Newbie, advice on barlow lenses.

[JonnyK]

Hi,

I bought a second hand 70mm refractor scope 3 days ago and im hooked. I've managed 2 nights looking at jupiter and saturn with amazement! My scope came with a terrible 1.5X erecting eyepiece which is o good for anything, but I was wondering if a 2X barlow lens would be a wise investment?

I only want to spend aroud the £15-£20 mark as my scope only cost £40, i've seen a few for this price on a few sites, would these be ok?

One last thing does anyone know of any good astronomy shops in or around the Lincolnshire area?

[bigbox]

Hi jonnyk, I'm in Nottingham the nearest shop to me is rother valley optics just south of rotherham. Im not entirely sure if there is any in Lincs to be honest...

Regards Ady

[JonnyK]

Thanks Andy, would I be right in thinking you just use a barlow lense with no eyepiece or photography?

[jflowers]

Your eyepiece fits into the barlow, effectively increasing the focal length either 2x or 3x depending on the barlow. I find it does decrease the contrast a little. It really depends on how powerful your eyepieces are. With a 70mm scope your maximum useable magnification is around 140x. Anything over that is going to reduce the quality of your image.

Do you know the focal length of your scope? if so, devide the focal length by the eyepiece size for the magnification i.e. 1000mm fl / 10mm eyepiece gives you 100x.

HTH

[JonnyK]

Thanks for the replies, it's a 700mm with 3 eye pieces which are 25mm 12mm and 4 or 6mm. Would it be worth getting a barlow lens for this?

[LukeSkywatcher]

I'd say its not worth the cost of buying one. You have 25mm,12mm and 6mm. A 2x barlow would only be giving you another 12mm and another 6mm EP. The view would be dimmer then if you just used the EP on its own.

There's a reason why i have not mentioned the 4mm EP. Most people have too much trouble using an EP of this size.

Stick with what you have.

[JonnyK]

To be honest I am getting some great views I was considering one mainly to try attaching a webcam for some video footage, don't think there is any other way of doing it?

[gurneyfan67]

Jonny,What type of eyepieces are they (eg Kellner Plossl etc). Look on the ep, if it says R or H next to the number the may be of poor quality anyway and the barlow will only decrease the image sharpness.

[JonnyK]

Kellner, not sure if they have R or H on them i'll check later. What do the letters represent?

[gurneyfan67]

The H stands for Huygens and the R for Ramsden. They were used on less expensive scopes usually with .965in diameter barrels. If yours are Kellner then they are better quality. The barrels are probably 1.25in.