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Lacking in-focus - Barlow required?


russ.will
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Evening all,

I thought about posting this in the Eyepiece forum, but as the subject is purely for solar imaging, I thought here might be more appropriate.

Athough I didn't buy the Messier 127L with a view to imaging, my first attempt at afocal with the EOS 450D/50mm F1.7 resting on the 14mm eyepiece piqued my interest. I've ordered a 1.25" T-mount, but whilst checking measurements by holding the camera body on the Lunt Wedge, there is insufficient in-focus. Probably only a few millimetres, ten at most, but a miss is as good as a mile.

Not being an imager, I assume that a barlow is the easiest way of moving the focal point backwards, as it would with an EP? I have a 1.25" ES Focal extender, but I think I'm also right in thinking that 4 element telecentrics don't move the focal point, at least not a significant distance.

If my assumptions thus far are correct and given that I'm not exactly bunced up after a string of recent purchases, I've homed in on the GSO/Revelation 1.25" 2.5x 3 element barlow, which seems a bargain for sub £40.

Any thoughts welcome. :)

Russell

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If the Lens assembly can be unscrewed from the Barlow body and can then be screwed into the 1.25" camera adaptor, you should be able to reach focus without as much amplification as you would with the complete Barlow. :smiley:

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Thanks Peter - That bit I did know. Presumably, by using the nosepiece alone for reduced magnification, you also move the focal point back by less too?

Russell

Edited by russ.will
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  • 2 weeks later...

If the Lens assembly can be unscrewed from the Barlow body and can then be screwed into the 1.25" camera adaptor, you should be able to reach focus without as much amplification as you would with the complete Barlow. :smiley:

Pete - Just so you know - The Barlow nose piece does unscrew, but the thread is larger than 1.25" and smaller than T-2. Unless it's C-Mount (and that would be lucky) I suspect that this is a 2.5x barlow only.

Russell

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