bad focus on same moon with SW ED120/900 26/12/2010 -

[luis]

Hi everybody. Sorry only now cameback.

Its the other single photo jpeg unstacked, I tooked with a barlow in my canon DSLR.

I don´t know why the focus got so bad. I don´t have a flat field, should be it the problem?

Greetings from Portugal,

Luis

[firstblooduk]

I know im a newb but could it be collimation out?

[firstblooduk]

Never mind you have a refractor :S

[jgs001]

It almost looks like a depth of field issue, although at these sorts of working distances I'd be very surprised... It might be distortions from the barlow at the edge of the field... Barlows aren't really designed for the large sensors that an SLR contains... How does the image come out if you don't use the barlow ? I use a teleconverter, instead of a barlow, which is optimised for the camera...

[Shibby]

Probably aberration caused by the barlow?

[luis]

It might be distortions from the barlow at the edge of the field... Barlows aren't really designed for the large sensors that an SLR contains... How does the image come out if you don't use the barlow ?

Since only center is in good focus, Yes, can be like a coma efect in the edge of the field.

Can be possible the weight of the camera in the focuser desalign the focus? (the camera is not heavy)

Without the barlow, the photos are field focus 100% great! so the problem is in the barlow.