integration. Subs are smaller, stacking runs noticeably faster, and the total storage footprint of a full session is lower. That might sound like a side note, but it matters for exactly the working mode this camera is meant for: through the workflow quickly, to a result quickly, able to process the next day instead of leaving the machine stacking overnight.

For my seeing, larger pixels are often the better match anyway. On most nights it’s the seeing that sets the ceiling, not the sensor. I want to take a closer look at that in a separate post: pixel size versus aperture – a comparison that in practice often clears things up more than any spec sheet ever could.

The 62AC would have been the “more consistent” choice. The 24AC is the one that matches how I actually work.

Adapting to both telescopes

One aspect that is almost as important to me as the camera itself: swapping cameras has to work in the dark, with cold fingers, in seconds. That’s why both telescopes – the Vixen VC200L and the Baader Travel Companion 95 – have a Baader M68 quick‑change system sitting right behind the focuser.

With that in place, either camera can be swapped onto either scope without a single tool, in a matter of seconds. And because I deliberately kept it in mind when selecting the SkyEye 24AC, the adaptation is identical in every respect:

• the same M68 mechanical connection,
• the same power connector (12 V / 2.1 mm),
• the same data connector (USB 3),
• two of each on the camera, with the second one used to run the guide cam.

In practice this means: whether 62AM or 24AC, whether VC200L or Travel Companion – the cabling stays the same, the adaptation stays the same, and nothing has to be rebuilt at the telescope. That kind of systems thinking is something I’ve come to really appreciate in my setup over the years.

The new workflow: mono luminance + color camera

What I had already tested in practice before buying the 24AC: it works beautifully to combine a luminance image from the SkyEye 62AM with the color information from a one‑shot‑color camera – up to now, that meant the Canon EOS R. I’m carrying this workflow straight over to the cooled SkyEye 24AC, and it gets noticeably better with the improved per‑pixel sensitivity and clean noise behavior of the cooled sensor.

A trick that has proven itself and that I will keep using: I drizzle the color channels from the 24AC by a factor of 2 during stacking and then scale the output back down to the size of the SkyEye62 picture during integration. It sounds like a detour, but it produces remarkably clean, fine color information – and the fact that the color camera has a slightly lower pixel count than the mono can be offset this way almost perfectly: the drizzled color data, reduced, integrates beautifully into the slightly larger canvas of the mono luminance.

In combination, that gives me:

• Full session, multi‑night projects, deep luminance, narrowband → SkyEye 62AM, classic mono workflow.
• One evening, one target, comets, weather‑uncertain nights, fast results → SkyEye 24AC as a pure OSC solution.
• Maximum detail → luminance from the 62AM, color from the 24AC, everything aligned on the full‑frame canvas of the mono.

Conclusion

On paper, the SkyEye 62AC would have been the symmetrical complement to the 62AM. In practice, the SkyEye 24AC wins out on exactly the criteria that matter for a second camera in my setup: more light per pixel, shorter path through integration, smaller files, a camera I can reach for on a short evening or on a comet without feeling conflicted – and one that, at the same time, pairs perfectly with the mono’s luminance or narrowband palette as a color provider.