EdgeHD telescopes by Celestron are great instruments also for astrophotography if you use an external focuser instead of the internal one: in this article we discover why ESATTO is the perfect microfocuser also for EdgeHD telescopes! In fact, by using an external focuser, you can remotely control the focus and you avoid all the problems related to image shift and mirror flop. And the advantages are not only for astrophotography but also for visual use since ESATTO comes with Virtual HandPad so you can use is also without a computer.
By adding ESATTO microfocuser to EdgeHD telescopes you can use the locking mechanism of the OTA that locks the primary mirror and you can use the external focuser instead of the internal one. Since the ESATTO has 67mm thickness, you can connect to the rear thread of EdgeHD telescopes and you will still have a lot of backfocus in order to let you use cameras with or without astrophotography accessories.
ESATTO is available in different diameters but the 2" model is the one we suggest with the EdgeHD telescopes. That's because the ESATTO 2" has a free aperture that is larger that the EdgeHD internal baffle tube so the use of the larger ESATTO is really not needed. In order to use the ESATTO 2" with EdgeHD telescopes we have the PL3600209 adapter for the 8" model and the PL3600212 for the 9.25", 11" and 14" models.
You can use the ESATTO also if you have the EdgeHD telescope 0,7x focal reducer. In fact since the backfocus requirement with the focal reducer is the same in case you use the telescope without focal reducer, you can install the ESATTO 2" after the 0,7x focal reducer and you still have a lot of back focus in order to use camera and accessories. By doing this, you can also use the ESATTO to perfectly set the sensor position in respect to the reducer: with the ESATTO draw tube all in, install the camera with accessories and adapters in order to have the sensor a few millimiters shorter than optimal backfocus (for example, it may be 140mm if you have the 9,25", 11" and 14" that are designed for 146mm backfocus), then extract the ESATTO drawtube of the missing lenght. Under the night sky, focus the EdgeHD telescope until you reach focus and lock the primary mirror. This way during acquisitions you will use the ESATTO just for micro adjustments that has no impact on telescope performance.
The only thing to consider here is that backfocus of the 8" EdgeHD telescope is a little bit shorter (133mm instead of 146mm) and, only for this model, if you add the 0,7x focal reducer the backfocus is reduced to 105mm. So, if you want to use the ESATTO with EdgeHD 8" telescope with 0,7x focal reducer, there's not enough backfocus to let you use DSLR cameras but you will be able to use cooled cameras (that have the sensor closer to theit front thread).