help with shooting nebulas

[ajc518]

I have deep sky stacker, and was wanting to know exactly how to shoot nebulas. Mostly I need help with pp in showing the actual gas clouds. I read somewhere that you have to play around with the channels for them to show up.

I tried searching the forum for this topic, but all the how to's seem to all be on star trails, ect. So if this has already been discussed then just shoot me a link to the post.

thanks

[Nighthound]

Are you planning to use a mount or similar device that will track the objects you want to image?

Without a means for tracking your nebula shots will appear very much like the star trail images you mention. You'll need to be able to lock on to the objects you image to remove movement produced by the Earth's rotation.

Most nebula are very dim and require a lot of exposure time to do them justice. By stacking multiple exposures within the capability of your mount/tracking device you can get enough total exposure time to get 'er done. I would aim for between 3 and five minutes with your 50D(ISO 800-1600), in order to go deep enough for subtle detail. Dark skies can be a huge asset when shooting deep sky, making processing much easier and the data collected much cleaner, i.e. background gradients produced by city lights.

Once you have good data and stack them in DSS you will then want to take a TIF file of the stacked subexposures into Photoshop and "stretch" the image. This is best done using curves and takes some practice and finesse, a light hand is best.

I may be babbling below your skill level, if I am I apologize. I, or others here can elaborate on things when you tell us more about the equipment you plan to use and your experience level.

[ajc518]

No I dont have a tracking mount. I am on vacation in Russia, so I really wont be able to get on till I get back to the states. From the ones I have seen they seem really expensive. Are there any fairly cheap ones that are good. I have also seen people make them too.

I was going to attempt to at least get something of a nebula, so I can at least play around some with the PP to get good at it for when I get back.

Some more details on stretching the photo in photoshop would be good.

Whats also a good range for lens? Right now I have my 70-200L f/4. Will that be enough to see anything. When I get back, I can use my uncles 100-400L.

[Catanonia]

You will need to zoom in a far bit and with any tracking it just is not going to be possible as you will need such short sub pictures to avoid star trails, less than 5 seconds, that the data / light just will not be recieved.

Not unless you try the bigger nebs such as NGC 7000 American Nebula.

[Jaxdialation]

Correct. Nebulae take looooong and steady exposures. With a CCD (single color channel at a time) camera some of my exposures are 30 minutes each! With a DSLR on a non-tracking mount you are out of luck.