new eyepiece problems

[cutepetgroomer]

okay so I got some new eyepieces in the past few months.. The problem is they don't seem to focus at all in my short tube telescope .. my longer tube telescope they work no problem.. Here is as much information as I can give right now .

Problem scope specs:

Aperture 70mm

Focal length 300mm

 

Not problem scope specs:

Aperture 50mm

Focal length 500mm

Problem eyepieces:

Celstron 15mm (kellner)

celestron 9mm (kellner)

 

I do wear glasses for astigmatism and nearsightness. I honestly can't figure out what I am doing wrong.. IN theory the eyepieces should work fine as I have 6mm and 20 mm eyepieces in my collection that work no problem for either scope.. 

[Dave In Vermont]

Let's see if I have this right: The scope the 2 Kellners won't focus has an aperture of 70mm, and a focal-length of 300mm. This gives the scope 4.28/f. This scope sounds more like a large finder-scope! That's a mighty fast' refractor. I'm not surprised it won't come to focus.

Very fast optical-telescopes often have problems with certain eyepiece (EP) configuration. That the EP's in question are Kellners is rather odd - at least to me. But your Celestron Kellner's focus no problem in your F/10 50mm? Okay - it looks like these EP's don't like very fast telescopes. But I'm not really surprised you have a problem with the old Kellner EP design. But then when Kellners first came onto the (small) amateur-astronomy market, such fast scopes' weren't as prevelant as they are today. They were quite rare.

So I'm not surprised this has happened. You just don't hear about Kellner EP's these days. They were considered good EP's back when I first got a telescope in 1972 - a 75mm F/15 refractor. Which I fed on Kellner EP's, while wishing for an orthoscopic or two. No problem with Kellner's in that beast. What sort of EP's have you tried in your 70mm F/4.28 that do work? And what is your 70mm telescope? Brand-name, etc?

If no one else can find an answer, I'd say you need to try a different typs of EP in your speedy, little telescope. Low-cost zoom 8 - 24mm EP's work great in my 80mm F/5 refractor.

Keep us informed, please,

Dave

 

 

[cutepetgroomer]

The brand of my 70mm scope I'm not sure of.. But the eyepieces at do work are different sorts. There's an sr4mm, h6mm,h20mm, a Meade ma25mm, a Meade ma40mm and there's a 10mm I'm unsure of type. I also have a 3x Barlow.