Barlow for Imaging?

[pauldaviesuk]

Hi all,

I'm having lots of fun shivering under the stars waiting for my DSLR to soak up those photons, but so far the image scale of the images I've been capturing have been rather small.

I'm not surprised - I'm using an 80mm f/7 OTA with a 22.2x14.8mm sensor, which should give an image about 2 degrees across, which is exactly what I see - M57 comes out at about 40px.

That said, it'd be nice to be able to capture some larger (scaled) images, so I'm thinking a 2x or 3x Barlow might be the solution.

However, when imaging at the moment, the draw tube on the 'scope is (almost) fully extended, and the camera is attached to the 'scope with a WO Photo Adapter . I'm wandering whether adding a barlow into the mix will push the focal plane of the system so far back I won't be able to achieve focus.

Am I worrying over nothing, of might I have a problem here? And if all is well, which barlow would be recommended (I don't have an infinite budget for this, so a TeleView, while desirable, is not really an option!) ?

TIA

Paul

[Pete Presland]

tal barlows are well recomended on here for vaue for money.

i have just upgraded to a celestron ultima,and while it is better than the tal i used to own, the tal is not far behind.

you can also pick up a meade shorty for around £20 2nd hand

[pauldaviesuk]

Are those 2" or 1.25"?.. I was pondering a SW 2" ED barlow @ about £60..

Paul

[Merlin66]

A costly but very very usable solution is a TV powermate. The amplification doesn't vary with back focus....

Ken

[SteveL]

Dont forget that adding a 2x barlow to a f/7 scope will make its a very slow f/14 system... isnt that 4 times slower or something?

I did add a 2" 2x Powermate to my Skywatcher 190 MakNewt to get a 2000mm FL f/10.6 imaging system. OK for bright objects like globs, but I really wouldnt want to be imaging anything dim with it....