M83 and Centaurus A

[Nico13]

Well finally got some time out with the gear last night and was trying different things to reduce the vignetting when taking images through the 8" Meade SCT.
Had been using the f6 flattener reducer and running focus right out to the furthest back focus point and while this reduced the vignetting some what it didn't do much for the focus and aberrations at the edge of the image even with the corrector in so I wound up working with just the camera and cropping the edge slightly to remove the worst at the edges.
Sky was clear, seeing was average to good, more average I think.

Centaurus A was
102 min of 6 and 3 min subs with darks applied in images Plus and CS6
Pentax K5 at ISO 800
M83 was
72 min of 5 min subs with darks etc, I stopped there as I needed to flip due to crossing the meridian.
I should have done some 8 min subs as I had done some test shots on this last month and got better colour but forgot that I'd done them so went with the shorter subs. I've added an inverted image of M83 just for interest so you can see the galaxy structure a bit better.
ISO 800 again Camera seems to give best results at that as its not cooled.
Mount and guiding details below.
Thanks for looking and comments welcome as usual.

[Larryp]

Nice images, Ken:thumbsup:

[Peter Ward]

Ken, if you want to improve your images, you'll need attention to detail after this.

Is the image truly in focus?
Are the stars eggy or round?
Points or doughnuts?
Is the colour balance cyan (or something else) or neutral?

I won't say these are great examples of well known objects....sorry they aren't... as you've not ticked the boxes above....but you are headed in the right direction :thumbsup:

Stick with it.

[Nico13]

Thanks Laurie and Peter,
Yes Peter you're comments are so right and focus is an area I struggle with, inparticular with deep space objects on the SCT with a DSLR camera and multi focal lens glasses. I think that let's me down much more than anything else.
I,m able to get much better results when shooting through my ED80 as the wider field is less critical.
I,m not happy with SCT and its field curvature so would love to go to something a bit faster and with a flatter field like the GSO RC for instance, if the Tax man is kind to me this year I may invest.
Thanks very much for your honest remarks.:thumbsup:

[jjjnettie]

If you invest in a copy of Back Yard EOS, it has a focussing tool that is very simple to use. Just keep tweaking until it gives you the lowest number.
If you aren't using a field flattener you can use the Lens Distortion filter in Photo Shop to correct the field. It's in the Filter section.
I use it all the time with my new scope, it works a treat.

Love the pics btw.

[astronobob]

Not too shabby Ken, long focal lenths arent very forgiving with mentioned focus & coma !
Im a little baffeled with how many exposures you have taken, ie -Centaurus A was
102 min of 6 and 3 min subs ! so can it be 17x6min & 34x3mins or were they more aprox, 10-11 images of each totaling 102 mins between them there abouts ?
I do like the scale of these targets too :thumbsup:

[Nico13]

Thanks JJ,
Yeh normally if I take the Meade flattener reducer out I'll put the Orion Flattener from the ED80 in as it works reasonably well in the SCT as well but I was a bit peeved with the setup not working as well as wanted and so when I pulled out Meade reducer flattener I just plain forgot to put the Orion one in.
Backyard Eos is a nice idea but unfortunately I'm using a Pentax, not sure it would work with that. I will give PS filters a go though.


Hi Bob,
Yep you're right about the long focal lengths being fussy, it's gotta be just so, so correct so I definitely need to do something about a focus aid of some sort.
The Centaurus A subs shot were 12 x 6 min and 10 x 3.
I did that to try and help with reducing star saturation and bloom.

Just going back to what Peter had said while these are far from being really good they are better than previous efforts and so from that point I'm pleased to be improving and happy I still have a challenge because this is what we enjoy I think, the challenge.

Thanks for the feedback. :thumbsup:

[Peter Ward]

Ken...thanks for accepting my comments in the spirit in which they were given.

There is so much mis-information on the web.

It can also be hard to progress with the usual PC "that's a great pic" responses.

If there is one aspect to my own images that I can do well with, it's getting great raw data. You can't...as my son likes to say... "fix it in post-production"

Things you can nail are focus & tracking. To try afterwards with software is folly.

NASA made that pretty clear when they fixed Hubble.

Starlight is free... hence you can have a lot of fun trying to understand why focus/tracking isn't perfect, and making adjustments to make them so.

[Nico13]

Thanks again Peter,
Yes I only have to look at my own work and do a quick comparison to a good image of the same target to see I have a way to go and as I mentioned I really enjoy the challenge it give me something to aim at and yes I would rather work with good data than try and fix not so good afterwards.

[whale]

Great work Ken!