Barlows and imaging

[Kevdan]

Hi Guys and Girls,

Is there a limit to what barlows can be used when imaging? I am under the impression that for example my scope is a skywatcher 150p and maximun magnification should be around 40x per ich of primary mirror diameter = 40x6" = 240x, But how does this relate to imaging as in the POW there is a fantastic image of M31 taken with the same scope as mine and (now i am asuming by the guys signature) a 5x barlow and a DSLR.

With my scope and a 2x barlow M31 is a smudge, Im probably wrong and do not want to take away anything from the guy that posted the pic but I wouldnt have thought a 5x barlow would make that much difference and what it makes up for in mag would lose it in quality.

Once again Please dont think im trying to belittle the pic or say it is a fake or anything like that, Im not, im just trying to work out how I go about getting pics like that with my scope and set up.

Im actually jealous.

Kev.

[Capricorn]

I assume that you are saying that when you look at M31 it is a smudge.

A DSLR (any camera) operates differently to the eye.

If you look at M31 for 10 minutes it doesn't change.

If a DSLR collects light for 10 minutes it builds up a picture.

In the eye the photons hit it and get absorbed, the next one does not add to the previous, on a DSLR it does.

Look at it the other way, if you look at a scene for 2 hours it remains the same. point a camera at it and open the shutter for 2 hours and the whole thing is blank due to overexposure across the sensor - soilid state or film.

[Kevdan]

Ah, My other problem with my Pentax is the viewfinder is frosted making it very hard for me to focus on "smudges", the moon is so big an dbright there is no problem but DSO's are very hard.

Kev.

[sirmetin]

This link seems to cover most focussing methods

Focusing Methods