First Tracked Canon 300D Shot

Hi All, I'm really posting this shot for some help with regard to processing techniques, It was super transparent and clear from my moderately light polluted backyard last night, so I decided to set up my motorised C8 and get a decent shot with my Canon 300D using a canon ef 50mm f1.8 II lens recommended to me by John O' Brien (cracking lens John!!) I got this shot of Cassiopeia and the double cluster, - I took multiple exposures at IS0200 F2.2 for 60 seconds each, at different white balances, the best 2 i've stacked - I took at darkframe as well for the same set up, but I don't know how to apply it, anybody know how, I have photoshop also. There's little processing done, I could darken it by retouching, but is'nt it better to use the darkframe? Any idea's for improvement. Overall, i'm happy with this shot as it is only a 2 minute exposure, next time i'll get a LOT more

Keith..

Keith - this is potentially a super wide-angled shot. You have a lot of detail in there that is currently not visible. If you process this right, it'll make a great picture.

You need to subtract the dark frame (I assume its the same exposure length and temperature as the light frames) from EACH of the images you propose to stack. Then stack them.

This article will help you use a 'calibration' frame in Photoshop.
www.photo.net/learn/dark_noise/

This website is well worth a look for general processing techniques
www.astropix.com/INDEX.HTM

I noted a light-pollution gradient in yor image - you can also remove this in Photoshop. Try this article: www.wodaski.com/wodaski/gradient.htm

As with anything, the effort you put in will determine the final image. Some of this stuff is very time-consuming. Only do as much as you need to to get an image YOU are happy with!

As far as taking the original pictures are concerned, the more you get, the better. More images means a better signal-to-noise ratio. Keep them coming!

The DSLR images posted on these boards really are superb. Maybe I should get one...

All the best

Dave McD

Hi Keith thats a really great shot. Well done!! What were the exposure lenghts you used?

I got a short loan of one of those 50mm lens. Although I didnt get to use it for astrophotography. I did try it out with ordinary shots. It is a lovely lens. The example I was using had a problem though. It had an obvious problem with 'front focus' that is, it focused a little short of where it should. I pointed this out to the guy who loaned it to me and he sent it back for repair/replacing. Its still a lovely lens and one I'm definitely gonna get.

As for your processing. What you need to do with a dark frame is subtract it from your image. To do this apply it as a layer in photoshop or whatever you do and set the layer mode as 'difference'. This will have the result of removing any 'noise' which is on both your shot and on your dark frame. But leaving everything else untouched.

Hi Keith,
If you have photoshop, there is a very simple and effective way of removing the background glow.

Here are the exact instructions on what to do.

Open photoshop and open your original image in it.
In the image tab, click on the duplicate button.
A small window will appear, click yes, this is just for naming the duplicate image.
In the filters tab, and then in the Blur subtab, select gaussian blur, and a slider window will appear, move the slider until all star images are gone and all you are left with is the background glow.

Then click on the original image, click the image tab and then select apply image. Change the source name to the duplicate name and select the blending button to subtract.

What this does is subtract the glow from the original image while leaving the star points alone.
Then adjust levels/contrast etc to further enhance.

It takes about 30 seconds and works very well on stars, it gives limited results on nebula and other diffuse objects.
I tried it out on your image, I hope you dont mid, but I wanted to show how useful this trick is.
All credit to Michael O Connel who told me about it.


www.irishastronomy.org/user_resources/fi...le%20Cluster_MOD.jpg

This is a quick enhancement, if you spend more time at it Keith, you can improve the image further. Let us know how you get on.
Have fun.

Hey 3 Dave's! , Thanks for all that info, I have time on my hands today so i'll follow everything to the letter, This shot is simply a stack of 2 shots, 60 seconds exposure at ISO 200, F2.2, I had more shots, same exposure settings, but i played around with the white balance a little bit, so they did'nt suit, these 2 are just taken with the Auto White Balance.

I'm on a steep learning curve, but you gotta start somewhere!. As I said, last night was super clear, really good conditions, and that 50mm lens is one great lens - I think it was for only 55pounds sterling from www.7dayshop.com

Looking at that enhancement photo, it looks absolutely great, I can't wait for the next clear night, I'll get plenty of exposures again, the 300D is proving it's worth...

Keith..

Hi Keith, glad you like that lens - can't be beat for the price. If your looking to move up in the lens world consider the F4 70-200 L zoom for around £430 (on 7-Day). This is a bit of a jump money wise but is actually good value for money if ya know your lenses - this is one of Canon's high end lens and on your 300D's 1.6 crop sensor gives the equivalent of 320mm on the long end, quality is fantastic.

I don't know if you shoot using RAW mode - give it a try, there's a lot of detail to be pulled from RAW and you can set the white balance to whatever you want later rather then being forced to use a preset in-camera for Jpegs.

Dave, I know about the 50mm front focusing a tad but it only really shows up when using F1.8 or F2 or so, any of the higher F stops and you will get cut from the sharpness on this lens - for astro work you'll probably be on manual focus so it's not really a concern here. Canon should be able to calibrate it.