Barlows

[mcut]

if there is a thread already on this please direct me.

awaiting f6 megrez 72 apo.

have: baader ortho 7mm, Swan 9mm, and skywatcher eyepieces supplied with my Mak.

simply looking for answer regarding

1. focus travel, and linked to this question, shorty barlows (explain please)

2. recommendations sub £80

3. do i need something like the Meade APO barlow

read about the UO Klee in USA but have also read that the Ultima Barlow from celestron is as good.

any answers would be greatly appreciated.

[John]

I use a Celestron Ultima 2x Barlow with my Vixen ED102SS F/6.5 and it works very well. There is virtually no difference in image quality between barlowing my Nagler 9mm and using a Nagler 4.8mm on it's own. The Ultima is a shorty barlow and goes between the eyepiece and the diagonal. It introduces the need for about 5mm of inwards focus travel with my scope.

One little thing about the Ultima Barlows is that they are reckoned to be more like 2.2x rather than exactly 2x.

I have not used the Meade APO barlow but I have compared the Ultima to a Tele Vue 2x barlow which are well thought of and found the performance comparable - I prefer the shorty format which is why I stuck with the Ultima.

John

[russ]

Or the Orion Shorty Plus 2x. Identical to the Celestron John recommends but £27 cheaper

[mcut]

It introduces the need for about 5mm of inwards focus travel with my scope.

The Megrez 72 specs say this.

50.8 mm (2") Crayford Focuser

with 1:10 Dual Speed microfocuser

81 mm (3.2") Focuser Travel Length

360° Rotatable Design

i am not sure whether 81mm focus travel is good or bad. i am assuming that i would normally reach focus somewhere in the middle of the range, if that makes sense, and therefore have about 1.5" either side. NOT VERY BRIGHT on the whole focus travel bit.

[John]

Well the Megrez 90 that I had was excellent on focus travel - much better than other refractors I've tried. I never had any problems getting an eyepiece to focus in the Megrez wheras I always seem to be right at the end of the inward focus travel on Skywatcher and my Vixen refractors.

Of course 2 inch diagonals swallow up an extra bit of inward travel themselves which does not always help

John

[The Warthog]

Shorty Barlows are advantageous in Refractors and catadioptrics when you are using a diagonal, as long Barlows usually hit the diagonal mirror before they are fully seated.