Tasco Starguide 114 mm reflector versus larger Dobsonian
I have just read your book 'Stargazing with a Telescope and just want to get a bit of advice.
The telescope I may go for is based on your info. on page 48 regarding the 115mm reflector as I wish to see planets in some detail, galaxies, nebula and track down comets. I will be going mobile to avoid light pollution, but i'm fairly fit so lugging weight is not a problem. I may be doing an Open Uni. course on the subject.
The telescope I'm thinking of is a 'Tasco Starguide 114 motorised telescope', Argos catalogue page 571.
Am I wasting money on the motorised drive or will assist adequately in my work?
Also £400 in book but internet £350 is this realistic price?
Thanks very much in anticipation and I thought your book to be most informative. – Rich
This telescope is identical to the Celestron 114 NexStar. Tasco for a while owned Celestron, so this can be no coincidence. As I say above, Tasco have a poor reputation among many amateurs although some of their telescopes are OK. I would imagine that this is in the latter category, and until I find out otherwise I will have to assume that the Tasco and Celestron models are the same in every way.
The NexStar 114 is indeed 114 mm aperture. The focal length is quite short, hence the short tube, but there is a lens (effectively a Barlow lens) within the focusing barrel to increase the effective focal length. This give you a more powerful telescope in terms of magnification than it would otherwise be. It is a GO TO telescope, with a handset that will find a chosen object from a wide range, including planets, once you have set it by telling it the location and time, and aligned it on two bright stars (in theory).
On the test model of the NexStar 114, the azimuth motor stopped working within a few minutes of use and the unit had to go back to the importer for repair. I have another NexStar on test, the NexStar 4, and this fails to track objects after finding them. My conclusion is that the reliability of these instruments leaves something to be desired, and you should always buy from a supplier that you can be sure of in terms of after-sales service, particularly where returns are concerned. You don’t want to have to send the thing back by post, then wait months while they get it repaired in the US!
As for performance, the 114 is by no means perfect. It takes a lot of collimation – alignment of the mirrors – and even when well aligned there is noticeable astigmatism in the images. They aren’t bad, but I have seen better. As I often find, the £200 Russian TAL-1 was superior in its optical quality. The NexStar 4, however (the Maksutov) gave good images.
The tripods do need to be levelled very carefully before use, which the manual doesn't make clear, and nor is there an easy way of doing this without extra expense. Having aligned the instrument according to the manual on two stars, including Vega, it then placed Epsilon Lyrae quite close to the edge of the field of view, even though that is only a short way from Vega!
Other people tell me that they don’t use the GO TO facilities on their telescopes, whether they have the cheaper Celestron (such as the 114) or Meade products. The whole point of these instruments is to be able to locate hard-to-find objects, but if they are not in the field of view there is little point in having them. It would be far better to spend the money on a larger aperture which will show the objects better in the first place.
Having said all that, I found the NexStar quite easy to use, and the red pointer system is nice.
So, to answer your question, my feeling is that if space and weight is not critical you would get better viewing with a non-GO TO instrument such as the TAL or possibly the Celestron equivalent, the Firstscope 114 EQ for £150 (though NOT the Tasco reflectors which I have my reservations about – see above). Alternatively, for the same price you might be far better off with a larger Dobsonian. Whether in the suburbs or in the country, it will show more objects anyway. For anyone who wants to actually observe rather than carry telescopes around, the larger the aperture the better, within reason. A 15 cm Dob is about the same price as the 114. A Dobsonian with a good finder is easy to use and having to locate the objects for yourself isn’t such a hardship. I think that GO TO instruments come into their own in the larger sizes, partly because they are more accurate anyway but also because the range of objects that you can observe is much greater.
Further message from Rich:
Based on your information I have closed the Argos catalogue and have further researched Dobsonian telescopes. In fact I phoned Beacon Hill Telescopes and spoke to a Mr Barry Watts, who was very, very helpful.
Anyway, he agrees with you that the Dobsonians are very good and stocks the Skyliner 8 inch for £300.00 and he also has a Beacon Hill-made 8¾ Dob.
BHT say they do not compete with smaller Dobs these days because imports are that good & cheap.Barry says import mirrors he gives 8 out of 10. But home mirrors he uses, 10 out of 10.
Would 8¾ inch be too much for a beginner or is bigger the better even
for a novice like myself? – Rich
I wouldn’t be put off by an 8¾ inch. It just gives better images than a smaller telescope, that’s all! And with a Dob that size, it stays put while you are looking at something, unlike smaller instruments that dance around while you are trying to focus. The main thing, however, is to make sure that it has a decent finder. The 6 x 30 finders that are often used are good compared with the rubbishy 5 x 24 (actually they are not usually even 24 mm aperture anyway), but are by no means ideal. However, a good finder could cost a fair fraction of the price of your telescope so you may begin to find your purchase exceeding your budget.
If you begin by looking at the obvious things such as planets (and the brighter Messier objects) you will soon get the hang of it and will want to find fainter objects. The main drawback with Dobs is that they can be hard to nudge slowly, particularly when observing close to the overhead position, to follow objects through the sky. If you get a chance to try the telescope first, test it nearly vertical and see how easy it is to move slowly. It should glide rather than jerk. Often you have to apply a certain amount of foot pressure to make them move!
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