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Old 17-06-2014, 10:12 AM
209herschel (Herschel)
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209herschel is offline
Join Date: Apr 2014
Location: Sydney
Posts: 87
Originally Posted by astro744 View Post
Note the 8.8mm will give similar magnification to your 9mm. If you 2x Barlow either later you effectively get 4.4 or 4.5mm which would be good for only the best of nights. I've not used ES eyepieces and cannot comment on whether they would be better than the GSO Plossl but may I suggest that rather than a Barlow you do get the 6.7mm since it gives you an ideal high power in your telescope for nights of reasonable but not necessarily exceptional seeing.

Magnification at f.l.=1270mm

GSO 9mm = 141x
ES 8.8mm = 144x
2x Barlowed GSO 15mm = 169x
ES 6.7mm = 189x
2x Barlowed GSO 9mm = 282x
2x Barlowed GSO 8.8mm = 288x

I personally find the 150x magnification tantalisingly close to ideal but not quite just there for planets. You will find 170x to 220x your most useful power range. That's not to say 150x is no good and on many nights it will be sharper than the higher powers but you cannot get sharper and larger at the same time even on nights of good seeing although on such nights you will likely see more in the larger image.

My first and most useful high power eyepiece was a Vixen 5mm Ortho and it gave me 170x in my 6" telescope and although I craved for something larger at times I learned how to see small low contrast detail on planets which if you can master and you will with time will give you a skill that forms the basis of the art of observing planets.

Note and this is very important; the ability to see very fine detail on planets is greatly enhanced when the object is being tracked and does not move across the field of view. That's not to say that you wont see detail on a non-tracked telescope but for long duration study of a planets features tracking is highly beneficial. Ultra wide field higher power eyepieces can help with non tracked viewing at some extra expense but the object is still moving and the brain needs lock onto the image and not the edge of field to overcome the motion until again the telescope needs to be nudged to bring the object back. I'm speaking from my personal experience and others may have different opinions on the matter.
Thanks very much for all of that information, I really appreciate it. When looking at Saturn last night with the 9mm plossl, it's a very yellow colour and I see the band almost as thick as the disc. I don't think I really saw any separation in the band at all. The image is still pretty small in the eyepiece. I don't currently have any eyepiece to try any higher magnification but am I right that a 6mm would make the object larger in the FOV but perhaps lose clarity? Would it mean that I'd have a better chance of seeing the split in the bands at some points? I'm just trying to get an idea of what it would look like assuming my scope is well collimated and viewing conditions are my inner west of sydney backyard but it doesn't seem too bad late at night and if the neighbour's lights are off. Cheers and thanks again.
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