where to locate the Barlow?

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where to locate the Barlow?

Postby andrewt » Sun Jun 11, 2017 12:46 pm

I lost my post !

Starting again
I have bought a refractor to replace my not good 6" Newtonian.
The scope has a 2" focuser, and I ordered a 2" diagonal and a 2" Barlow.
What order do it place the diagonal and Barlow?

Focuser > Barlow > diagonal > eyepiece
or
Focuser > diagonal > Barlow > eyepiece

The Barlow came with 2" to 1.25" adaptor, so I can use either 2" or 1.25" eyepieces.
It also has a short (16mm) extender.
What does that do?
andrewt
 
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Location: Scottish Borders

Re: where to locate the Barlow?

Postby Aratus » Sun Jun 11, 2017 1:37 pm

A barlow effectively increases the focal length of the telescope. 2" is good, but we are talking about large and heavy components. From a practical point of view I would recommend the barlow goes into the focusser first. Then the diagonal and eyepiece in the normal way. The extender could be used to increase the magnification further especially if you are imaging. Place the tube between the barlow and the eyepiece/camera.

As usual beware of increasing the magnification beyond the capabilities of the telescope. In most cases going beyond 40 or 50x the inches of aperture will give unsatisfactory results.
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
Aratus
 
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Re: where to locate the Barlow?

Postby andrewt » Mon Jun 12, 2017 12:11 pm

Thanks for that.
At the moment I am awaiting delivery and doing lot's of reading to make set up a simple affair after it arrives. The retailer has just Emailed to say that none is in stock and one item is on three weeks delay !
I await a phone call from RVO to explain themselves.

The Focal length is advertised as 952mm and aperture as 127mm
The eyepieces are 40mm, 28mm, 16mm, all are 68degree, widish angle.
Magnification ranges from ~24x to ~60x without the Barlow
and from 48x to 120x with the Barlow.
Those are well below 50x 5" (or 2x 127) = 250 for maximum magnification.
I want to work with these before I decide whether to go for short eyepices, or go to astrophotography which would not use any of the eyepieces.

I like the idea that I could view on a Laptop and use the Goto without having to touch the telescope. If I can use extended cables and view indoors while the gear is outside in the cold, I'm already halfway up a mountain at 310m AOD. That ease of use is likely to determine my adoption of photo imaging, or not.
andrewt
 
Posts: 16
Joined: Tue May 23, 2017 5:08 pm
Location: Scottish Borders

Re: where to locate the Barlow?

Postby Aratus » Mon Jun 12, 2017 8:57 pm

A 9mm eyepiece and the barlow would give you a good 'top' of your range.

I'm out of the wind in the observatory but a ski suit with plenty of layers is essential in the depth of winter. I've not yet got to the point where I feel it is neccesary to extend all the leads to heated room, but the technology exists.
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
Aratus
 
Posts: 843
Joined: Tue Jan 12, 2016 2:17 pm
Location: East Lincolnshire

Re: where to locate the Barlow?

Postby andrewt » Sun Jul 02, 2017 1:30 pm

I have installed the Barlow between the diagonal and the eyepiece. I am able to focus all three eyepieces.

I removed the diagonal and installed the Barlow between the scope and the diagonal with the same 37mm extn attached to the focuser. Then added on diagonal and eyepiece.
I could not focus any of the eyepieces.
I removed the 37mm extension on the focuser, still no focusing. The scope came with two 37mm extensions that screw into the focuser, if needed.
I added a second 37mm extension to the focuser, still no focusing.

I have now ordered two 40mm 2" extensions to go between the diagonal and the eyepiece in the hope that the extra distance between the scope located Barlow and the eyepiece will allow focusing.
andrewt
 
Posts: 16
Joined: Tue May 23, 2017 5:08 pm
Location: Scottish Borders


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