Centaurus A last night

[telecasterguru (Frank)]

Went to Crago last night and the seeing was pretty good until the moon come out.
This is 30 minutes of Centuarus A with matching darks (yes darks). 200mm Newt Canon 1000D iso 400 DSS ED80 guided PHD. Processed in PS but didn't like the way it was heading so very little processing. I need a lot of help with PS.

Thanks
Frank

[gregbradley]

Hi Frank,

Nice start.

I'd be using a much higher ISO than 400 though. I always used ISO1600 or 3200. Some say to use ISO800 as it gives better dynamic range although in this case you are imaging a dim object and your first target is capture enough signal to get a bright enough image. Photoshop can't sure inadequate signal so use a higher ISO and when you get a chance go for more exposure time.

So whack it up to ISO3200 and if you can go for an hour or more.

Is that a bit of coma occurring in your system or was it tracking errors?

First step there with autoguiding is accurate polar alignment and drift alignment is popular for that.

Greg.

[telecasterguru (Frank)]

Thanks for the advice Greg. There is a bit of coma in the scope as it is a f5 Newt. I would like to get an MPCC.
I will be out again tonight with a higher iso (weather permitting). I am used to imaging right in the centre of Sydney and I find if I push the iso higher than 400 it washes the whole image out and vignetting becomes a huge problem.
I spend a lot of time drift aligning to make sure it is right but I find that getting focus is the biggest issue.
Frank

[peeb61 (Paul)]

Hi Frank,
I would be happy with that outcome especially from the 'burbs.'
Keep at it mate.

Paul

[Peter Ward]

G'day Frank,

The scope looks like it needs some serious colimination to me due the fan shaped stars. No amount of post processing will fix that. A coma corrector is also a great accessory for Newtonians, which you might want to look at getting next.

Also take the time to really nail the focus, 5-10 minutes spent there can make a significant difference to the end result.

Stick with it!

Regards
Peter

[gregbradley]

Originally Posted by telecasterguru

Thanks for the advice Greg. There is a bit of coma in the scope as it is a f5 Newt. I would like to get an MPCC.
I will be out again tonight with a higher iso (weather permitting). I am used to imaging right in the centre of Sydney and I find if I push the iso higher than 400 it washes the whole image out and vignetting becomes a huge problem.
I spend a lot of time drift aligning to make sure it is right but I find that getting focus is the biggest issue.
Frank

Hi Frank,

That makes sense. I used ISO3200 at a really dark site.

Definitely get the MPCC and hopefully that will be the end of the comet shaped stars.

Images Plus has a nice focus routine. You use it just like a CCD camera. You take short exposures, they are downloaded and displayed along with a graph plotting sharpness or brightness and that helps show the improvement or worsening of focus.

Or you can use a Stiletto focus aid (ads for this are on Astromart all the time) or use the live preview of your Canon (does it have live preview?).

I am pretty sure you can zoom in on a section of the live preview on a Canon DSLR and that helps. Its hard to tell if something is in focus on a small screen on the back of the camera.

Stilleto is probably the way to go if you don't want to be stuck with having to use a laptop.

Once you sort your coma and focus it'd be worth finding a nice dark site to go to on weekends. You'd have a ball and you whack the ISO up and get a brighter image in 1/3rd the time.

There's something very peaceful about a dark sky at a remote location.

Greg.

[telecasterguru (Frank)]

Peter and Greg,
Thanks again, I take on board all that you say.
Also, I have posted an image of M83 that I took last night as well. Every thing was identical with the Centaurus image although with the M83 image I'm sure that I nailed the focus. I think it came up pretty well.
Been outside tonight but almost blown off my feet so it's back to practicing processing!

Frank