Explore Scientific 8x50 Viewfinder and Guider Scope with Helical Focuser 1.25/T2
The Explore Scientific 8x50 Viewfinder and Guider Scope with Helical Focuser 1.25/T2 is an excellent 8x50 viewfinder scope with detachable eyepiece and reticle with adjustable red illumination. The precise Helikal focuser and the connection option via 1.25-inch/31.7-mm plug connector, as well as the T2 camera connection thread (M42x0.75 mm), enable the autoguiding needed for long exposures to obtain a spot-shaped star image. It can also be used as a mini travel telescope.
The image sharpness and performance lift this viewfinder far above the level of usual 8x50 viewfinders. The field of view produced is bright and sharp. Moreover, this viewfinder has a very large field of view (FOV) of 6.96 degrees. This makes it much easier to find and adjust objects. The existing scale marks (graduation=1 degree) of the reticle are a good reference for estimating distances and the open centre mark also facilitates accurate centring of objects. All lens surfaces are protected from weathering by multicoating and guarantee a clear viewfinder image thanks to high light transmission values. The adjustable red LED illumination is powered by two LR41 button cells. The main lens and the reticle can be focused independently, allowing you to focus your eyes perfectly.
One of the main applications of this telescope is so-called autoguiding. Here, the usually larger photographic optics are actively corrected by a smaller aiming telescope with a second tracking camera. This means that the mechanical fluctuations in tracking accuracy that occur in all astronomical telescope mounts are measured by the tracking camera and compensated accordingly. This is necessary to obtain a spot-shaped star image on astrophotos during long exposures and avoid line marks. For this purpose, the aiming telescope is inserted into the existing viewfinder shoe of the shooting lens and aligned parallel. If the existing viewfinder shoe is not compatible, a matching viewfinder shoe is also supplied. A tracking camera can then be mounted using the 1.25-inch/31.7 mm plug connector on the back or via the T2 threaded connection (M42x0.75 mm). This is held securely by a brass ring clamp and 3 clamping screws. Note the required backfocus for the tracking camera. The focusing plane (backfocus) is approximately 22 mm behind the T2 thread. Sensitive focusing on the guide star is performed by means of a large knurled wheel of the mechanically precisely manufactured Helikal focuser. This has a white laser-engraved millimetre scale from 0 to 28 mm for easy display of the focus point. After connecting the tracking camera directly or via computer to the telescope mount and making the necessary basic settings, the first long-exposure astrophotos can be taken.
This viewfinder and directional telescope can also easily be used as a mini travel telescope. With the optionally available eyepieces, magnification can be set from approx. 8x to 40x. Almost all eyepieces with a focal length of 5 to 26 mm and a plug connection of 1.25 inch/31.7 mm are suitable. Particularly recommended are the Explore Scientific eyepieces of 52 degree and 62 degree LER series. Note: Only straight use is possible.
The holder of this viewfinder and directional telescope is made entirely of aluminium and provides a stable base. The viewfinder holder is suitable for many common telescope types, such as Explore Scientific, Bresser Messier, etc. If the existing viewfinder shoe is not compatible, a matching viewfinder shoe is also supplied. This can be attached to the telescope tube using 4 M5 screws. The distance between the holes of the viewfinder shoe is 31.7 mm on the longitudinal and latitudinal axis. Thanks to the 6 large adjustment screws with easy-to-grasp knurled edges, the viewfinder can be effortlessly aligned even with clammy fingers. All adjustment and clamping screws have plastic ends that effectively prevent scratches on the viewfinder housing and viewfinder holder.
