tilbrook@rbe.ne
14-09-2012, 02:28 PM
Hi,
In the past two weeks I've been doing some testing with a recently purchased 2x ED barlow. The reason for going in this direction is there has been some good images obtained on smaller bright planetaries with barlows.
My main concern was that my tracking was good enough to run at 1600mm F/L, fortunately no problem there.
I picked NGC 253 becuase it's bright, but also has fine detail to see if the resolution with the barlow was acceptable. It turns out not too bad, considering the night I imaged was warm, so there was a fair bit of noise and the seeing was not good.
The other thing I've been doing is modifying my 8" F6 scope to use with the barlow. I had to completly remake my home made tube assembly, make a new mirror cell and mount a 2" focuser. Another test image of NGC 253 shows it has good contrast, but there's flexure in the optical train. This has come about by trying to make things too light, to keep it to a weight that the HEQ pro 5 mount could handle.
So it's back to the drawing board on this one.
I nearly stuffed up my mount , with the extra length of the f/6 when I slewed the scope. It hit the shelf in the dome and made a horrible noise in the drive. My heart was in my mouth until I reset the mount and tried again! Phew!!
Anyway here's two images one throught the 8" f/4 astrograph with 2x barlow, and one through the 8" f/6 parks optics.
Cheers,
Justin.
In the past two weeks I've been doing some testing with a recently purchased 2x ED barlow. The reason for going in this direction is there has been some good images obtained on smaller bright planetaries with barlows.
My main concern was that my tracking was good enough to run at 1600mm F/L, fortunately no problem there.
I picked NGC 253 becuase it's bright, but also has fine detail to see if the resolution with the barlow was acceptable. It turns out not too bad, considering the night I imaged was warm, so there was a fair bit of noise and the seeing was not good.
The other thing I've been doing is modifying my 8" F6 scope to use with the barlow. I had to completly remake my home made tube assembly, make a new mirror cell and mount a 2" focuser. Another test image of NGC 253 shows it has good contrast, but there's flexure in the optical train. This has come about by trying to make things too light, to keep it to a weight that the HEQ pro 5 mount could handle.
So it's back to the drawing board on this one.
I nearly stuffed up my mount , with the extra length of the f/6 when I slewed the scope. It hit the shelf in the dome and made a horrible noise in the drive. My heart was in my mouth until I reset the mount and tried again! Phew!!
Anyway here's two images one throught the 8" f/4 astrograph with 2x barlow, and one through the 8" f/6 parks optics.
Cheers,
Justin.