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SW 2" 2x Barlow

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Anyone have experience of this barlow ?? Is it full aperture ? I'd like to hear about your pro's and cons, since I can't really afford to replace the WO or buy a TV tho I have had a look at the Stellaview.

All opinions gratefully rec'd

Karlo

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Kevin Ellis

Kevin Ellis

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I have just purchased and returned a Sky Watcher 2" x 2 ED Barlow.

I took it to the Kelling Star Party to use with my 13mm Ethos in my 8" f4.5 newtonion. It was horrible as it would not come to focus correctly. A star test showed a large central obstruction on one side of focus and a very small central obstruction on the other. I got the same result in friends 20" f4.7 Dob. I was surrounded my many experienced astronomers who all confirmed my observations. By chance a vender at the Star Party introduced me to a customer who had purchased an identical Barlow. I found that his barlow gave the same horrible results as mine. I was also loaned a Meade 1.25" x 2 barlow and it worked just fine. There was very little difference between my barlowed 14mm Radian and my non barlowed 8mm Radian. It could be that the SW 2" x 2 ED Barlow does not like fast scopes which is a shame as I wanted to get more use out of my 13mm Ethos. It could be that both of the SW Barlows were just poor examples.

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John

John

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Thats very useful feedback Kevin - thanks. I was considering a similar barlow for use with my Ethos - looks like I will have to think about either a TV Big Barlow or a Powermate 2x.

John

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Kevin Ellis

Kevin Ellis

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John

I also considered the TV Big barlow or 2" Powermate, but was concerned about the weight and length when used with the Ethos. I have no need for a barlow with my other eyepieces. Also for the cost of the TV Big barlow or 2" Powermate I could buy another Radian. Ok smaller field but less glass. I would also be half way to the cost of a 6mm or 8mm Ethos.

I beleive the SW 2" x 2 ED barlow is a GSO barlow and is sold under difference brand names. I purchased it because I had read good reports on the GSO barlow on Cloudy Nights.

Has anyone else had a different experience.

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Astro_Baby

Astro_Baby

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I havent really had a chance to use mine much. I had a quick crack with it a few nights ago and it seemed 'odd' but in fairness it was being used to boost up a 5mm Hyperion to 2.5mm against Saturn and the atmosphere wobble was quite bad.

I couldn't say for sure how well or badly the Barlow might have performed on that test.

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FLO

FLO

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For regular eyepieces like Plossls, kelners, orthos, super-plossls and the like it ought to work fine. I certainly haven't noticed any problems and have yet to recieve a return. You don't normally barlow complex ultra-wide eyepiece designs as they essentially incorporate an optically matched barlow (similar to) elements into their design. If I owned an Ethos eyepiece and wanted to barlow it I'd seek TeleVue's advice, I certainly wouldn't use a budget generic barlow.

HTH

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Kevin Ellis

Kevin Ellis

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Karlo

I dont know if this link will work

Telescope Reviews: Skywatcher 2" 2x Super-Deluxe ED Barlow Lens

On Cloudy Nights the thread is in equipment, first posting is 2749645 on 13/11/2008.

The subject heading is Skywatcher 2" 2x Super-Deluxw Barlow Lens

Not a review but some comments by users.

My prefered choice was the inexpensive Antares 2" 1.6x. This has received good comments on Cloudy Nights when used with the 13mmm Ethos, but I was told that they are no longer availiable in the UK.

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Kevin Ellis

Kevin Ellis

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Steve

Posting 1.27am. Were you out observing last night?

I can only comment on my own experience. Both barlows were just horrible to the point of being totally unuseable. My TV Plossl, Radian and Ethos eyepices all gave the same horrible results when viewed on axis in my 8" F4.5. I only tried my Radians in my friends 20" F4.7. It could be that these are the only two bad examples.

I purchased the barlow because of good comments received about the budget Antares 2" 1.6x when used with the 13mm Ethos. As previously mentioned I have been told that the Antares barlow is no availiable in the UK.

The old meade 1.25" 2x barlow I was loaned worked fine, but it's not 2".

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Mikea

Mikea

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I have one of these and it seems to work fine with the stock EPs supplied with my Skywatcher 130P. I did also manage to grab a couple of moon shots via the webcam plus the Barlow - again it seemed ok. However, I am now starting to wonder if I missed something! Is the "obstruction" something that would be apparent even to a beginner such as myself?

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Kevin Ellis

Kevin Ellis

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Mikea

In my newtonion, the central "obstruction" is the secondary mirror that reflects the light from the main mirror to the eyepiece. When you look at an out of focus star, the central obstruction will be the black circle at the centre. The out of focus star should look the same on either side of focus.

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Mikea

Mikea

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Mikea

In my newtonion, the central "obstruction" is the secondary mirror that reflects the light from the main mirror to the eyepiece. When you look at an out of focus star, the central obstruction will be the black circle at the centre. The out of focus star should look the same on either side of focus.

Forgive my total numptyness, but why does that matter? (sorry :icon_rolleyes:)

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beamish

beamish

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Karlo

Another vote for the 2" GSO barlow.

Telescope Reviews: 2X Barlows go head to head on Saturn

Just not confirmed by my own experience.

Thanks Kevin-that's pretty much made my mind up. I do miss not having a 2" 2x Barlow and now can't afford to replace the WO 2.5x :icon_rolleyes: .Am I right in thinking that the Revelation and the SW both have full aperture optics ??

Karlo

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Kevin Ellis

Kevin Ellis

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Mikea

Because, if they are not your telescope will show, to various degrees, optical errors when infocus. ie will not come to focus correctly. Therefore by doing a star test you can evaluate the quality of a telescopes optics. You must however allow your telescope to cool down, that is adjust to the outside temperature, before doing a test. You also need an understanding of the differences seen. You will find that your own telescope will perform better when you have allowed the optics to adjust to the outside temperature. This could take between 1/2 hour to several hours depending on the type and size of the telescope, and the outside temperature.

I have some understanding, but best of all I have a very good friend who has a very good understanding of telescope optics as he makes his own telescope mirrors including his 20" Dobsonion. He also used the word horrible when he tried the 2" barlow.

If you join a club there will always be someone who will have some knowledge of star testing.

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