can't work out my sums...

[estwing]

hi there clever people, please help me i thinkin of getting a x2 meade barlow but what magnification will this give me with a 16 and a 25 eyepiece on a telementor. sorry as you guys must get fed up with basic questions like mine..

[John]

What is the focal length of the Telementor ?.

To get the magnification, divide the focal length of the scope by the focal length of the eyepiece. To calculate the effect of a 2x barlow lens just double the magnification figure for each eyepiece.

[estwing]

f13.3 i think i've read somewhere?

[estwing]

sorry 840mm...i'm thick me.

[John]

So:

840 / 25 = 33.6x (25mm eyepiece alone) or 67.2x (25mm plus 2x barlow)

840 / 16 = 52.5x (16mm eyepiece alone) or 105x (16mm plus 2x barlow)

[estwing]

yep sorted now thanks john

[estwing]

i suppose too much magnification and planets will be moving at a fair old pace across my view?

[Ad Astra]

Magnification makes tracking with a dob a bit challenging over 150x, but my students & I have no problems at mags less than that.

Make sure your bearing surfaces are clean (sticky bearings makes it tough to move the scope smoothly and makes tracking a chore).

Dan

[AndyH]

Hi.

I'd virtually guarantee that your scope can take a hell of a lot more magnification than 100x. It's a top notch lens that either will be similar, or perhaps a shade better than my Carton 60mm lens. I use around 150x with no image breakdown on mine. Gives lovely views of the planets.

I use mine on an alt/az mount and with a bit of practice, it becomes second nature to keep the object in view, with a few nudges now and again.

Go for it.

Andy.

[estwing]

hmmmm maybe 0.965=1.25 adapter then x3 barlow and a new 10mm eyepiece? would that be pushing a telemetor?

[AndyH]

How are you using your telementor?

Straight through with a 0.965/1.25 adapter or a 0.965/1.25" diagonal?

I'd guess, going with my experience with my Carton, a 5mm eyepiece(or barlow/eyepiece combo giving 5mm) may be the highest you want to go for planets, giving 168x. If the seeing is good, it should hold up okay.

A 6mm giving 140x, may get more use.

Cheers,

Andy.

[estwing]

straight through...i really wanna go as much as i can for about £100

[AndyH]

Have you come across this Zeiss Telementor site?

Lots of interesting stuff.........

Unofficial Zeiss Telementor Web site

Andy.

[AndyH]

If it were me, I'd forget about the barlow and simply have 3 eyepieces.

25mm giving 34x

9mm or 10mm giving 93x or 84x

6mm giving 140x

A nice range of magnifications.

Along with the 0.965"-1.25" adapter, you should be able to get them all for under £100. With careful shopping around, you may be able to squeeze in a decent diagonal, which will help with the neck strain, when viewing higher up objects.

Cheers,

Andy.

[estwing]

just found a 0.965 4mm on fleabay for a tenner and SnS have a meade x2 0.965 barlow at £30...thanks for the link mate..cann't believe how much the jena eyepieces are!