Yeah folks, I know I probably shouldn't share these but these were taken on my first imaging night before I'd had expert help with my polar alignment. Therefore, the stars are bloated and a little elongated, but still...I'm surprised what signal was there.
Canon 1100D attached to a C8 Edge HD with 0.7x reducer on my EQ6.
The Dumbbell M27 stack consists of 36x 50s exposures at ISO1600
The Ring M57 stack consists of 31x 30s exposures at ISO3200
No darks, no flats, and biases only for the Dumbbell. I had intended to go back to these and get more data, and get darks, etc, but got distracted by other objects (see my previous AstroFest posts!)
I wasn't going to share until I saw how they came out...I'm not unhappy with them but I know I could have done better with a little more effort
They also need more exposure time...I think another hour or so would bring out the Dumbbell a bit more and allow me to dump some of the lower scoring frames in DSS
The Ring is an interesting one...I'd like to set the scope on it at f/10 one day, and obviously for much longer...I feel the image is lacking in definition compared to what I've seen visually, although the colours and central star are not things I can claim to have seen through the eyepiece
As an aside, from another thread where we've touched on the difference between single frames and stacking...I've added two more images - first the best scoring frame from the sequence untainted other than saving as a jpg within the file size constraints, and second the same frame with exactly the same processing steps applied as they were to the stacked output.
One interesting point here is that I don't think I've done the green hue enough justice in my processing...it's more cyan in my end result and more aqua in the original shot. Looks like I need to go back and add a few more steps
Not bad Dunk you should be happy with those. I have noticed lately that there seems to be a trend to image short exposures at high ISO. The high ISO seems to get more colour into the image. Did you have any difficulty removing the noise ?
Thanks Rob! For the Dumbbell, the stack was pretty clean already. For the Ring...I struggled with that one...not because it was particularly noisy, but just because - having spent a lot of time visually observing the object - I was having a hard time deciphering the noise from the texture I know is there in the object. Need more subs and a bigger scope
Incidentally, most of my shots taken at AF were at ISO1600... a bunch of things I'd read around claimed that's the sweet spot for signal:noise , where the noise is kept under check up to 1600, then goes crazy beyond that. I've disabled all the in-camera noise reduction functions that I'm aware of.
Last edited by Camelopardalis; 16-08-2014 at 12:32 PM.
So I started from scratch again with this one, employing quite a different "technique" than the first one...
It was interesting to do, but I think there's a little too much green push and the red edges are more magenta/purple than I'd like, although to be fair I'm looking at images on the web and the colours really vary quite a bit
Any thoughts chaps? Where to go with this? Besides gathering heaps more data and starting again Which one is more "true" ?
Hi Dunk, They all look pretty good to me. At some point I think it comes down to personal choice. For me I think somewhere between the blue and green would look smashing. Sometimes if I'm struggling to know what colour an object should be I take a single raw shot and stretch it with the channels linked. I don't do anything else to it just stretch it to see what colours the camera picked up for different parts of the object. Of course this doesn't always work depending on ur filters and set up, but sometimes can help.
You know, I don't think I've ever processed an image the same way twice. They always turn out different lol. There is no spoon, er I mean true. That went out the window ages ago. Even different coatings on a refractor lens will make for a different result.
I try and follow a couple of personal rules in processing. Make the background colour neutral, unless in the milky way or the guts of a big nebula. Don't black point clip. Get rid of vignetting / flat field the pic. Feed the cat before processing lest the animal walk all over the keyboard. The rest are subjective.
Not bad Dunk you should be happy with those. I have noticed lately that there seems to be a trend to image short exposures at high ISO. The high ISO seems to get more colour into the image. Did you have any difficulty removing the noise ?
Rob
With camera sensors that are not so sensitive to the red end of the spectrum short exposures tend to lack the red details which these pictures though nicely detailed and showing a lot of depth are missing . More photons has got to give better colour detail in pictures ! What you don't collect you can only imagine !
This is not a criticism of the pictures which are really nice !
Regards philip
Thanks for the tips chaps, I'll try again the next time I have a decent polar alignment it seemed to be gathering data quite nicely at f/7 for the Dumbbell, but I want to try f/10 for the Ring. I know it'll take ages
I suggest that you take a single longish exposure, say 60-90 secs
at high ISO, say 6400; disregard noise, trailing etc: A look at the
camera screen will give you a good idea of what the colours should look like,[not the intensity, of course], when the subs are stacked. The
colours in the single subs that I posted recently are exactly the same
as in the final stacked result.
raymo
Thanks raymo, yeah luckily I did have a positioning/framing shot which was 30s at ISO6400, and this repro is pretty close. I fear I may have lost a little of the red detail crossing the core that was visible in the original (paler blue) version but I'm done trying to tease out aqua so this is the final offering
but these were taken on my first imaging night before I'd had expert help with my polar alignment. Therefore, the stars are bloated and a little elongated, but still...I'm surprised what signal was there.
(see my previous AstroFest posts!)
