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Barlow/Powermate

Colinlp

By Colinlp
in Getting Started With Imaging

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Colinlp

Colinlp

Posted
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Hi all, a bit of advice if I may trouble you?

I have a CPC1100 and a ZWO ASI224MC for planetary imaging. I have a cheap 2x Celestron Barlow but it's not brilliant but passable, I'd like to get a better one but like most I'd rather not break the bank unless I have to. Could you recommend a suitable Barlow or Powermate as a first buy to replace the Celestron. I'm concerned the power might be too much or even too little, the current one more than half fills the FOV on the CCD with Jupiter. In an ideal world it would be nice to try one first but I don't know anyone with such things .

I appreciate it's a bit of an open question but I'm open to advice and suggestions

Many thanks

 

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Ken82

Ken82

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It's all about your pixel size for planatery imaging . As a rough guide 5x your pixel size is the optimum focal ratio . Yours gives a perfect ratio of 18 which is good with your 2x Barlow already . I don't see you gaining much by changing to be honest the difference will be neglilable in my opinion . If you must change maybe buy a better 2x Barlow ?? 

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Colinlp

Colinlp

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9 hours ago, Grotemobile said:

http://www.telescopehouse.com/barlows/bresser-barlows/bresser-sa-barlow-2x-1-25-inch.html

Bought one of these. U can undo the end of the Barlow, & screw onto 

the end of the camera, to give U, 1.5x. mag. It has got 4 lenses .

 

Steve.

How would something like this compare with a Televue Powermate?

Edit: I've had a look at the web for information and they sound the dogs .... Are they really that good? I'm just worried that I would end up wishing I'd paid the extra, on the other hand I could get a couple of Bressers for the price of one Televue if the difference is truly negligible

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Colinlp

Colinlp

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Sorry I didn't really make my question clear as I should. I'm more concerned with the quality of the build of the components and optical performance than FOV although the 2x I have is about right, the calculator above is very useful, I didn't realise it did cameras. Having never used any other barlow than the one I have I don't have any benchmark for optical performance either of the Barlow or the Powermate type let alone any differences between different makes. It does seem like the four lens types win over the 2 lens from what I've read but is it a lot? How do Televue, Bresser and ES compare for similar products

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brantuk

brantuk

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I've tried a lot of different barlows but not the ES or Bresser. I now use a TV 2x Powermate and imho it is the benchmark - optical performance as near to perfection as you'll ever need. It just does the amplifying and gets out of the way. It's even difficult to see the glass when you hold up to the light and look through it. It may cost a bob or two but you'll never need anything else and you'll save money in the long run. You can also get a camera adaptor for it. :)

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John

John

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I don't image but I've found the Tele Vue Powermates the best extenders that are around. I have used the ES Focal Extender and the Meade TeleXtenders which are very close but the Powermate is the best IMHO - it just "gets out of the way" like all the best optics. Many of which seem to come from Tele Vue as it happens ..... :rolleyes2:

 

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Tommohawk

Tommohawk

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FWIW I have a 3x BST 4 lens "apo" which I thought was really good, miles better than the SW barlow. Then i got a x5 powermate and I have to say its really excellent - somehow the image is enlarged without losing any brightness. Maybe the x5 is too much for your purposes, but the Powermate type does seem very good.

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Colinlp

Colinlp

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Well I ordered the ES 2x from the above website, it has good reviews so got to be worth a go at £80 delivered. When I upgrade my focuser I'll shell out on the 2x 2" Televue but I feel the 2.5x 1 1/4" is just pushing it a little far for now

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RSM

RSM

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On 21 March 2016 at 21:46, Ken82 said:

It's all about your pixel size for planatery imaging . As a rough guide 5x your pixel size is the optimum focal ratio . Yours gives a perfect ratio of 18 which is good with your 2x Barlow already . I don't see you gaining much by changing to be honest the difference will be neglilable in my opinion . If you must change maybe buy a better 2x Barlow ?? 

Hi sorry to go sort of off piste on this thread but I'm thinking of buying a 4x power mate for my 200PDS scope with a focal ratio of f/5. I use a canon EOS 500d which if my calculation is right has a pixel size of about 4.7 micron. Following your  advice above, 5x pixel size would be around 24. Am I right in thinking my focal ratio with 4x magnification is 5 (from f/5) x 4 = 20 or have I got completely the wrong end of the stick? 

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Colinlp

Colinlp

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The ES 2x extender arrived yesterday and because I am such a righteous sod the skies cleared so I got a chance to have a play with it. This is my first attempt, not the best seeing but I need to practice on my self righteousness a bit more for that :icon_biggrin:

 

20_36_30.jpg

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jimboozle

jimboozle

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On 3/21/2016 at 10:46, Grotemobile said:

According to this video, U  end up with a 75% drop in light, :happy9: by using a 2x

Barlow. But a doubling of the image size. Learn something every day.

Need a bigger, faster, scope.:grin:.

 

Steve.

i'm pretty sure that the answer to every question in astronomy is a bigger, faster scope!  My expenditure is exponentially higher than my imaging time / sky knowledge at present!

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