DSLR Constellation Imaging Problems

[Knight of Clear Skies]

Had a lovely clear night down in Cornwall yesterday, could see the Milky Way straight after going outside from a brightly lit room. Thought I'd have a go at capturing it with my Canon 1100D on a fixed tripod, but ran into some problems.

The biggest problem (I think) was getting a sharp focus. I've taken a few reasonable constellation images before, but I always had either the Moon or a planet to focus on first. Stars are not bright enough to show up on my liveview, even at maximum zoom on the screen. I tried focussing on some distant lights on a TV mast (at least 15 miles away) - should that have been close enough to infinity?

I was using 30 second exposures at ISO 800. This gives some star trailing, but I also have some wobbly streaks in my images. I was using a 2 second timer, but could the wobble have been caused by the mirror flipping? Can I lock it beforehand by taking the image on liveview?

My expectation is that if I can see the Milky Way by eye I should be able to see it faintly on a 30 second exposure, hence my assumption that fine focus is the problem. Am I being realistic here?

Any help or tips would be much appreciated.

[Bhm2344]

Yes the wobble is more likely to be the mirror lock, it can be taken care of in the custom functions. On my EOS 350D I use mirror lock up and a 10 sec delay, although using a remote shutter release has helped a lot too. What lens are you using? You need also not to use auto focus. I agree focusing on stars are a problem, ESP as I have no live view. I use the view finder, and a bright star to get as close as I can. Hope that helps a bit

[VigdisVZ]

Hi

Here's what I do:

I set the tripod and camera up and point it at a radio mast, or a bright star. I enter live view, and zoom the screen up on the object and then try to dial in focus and then exit live view.

On my Nikon I have a setting that starts the exposure 2 seconds after the mirror has flipped, I use that, but you could emulate that with the black hat method (ie holding someting black in front of the lens and removing it 0.5 seconds after you've started the exposure).

I generally try to keep exposures at 15 seconds. My Nikon handles ISO very good so I can bump it to 1600 or 3200 or even more.

You should be able to see the milky way really good on 15 second/ISO 3200 unless you're standing under a streetlight.

Also make sure you're opening the aperture up max, ie the lowest F-number. If you're unhappy about the quality you can step down (increase the F-number a click or two). I usually shott my 28-55 at 28mm at F/3.5.

Here's a single exposure example of what I did the other day with the above method.

And here is the stacked result with 8x15sec:

Any chance we can see your and picture maybe figure out what you're missing?

[Knight of Clear Skies]

Thanks for the suggestions.

What lens are you using? You need also not to use auto focus.

It's a 18-55mm lens set to 18mm.

You should be able to see the milky way really good on 15 second/ISO 3200 unless you're standing under a streetlight.

That gives me a useful reference point thanks, I need to adjust my light curves. Giving this a go, I can see the Milky Way, and I think I've also captured Andromeda. I've got one decent shot with reasonable focus and minimal wobble.

Also make sure you're opening the aperture up max, ie the lowest F-number. If you're unhappy about the quality you can step down (increase the F-number a click or two). I usually shott my 28-55 at 28mm at F/3.5.

I was shooting at F5.6, I'll give that a try next time thanks.

Any chance we can see your and picture maybe figure out what you're missing?

Sure, I'll try and post a couple examples.

[steppenwolf]

Focusing a DSLR and wide angle lens can be a pain but if you are prepared to take a laptop PC outside with you, this will make things much easier. Download the free and excellent EOS Movie Record software, point at a bright star (say, Deneb, Sadr or Vega) set the zoom to x5 and focus manually on the star - you will find that focusing on the laptop screen is much easier than any other method. Once focused, you can turn off the PC and take it back indoors. swing the camera to point at the desired part of the Milky Way and use your remote controller to actuate the shutter.

[Bhm2344]

I've not used that lens as mine came up with an error code. I have used a f1.8 50mm which is good and my sigma 70-300mm f4 -5.6. After you try the mirror lockup and also dropping the f stop as the poster above said, go to the 50mm side and see if you can see brighter stars. Do you use manual mode on your camera?

[VigdisVZ]

Oh, yeah, my reference pictures are post processed in Photoshop. If you dont have access to that program you can do a simple stretch and sharpness in the freeware program GIMP.

I also mistyped earlier. My lens is 18-55 and I was shooting at 18mm.

[Knight of Clear Skies]

Can't upload my images for some reason, either to here or Flickr - will have another try tomorrow. I'll put up my best image and one that went wrong.