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A descent x3 barlow

Bungielad

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Bungielad

Bungielad

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Hi all,

Can I have some advice on a good x3 barlow please!

I know more you spend the better but I dont wanna spend more than about £35-40 ( all I can outlay at mo) any advice on model or makes would be appreciated.

Bungielad.

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nephilim

nephilim

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I cant think of a decent 3x within your budget, the only difference between the 2.5x & 3x would be image scale but it'll only be slight, plus the Rev 2.5 is a 3 element apo & not achro which is a much better bet for imaging & visual IMO.

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SnakeyJ

SnakeyJ

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I've got both the Revelation x2.5 and x5 APO Barlows and find them both excellent for the money. The only thing I would say is that I believe my 2.5x is somewhat overrated in terms of power, in that it just delivers x2 with my QHY as far out as it can securely fit - though I can achieve x2.5 with the extended nosepiece or x3 with a 2" extension tube. The x5 appears to be on the money for magnification, though I can achieve anything between x4 (inserting camera well in and x6 with the extension nosepiece). Both feel very well made and benefit from compression fittings that are good and solid for imaging.

If you do come across a second hand tal x3 these do have an excellent rep, so probably worth a go for sensible money.

Forgot to mention the baader x2.25 barlow which I find despite the published numbers is actually more powerful than the Rev x2.5, in that I can achieve more magnification at shorter extension.

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Bungielad

Bungielad

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Probably bieng a bit un knowledgeable here but with imaging does the amount of the Barlow scale. .ie..x3 or above affect the scope focal length. ...let me explain that again. ...my 130p has a maximum output of x260 but when imaging does it matter if putting something higher than a x3 ??? Or does it just mean I have to take longer captures??

I wouldn't use a x3 on a 130p scope usually so does it have the same affect as when using an eye piece or totally different?

Really hope you understood that!!

Bungielad.

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nephilim

nephilim

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A 2x barlow will double your scopes FL but u also have to add the distance between the lense and the cameras chip (as Snakeyj mentions, an extension will increase it further....'it' been the image scale).

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SnakeyJ

SnakeyJ

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There is quite an interesting review/comparison of the Revelation APO Barlows (Made by GSO and also marketed as SmartAstronomy brands) with Meade Telextenders and TV Powermates here: http://www.astromart.com/articles/article.asp?article_id=600 (link provided by John in earlier SGL Thread).

Probably bieng a bit un knowledgeable here but with imaging does the amount of the Barlow scale. .ie..x3 or above affect the scope focal length. ...let me explain that again. ...my 130p has a maximum output of x260 but when imaging does it matter if putting something higher than a x3 ??? Or does it just mean I have to take longer captures??

I wouldn't use a x3 on a 130p scope usually so does it have the same affect as when using an eye piece or totally different?

I'd recommend the http://www.12dstring.me.uk/fov.htm for checking focal length, fov and resolution per pixel for difference scope, barlow and camera settings. Quick check against the SW130P and SPC900NC gives:

Unbarlowed: F ratio: Focal Length: Field of view: Resolution: f5 650mm 18.96' x 14.22' 1.78 "/pixel

x3 Barlow: F ratio: Focal Length: Field of view: Resolution: f15 1950mm 6.32' x 4.74' 0.59 "/pixel

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JamesF

JamesF

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If you do go for the Revelation 2.5x you can always add an extension between it and the camera to get a bit more image scale when conditions allow. I reckon I need about 50mm extension to give me 3x, perhaps a little less.

James

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Bungielad

Bungielad

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I think what im basicly asking is.....would a x3 barlow of desent make be better than a x2 barlow for imaging with a SPC900nc?? i just want to make the image bigger on my PC when using sharpcap!

obviously i know price comes into it and i dont really wanna fork out £100 for a Tele vue...( although id like too, thats £100 i could put towards my 200p)

the x2 im using at mo is the delux skywatcher..........could really a x2.5 Rev make much difference???

lots of advice please because i got money to burn..........just not that much!! lol.

Bungielad

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Bungielad

Bungielad

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This is something else im learning from JamesF.........so are you saying that if you extend the colum from focal tube to camera it gives more enhancment of picture??

also if this is so can i just NOT insert my x2 barlow all the way inn the focal tube and it will give me more??

sorry i know these questions may sound dumb to some but i need to know.

Bungielad

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SnakeyJ

SnakeyJ

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Yes with a true barlow more extension between the barlow lens and camera will increase magnification.

The Revelation APO 2.5x is great value and better quality than the SW Deluxe - this coupled with a 50mm extension tube should comfortably provide x3 magnification, but the combination also allows you to drop back some if the seeing is not so great.

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Bungielad

Bungielad

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That is fantastic advice......cheers for that Snakeyj and jamesF......So the question now is......what is the 50mm tube i should buy??? and will it all corespond with a 130p explorer and a SPC900NC??

Bungielad.

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JamesF

JamesF

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I don't do so with my ASI120 camera because the much smaller pixel size doesn't suit, but when imaging with my SPC900 I regularly used the Revelation 2.5x barlow with an extension. To make the extension I used the original barlow that came with one of my scopes and just removed the lenses. The kit barlow seems to be of variable quality and mine wasn't at all good so it has been far more useful as an extension. You can buy purpose-made extension tubes, eg:

http://www.rothervalleyoptics.co.uk/antares-1-25-diameter-extention-tube_d2475.html

but if you can find someone selling one of the kit barlows second hand (assuming you don't have one yourself) that may be the cheapest way to do it.

You will find that as the effective focal length gets longer the image becomes much harder to keep on the sensor (which may also be a good reason for going with the 2.5x and having a bit more choice of focal lengths).

James

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nephilim

nephilim

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Interesting that no mention has been made of TAL barlows.

I had heard they were good for the money, but have no experience of them.

Anyone have any thoughts on them?

Getting hold of one for a start, they do come up 2nd hand now again though but u need to be quick when they do.
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Bungielad

Bungielad

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yes it was that one.....cheers james!!....had a panick on for a second then.......next question......50mm extension tube.....where from?? i dont wanna take the lense out of my x2 barlow!

bungielad.

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