作为不少Lunt Solar System H-alpha 望远镜和滤镜（包括双滤LS100T 和LS152T）的长期用户，我对Sky-Watcher 的HelioStar 76Ha 望远镜很感兴趣，因为这是 该公司的第一次踏进H-alpha太阳观察领域。有幸获得一台 HelioStar试用，而且用 Lunt Solar Systems  LS100T 望远镜作对比。

HelioStar 中太阳表面丝状物(filaments)与背景形成了非常高的反差对比。使用 TeleVue Panoptic 19mm、Ethos 13mm 和 DeLite 11mm 目镜观察，影像清晰迷人，类似经过处理的图片。

与 LS100T  的频宽(bandwidth) <0.7 Angstrom相比，HelioStar的频宽为 <0.5 Angstrom，因此预计影像的对比度会更好，而这确实和观察结果吻合。  LS100T 的丝状物对比度明显较低，我们需要在前面添加一个 LS100F，即用双滤模式，才能获得与 Heliostar 般的影像。当然，Lunt LS100T配合LS100F 双滤的价格要高得多。

我们尝试使用Binoviewer。可是，HelioStar 无法对焦，但 LS100T 却没有这问题。

HelioStar的设计使观察更方便。例如，箱内的檔板为为观察者提供遮荫，调频方法比Lunt Solar Systems 压力调频器更容易使用。

第二天，太阳表面爆发出一个直径约 20-30 个地球直径的巨大日珥。LS100T 中的影像比 HelioStar 的影像更光亮，解像度（resolution）也好得多，这也是 LS100T的较大口径产生的预期结果。

第三天，我们使用 ZWO ASI290MM 单色相机拍摄太阳影片，可是HelioStar的调焦器质素一般，难以准确对焦，但拍摄出来的效果相当精彩。我们也尝试加入 Barlow或Powermate 来提高放大倍率，但我们只能使用 Celestron 2x Barlow 来达到对焦。此外，较高倍数也导致曝光时间更长，视宁度开始明显影响影像质素。

总而言之，Sky-Watcher HelioStar 望远镜合符其频宽和口径的表现，是性价比很高的产品，非常适合目视太阳圆盘(solar disk)和低倍摄影，尤其是长长的丝状物。可是，对观察日珥和高倍摄影则比LS100T差，调焦器质素也有很大进步空间。

作者：David Leong

星河科研社为SkyWatcher香港代理，此镜eshop有售 https://eshop.astro.hk/hk/catalogs/products/22054624-94cb-4cd0-a0ab-9c534dcf8402

As a long-time user of numerous Lunt Solar System H-alpha telescopes and filters (including the LS100T and LS152T with an additional filter in double stack mode), I am intrigued by Sky-Watcher’s HelioStar 76Hα Telescope – the first venture of the company into the hydrogen-alpha solar territory.

This is a review of our testing of Lunt Solar System LS100T telescope and Sky-Watcher Heliostar 76Hα.

With an advertised bandwidth of <0.5 Angstrom, compared to <0.7 Angstrom for the LS100T and LS152T, I expected better contrast in the image, and this was indeed what I observed. The numerous twisting long filaments on the Sun in the HelioStar appeared with very high contrast against the brighter surface in the background. Using a TeleVue Panoptic 19mm, Ethos 13mm, and DeLite 11mm eyepiece, the image was crisp and mesmerizing, resembling a processed picture.

Setting up the LS100T for comparison, the disk appeared brighter with less contrast in the filaments, as expected with the slightly wider bandwidth. We needed to add an LS100F at the front to use the scope in double stack mode to achieve a similar contrasty image as the Sky-Watcher scope. Of course, the cost of the Lunt Solar System double stack setup is much higher.

We then tried to use a binoviewer with the telescopes. Unfortunately, focus could not be reached for the HelioStar but it poses no problem with LS100T.

Some special features of the new scope made the experience hassle-free and enjoyable. For example, the included card is great for providing shade for the viewer. The tuning mechanism is much easier to work with compared to the pressure tuning knob of Lunt Solar System telescopes. Therefore, for visual enjoyment of surface details, especially the long dark filaments, the Sky-Watcher scope is a clear winner.

The next day, a huge prominence about 20-30 Earth diameters across erupted from the surface of the Sun. This time, however, the image in the LS100T was much brighter and thus more stunning than in the HelioStar, which is expected due to the larger aperture of the Lunt scope. The resolution of the fine details of the prominence was also much better, which is to be expected because of the larger aperture of the Lunt telescope.

We also tried to take videos of the Sun using a ZWO ASI290MM monochrome camera. While adjusting the focusing knob of HelioStar, sometimes the focuser either didn’t move or suddenly slipped down, making it difficult to achieve accurate focus. We also tried to add a Barlow/Powermate to increase magnification, but we could only get the Celestron 2x Barlow to reach focus. The smaller aperture also resulted in longer exposure times, which isn’t ideal for the usually average to poor seeing conditions during day time at my shooting location.

To conclude, the Sky-Watcher HelioStar telescope performs as expected based on its specifications. It is great for visual observation of the solar disk. Its performance for observing prominences and photography aligns with our expectations given its aperture size and bandwidth, and it would benefit significantly from a higher quality focuser.