I could not resist the urge to go out last night despite a waning gibbous Moon, so pointed my scope in the opposite direction.
Guiding was crap (but can we discuss this in a separate thread please).
Only 3 subs as the clouds rolled in.
3 x 5mins ISO 800, flats, darks Canon 450D Modified, guided (Hmm)
Processed in DSS and photoshop.
(http://www.caroleastronomy.webspace.virginmedia.com/_wp_generated/wpf4d7710a_0f.jpg)
Other than needing flats applied it's very, umm, purple ...
Robert, it's got flats applied, the new style ones I did. Yes I couldn't seem to get rid of the purple. Do you think the colour overall is too red anyway?
Carole, you've resolved the nebulosity well there, and with more subs you won't have to stretch it so much to pull out the detail, also as Robert mentioned, some flats would do this the world of good
Daniel
:O)
QuoteOther than needing flats applied
Quotesome flats would do this the world of good
There were 12 flats applied to this image!! Should I have only used the same number of flats as subs (i.e.3)
I'm pretty disappointed with this as it could have been so much better
a) Because of the guiding. b) Because after all the effort of setting up I only managed to get 3 subs.
But still pleased to have got my first NA nebula.
Quoteit's very, umm, purple
Is this slightly better colour wise (or not).
(http://gallery.orpington-astronomy.org.uk/albums/userpics/10047/normal_NA_nebula_25_10_10_3_x_5min_%2B_darks_0_5_degrees_processed~0.jpg)
Carole
Carole,
You've chosen an ideal size of target here! All the main features of the Nebula are visible - so very well done on that front.
It doesn't look as if flats have been applied. Or maybe you didn't give DSS the bias frames and so it couldn't apply the right amount of correction.
There's also something really bad with the colour balance - far too red. It may be that DSS has screwed up your data with some kind of colour balancing/scaling. I had the same (horrible red) problem with DSS on one of the few occasions I've used it. Duncan (AKA "The Thing") also created a DSS image with weird brown colours recently.
unfortunately, I'm not familiar enough with DSS to know what the issue might be.
Mark
QuoteOr maybe you didn't give DSS the bias frames and so it couldn't apply the right amount of correction.
Aha, just remembered I forgot to add a bias frame. Might do a re-stack.
DSS was definitely processing the Flats.
Maybe the red is me processing it too red.
Carole
QuoteDSS was definitely processing the Flats.
Should read...
DSS is definitely buggering up the Flats.
It is most definitely!!! Probably because of the Bias which should always be used with flats. Not sure about DSS but MaximDL definitely needs them.
Too much RED, get the star colours looking right then it'll look more natural.
Robert
OK, I've done a re-stack and re-process this time remembering to apply the Bias frames and it has come out completely different with much less processing required. It is interesting how much difference Bias frames have made to this.
(http://gallery.orpington-astronomy.org.uk/albums/userpics/10047/normal_NA_Nebula_Re-Process_adding_Bias_frames.jpg)
Great improvement Carole
That's much better - the flats are working now. The colour is also looking better. For 3 short subs from a light polluted area this is not bad at all!
The top left is still too black - you need to adjust the black level to bring out the detail here.
Once you've done this, you'll then notice quite a lot of backround gradient across the whole image that needs to be removed. Such gradients are always expected when imaging in light polluted areas (even when using a CLS filter). Unfortunately they are always a pain to remove.
Thanks Mark, some good lessons learnt there. I'll have a go at the black level, but I already tried removing the gradient without success.
Carole
Good capture,
Colour balance,...............................your getting there.
Just need to add a few more light frames.
And get your processing up to scratch, still you do like a challenge ;). Light blue touch paper and retire.
Above all, you are getting images, so thats all that matters.
Mac.
Thanks Mac.
I don't expect to get it all right first time, so long as the next time I do an object it is an improvement on the previous time I am happy, and hope to "get there" eventually.
Yes I do like a challenge.
Carole
One last go at the processing before I put this one to bed.
Have reduced the gradient on the right hand side a little.
(http://www.caroleastronomy.webspace.virginmedia.com/_wp_generated/wp2d6f00e9_0f.jpg)
Carole,
You're there! Just compare that to the "purple monster" you produced earlier!
You have processed that almost as well as it can be - the only thing lacking in that image is good data. If you could go to DSC and shoot 2 hours of NGC 7000 data you would be stunned by how different the result would be - you would have your first really good image.
Even if you take 2 hours of data from home (24 subs) you would greatly improve the signal to noise ratio - it would be 3 successive doublings of the number of subs (3,6,12,24) and you can predict what a difference that would make by looking at the example in my earlier posting: http://forum.orpington-astronomy.org.uk/index.php?topic=6656.0 "How image quality increases with number of subs "
Mark
Thanks Mark, yes I realise that the number of subs was insufficient but clouds intervened, and yes I understand about
Quote"How image quality increases with number of subs "
At the end of the day all the subs I have taken are just my first stab at each object and that alone is a lesson, not even knowing how big and object is until I've actually captured it, so I am glad to get even something as basic as this and use it as my starting block so to speak.
I first of all need to get my guiding problems sorted out, and I think I am getting there with my flats now.
So hopefully the only way is up ;)
Many thanks Mark.
Carole
Quote from: Carole
... not even knowing how big and object is until I've actually captured it
Use your planetarium program to show you in advance how big it will appear in your FOV.
Mark
This also gives a good visual guide
http://www.newastro.com/book_new/camera_app.php (http://www.newastro.com/book_new/camera_app.php)