Deterioration of image with Barlow

[yagon]

Does image quality deteriorate with use of a Barlow?

That is, is one better off using 10mm eyepiece or a 20mm eyepiece with 2x barlow?

[janoskiss (Steve H)]

This is a very FAQ. It comes down to what is the weakest link in the optical train. If the barlow is the weak link then yes. A good barlow will not disappoint. In some respects it improves the performance of the eyepiece (EP).

Do you have any particular EP and/or barlow in mind?

[davidpretorius]

ok i have series 500 freebies in 6.5mm, 12.5mm, 25mm and the 25mm in a 5x powermate is heaps better in quality than the 6.5mm.

however it is not as good as a 5mm vixen LV.

so if you have great ep's and crap barlow then yes it will, turn that on its head and cheap eyepieces in a great barlow / powermate and i reckon it is better!

[Starkler (Geoff)]

Originally Posted by yagon

Does image quality deteriorate with use of a Barlow?

As you are adding more glass to the light path yes it will.
The question is by how much and a good quality barlow with good multicoatings will give you a decent view, whilst a cheapy will be less sharp and suffer from reflections on bright objects and excess light scatter (think driving with a dirty windscreen at night).

To answer the other Q, its a matter of comfort while viewing. The eye relief on a 10mm plossl can be a bit tight for some tastes whilst the 20mm will be more comfortable due to the greater eye relief.

[mickoking]

Originally Posted by yagon

Does image quality deteriorate with use of a Barlow?

That is, is one better off using 10mm eyepiece or a 20mm eyepiece with 2x barlow?

I personally don't like or use Barlows. That's my 2 cents worth

[rmcpb (Rob)]

Barlows have their place in a kit and I use mine from time to time but generally I try to avoid using it. Apart from adding more glass into the light path it makes the setup at the focuser clunkier.

If you use one get a good one is my tip and don't get into the cheap ones.

[RAJAH235]

IMHO, there is nothing wrong in using a barlow, provided it is a good quality one. They do not detract from the view, but do rely on good seeing conditions & of course, their design & manufacture.
Just buy a Meade #140 or the Orion Shorty +. L.

[janoskiss (Steve H)]

If you need short focal length (<10mm) EPs to get high powers (which in the ED80 you certainly do), and you want comfortable eye relief, then you spend a lot of money on EPs or use a barlow on longer focal length EPs. A 2x barlowed 15mm plossl is going to be a lot more comfortable than a 7.5mm plossl. Just make sure you get a good barlow, and you'll be in business.

[rmcpb (Rob)]

I think the general vote is not to try and save when buying a barlow. Get the best you can afford and it will be a worthy addition to your kit, otherwise it is a pain in the b*m.

[Mr Bob]

OK, what is a 'good' barlow (make etc)? thanx

[rmcpb (Rob)]

Meade #140, Orion Shorty Plus, Celestron Ultima, Tele Vue barlow in the 1.25" bracket.

I have no experience in the 2" bracket so will not comment there if it is your choice to get into this size then someone else will have to advise you.

Cheers

[janoskiss (Steve H)]

Originally Posted by Mr Bob

OK, what is a 'good' barlow (make etc)? thanx

Under $AU200: Meade #140 Apo, Televue 2x barlow, GS ED 2x (? someone please buy one of these and tell us what they're like!)

Others will also recommend the Orion Shorty Plus, but I'm no fan given my experience with one.

[cahullian]

I have the orion shorty + and I'm not a big fan of it. Then again I'm Irish so what do I know???

[yagon]

Can someone please explain the difference between a Barlow and a Powermate?

How much difference is there in quality/performance?

[janoskiss (Steve H)]

televue website is your friend: www.televue.com