More GSOs, bad seeing, and . . .

Well – this morning wasn’t my best observing experience. But I did accomplish my main goal, which was to retest the 10mm GSO SuperViews in a scope with long focal length – the LX90 which is an F10. (Earlier test was in an F5.) If you had asked me in advance I would have said I expected them to do fine in the F10, marginal in the F5. Not the case.

They were atrocious in the F5 and simply terrible in the F10. (Terrible isn’t quite as bad as atrocious, but almost.) Essentially these eyepieces have the following advantages:

1. The center of the FOV is sharp and you can see this without looking through the kind of peep-hole opening of an orthoscopic, for example. And . . .

Well, that’s it. Unless you wanted an eyepiece around to help newbies judge eyepieces – or see what they should avoid, these are useless. I’ll try to return them. I could not, in good conscience, sell them to someone else. Interestingly, this experience sent me scurrying back to the 15mm and 42mm GSO SuperViews I have to see if I had just imagined they were OK when I tested them originally. Nope. They’re acceptable. Sure, they fall off some in the outer areas. I found this most noticeable with the 15mm. It is there in the 42mm, but here the stars are so small – the field so large and the power so low – that it doesn’t bother me. In fact, I was really pleased to see that I could fit both M35 and it’s companion , NGC 2158, very comfortably in the same field of view using the LX90 at about 48X. That’s cool because M35 is about 2,700 light years away while NGC 2158 is a similar cluster, but about six times further. Nice for illustrating how size and light falls off with distance. (There's anice image of the two open clusters here: http://www.robgendlerastropics.com/M35.html - M35 is on the left, NGC2158 the smaller, tighter, fainter group on the right.

So what am I learning? I guess that with inexpensive eyepieces it’s something of a crap shoot. If the eyepiece is inexpensive because it’s a simple design – such as Plossl - you may get a good deal. I really like those Orion Sirius Plossls – especially when you can pick them up for $25 or less used. If the eyepiece is real low power and you are using it on a scope with an F8 or longer focal ratio, then you can probably find a bargain eyepiece that will be satisfactory – not great, but acceptable. I’m getting suspicious, however, of bargain eyepieces of medium to high power. My 15mm works OK – but from this point forward, given both experience and what I have read, I think I’ll go for the high-priced eyepieces when it comes to getting something wider than the 9mm Orthos. And for use in fast scopes there’s no choice.

The rest of the observing session? Well, I spent 45 minutes trying to get a good two-star alignment with the ArgoNavis on the 15-inch and never did and still don’t know why. Truth is, seeing was so bad, it didn’t much matter. And I’m not sure why seeing was so bad. Quite a bit of humidity, but the air seemed steady. Maybe a temperature inversion? At any rate, using the LX90 the most I could use on Mars was about 100X and that was not satisfying. The seeing, howver, had nothing to do with the poor showing the 10mm GSOs SuperViews. I tested them against the 9mm orthos just to discount the poor seeing factor – the orthos did fine – not that the seeing was good enough for them, but in comparison with the GSOs they were far, far better.