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Miscellaneous ramblings...

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Barlow or telecentric amplifier - What's the difference?

It's a question that comes up regularly, but what is the difference between a Barlow and a telecentric amplifier (TA), otherwise known as a Powermate, ES Focal Extender. Meade Telextender, Bresser SA Barlow, etc? A telecentric amplifier does give a 2x magnification, just like a Barlow but that's where the similarity ends. A Barlow is a negative doublet (Smyth lens) that causes the exiting light rays to diverge and hence deliver the image amplification. If you move the EP further from the Barlow
russ.will

russ.will

0

Established wisdom, or opinion parroted as fact?

I threw an opinion into the mix in the beginners forum the other night and decided I should expand on my reasoning here. Even somewhere as benign as SGL, you still have to remember this IS the internet. That means opinions repeated enough by people with large post counts, gain credence as fact among the rest of the forum. It does not hurt to challenge that, if only to get people thinking, as long as you do it in a reasoned way. So..... What got me thinking was the humble 8" Dob. For instance, I'
russ.will

russ.will

6

Ye Gods, I've just counted it all up....

I've only been doing this hobby seriously for about four and a half years. For some reason, I decided to list everything I've owned in terms of the major items - If you included freebie EPs, cables, adapters, etc, I'm sure the result would be even more scary. Skywatcher Explorer 200p Williams Optics Zenithstar 80ED II Skywatcher Startravel 80mm Skywatcher FlexTube 300p Auto Bresser AR-127L Orion Optics UK VX-8L Explore Scientific 305mm Ultra Light Dobsonian Explore Scientific ED80 Triplet* Meade
russ.will

russ.will

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