Barlows - The Emperor's not wearing any pants!

[Dog Star]

Why is it that any newbie stumbling onto this site and asking what he, or she, needs in the way of start-up equipment is almost invariably told that at some stage that they'll want a Barlow?
"Oh yes, a Barlow is a most wonderful accessory. Doubles the range of your eye piece collection, doncher know?"
My brother, Gargoyle Steve, recently gave me a 2.5x Televue Barlow, but warned me that I might be disappointed with it. He owns a few of decent quality and tells me that he's not particularly impressed with any of them and doesn't know why they're held in such regard.
Nevertheless, I excitedly lined up on Omega Centauri with my 15mm ep and admired the view.
"Right," I thought, "15mm in a 1500mm OTA is giving me 100x views. If I pop in my new Barlow, I'll get 250x views but with the same fov. This is gonna be great!"
Popped in the new Barlow and initially thought a mud wasp had built a nest in it! Couldn't see a damn thing! Fiddled with the focus and altered my eye relief somewhat and yes, there was Omega Centauri, bigger but as dull as an old daddy-long-legs spiders year old web. As dim and feeble as I am on a Saturday morning after a big Friday night!
Must admit that I agree with Steve. The Emperor is trouserless.
Tried it with a couple of other ep's, but finally put it away as a bad joke and stuck to Barlowless ep's.
So, my simple question is this - Why do so many people reccommend them and why are they held in such regard?:screwy:
(Or in the dim view, does it just look like the Emperor has his pants on?)
Considred posting this in both the Beginners Start Here and Equipment Discussion forums but decided to split the difference and post it here. If a Mod wants to move it, they can put it where they like.

[[1ponders]]

It's a serious question Phil so I'll move it to Equipment Discussion.

For what it's worth the only thing I use a barlow or powermate for is to get a bigger image of Jupiter onto my ToUcam. ;)

[Gargoyle_Steve]

My understanding Phil is that when you magnify 2x, you are therefore spreading the same amount of hard-won photons across a 2x by 2x, ie 4 times larger area, thus double the magnification, reduce the brightness by 4.

Therefore the only times maybe they are of benefit is when visually observing an object so bright that the loss of brightness still leaves it as an acceptable object (the moon, maybe 2-3 planets), or as Paul pointed out when you're capturing frame after frame after frame several hundred times, to then stack these frames together and rebuild that original intensity.

That's how I figure it anyway, I'm still prepared to have someone change my mind about Barlows as long as the proof of the pudding is to be found in the visual observing of that same pudding!

I WILL state for the record that the only Barlow that I 'own AND use' at all is the cheapest one - my 2" 2x GSO barlow, which when used with my cheap Andrews 80° 2" eyepiece changes it from a great 30mm wide angle view with terrible seagulling in the outer view field, to a 15mm wide field view with absolutely zero seagulling at all!

[astroron]

With large objects there is no need to use a Barlow.
Any increase in magnification decreases light,so why would you use a medium to high power eyepeice and a barlow in the first place.
I only use the barlow on small bright objects ,or to look for stars as bright points of light in galaxies.

[Dog Star]

That's fair enough Ron, but you're an experienced observer and you knew that.
Poor dumb buggers like me (and other newbies to the game) don't know that. Instead, we are told that a Barlow will double our eye piece collection.
It may not be outright bad advice, but it's certainly misleading and as such, it shouldn't be given.
Fair point?

[astroron]

Fair point Phil, maybe a little bit more information should be imparted when advising people what eyepeices they should get.
In fact I had a person up here just last weekend asking me about eyepeices and told him the value of barlows and their uses:)
Like all eyepeices barlows have their uses but they are not really in place of another eyepeice, but can be a useful tool in your eyepeice box.:thumbsup:

[marki]

They certainly cut the light a fair bit thats for sure. I do tend to use them on my refractors a fair bit but thats because I am used to higher focal ratios and even then only with a 20mm EP because I don't have a ten.

[Tandum]

I also have a barlow in my kit. I think I used it once for a moon shot. I also have a 1/2 dozen eyepieces I've never used. Why did they tell me I'd need eyepieces ..... The camera see's it just fine.

[Chippy]

I use a barlow regularly, and would certainly recommend them to anyone starting out with a limited number of EPs. I can't say I've found a huge degradation in image or brightness (given the extra magnification) at all. Indeed they actually seem to help clean up images of some poorly performing EPs. Horses for courses I guess.

[omnivorr]

I'm sure William Herschell might've appreciated not having to build a forty foot monster, had he had a barlow..

similarly anyone with a scope of reasonable aperture but shorter focal length might benefit from a barlow, at considerably less expense than the price of a larger scope.

there's image-scale, as mentioned... there's using an EP of wider fov and fieldstop than a shorter focal length EP... for the same magnification.

...the televised world stopped to watch dim grainy Apollo pictures... and since, no such airtime but for the two Shuttle disasters has been so eye-grabbing .. that 'barlowed' view way back then can't compete with the big bright splashy expectations now....

the energy and enthusiasm of unjaded youth has yielded to the artery-clogged mentality of geriatric Porsche's unable to merge with the traffic...

it might not be the barlow letting down your expectations.. it might be that 12" - 24" that you've outgrown... the sheer joy of reaching out to the cosmos might now be the "Ho Hum" of wearing last year's fashion..

I wouldn't say a barlow is a "must have", but I get plenty out of mine.

I also like the views through my 70mm refractor, barlowed sometimes, and all the rest that I have at my disposal... affording me many views in many ways. Sometimes I even forego aperture and magnification to look with my bare eyes!

...some people prefer bicoculars! it's a crazy world, I know.. but hey,

let them barlow who would not tresspass against us... as we would not Retchie Chriten against them, ..ok? ;)

[Dog Star]

For what it's worth, I think that if someone is kind enough to give you a Barlow, then you've got it at a fair price. If you're going to pay for one, then you may well be better off putting that money towards a new or used GSO plossl.
"Double the range of your eye piece collection?" - not what I'd tell a newbie.

[jjjnettie]

I gave away my barlow when I sold my big scope last year, thinking that I'd never want another.
My new apo barlow arrived in the mail the other week.
To me it's an essential part of my kit.
I wouldn't and at times couldn't view the moon or planets without it.

[Starkler]

If you're starting out with a dob and not predisposed to spending a lot of money on short FL, long ER eyepieces for high power and planetary viewing, then a barlow makes a lot of sense.

Try squinting to view through a 6mm plossl and tell me if you enjoy the view.
For years I was using my 10.5 and 14mm Pentaxs both barlowed and native and every combination of powers these gave me were useful.

[rmcpb]

I use my barlow mainly on the moon and planets for those higher power views where I have plenty of light to play with. As for an object like Omega Cent I woudl never barlow that, its a great target for low to medium magnification IMO.

cheers

[Dog Star]

Many thanks for the generally positive responses to my question.:thumbsup:
It would appear that the Emperor does indeed wear fine new clothes, depending on the light you are viewing him in.
I dare say that I will indeed find uses for this piece of kit, although I am still inclined to believe that they are somewhat over-rated.:shrug:

[astroron]

Only time will tell Phil:)
Enjoy your observing whatever eyepeices you use:thumbsup:

[Paddy]

When I first got my 9 mm nagler, I compared the view in my GSO 12" dob with that through my 17 mm LVW and 2x Barlow. And was not pleased because I wondered why I'd spent $330 on the Nagler (the $AUD was good then!). Apart from the field of view, both set ups were superb. Siilarly, Ihave found my 24 mm panoptic in a 2x barlow also gives magnificent views. This I've found to be true with GSO barlow and my teleview.

IMO the place for a Barlow is not necessarily to increase the range of magnifications, but to fill gaps in the range. this can allow a smaller number of premium eyepieces. I have my 13 and 9 mm Naglers because I can afford them and its a little more convenient than using a Barlow but I would be quite well served by having only a 24 Pan, 17 LVW and a 2x Barlow. But not many things are going to look great at 250x unless you've got exceptional seeing.

[JethroB76]

The only time I've been disapointed with barlowed views has been when I've exceeded the power that the conditions and the objects can support - AFAIK quality modern barlows shouldn't lose too much compared to an EP at the same f/l natively.

My main gripe with barlows would be that they add a lot of length or bulk to whats hanging out of the focuser particularly the 2"ers..

[Chippy]

Another important point is that they maintain the eye relief of the EP, whereas typically, shorter FL eyepieces have shorter eye relief.

FWIW I really like barlows. I do agree that the additional length/weight can sometimes be an issue. But hey, nobody complains about the length and weight of an ethos... they just rave about the views!

[astroron]

My main gripe with barlows would be that they add a lot of length or bulk to whats hanging out of the focuser particularly the 2"ers..

I use a type 1 13mm Nagler with a two inch GSO Barlow on my 16" scope and have no problem whatsoever:D
The eyepiece and the Barlow weigh about half a kilo.:eyepop:
Anyone who has looked through the scope with this combination has just said WOW:thumbsup:

[JethroB76]

As I said I have no problem with barlow performance; I've been very happy with my 13mm Ethos in my 2" barlow, but it is still a huge contraption hanging out of the focuser, I feel like I need to check that the thumbscrews are tight every few minutes

[astroron]

Go to a 16" and it wont seem so bad:P:thumbsup:

[JethroB76]

nah, 20" is the next step

[KaStern]

Hello Phil,

I find a well-made barlow to be a very useful equipment, with my Newtonians.
My Newts are a 8"f/6 ATM Dob and a 4,5" f/4 Newt.

I do never use a barlow with my 80mm f/18,25 Refractor and my 6"f/12 Yolo.

The f/ratio of the scope is an inportant factor to be considered.

Let us assume you own a fastish f/4 Newt with decent optical quality,
you have him well collimated and you want to reach high powers on a
night with good seeing conditions.

The scope will allow you to use 0,7mm exit pupil, magnification will be
about Diameter of the optics in mm x 1,4 or even x 1,5
You would have to take a 2,8mm eyepiece to achieve this magnification(!)
Or you take a 2,5x Barlow plus a 7mm eyepiece,
or 3x Barlow plus a 8,4mm eyepiece.

The eye reliev of the simple eyepieces like Plössl, Abbe Ortho, RKE, Kellner
is about 2/3 of the eyepieces focal length.
Eyerelief of a 2,8mm Plössl would be extraordinary short.
The shortest Plössl and Abbe Orthos I know have 4mm f.l.
eyerelief is around 3mm and you have to pres your eyeball onto the eye-lens
of th eyepiece to see the whole field of view. A 9mm or 8mm eyepiece
is way more comfortable.

For high mags with ma 112/450mm Newt or 200/1200mm ATM Dobsonian
I regularily take a 3x Televue Barlow or a 2,8x Univesity Optics Klee Barlow
and some 13mm, 12,5m 12mm and 11mm quality Plössl/Ortho/RKE eyepieces.

A single 4mm Ortho shows blown-up stars at the edge of field,
whereas
a 12,5mm Orth or 12mm RKE with one of the Barlows does not show
any edge star degradation.

One downside is that the exit pupil is moved further out if a barlow is used.
That is fine with short focal length Orthos/Plössl/RKE/Kellner, but it can be
disgusting with long focal length eyepieces and shorty barlows.

Greetings , Karsten