Barlow 3x Focus problem

[mickopla]

Hi Guys

I got a Barlow 3x for my Celestron 130EQ MD scope but i can't get it to focus with the 20mm or 10mm lens provided with the scope. Is a 3x Barlow not compatible with my scope?? Any advice would be appreciated as i'm new to all this. Tia

Mike

[Peter Drew]

Hello Mike.

Is this a case of no focus at all or just a poor focus. A 3x Barlow with a 10mm eyepiece would probably be a bit over the top on your scope and the 20mm might be marginal. Any Barlow should be compatible with your scope.

[angusb1]

Usually a barlow will make the eyepiece focus farther out. If you're using a refractor do you have the diagonal in when you're using the barlow? If not it might help.

[mickopla]

Hello Mike.

Is this a case of no focus at all or just a poor focus. A 3x Barlow with a 10mm eyepiece would probably be a bit over the top on your scope and the 20mm might be marginal. Any Barlow should be compatible with your scope.

@Peter No focus at all with either of the lens i have.

@Angus. The Celestron 130EQ is a reflector.

Cheers for the replies by the way guys. Would the Barlow be faulty or damaged i wonder??? It looks fine to me though.

[star_chaser]

what are you trying to focus on ? moon' planet. i have the same scope and when i first got it i was trying to look at jupi but didnt realize how small it would look through my scope (first scope) and i was trying to view it as it looks in the pics on the imaging section nice and big. maybe this is not your problem reading your post again

have you tried to focus on something in the daytime? . not to sure if iv'e been of any help as i haven't had a clear night since i got my barlow:mad:

star

[mickopla]

what are you trying to focus on ? moon' planet. i have the same scope and when i first got it i was trying to look at jupi but didnt realize how small it would look through my scope (first scope) and i was trying to view it as it looks in the pics on the imaging section nice and big. maybe this is not your problem reading your post again

have you tried to focus on something in the daytime? . not to sure if iv'e been of any help as i haven't had a clear night since i got my barlow:mad:

star

Tried to focus on the Moon first then went on to the Orion Nebula and then stars and finally Saturn with no joy. Didn't try in daytime so i might give that a go.

[John]

Can you focus the eyepieces OK without the barlow in there ?.

[mickopla]

Can you focus the eyepieces OK without the barlow in there ?.

Yeah can focus no problems with the 10mm and 20mm lens.

Edit; Went outside and tried to focus on a distance Chimney and managed to do so with the 20mm lens and Barlow. I didn't drop the Barlow the hole way down the lens chamber, maybe only one third of the way down. Its a clear day here so will try later on Jupiter and hopefully it will work.

[Dark Infinity]

Usually a barlow will make the eyepiece focus farther out. If you're using a refractor do you have the diagonal in when you're using the barlow? If not it might help.

I have a similar issue. Only mine seems to make the focus farther in. I notice when adjusting the focus in it starts to get more focused, but I hit the end before it is completely focused.

I have a Celestron PowerSeeker 70AZ if it makes any differences. I've tried the barlow with all three eye pieces, with and without the diagonal to no avail.

I can focus on jupiter with no problems without it. But with it I just can't seem to get anything in focus.

I will try playing with it in the daylight to see if that helps. If there are any other suggestions I am open to them.

[brantuk]

The scope has a focal length of 650mm so a 10mm eyepiece will give 65x magnification (Mag=focal length/eyepiece size). A 3x barlow will give you 195x magnification. In average UK seeing conditions you are hovering on the limit of around 200x for most scopes.

I do most of my viewing around 180x - more is possible but it depends on the "seeing" conditions and to go higher requires a really clear night and good transparency. It also depends on scope temperature (is it cooled enough), elevation of the object (higher is clearer as you're looking through less atmosphere), collimation of the scope, and with a focal ratio of f-5, quality of the eyepiece.

Supplied eyepieces tend to be a bit naff on the more basic scopes like this one - especially barlows. Imho this scope would be more effective with a 2x barlow of slightly better quality. The 25mm eyepiece plus 2x barlow will give 52x mag and will deffo come to focus. Try a Tal 2x barlow for around £35 - its a good vfm budget piece. With the 10mm ep + Tal 2x you'll get 130x mag which will be just useable.

[Starlight 1]

The way I get round this is to put the barlow and eye piece in ,put the focus tube all the way in ,Then move the focus tube out about 10mm and then slide the barlow out by looking in the eyeiece till it come in focus and carry on just past it and lock the barlow off, Now move the focus back in till back in focus.

(its not right but it will work.)I think this may work like turning a x3 into a x2 one.

[ronin]

Edit; Went outside and tried to focus on a distance Chimney and managed to do so with the 20mm lens and Barlow. I didn't drop the Barlow the hole way down the lens chamber, maybe only one third of the way down.

The focal plane of the mirror will be further out when using something like a chimney, they are simply closer to you so the image formed will be further out, so you would not have to have the place the whole lot as far in.

So I wouldn't hold out hope that this will solved the problems when on an astronomical object.

How well set up (=collimated) is the scope?

Also with the magnificationyou are using you are only looking at a small bit of the sky. The moon is small so even observing that you have to point at it accurately. A lot more then you realise.

May be a stupid question but, can you put the barlow in the wrong way round? If so have you? I don't have one so have no idea but it is a possibility.

[Starlight 1]

Hi Ronin I only way I can see geting a barlow the wrong way round may be if someone have put the glass in up side down is that a possibility.

[steelfixer]

Hi there.

If you cannot get enough inwards travel on the focuser try putting an extension tube in first.

[brianmc]

Brantuk says further up, and it's mentioned several places on these forums, that 200x magnification is about the best you can achieve in the UK. Is that for any scope? I have a 200p which is supposed to have a maximum practical magnification of 400x, am I wasting my time trying to achieve that?

[brantuk]

You can get more magnification than 200x when the seeing and transparencey are nothing short of excellent - but those ocassions are few and far between in average UK seeing. I've heard people reaching 300x-330x but it's very rare. Not been much over 220x myself - not even at Kelling

[cosmological]

Brantuk says further up, and it's mentioned several places on these forums, that 200x magnification is about the best you can achieve in the UK. Is that for any scope? I have a 200p which is supposed to have a maximum practical magnification of 400x, am I wasting my time trying to achieve that?

Who told you that?

For a 200p the maximum practical magnification is 200x but the maximum theoretical magnification is 400x, in reality you won't get up to 400x.

[Starlight 1]

I never try to work one out ,If I can see it that will do for me.

[brianmc]

Cosmological, it says on the FLO web site: "Highest Practical Power (Potential): x406"

[AstroTux]

Just a quick thought, I have the same 'scope as well and used a 40mm eyepiece quite effectively with it for some time until I learnt how to collimate. When I went through the collimation process I noticed that the secondary mirror was a long way from the primary and NOT centred in the eyepiece. I corrected this and achieved much better views with all my other eyepieces, but could not achieve focus using the 40mm.

I then realised that what I had effectively down was to move the focal plane further out along the focussing tube, so tried the 40mm with a 1.5" extension piece and can now get good focus no matter which EP I use.

Could it be that your 'scope is somewhat out on the collimation front? BTW I use a 2.5x barlow quite a lot with my 15mm EP and get (what I consider to be ) good views.

[LukeSkywatcher]

The focal length of this scope is 650mm (same as my 130mm SW Heritage). When i was seeking advice on a barlow for my scope i was told that a 3x barlow would be too much for it to deal with and i should go for 2X.

2X works fine with my scope.

Also you have to consider that the 10,20mm EP's that come with most scopesa really are not of great quality. Yes they work and are fine until you start to push the bopat out and get better quality EP's.

I think (from what i was told)...........................3x on a 130mm scope is pushing it beyond what it can actually do.

My first scope was a 90mm refrac (f/l 1000mm)...............could i see ANYTHING through it with a 2x barlow?

Not on your nelly.

[Dark Infinity]

May be a stupid question but, can you put the barlow in the wrong way round? If so have you? I don't have one so have no idea but it is a possibility.

I'm new so no question is a dumb question, but given that one end is a male end and one end is a female end it would be very hard to put it in backwards.

I think I will chalk it up to air quality and elevation. It was a bit cloudy that night and Jupiter was a little low in the sky. I may have to try again on a clearer night. I'll try some of the suggested tricks here with adjusting how far in the barlow is set as well. Thanks for all the help.

[LukeSkywatcher]

Any barlow will only fit one way.

[Patricia G]

I have the same problem with my 3x Barlow.  When I try to focus on Saturn with my 700 mm Explorascope, and I thought at first it was cheap optics, but Saturn appears as a blur and then disappears  altogether.  I am trying with my 10 mm scope.

[Peter Drew]

Hello Patricia, welcome to SGL. You have replied to a 2011 thread, might be a good idea to start a new one to highlight your problem so that we can start to help you resolve it.