This is an entry level 76mm reflector telescope produced under the Science Tech label. It is supplied on an Alt-Az mount/tripod arrangement and comes with a selection of 3 eyepieces and also a 3x barlow lens.
Tesco were originally selling these telescopes new for £50 but reduced them to £10 for a short period of time. Secondhand, they typically sell for around the £20-£30 mark on EBay.
The Science Tech 675x Reflector has the following technical specifications –
Focal Length: 900mm
Mount Type: Alt-Azimuth
Focusser EP Size: 0.965″
Eyepieces: 20mm, 12.5mm and 4mm
Other Lenses: 3x Barlow
This telescope is firmly in the ‘department store’ class of product but at first glance appears to be good value for a 3 inch reflector.
The initial set up of the tripod and mount is straightforward with the familiar budget type twin fork setup and vertical locking/slow motion rod at the side. I’ve found this same mount and tripod arrangement on several budget telescopes and it works reasonably well on smaller size refractors. However, although the mount holds the scope securely, it is inadequate for a reflector of this size and is subject to a significant amount of shake and shift (particularaly when locking in place) which can make it difficult to locate and fix a target in view.
The reflector tube itself actually isn’t too bad in quality terms. At this price point, you are not going to get a parabolic mirror but in terms of quality, the spherical mirror isn’t too bad for the money. The longish 900mm focal length of the telescope (giving a focal ratio of around f12) also makes the mirror alignment more forgiving than shorter tube models so the beginner is unlikely to have to collimate the telescope unless it takes the severest of knocks. The claimed magnification of 675x is complete nonsense for 3 inch reflector telescope and is based on the use of the 3x barlow lens with the highest powered 4mm eyepiece. In fact the best usable magnification that can be hoped for would be around the 100-120x mark.
The eyepieces supplied with the telescope are some of the worst that I have ever came across. They are Huygens type eyepieces in the inferior 0.965″ fitting size but the biggest problem is the quality of the lens construction which is well below par and are composed entirely of plastic. The 3x barlow is equally bad and is going to be pretty much useless for a low end scope of this quality.
My usual first test subject of the moon wasn’t too bad using the 20mm eyepiece by itself, presenting a fairly nice low power view. However, as already mentioned the show is somewhat spoiled by the wobbly tripod arrangement. Using the higher power 12.5mm and 4mm eyepieces presented images which were anything but sharp and no more detail was revealed. Using the 3x barlow lens was a wasted effort since it will simply placed another layer of inferior optics on top of the one already presented by the eyepiece resulting in excessive blurring of the lunar surfacegiving that ‘glowing bowl of porridge’ effect.
Test subject number two was Jupiter which was almost at opposition (i.e. closest point to Earth) at the time. The scope showed the 4 Galilean Moons as bright dots, however no surface detail could be resolved and Jupiter appeared simply as a bright white disk. Again, the 20mm eyepiece yielded the best views with the other eyepieces and barlow proving to be pretty useless on this scope.
The f12 focal ratio also means that the field of view is pretty narrow and so it isn’t really suitable for viewing larger astronomical objects, even if the primary optics were able to resolve them.
Although this telescope appears temptingly cheap and also looks the part, it is extremely limited and is not the bargain that it first appears. It is only really suitable for lunar viewing and even then you will not be able to see much detail on the lunar surface. Buying some better quality eyepieces (like a Kellner) would improve the views and fixing the tube on a more substantial mount would make the tube more usable but this would significantly increase the cost of the telescope.
The advice is therefore to avoid this telescope and spend a little more on something better.