Questions about 50az's 3x barlow lens

[falcrum]

Hello everyone, 

Firstly I'd like to say that it's great to be a member of a site that has lots of experienced astronomers. 

I have just started to use celesteron 50 az(refractor 600mm f/12 eyepieces 20 12.5  4) but have some problems about its 3x barlow lens. I tried to put barlow between star diagonal and eyepiece but in all eyepieces it was very blurry and impossible to focus. Then when i put barlow between tube and diagonal i was able to focus it but with 4mm eyepiece even the properly focused image wasn't very sharp, it was a little blurry. 

So my questions are: "Is it normal that I wasn't be able to focus when barlow is between diagonal and eyepiece? " and "With barlow used  the image was sharp with 20mm and 12.5 mm eyepiece but it wasn't very sharp with 4mm eyepiece as i mentioned before. So is it normal and what's the reason behind that?

Can we say that when magnification is increased the barlow will make image more blurry? 

Thank you for replying. 

 

[Waddensky]

With respect to your second question: a 4 mm eyepiece used with a 3x barlow produces around 450x magnification, that's too much for your scope and for normal atmospheric conditions in general, causing the view to be blurry and unsharp. Even the 4 mm without the barlow is a bit of a stretch for the scope. Keep it under 100x and you'll be fine. Good luck!

[John]

Hello and welcome to the forum

I agree with the above - stick to using the 20mm and 12.5mm eyepieces with the barlow lens only being used with the 20mm. The 4mm and the barlow lens used with the 12.5mm eyepiece produce too much magnification to get a clear and useful image with a 50mm aperture scope.

 

 

[laudropb]

Hello and a warm welcome to the SGL.

[falcrum]

Thanks for previous answers.

I am still curious about the first question which is :

 Is it normal that I wasn't be able to focus when the barlow is between diagonal and eyepiece? 

[John]

Using a barlow often requires a re-adjustment of focus and if this is quite substantial then you might run out of focuser travel.