Chat - Monthly Competition - November: 'Astro-Photography'

[Jediboy]

Originally Posted by Jimbojumbo

Supposed to be almost clear and dry every where over night, should be a good time to practice then...

Fingers crossed. And toes.

[Jediboy]

It's been a beautiful day here in Northants. Sunny with clear skies. I had high hopes for tonight, but alas, it soon clouded over and scupperd any photo opportunities.

[DigiDiva]

oh dear......im pinning my hopes on tenerife

[nick_gray]

As it was a such a clear night on Saturday, I thought I'd venture outside with my camera and tripod to have a go at this. A couple of my better photos are below, these have been reduced to about 25% of the original:



Canon EOS 500D, EF50mm f/1.8 II lens, ISO 800, f1.8 for 5 seconds. WB set to 3150K.
Pole star is in the bottom, middle and I think it's Perseus in the top right.




Canon EOS 500D, EF-S18-200mm f/3.5-5.6 IS lens, ISO 800, f3.5 for 8 seconds. WB set to 3150K.
Pole star is in the top, middle and Orion is just appearing bottom right, from behind a tree.

I'd say, as pointers to others:

Obviously use a tripod, and switch off image stabilisation.

Use the widest angle lens you have. My 100mm would only capture Orion's belt. I had a bit more success with my nifty 50, but had the largest amount of sky with the 18mm end of my 18-200mm.

Open the aperture as wide as you can. My 18-200 would only go to f3.5, but the 50mm opened to f1.8.

Noise is a problem, but it's a trade off, if you drop to 400 to reduce noise, you'll have to increase exposure time and therefore get star trails. I couldn't go above 800, or noise on my 500D is awful. I think full frame and newer cameras like the 7D and 60D could perhaps go to iso 1600.

Focusing should be switched to manual, but is really tricky to get right. All of the photos I took with my 100mm are out of focus, so have gone in the bin. They looked fine on the lcd screen on the back of the camera. I had read that you should find a bright star in the viewfinder, then using LiveView with a magnification of x10, adjust focus until the star is sharp, then recompose if necessary. I forgot to zoom in and check the photos when my 100mm was attached, but did with the 50mm and 18-200mm.

I set my white balance to the lightbulb setting - (3150K).

Any exposure longer than 4 seconds and you'll start to get star trails. I was really surprised how short the exposure time needed to be.

These 8 second exposures are the best I managed to get, but I might go out again if we have another clear night and experiment further.

BTW the lens creep on my 18-200mm is so bad that if I have it set to anything other than 18mm, the barrel closes up again, I'm not sure if it's bad on other telephotos, so you might want to get an elastic band on the barrel to stop any movement, when you point the lens upwards.

Overall I enjoyed doing this, and want to have another go, now that I've experimented with timings, settings and lenses.

HTH

Nick

[JonnyM]

Good to see your images Nick.

Regarding focal length it depends what you want to see obviously but it also affects apparent movement of stars and therefore shutter speeds. The further the stars are from the pole star the quicker they appear to travel, again restricts shutter opening if you want to capture point sources as opposed to trails.

I went to 1600iso at one point but that setting introduced too much light pollution and noise, and anyway the best results I achieved that night were at 800iso (on a Canon 60d). I used the viewfinder to focus and stopped lens creep with a bit of blue tack.

Just to add, switch off long exposure noise reduction if you are using it.

[Jediboy]

Nice photos Nick. And thanks for your tips. They will help when I finally get a clear night to go out and play.

[wavemachine]

Nice one Nick some great tips there and good shots.

Still cloudy here at this rate I may have to chuck salt on a black piece of paper and see if anyone notices

[JonnyM]

Only if we find out if you've had constant cloud cover wavemachine like the rest of us

[nick_gray]

Thanks for all the comments and further suggestions.

Now after dark, each time I pass a window, I look out to see if the clouds have cleared. I might be getting a bit obsessed!!.

I quite like the idea of salt on a black card, maybe it could be the subject of the weekend competition :-)

Nick

[Jediboy]

Originally Posted by nick_gray

Now after dark, each time I pass a window, I look out to see if the clouds have cleared. I might be getting a bit obsessed!!.

Nick

I do that too.