First Astro image

[Sierra Golf Mike]

Here is my first astro image as directed in the Sticky for Widefield with tripod. After stacking in Deep Sky Stacker the tif output is shown in image A (converted to jpg). Tried curves again as shown but very little difference. Then tried levels and brought out more stars but it's just not quite right. Obviously this one was done parrot fashion as I don't really know what I am doing but any help to get a more natural appearance would be most appreciated.

Steve

[jgs001]

Steve, what camera settings did you use ? Do you have the tif anywhere that we can get at it ?

Looking at the second image, I'm not sure DSS stacked any images... the branches are not blurred, which I would expect if the stars had been stacked. In fact, the branches look to be just about in focus, which would imply the stars won't be, which could well be the reason that DSS was unable to combine them. Run the stack again, and once the final image is displayed, look above the image, it should tell you how many frames were combined, I think it'll say 1.

[Ewok]

I like these images, I am hoping to have a crack at doing my own soon. Keep it up and promise to post back , if I get any i will share them with you too.

[Sierra Golf Mike]

Hi John,

Many thanks for the quick reply, I know this is going to be a very steep learning curve but I really want to crack it.

Camera settings 18-55mm lens opened wide then zoomed in slightly, F5.6, 30 Sec, ISO 800. My first run through DSS gave me a warning that only 1 sub would be stacked, eventually I found the threshold setting and dropped that to 2% then it said 8 images would be stacked (loaded in 10 images and 5 darks). The tif file is enormous, nearly 50Mb so don't know where I could put that (open to suggestions). Attached is a jpg version of one of the subs for reference if that helps.

Cheers

Steve

[jgs001]

That's a bit clearer... there's some cloud in there, and I'm not totally convinced on the focus... both of which will affect DSS's ability to stack. As for the TIF... something like megaupload ?

[Sierra Golf Mike]

John,

Currently uploading tif to megaupload I will let you know when it's available. In the mean time, the focus was set to infinity, I don't have live view but looking through the viewfinder anything less looked blurred. It was a very quick spur of the moment session when I spotted a bit of clear sky but I will look at the focus in daylight. I'll be happy if it's just clouds and focussing that are causing the problem.

Cheers

Steve

[jgs001]

What lens are you using Steve, some of the lenses, actually allow focusing a little beyond infinity (as odd as that sounds), I've heard it's too allow for thermal changes, but it means you can't rely on twisting the focus ring to the stop and leaving it there.

[Sierra Golf Mike]

Tif download link MEGAUPLOAD - The leading online storage and file delivery service Have a look and see what you think.

Cheers

Steve

[Sierra Golf Mike]

It's the standard kit lens 18-55mm, it's not a great lens I know but I think you've hit the nail on the head. Just tried manual focussing and it does indeed focus past infinity so that will be my starting point. I'll have another go and see what happens.

In the processing, what am I trying to do with the curves/levels to get a natural look?

Steve

[Sierra Golf Mike]

Thanks Ewok, this was my first attempt, lots to learn before I get good results but it's a start.

Steve

[jgs001]

Steve, a quick edit, GIMP is rather limited being only 8 bit with how far you can push it (using curves, rather harshly) but... I've taken a look and the stars do indeed look a little blurry

[Sierra Golf Mike]

John,

Next oppotunity I get I'll try a better focussing technique.

Thanks for your help.

Steve

[Photosbykev]

I think the basic problem, other than focus, is lack of data to process so I would suggest opening the aperture as much as possible. The D30 probably isn't worth taking over iso800 but shooting a number of darks i.e same exposure with the lens cap on, will reduce the noise and allow you to stretch the final image slightly more.

Turn off the in-camera noise reduction and use the darks in DSS to control it. Also turn off all the auto functions, set WB to daylight and have another go

[Sierra Golf Mike]

Kev,

Thanks for that, there was 10 subs at 30 sec and 5 darks at the same. Noise reduction was off.

Cheers

Steve

[Photosbykev]

Kev,

Thanks for that, there was 10 subs at 30 sec and 5 darks at the same. Noise reduction was off.

Cheers

Steve

I think you will need more than 5 darks, try taking 15-20 of them and more subs as well.

[themos]

There's also a red swirling pattern (seemingly going around the North Celestial Pole) in the sky background which suggests that the darks were too noisy, you need to collect more of them!

The NCP is just under the tip of the leftmost branch with Polaris and Lambda (orange star) nicely encompassing the NCP.

[Sierra Golf Mike]

There was one or two wispy clouds about, could have been that. Now darks, do you have to take new darks each time or can they be reused?

Cheers

Steve

[jgs001]

I reckon it's the clouds, as I mentioned earlier. If the temperature is about the same you can use the same darks, if not, then you really should reshoot them. I've only ever used 5 darks and found that beyond about 15 lights in this technique you lose the upper right and lower left corners to smearing thanks to field rotation... but try more and see how you go... Bear in mind I wrote the tutorial as a very basic method for people on a photorgraphy forum to try out some astro photography without investing in mounts, scopes etc.

[themos]

No, it wasn't the clouds, it was noisy sky background being rotated to match something and so the peaks of the noise were getting all smeared in a swirly pattern around the North Pole.

[Sierra Golf Mike]

Themos,

Sorry, I assumed that because there was cloud about that that was the cause. Many thanks for your input.

Cheers

Steve

[jgs001]

Sorry themos, I just figured that a lot of the oddities were down to posterisation from how hard I stretched it in 8 bit... it doesn't look anywhere near that odd stretched in 16 bit but it's not got enough signal...

[themos]

I downloaded the tif and opened it in IRIS, the red swirly pattern is just above the sky background level.

[jgs001]

Ah ok.. sorry

[themos]

This is like CSI:Image Forensics!

[themos]

Here's what I mean