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Old 08-10-2020, 04:44 PM
Renato1 (Renato)
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Renato1 is offline
 
Join Date: Mar 2014
Location: Frankston South
Posts: 1,202
Not sure how to answer your last question.

In 1.25", I have two Televue Barlows, an old Celestron Barlow, a Meade shorty Barlow and one or two GSO barlows. Plus a couple of 2" Barlows.

I could never see any difference between my Televue ones and the Celestron one.

The main problem with Barlows for me, was that I always knew I was looking through a Barlow. With a Powermate, I couldn't tell the difference.

Looking through a 4.5mm eyepiece - depends on the eyepiece. If it's a Plossl, your eye will be nearly stuck to the lens because of the very tiny eyerelief, whereas a 9mm Plossl eyepiece and Barlow will give you more eyerelief. With a 22.5mm eyepiece and 5X Barlow - if you have astigmatism, you will be able to wear eyeglasses while viewing.

But if your 4.5mm eyepiece is one of the newer ones with long eyerelief (like the inexpensive TMB type ones on Ebay), then the view is generally better than that from a 9mm Plossl in 2X Barlow - since these newer eyepieces in effective have a little matched Barlow built into them.

Remember also that if you have a refractor, an SCT or a MAK telescope, to get 2X magnification from a 2X Barlow, you have to put the Barlow into the star diagonal. And this is often a nuisance, especially if one has a heavy eyepiece in the Barlow.

If instead you put the Barlow into the refractor, SCT or MAK, and then put the diagonal into the Barlow, it is much easier to use - but you get approximately 3X magnification of the eyepiece.

I mainly used Barlows when I first started out and didn't have many eyepieces. Later I used them on short focal tube refractors, where I didn't have high enough power eyepieces. But I do now, so I rarely use them nowadays.
Regards,
Renato

Last edited by Renato1; 08-10-2020 at 05:07 PM.
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