Diagonal focussing problems

[Dazzalloyd]

Hi everyone, after buying my father a Bresser Messier R90 on a manual equatorial mount with great success viewing Jupiter,Saturn, Mars and the Moon, I decided too invest more heavily on a Telescope for myself. It took a year to come into stock but I have now finally taken delivery of my Bresser Messier AR 152S/760 F5 on a Meade LX75 mount with Autostar.

So far so good, it came with a 2" diagonal and a 2" 25mm wide angle eyepiece. Views were good but distant so I borrowed my fathers 1.25" Barlow and his 14mm and 9mm eyepieces. If I place these after the diagonal using the step down (to 1.25") adapter I cannot focus the image, if I take the diagonal off and just use the step-down adapter and 1.25" eyepieces I can focus and see a good image, however I had to kneel or lay on the floor to get a look in!

Should therefore the step down adapter go first in line and then must I buy a 1.25" diagonal to match the eyepieces? Or would it be better to get a 2" 3x barlow and keep using the 2" diagonal and 25mm eyepiece to get a bit more magnification?

[Mr Spock]

It's probably a focus range issue. Is the focusser all the way in or all the way out?

Try lifting the barlow out of the adaptor to see if it will focus that way.

[Dazzalloyd]

Hi, I tried with and without the Barlow attached, each eyepiece in turn.

The focus tube is all the way in, although I went through the whole range to be sure.

I tried all variations and the only way the 1.25mm eyepieces worked were without the 2" diagonal.

This a an achromatic refractor so there are no other adjustments I can make to the tube, but surely this should not be such a complex issue, as it was supplied like this and the step down adapter included.

I have also tried pulling out the diagonal a few millimetres, and the eyepieces too but this makes matters worse.

Any further help appreciated as it looks like clear skys tonight!

[brantuk]

Hi Darren - welcome to SGL Please check your private messages (pm's) thanks.

[AndyH]

I have turned into an in-focus junkie, so long have I strived to squeeze the last bit of in-focus available from some of my scopes.

So it defo sounds like a lack of in-focus. But a 1.25" diagonal will let the smaller eyepieces work. A low profile 2" diagonal may be a way round the problem and let both sizes of eyepieces to work in the one diagonal, but you'd need to measure just how many millimetres of infocus is needed. A high quality 2" prism diagonal(eg: Baader or Tak) would definately let both the 1.25" and 2" 'pieces work, but really good ones are very expensive. High quality star prisms are great but it's the cheapo ones that give them a bad name in the astro world.

There's another way round the problem, but it's a bit more drastic and involves using a hacksaw !!

Andy.