Starguider 7-21mm 1.25" eyepiece?

[robhatherton]

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Anyone have experience of this budget zoom being sold on ebay by the same company marketing the well regarded BST Starguider (Explorer)?

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[russ.will]

No experience, but assuming you have at least the standard EPs that come with a scope - typically a 10 & 25mm Modified Achromat, I'd personally buy a couple of GSO or Skywatcher Plossls to fill the gaps in your range.

This has nothing to do with a personal distrust of zooms, but that is a cheap zoom and even if it is sharpish, the field of view is published as 30-43 degrees (7-21). The image circle that it will present to your eye will go from that of an Ortho (looking down a toilet roll) to that of a Monocentric (looking down a straw). Those eyepieces are forgiven their restricted views, because they are unparalled in sharpness for anything like the price. A cheap zoom, will be along way off the quality of a cheap Plossl (£10-15 second hand) which will also offer a 50 deg FOV. That means the image will be the same size, but with far more to see around it. Picture this as the difference between looking at a landscape through a toilet window and the same view through the window in your front room - Same size, but the front room has a much wider, more pleasing vista.

For £4 more than that price, you could buy the aforementioned 12-15mm and a 6-8mm Plossl from FLO and end up with a far better quality and wider field set of views.

This of course is stated without knowing your scope, but the advice, if not the suggested focal lengths would remain the same.

Russell

[John]

I agree with Russell on this. The zoom in question looks very like a number of other 7-21mm zooms (including the Skywatcher one) and they are not as good as the 8-24mm zooms. Decent fixed focal length plossls will perform a bit better than even the 8-24mm type so the 7-21mm ones are hard to recommend.

I did try one of the low cost 8-24mm zooms recently and it was not bad in the 8mm-15mm range. Personally I'd prefer some decent fixed focal length eyepieces instead though.