Guan Sheng GS-880 LTD (10" f/5 Dob)
Submitted: Friday, 13th January 2006 by Chris Ruwoldt
I had purchased a 90 mm short tube reflector some months ago but it wasn’t enough to satisfy me. It was a great first scope for $299 you can’t go too far wrong. One of the great pleasures I have with the 90 mm refractor is seeing the crescent of Venus, the rings of Saturn and the bands on Jupiter, but then what? There is only so much visual observing of the planets that you can do and then you want to point it at something else.
But I wanted more power – and the azimuth mount has severe limitations for astronomical use. It’s no good for observing the heavens if the target is more than about 45 degrees above the horizon. When attempting this all the weight of the telescope is on one side of the mount and it becomes very unbalanced - it is nigh impossible to keep the target in view as a result.
I could have bought a scope on a german equatorial mount. I didn’t because they are a hassle to set up. If are only interested in visual observing as I am – and not photography, then the time in setting up a equatorial is wasted viewing time.
I did consider getting a small computerised scope such as the Meade ETX-125PE, but here the web helped me out. I read that this scope has a focal ratio of f/15 – which means very high magnification and small fields of view. This is ok for planetary work but no good for deep-sky observing. A smaller f-ratio gives a wider field of view and a richer field of view – which is what I was after.
The factors in buying where:
So I started looking at scopes on a Dobsonian mount. There are a lot to choose from nowadays. Doing a Google search for Australian suppliers shows that. I decided to have a closer look at Andrews Communications. They have a range of telescopes on their web site at very reasonable prices. They generally have them “in stock” – but not on display because of the very limited floor space in the shop. Its best to ring ahead so that they can get in the model you want to look at from their warehouse. Here is the link to their web-page:
I finally settled on the Guan Sheng 250mm model. Andews Communications sell this in two versions – the more expensive version has a Crayford style focuser and a mirror fan. I settled for the cheaper version which sells for $599 and includes two eyepieces. . I chose this scope because it gave me the biggest mirror with a tube length that fitted into my car. The scope is f/5 – some other reflectors are f/6 and so have a longer tube. In addition to the scope, Andrews throws in an additional two eyepieces and a pair of binoculars! So I now have 4 Plossols – 30, 25,15 and 9 mm and a pair of 10x50 binoculars.
The scope comes in two boxes – a very large one for the OTA and a small flat-pack for the mount. Putting the mount together took about one hour –the instruction leaflet is next to useless but there is only one way to put it all together and all the components fit – all the holes are predrilled and align perfectly so putting it together was no hassle at all.
So soon I had it all assembled and ready to go. I packed in it the car and went off to the nearest park to use it. And here I found another problem. Finding a dark spot in Sydney is near impossible – and by dark I mean away from street lights and other bright lights that interfere with night vision. Whilst you cannot do anything about the light pollution I was hoping to at least get to a spot where there were no bright lights.
I was eager to try out the scope so I put up with a less than perfect spot for first light – was it worth it? Oh yes – but first I had to align the finder scope. The supplied finder scope is so much better than the one supplied with my refractor, and here I put that pesky street light to good use to help in the alignment.
I first looked at Venus – wonderful thin crescent low in the west. Then Mars – harder to resolve - ok under lower power but no good with the 9 mm eyepeice. Then the Orion nebula – pretty good, but maybe not perfect. The scope’s collimation may need tweaking, but out of the box it’s not bad – just not perfect. But hey – now I have a decent scope that can travel with me. So I’ve booked in to the IceInSpace Astronomy Camp at Lostock on the long weekend in Jan 2006 where I’ll get some dark skys and hopefully some experts to help tweak that collimation!
NB – I have no financial links with Andrews Communications – and this is the first item I have purchased from that store.