Cold, dewy, non focusable Canon

[rainwatcher (Peter)]

Hi all,
I have been taking shots with my 1000D in the backyard and have been happy with the results, given Tulla sky glow, the neighbours and their backyard spotlights etc. Any way I though I would go out somewhere dark on Wednesday night and see what a good dark sky could produce just the camera and tripod. Picked my spot about 15 k past Lancefield on a minor road and set up.
The sky was clear and the stars glorious. The day had been quite hot. By the time I set up and started at 10:45 the temperature had dropped staggeringly, I had no mittens or face cover and soon it was too cold to continue, my fingers would not operate the tiny buttons on the programmer. Of course with the temp drop came a very heavy dew, it turned quite foggy on the drive home, and when I checked the photos they were terrible. Not only had the lens fogged but I had failed to focus most of them correctly.
I will be making a dew shield for the camera, but frankly I am at a loss on how to focus, the stars do not show up in live view well enough, unless it is Sirius, and the focus ring on the 18-35 is so soft that I am sure the bloody thing moves when simply realigning the camera after focusing on the closest bright object.
One of the fogged shots is below – got a lovely twin spike on Canopus though. ISO 1600, 50s. at 5.6, Camera @ 16 C. It’s a crappy shot – I am still cursed with the horizontal banding and the detail and colour is appalling. My backyard shot of the same view and directly over Tulla glow at about 25 sec is far superior with TUC 47 showing as a fuzzy object rather than looking like a star. Not giving up, lots to try yet.
Any advice on focusing would be most welcome.

[Daveskywill (David)]

Hi Rainwatcher:

I've got a Canon Rebel T2i. First, I guess if you're having dewing is like

you said a dewshield could help. But also maybe a small portable, battery

powered heat strap, thing. You know we've got a supplier here in Canada

called Kendrick: but those use big batteries. Well on focusing with mine

using those small lenses, changing the ISO in liveview (doesn't) seem to

make a difference to how bright lights look in the LCD window. But it

might help to get somewhere where there's a small bright artificial light

(I'm not sure if this is the greatest advice), and do your focusing there.

Also maybe to make the light pollution better on your photo's maybe you

could try to find a glow filter for your lens.

[naskies (Dave)]

Peter,

I've found that the disposable heat packs used for warming hands or relieving muscle aches work quite well on camera lenses. Open up the heat pack, tape it to the lens or hood, put some insulation around it (e.g. a thick sock) and you'll be dew free for hours. There have been a few threads on it here - worth a quick search.

Focusing camera lenses is tricky at the best of times, but it's even trickier with zoom lens that have a small/slower maximum aperture. I generally point the centre of the camera on a bright star (Alpha Cent, Sirius, Canopus, Achernar, etc), use LiveView with the camera set to Manual mode, ISO at the highest possible setting (e.g. H1 with the ISO Expansion custom function enabled), shutter speed at the slowest setting (e.g. 1/30 sec), and the lens at the widest aperture.

As you turn the focus ring, watch the star carefully - aside from becoming smaller and brighter as it comes into focus, it may also change colour (red/green chromatic aberration in front or behind the focus plane) or shape (from circular to egg shaped). Using a combination of these cues, I can usually focus the lenses I use.

Alternatively, you can draw/stick something onto the focus ring and lens barrel to help you keep track. Just do a bunch of test exposures at different focus settings, check the exposures, and you'll know where the true focus point roughly lies.

If you have a computer available, it's even easier - software such as Backyard EOS can automatically take a series of exposures at different focus points and analyse the exposures to tell you where the optimum focus is.

Good luck!


Cheers,

Dave

[rainwatcher (Peter)]

Thanks Guys, i will be trying all suggestions. I have recently purchased BYE so i think that may make the task easier when i have my laptop. The thing is i sometimes just go with the camera and tripod and dont take my laptop with me.
Thanks again, by the way if any of you have got drift alligning working in BYE i could also use some help with that - see my other post.
Cheers
Peter