Celestron Ultima 2x barlow......

[Solar_observer]

It's sold as a 2x barlow but I here it's not that. I see in various places it's 2.2x or 2.3x,can anyone confirm exactly what it measures at please? Thanks

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[rory]

I remember looking into this when i was thinking of getting an ultima.

I think generally speaking it's agreed that they magnify higher than x2 , and between 2.2 and 2.4 is the figure I found most mentioned.

[Solar_observer]

So if I say 2.3 being in the middle, using this figure to calculate the magnification would be best?

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[rory]

I can't say for certain , I read snippets from cloudy nights , where it said the slight variation can be down to focuser position with different eyepieces, but as someone who doesn't understand fully the workings of lenses and focal plains and do on , I can't give a confident answer. If it were me working out mags , I'd probably go for 2.2 ,

I'm sure someone like john could offer better advice.

[Solar_observer]

John did say to me 2.2. What would be a true 2x quality Barlow?

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[faulksy]

does it realy matter ? at the end of the day they are great barlows

[rory]

Skem, have you aquired a ultima Barlow then ?

I can't see 0.2 being of any real significance , but I'm possibly being naive as a novice.

The ultima / shorty plus barlows are highly rated . I'm not sure how many x2 barlows out there are true x2 magnification.

[great_bear]

The magnification in all Barlows varies depending on where the focal plane of the eyepiece is.

The "standard" is to have the focal place lie where the nosepiece meets the barrel, but many eyepieces vary from this, which affects the magnification the Barlow provides. The shorter the Barlow, the more dramatic this effect becomes.

[Rustysplit]

I have to agree with Mike. It is a really good barlow, so don't let a little extra mag put you off. I am very happy with my Orion shorty plus, the exact same optics in a different coat.

The magnification in all Barlows varies depending on where the focal plane of the eyepiece is.

The "standard" is to have the focal place lie where the nosepiece meets the barrel, but many eyepieces vary from this, which affects the magnification the Barlow provides. The shorter the Barlow, the more dramatic this effect becomes.

Fully agree with above. Eyepiece designs all vary a bit, so a constant 2x with every ep you own is unlikely unless you use a single parfocal range. Even then it depends on the above. I would not sweat over it, just enjoy it knowing it is a quality bit of kit.

[John]

The Ultima and Shorty Plus are very good barlows. They do vignette a bit when eyepieces with large field stops are used.  

[AlexB67]

On thing you may want to bear in mind, short barlows will increase eye relief more drastically than long ones, you may find this uncomfortable having to hover over the eyepiece, if you plan to use something which has fairly long eye relief already and  long focal length eyepiece, the multiplication factor of eye relief grows accordingly but is more drastic in a short one.  You may not find this desirable, though if you have a very tight eye relief eyepiece this can be a good thing. 

I have what I'd consider a fairly standard length skywtcher barlow, when I use it in conjunction with some of my eyepieces like the pentax on the occasion I have tried ( which already has 20m  eye relief) this is not ideal. It is useable but you will find yourself backing away from the eyepiece a bit to avoid blackouts. 

May be worth considering which eyepieces you are going to use it with mainly, check the eyepiece exiting eye relief. If you know the focal length of the barlow you can make a reasonable stab at calculating what the new eye relief will be form what I recall. 

[Solar_observer]

Thanks guys for the input. It's me really being too picky,I got a bit panicky cos it's added a few more mags too each eyepiece but I suppose I don't make much difference. As someone said,just enjoy my quality Barlow,which I intend to do :-)

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