3x Barlow lens.

[MarkST24]

As a newbie I don't know much about telescopes but after lot's of trolling the 'net and reading ALOT of reviews I've settled for a Celestron Traveller 70 as a budget starting point. I've read that an essential bit of kit for increasing magnification cheaply is a Barlow lens. Well i've purchased a 3x one for mine. I intend to use it with the 20mm eye-piece. What kind of results will I achieve with this set-up? eg. Jupiter bands, Saturn rings and general objects? It hasn't arrived yet so any info would be great!!!

[brantuk]

The scope has fl=400mm so with a 20mm eyepiece you'll get 20x magnification. If you treble that with a 3x barlow it becomes 60x magnification. I would only expect to see Jupiter and Saturn as small bright circles at that depth - with the moons of Jupiter as a row of 4 dots and Saturns Titan as a single dot next to the planet.

I wouldn't expect to see any surface features of either much below 150x mag. Bit like the view in binocs really. But you'd see reasonable detail on the moon and be able to determine Venus phase. Hope that helps and here's a good review of your scope:

http://www.cloudynights.com/item.php?item_id=2563

[Superdavo]

The scope has fl=400mm so with a 20mm eyepiece you'll get 20x magnification. If you treble that with a 3x barlow it becomes 60x magnification. I would only expect to see Jupiter and Saturn as small bright circles at that depth - with the moons of Jupiter as a row of 4 dots and Saturns Titan as a single dot next to the planet.

I wouldn't expect to see any surface features of either much below 150x mag. Bit like the view in binocs really. But you'd see reasonable detail on the moon and be able to determine Venus phase. Hope that helps and here's a good review of your scope:

http://www.cloudynig...hp?item_id=2563

I'd say you could also see saturn's rings

[Grotemobile]

Just found it on Amazon. It does not look a bad buy.

http://www.amazon.co...=70mm telescope

Great for terrestrial viewing.

Steve.

[umadog]

I think you should see the bands on Jupiter at significantly lower power than 150x. If I recall correctly, I was seeing them last night at 50x in an 80 mm refractor.

[LukeSkywatcher]

I have this scope. Its a widefield scope. It really isnt suited to high magnifications. As brant says...........even the larger planets will only appear as very small dots.

[umadog]

I re-read your post and realised that you are a first-time buyer. You might benefit by having a read of this page: http://www.cloudynig...php?item_id=547 See that 60x on your scope (which has a 2.75" objective) is getting into the high power region at 60x. 80x is about the most you can realistically expect from it.

Think of a telescope like an engine. An engine of a particular size has a limit to the amount of power it can produce. It has an optimum power and a maximum power. The closer you get to that maximum the more you're stressing the engine and the more likely you are to see it hiccup. And so it is with telescopes. In theory you should get about 50x per inch, but whether you hit that depends on having good optics. So if you want good performance at, say, 150x you'll get better results with an objective that's doing that at 20x per inch than one that's doing it at 50x per inch. For starters, the image will be brighter at 20x per inch than 50x per inch.

As Paul says, a instrument of the sort you have will perform best with the larger deep space objects. The atmosphere rarely supports more then 200x an absolute number so for every inch of aperture you add, you make it easier to hit 200x and still get good performance for the instrument. Up to about 8" of aperture, each extra inch makes a substantial difference. After that, not so much because you need to add progressively more aperture to see a difference at the eyepiece.

Hope that helps.

[LukeSkywatcher]

My best advice for this scope would be to chuck the supplied tripod in the bin and get something more stable. This WILL allow you to use higher magnifications on the scope. The stock tripod supplied is a complete waste.

[cadno]

Thought I'd just jump in here as even though I've been playing around with my scopes for a bit, I am still utterly at the beginners I've not a clue what I'm doing phase lol. Anyway, playing with my refractor which is a Celestron Powerseeker 60AZ with the following:

OPTICAL PERFORMANCE Field of view (@1000 yds)

61 ft (19 m) Angular field of view 1.2 ° Aperture 60 mm Focal Ratio 12 Focal Length 700 mm Eyepiece 2 4 mm Eyepiece 1 20 mm Magnification 2 175 x Magnification 1 35 x Optical design Refractor

It also comes with a 3x Barlow lense which is where I'm confused completely as a lot of posts I've read I get a little lost. So literally I want to be treated like a 6 year old and have the lense explained. I was viewing Jupiter, managed to line it up and see it as a bright disc (no real colour) and 4 of the moons. So, my brain goes, aha, 3x the magnification and put on thhe barlows lense. Now all I could see was a BIG white blob as opposed to anything else and though I tried to focus on it (remember its taking up the entire field of view) I could not see any detail. Now I know I'm doing something wrong and from what I've read barlows don't quite work in that fashion. But I'm desperate to learn and I'm really hoping somebody has the patience to just break it down for me as reading is an issue right now (long story about my ability to concentrate).

Cadno

[cadno]

OK, that didn't post as intended, the eye piaces are eyepiece 1 - 20mm and eyepiece 2 - 4mm

[x6gas]

The Barlow will change the focus point so it sounds like you were on the right track trying to adjust the focus - did you rack the focuser all the way in and out? Some cheapo Barlows are a complete disaster, though... and best avoided.

[RichieP]

Using the 4mm eyepiece with the barlow will give you a magnification of x525. This is far beyond what your scope can handle.

Have you tried it with your 20mm eyepiece? That would give you a much more manageable 105x

[cadno]

I did try the 20mm, that was the blurred image, I just gave up on the 4mm lol, now I know why that was a 'good' idea lol. This was a barlow that came with the scope, no make label of any kind on it, just assumed it was the same as the lenses and made by Celestron. I pretty much went to both extremes trying to focus but it wasn't having any of it, I will say though it was very bright and I'm wondering perhaps a filter of some description (learning about them now lol) would actually help. Also, I do have a reflector with a 4.5 ap and a 900mm focal length, maybe try the barlow in that?

Also, cheers everyone for helping, I so need it lol

Cadno

[cadno]

Beginning to think its the lense in general, thought who not look at Polaris, nice easy star, something I can zoom into nicely with the lense. I had EXACTLY the same kind of problem. All I had was blurred light, moved a little to see if I could change it and it pretty much was a solid disc of light. Now I know stars will look bright etc, but there was no difference between looking at Polaris and Jupiter. Now I'm wondering if the moonlight was causing problems but I feel that isn't so, so I'm giving it one more go with the barlow during the dark moon and seeing if there is any different. If not, thinking what x6gas was right and it might be a bad lense. Still though, any advice, more than welcome, slowly getting my head around things lol