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I just ordered one of these:

LukeSkywatcher

By LukeSkywatcher
in Discussions - Eyepieces

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LukeSkywatcher

LukeSkywatcher

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It's the Antares 1.25" Deluxe 2x (and 1.5x) dual magnification barlow (to replace my Tal 2x which i have sold to a fellow SGL member).

Antares Deluxe 1.25" 2x (and 1.5x) Barlow lens

I was tempted to buy a 3x barlow but i didnt think my 130P f5 scope would be able to handle it, so played it safe with a 2x.

I like the idea that i can unscrew the lens from the barlow body (to give me the 1.5x) and attach it to any 1.25" EP i have directly or even attach it to my camera t-ring and adapter for imaging through scope (LEAST I THINK I CAN). If not i'll just use it as its designed to be used as a 2x.

I just hope its as good as the Tal. Reviews seem very favourable.

Please feel free to now tell me that my scope is more then able to handle a 3x barlow.

LOL.

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LukeSkywatcher

LukeSkywatcher

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Sorry i should have said that imaging really isnt my thing right now and the 130P scope i have is the SW Heritage mini Dob. Not ideal for imaging.

For imaging (i have experimented a BIT) i have a Celestron 70mm f5 refrac.

I really meant that this barlow is just for observing on the 130P (and my other scopes)..........wondering/hoping it lives up to the Tal 2x (superb barlow).

If not, i know a guy with a Tal 2x that will do a swap.

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Stephen

Stephen

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Sorry i should have said that imaging really isnt my thing right now and the 130P scope i have is the SW Heritage mini Dob. Not ideal for imaging.

For imaging (i have experimented a BIT) i have a Celestron 70mm f5 refrac.

I really meant that this barlow is just for observing on the 130P (and my other scopes)..........wondering/hoping it lives up to the Tal 2x.

I'd work it backwards then (just for fun!!!!)

Max useable mag on most nights will be (about) 35 x 5" = 175X

Divide that by 3 (for the barlow) gives 58X (ish)

Focal length 650 / 58 = 11.2mm

So yes, a 3x Barlow is possibly useable, so long as the EP you are putting in it is about 11mm or greater :)

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LukeSkywatcher

LukeSkywatcher

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I'd work it backwards then (just for fun!!!!)

Max useable mag on most nights will be (about) 35 x 5" = 175X

Divide that by 3 (for the barlow) gives 58X (ish)

Focal length 650 / 58 = 11.2mm

So yes, a 3x Barlow is possibly useable, so long as the EP you are putting in it is about 11mm or greater :)

So an 11mm ep (lets round it off to 12mm) plus a 3x barlow would make that ep a 4mm.

I have a 4mm Celestron Omni. Would i not just use that instead (without any barlow)?

I really just want magnification while observing planets. But i know that "seeing" in this part of the world rarely allows me to use the 4mm Omni.

So for planets..............a 3x (and say a 10-12mm ep) should work with my scope?

Damnit...........

I knew i should have gone 3x.

Good thing Christmas is around the corner.

Thanks for assuring me that my scope just might be able to handle 3x. I was convinced that that would be pushing the 130P just over the limit.

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Stephen

Stephen

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So an 11mm ep (lets round it off to 12mm) plus a 3x barlow would make that ep a 4mm.

I have a 4mm Celestron Omni. Would i not just use that instead (without any barlow)?

I really just want magnification while observing planets. But i know that "seeing" in this part of the world rarely allows me to use the 4mm Omni.

So for planets..............a 3x (and say a 10-12mm ep) should work with my scope?

Damnit...........

I knew i should have gone 3x.

Good thing Christmas is around the corner.

You can't "cheat" with a Barlow - the maximum magnification is always the same whether it's a 4mm EP or a 12mm with a 3X Barlow (which is the same as a 4mm.)

Barlows are there for the cases where you don't have the smaller EP, or you just prefer the style (comfort) of the bigger EP. Really small EPs are pretty nasty (in my opinion.)

To sum that up, yes you may as well just use your 4mm :)

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LukeSkywatcher

LukeSkywatcher

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You can't "cheat" with a Barlow - the maximum magnification is always the same whether it's a 4mm EP or a 12mm with a 3X Barlow (which is the same as a 4mm.)

Barlows are there for the cases where you don't have the smaller EP, or you just prefer the style (comfort) of the bigger EP. Really small EPs are pretty nasty (in my opinion.)

To sum that up, yes you may as well just use your 4mm :)

I agree. You cant "cheat" with a barlow (thats not my idea or thought). What i mean is (and as you say) looking through a 12mm EP with a 3x barlow is a lot more comfortable then trying to look through a 4mm EP.

Although i have to say that the 4mm Celestron Omni is pretty nice to observe through.

I had a 4mm EP that came with the Celestron EP kit i bought when i was starting out and it was physically impossible to see anything.

I normally observe planets with 9-10mm ep's (COMFORTABLE), a barlow will still allow the same level of comfort while offering the higher magnification.

Thats essentially why i use a barlow.

I think i'll push the boat out a bit and get a 3x.

I really wasnt sure if my scope could handle 3x.

Thanks Kh3ldar.

p.s.~~~Hey when i get my Antares 2x and i buy a 3x barlow i can stack them. Is that 6x?

LOL.

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Stephen

Stephen

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f30 WOAH!!! ;) Yes, it is indeed 6X LOL

This is why I love my 8mm Hyperion + FTRS.

It's an 8mm

and it's a 6.9mm!

and it's a 6.0mm!

and it's a 5.0mm!

and it's a 4.3mm!

All the zoom, none of the discomfort!

(Inbuilt Barlow effectively :))

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LukeSkywatcher

LukeSkywatcher

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f30 WOAH!!! ;) Yes, it is indeed 6X LOL

This is why I love my 8mm Hyperion + FTRS.

It's an 8mm

and it's a 6.9mm!

and it's a 6.0mm!

and it's a 5.0mm!

and it's a 4.3mm!

All the zoom, none of the discomfort!

(Inbuilt Barlow effectively :))

Ok sorry you just lost me there.

So stacking an f5 scope by 6x = f30? (makes sense i think)

Is that a good thing?

Will planets appear bigger then a flies testicles?

While affording comfort.

LMAO.

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Stephen

Stephen

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Ok sorry you just lost me there.

So stacking an f5 scope by 6x = f30? (makes sense i think)

Is that a good thing?

Will planets appear bigger then a flies testicles?

While affording comfort.

LMAO.

Sorry I was thinking imaging again, it's a complete non starter for visual :)

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Stu

Stu

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That's not right, the numbers do multiply. If you use a x2 and a x3 barlow, it is the same as a x6.

Luke, the image scale in the ep will still be totally related to the magnification given by the combination if ep and barlow. You always want to stick within a sensible range otherwise the image will just go soft.

One further thing, barlows change the eye relief of the lens being used. They push it out further I believe (someone will correct me if I got that wrong!) TV power mates keep exactly the same relief as the lens on its own but with the extra mag. They are expensive but very good

Stu

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great_bear

great_bear

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Actually I think you're both wrong :)

(I'm serious too!)

Not that this is about opinions - it's about the laws of physics, lest we forget that.

Now, to the point: Think of a 1x Barlow - i.e. a piece of clear glass. Would that add an extra "x1" to the magnification of a Barlow that precedes it? Well - it could - if it adds the correct extra length to the optical path for such multiplication as required by that Barlow.

However since this precise length relationship between the Barlows involved is not known in the context of the question, the correct answer is:

You cannot say without knowing the specs of the Barlows.

rgds,

Jeremy

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Stu

Stu

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Great bear, I think you are probably closer to the correct answer. TheThing, do you have the background to starting that it is an additive calculation?

I am fairly sure that it is not an additive effect, it will be a multiplier of some sort. Thinking about it, it won't be as simple as 2x3 because of the way barlows work. Does anyone else know how this works? It's all hypothetical because I'm unlikely to do it but am curious to know

Stu

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great_bear

great_bear

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If it was possible to stack three 1x barlows I would not end up with a 3x barlow so it can't be additive.

True - yet if you had a x2 followed by three x1 of the right spacing, you would then have an additional x3, making it a total of x5. But connect them in reverse order, and you'd only have x2

Similarly, if you take two x2 Barlows, one is a "normal" Barlow and the other one a "shorty", then the amount of stacked magnification you get will depend on which goes first.

(if the normal Barlow goes between the shorty and the eyepiece, then you'll get more magnification)

Even with a single Barlow, the exact magnification you get can vary wildly because eyepiece manufacturers have so much latitude in where to place the focal plane for a given eyepiece. A 40mm Plossl for example might have its focal plane near the bottom end of the chrome nosepiece, thus gaining little magnification, whereas a 6mm Plossl typically has a focal plane about 10mm from the top of the whole eyepiece, thus producing more magnification from the Barlow.

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Damo636

Damo636

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True - yet if you had a x2 followed by three x1 of the right spacing, you would then have an additional x3, making it a total of x5.

You would also have around 18" sticking out of the focuser with around 12 glass elements, be out the price of an Ethos and an image not worth looking at :)

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LukeSkywatcher

LukeSkywatcher

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Whether stacking barlows adds or multiplies seems to have divided the group,LOL.

Great Bear. You have me worried now in case the barlow i have ordered is the same as the barlow that came with the Celestron EP kit. I didnt get on with that one so gave it away. Maybe i got a dud barlow in the EP kit.

I hope its not the same. It looks a bit different (IIRC) and i'm sure Celestron would have said if the barlow in the EP kit could be used as both a 1.5x and a 2x.

I'm sure i'll find out in a few days.

Paul

*EDIT*

Great Bear i have just had a look at both the Antares and Celestron barlows and compared them. They are frighteningly similar in appearance. One slight difference on the silver barrel.

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