Sky-Watcher Esprit 100 Review
A Flat Full-Frame Field
The included thread-on field corrector (flattener) ensures that images captured using my full-frame DSLR camera have sharp stars to the edges of the frame.
I appreciate when brands offer a package that includes the recommended field flattener as a package. This is one aspect of your imaging train you want to get right. The correct spacing between your camera sensor and this flattener have been discussed in detail in the Cloudy Nights forum.
The 40mm imaging circle of the Sky-Watcher Esprit 100 ED was designed with full-frame DSLR imagers in mind, as the package I received even included a Canon EOS M48 adapter ring.
The camera I have used most with the Esprit 100, however, is the ZWO ASI294MC Pro. A cooled one-shot-color CMOS dedicated astronomy camera. I have found that the image scale of this camera to be a perfect fit for the Sky-Watcher Esprit 100 ED.
For reference, have a look at the native field of view using this camera and telescope combo on the Horsehead Nebula:
The Horsehead and Flame Nebula (4 Hours, 8 Minutes Total Exposure)
The imaging performance of the Sky-Watcher Esprit 100 ED is evident in this photo. This image was shot from Bortle Class 8 skies in the city, using a one-shot-colour camera and narrowband filters.
Capturing detailed portraits of nebulae like this from my light polluted backyard is truly a remarkable feat, and one that can be replicated using similar equipment.
2.7″ Linear Power Focuser
The robust Helinear track focuser on the Esprit 100 holds its position firmly in the imaging train. A great example of this is being able to retain perfect focus after a rather jostling meridian flip. I use a Bahtinov mask to re-check the focus again after this routine, but the Esprit 100 has always kept the focuser in its precise position.
The focuser includes a secondary linear rail, which adds to its rigidity. It includes micro-focusing abilities, which can be very handy when shooting with strong narrowband filters as there is no image shift to worry about.
The smooth and reliable focuser on the Sky-Watcher Esprit 100 ED is one of my favourite features of the telescope overall. I think you’ll find a similar response from fellow owners of this Esprit, and the larger models.
Since receiving the telescope in August, I have tested the Esprit 100 on a number of deep sky objects. The F-Ratio of this APO (F/5.5) makes a 4-minute exposure the sweet spot for my astronomy camera when shooting in narrowband.
Using a Gain setting of 120 (Unity Gain) on the AS294MC Pro, has resulted in images with an attractive histogram when in use on the Esprit 100. Image sharpness and contrast are this telescopes specialty, a trait I experienced first hand from the backyard.
Using a duo-narrowband filter, I was able to collect some much-need H II details on the Triangulum Galaxy using the Esprit 100. The composite image adds new narrowband details to existing color data for a new and improved image of M33.
The Triangulum Galaxy with H II region details captured with the Esprit 100
The image of the California Nebula below is a great example of the wide field of view the Esprit 100 provides. NGC 1499 is a massive target (2.5 degrees long), that can be tough to capture in a single image.
With the 550mm focal length of the Esprit 100, it nearly fits into the image frame using a 10MP 4/3″ camera sensor. A full frame 35mm image sensor will capture the entire target with room to spare.
NGC 1499 – The California Nebula
I’ve tested the Sky-Watcher Esprit 100 ED in terms of astrophotography performance with both a full-frame DSLR camera (Canon EOS 5D Mark II), and a cooled CMOS camera (ZWO ASI294MC Pro).
I am certain that users will find the visual performance of this refractor to be more than satisfactory, but this review focuses on the deep sky astrophotography capabilities of the Esprit.
If your interests lie in deep sky imaging, particularly in wide-field targets such as emission nebulae and large galaxies like Andromeda – the Esprit 100 is for you.
The premium optics used in this telescope prove their value by consistently producing incredibly sharp, high contrast images. Whether you’re looking to connect a full-frame DSLR, or a cooled dedicated astronomy camera to the Esprit 100, I think you’ll be truly amazed at what’s possible with this compact APO.
The convenience, portability, and premium features such as the 3″ focuser result in an enjoyable user experience that’s tough to match in this category.
See the original review on the AstroBackyard website.