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5x Barlow?

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#1 AlbertaSun

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Posted 16 February 2013 - 01:05 PM

I am new at this and could really use some words of wisdom. My scope is a 500mm F6 - 80mm tube. For some planet and moon shots I would like to crank up the magnification so I can still use a primary lens arrangement. If I put a 5x Barlow in line with my camera, I believe I will achieve a magnification of around 80x (plus).

Although, this isn't a huge number compared to using some of the larger scopes, I think I could be quite happy with images that I would attain. It does cause me to have a lot of questions in my mind -

- Does this make sense??
- How long of an extension tube will I need to achieve focus? Will it be larger than the one I use for my 2x Barlow?
- Because I am starting on bright images, with an F6 tube and a guided mount, will there be any problem with "enough" exposure?
- Should I just bight the bullet and look at and afocal setup? This would come with a whole new string of questions for me.

I know, I know - too many questions (and I probably missed the important ones). Any thoughts, input,experience, would be appreciated. Oh, and one more, if this does make sense, any suggestions on an affordable, reasonable quality product.

Thank you
Larry

#2 johnnyha

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Posted 16 February 2013 - 03:19 PM

Sure, F30 is good for planetary imaging. I'd go with the 1.25" 5X Powermate to avoid vignetting and focus issues. Also, if you are using a DSLR you can unscrew the top of the 5X Powermate and add a T-ring adapter to attach the camera directly.

#3 AlbertaSun

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Posted 16 February 2013 - 06:00 PM

Johnny - thanks for the confirmation on F30 being suitable. I will alos follow-up on your suggestion. This does lead to another question/curiosity in my newby head.

I presently am using a 2" diagonal and my other Barlow is 2" at 2x. When should I be pursuing 2" pieces and when not? Comments??

Thanks
Larry

#4 howard929

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Posted 16 February 2013 - 06:29 PM

There's a limit to the size of the field stop in a 1.25" eyepiece that forces a jump to 2" eyepieces for large AFOV combined with long focal length. For instance, at 82 degree AFOV, that limit is smaller then 18mm in focal length. Longer focal lengths with the same AFOV requires the larger field stop of a 2" eyepiece. So basically, a 2" eyepiece isn't better, it usually has a wide AFOV and is long in focal length.

#5 AlbertaSun

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Posted 18 February 2013 - 12:07 AM

Good info Howard - I am going to have to read up a little more on the Powermates(a bit different from a standard barlow). I also need to bone up on some on the technical jargon (ie field stops, etc.)

I would be interested in any additional experience or recommendations out there on using 5x barlows.

#6 AlbertaSun

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Posted 18 February 2013 - 02:36 PM

As a less expensive option has anyone tried the Antares "1.25" 5x Barlow with twist lock eyepiece and t-thread"

Larry

#7 rodnocjolly

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Posted 24 February 2013 - 06:30 AM

TV 5x Barlow is a great piece of glass.

I use it with success with TV 24 Panoptics and a Baader Hyperion Zoom 8-24.

#8 csrlice12

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Posted 24 February 2013 - 11:09 AM

If you're using it for AP, go for the Televue Powermates, with a regular barlow, you could see some field curvature with some eyepieces (especially wide-fields, and it could be from the scope OR the eyepieces). Powermates are telecentric and are better for AP then nontelecentric barlows.






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