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The Celestron EdgeHD 925 is the evolution of the famous Celestron SCT telescopes. The new EdgeHD with aplanatic optics offer a large perfectly corrected field of view, excellent for visual use but ideal for deep-sky (or planetary thanks to the great optical correction) astrophotography, all in a compact and lightweight instrument at a very affordable price.
The Celestron challenge was to further improve their famous SCT and the intention of creating a instrument without compromise, it brought the realization of these aplanatic optics, that return a stellar image comparable only to the famous RC or the CDK. The EdgeHD optics in fact guarantee a perfect images, both in color level and geometry in all 42mm diameter field of view. Maintaining the same quality standards, Celestron has succeeded in creating a new generation telescope at a very affordable price. The construction of these optics is done by the combination of the best features of CDK and SCT. Edge HD in fact are made with a primary mirror and secondary perfectly spherical. Unlike the SCT, in the optical path are installed two lenses that correct aberrations, in addition the stars appear perfectly point, without coma or field curvature.
The high performance of this instrument can be noticed immediately during an observation, thanks not only to the optical design and the long focal given by the instrument, but the further optical correction to the diffraction limit, the result is the ability to perceive details that only few instruments can provide. In addition there are accessories to maximize the quality of this instrument, such as the full range of eyepieces and Luminos barlow. Even with the wide-field eyepieces stars appear perfectly round from the mirror center to the edges. The resolution capabilities of this instrument is amazing, the separation of double stars can be easily seen, the details of nebulae or galaxies observed under a sufficiently dark will be impressive. Being a astrograph, this telescope is excellent for use in astrophotography. The obstruction is 36%, providing useful 42mm clear aperture is also ideal for large format sensors. Celestron also created some dedicated accessories in order to be able to use this tool to the maximum performances, such as the focal reducers and adapters made specifically for the EdgeHD. In addition, these optics are compatible with the Hyperstar system, which leads the focal instrument from f/10 to f/2, much brighter and greatly reducing the exposure times. Photographically they are comparable only to high-level instruments with much higher costs.
The EdgeHD, in addition to the optical evolution, is also mechanical improved. The support of the primary cell was equipped with an air cell aperture, which contributes to acclimate faster the mirror. Cassegrain optics "construction" have always had the problem of mirror-shift or mirror-drop, this caused by the focusing system (mirror moving forward or backward). To avoid this problem the EdgeHD are equipped with two mirror lock knobs. So when you aim the desired object and focus, you can simply lock the mirror by closing the two side knobs.
- Celestron EdgeHD 925 optical tube
- Luminos 23mm 102x eyepiece (diameter 50,8mm)
- Adapter 50,8mm to 31,8mm
- Mirror diagonal 90° (diameter 50,8mm)
- View-finder 9x50
- Dovetail bar Losmandy type
- OnAxisLock 50,8mm visual back for SC telescopes
OnAxisLock 50,8mm visual back for SC telescopes is screwed directly onto the rear thread present in EdgeHD telescopes and lets you use all the 50.8mm diameter accessories. OnAxisLock is the accessories locking system that, compared to the one using normal screw, offers a greater clamping force, avoiding any possible flexure.
|Optical Design||Aplanatic Schmidt-Cassegrain|
|Optics||Primario e secondario sferici, con lastra correttrice e gruppo spianatore|
|Focal Length (mm)||2350 mm|
|Field flattener/corrector||Included and not removable|
|Secondary Mirror Obstruction||No|
|Focuser||Interno (spostamento del primario)|
|Eyepiece holder||50,8mm with 31,8mm reducer|