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Using a Barlow

Beagleboy

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Stu

Stu

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Posted

Sounds like counting angels on pinheads!

I would say that, as the barlow goes between the primary and the point of focus, it acts to effectively increase the focal length of the primary. To have an effect on the eyepiece it would need to be between the eyepiece and the focal point, in which case it would increase the focal length of the eyepiece and reduce the magnification.

Yes.

Is that not what I just said?

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Beagleboy

Beagleboy

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Aha! I finally got the answer I was looking for from a very nice chap at the shop where I bought the Barlow!

Hi this is quite a common problem with any Newtonian. I can depend on the make of eyepiece, design and style. Most will just about focus as you describe. &you will also find that sometimes the main mirror has been collimated very low down in the cell. When collimating a main mirror people tend to always go in one direct and the mirror moves lower down the tube, this is also how the factory do it. You might find that if you back all the screws anti clockwise and then re collimate you will gain some more distance at the focuser end.

And as to your other question the moon is made of Edam cheese.

Dave

Thanks for all the help guys, I just wanted to check that I hadn't bought something incompatible with my scope. It would now seem that it's more likely an issue that will be resolved when I finally need to collimate Dobby. Mind you, I'm gutted about the other thing....I honestly thought it was a nice Wensleydale, maybe with some Chives mixed in.... :grin:

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Stu

Stu

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Posted

Aha! I finally got the answer I was looking for from a very nice chap at the shop where I bought the Barlow!

Thanks for all the help guys, I just wanted to check that I hadn't bought something incompatible with my scope. It would now seem that it's more likely an issue that will be resolved when I finally need to collimate Dobby. Mind you, I'm gutted about the other thing....I honestly thought it was a nice Wensleydale, maybe with some Chives mixed in.... :grin:

Great stuff! That makes sense.

Btw, he's lying to you, it is made of Wensleydale ;)

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