Star trails over the obs

[lukebl]

Hi all,

Here's a quick capture of star trails over my obs this evening. OK, it's light-polluted but I can still see stuff! It is based on 24 x 60 second exposures with my Canon 450d and standard 18-55mm lens, set at 18mm. Stacked using Startrails.exe. Note the weather station in the centre which provides all the weather data in my sig!

Two queries:

Firstly, I am using one of those small exposure controllers which you can get cheaply off Ebay, which you can programme exposure length, number of exposures, and interval between exposures. When using 'shutter lockup mode' (to avoid vibration), you have to set the interval between exposures at at least 8 seconds or it won't work properly. The upshot is that there is an interval between exposures which shows itself as a little gap in the star trails. Is there any way to avoid having this interval (apart from not enabling morror lockup)?

Secondly, I would have got more frames but the lens fogged up with dew. How can you avoid this without a heated dew strip? It's a wide angle view, so a dew shield wouldn't work as it would cause vignetting. Any ideas? I don't really want to sit over it with a hair dryer!

[twotter]

Sorry, can't help with your queries but I do like pics of star trails and yours is great

[Ags]

Not altogether sure you need mirror lockup for long exposures. I've done star trails and DSOs with my 1100D, which does not have mirror lock, and saw no ill effects.

Mirror lock was more of an issue for me with long lenses and short shutter speed, which I found out when using my ST80 in daylight. I had to wedge stuff between the scope and the mount to deaden the vibrations.

[barkis]

It does make for an attractive scene Luke. The tree, weather station detector, the Obs. itself with subdued light, and of course the polar star trails themselves. Everything combines so well, so nothing to be critical about at all.

These type of Images epitomise practical amateur astronomy.

Pat on the back maty.

Ron.

[lukebl]

Thanks gents, muchly!

Ags, you're right. I'm so used to engaging mirror lockup for imaging when attached to the telescope, that I forgot you don't need it for 'normal' photography! Oh well, but not a bad pic all the same.

[saturn5]

Lovely traails,i never bother with mirror lock up,dont think its really required for wide angle shots.

As for the foggy lens,i use one of those handwarmers that you recharge by putting into boiling water.I have a high tech method of attatching them to the lens,an elastic band.

When i was out at Loch More i just went into my mates car to warm the lens up.10 minutes with the heater blasting and they cleared but for those places that you've walked to the hand warmers do the trick.

[JonH]

Nice shot.

I use a dew strip with a 15mm full frame fisheye on a full frame body with no vignetting. It's a snug fit and needs to be wrapped around the body of the lens twice, but it does the trick.