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  #1  
Old 05-01-2010, 02:07 PM
BullyBoy (Mark)
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Unhappy Barlow focus

Hi All

I'm a newbie to this site and glad to have joined. I'm also very new to this wonderful, interesting world of astronomy. To see if my interest would turn into a hobby, I purchased a Skywatcher Heritage 76mm (miniDOB) beginners telescope which came with 2 eyepieces (SR4mm and H20mm) and have been using it to find my way around the night sky, which has been great.

To enhance this, I purchased a ProStar 2X Achro Barlow but have been unable to get anything in focus once I use it. For example, an object I can focus on with both eyepieces suddenly cannot be focused with the Barlow and either eyepiece.

Can somebody please explain what's wrong without getting too technical in the first instance ?

Any help would be greatly appreciated !

Many thanks
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  #2  
Old 05-01-2010, 02:09 PM
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erick (Eric)
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Which way is the focusser travelling to try and achieve focus with the barlow in place - all the way out or all the way in?

Last edited by erick; 05-01-2010 at 03:01 PM.
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  #3  
Old 05-01-2010, 02:26 PM
BullyBoy (Mark)
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Hi Erick

Not entirely sure - tried both ways ! I will give it a go tonight and let you know. Many thanks for the reply.
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  #4  
Old 05-01-2010, 02:45 PM
BullyBoy (Mark)
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Hi Eric

Some success - just tried the telescope during the day with the following..

1. H20mm focused on an object
2. Put the SR4mm in and have to move the focuser IN to achieve focus
3. Barlow + H20mm nearly reaches focus but can't move the focuser IN any further

Does this help ??
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  #5  
Old 05-01-2010, 02:59 PM
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erick (Eric)
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Quote:
Originally Posted by BullyBoy View Post

Does this help ??
It probably doesn't help you . Lack of outwards travel on the focusser means that you can add extension tubes. Lack of inwards travel on the focusser is not so simply solved.

There might be a trick you can try. Look at post #28 in this thread:-

http://www.iceinspace.com.au/forum/s...ad.php?t=47260

See how I unscrew the barlow lens off its holder and screw it onto the diagonal. See if your barlow lens will come off its holder and if you can screw it into the end of your eyepieces. (I'm guessing both eyepieces are the same diameter.) But neither of those steps (unscrew and screw on) may work - different style barlow? Eyepieces have no filter thread? But if they do, put the eyepiece with added barlow lens into the focusser and see if you reach focus now.

ps. during the day, make it as distant an object as you can - a far away mountain top or TV transmitter tower - not your back fence.
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  #6  
Old 05-01-2010, 03:10 PM
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erick (Eric)
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At the risk of depressing you, Mark, you might like to read this review of a similar telescope.

http://www.iceinspace.com.au/forum/s...ad.php?t=48171

I haven't had time to read it all again to see if it helps solve your focus problem.
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  #7  
Old 05-01-2010, 03:40 PM
BullyBoy (Mark)
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Thanks for all your help Eric - I'll keep trying ! I did have a go at the screw / unscrew and I think I now understand the issue. It may not be such a waste if I decide to upgrade at a later date and I'm still just having fun finding my way around and looking for objects.

Will have another go tonight anyway and see what effect it all has.
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