This image was more an experiment with a Newtonian I bought in March and not used it yet. Its a Skywatcher 150P (not the PDS version) so was not even sure I could get focus, I had been planning to get a SW130PDS, but as this came along for half the price, I thought it was worth a punt.
I definitely think this needs a dark site as it is quite noisy, but am posting up for feedback and advice.
a) I had a coma corrector in place which I bought with the scope, but I think it is probably designed for a DSLR and have no idea what the spacing should be with a CCD camera, there does seem to be a bit of coma, esp top right.
b) Some of the stars look a little flattened at the top, not being experienced with a Newtonian, could this be something to do with the focusser?
Well at least I got myself out and imaging for the first time from home for about 6 months, but running out of targets that are suitable from Bromley. There is a definite difference between data done at home and a dark site even with narrowband.
No idea what this is supposed to look like.
Ha 9 x 900 secs
Oiii & Sii each 7 x 450 secs binned
Atik 314L & SW 150P
(http://cdn.astrobin.com/images/thumbs/4a2bda39352003c3078f190ba15c6b61.1824x0_q100_watermark.jpg)
Well I was hoping for some sort of feedback. I know this is not the greatest image in the world, but it was the technical issues I wanted advice on.
I seem to have found an answer to the coma question myself and it's a personal gaff.
I have just de-rigged ready for Kelling, and found the extra "nosepiece" I had put on the end had a lens in it !!!! I had put on my field flattener instead of just a spacer/extender, so there was double flattening going on. (Hmm, the trouble with doing things in the dark).
I am probably not going to stay with this coma corrector anyway as it is not a reducing type.
However would still like some feedback on the major stars which seem flattened on one side, is this something to do with the focusser? I know many of you don't use Newtonians, so maybe I have to take my question elsewhere.
Carole
The stars are flattened on one side and they have a diffraction spike running through the flat part. The flat part is difficult to explain but the diffraction spike will be caused by the edge of some component or a wire interrupting the cone of light. Maybe that also explains the flat bit, I don't know.
Do you see it on all 3 filters?
Mark
I am on holiday ATM but mark this is a Newtonian so is supposed to have spikes.
Quote from: Carole
I am on holiday ATM but mark this is a Newtonian so is supposed to have spikes.
The spike in one direction is far stronger than the spike in the other.
To diagnose this I would:
1) Check the collimation
2) Take some defocused images of a star - defocused inwards and outwards and with successive amounts of defocus
The results might give some clue as to what is going on.
Mark