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Night sky 60 second exposures

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Offline Posco

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Night sky 60 second exposures
« on: 30 / January / 2008, 23:44:50 »
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I had the opportunity to try out Albest'st long exposure feature on my S3 IS recently. It was at a site with very a dark sky and no moon. The camera was mounted on a Meade ETX-125EC telescope and roughly aligned so it would minimise the star trails. I had trouble with the weight of the camera on the telescope so did not want to mess around with it once I had managed to get it set up. In future, I plan to reduce the camera weight by removing the batteries and use an external power supply to run the camera. As a first attempt, I am delighted with the results.

The photo of the Southern Cross and the bright band of the Milky Way stars is a wide angle view made up of two single 60 second exposures taken at the widest angle. I left noise reduction on and the resultant images were remarkably noise free. Each photo was enhanced in PS Elements and then joined  to make the final image. For those who may have trouble determining where the Southern Cross is amounst the stars on the reduced size image I have put two lines along the long and short axis of the Cross and between the two Pointers. The darker patch just below the top and to the right of the Cross is known as the Coal Sack. The Orion Nebula was a single 60 second exposure taken fully zoomed (optical) and cropped.  (Note that the Southern Cross is mainly visible from the Southern Hemisphere and only at lower latitudes of the Northern.) There is still more detail contained in the Southern Cross photo if it is lightened, below the trees there is a gate and cattle stop just visible. Remarkable for being taken only with star light!!

I can't wait to try out my wifes A560 which is a much smaller and lighter camera now that there is firmware for it. Thanks to all who have been involved in developing the CHDK firmware, being one who tries to do "more with less", it has made all sorts of previously impossible or horrendously expensive ideas now achieveable.
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Offline mx3

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Re: Night sky 60 second exposures
« Reply #1 on: 30 / January / 2008, 23:48:56 »
I like these pics
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Offline wontolla

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Re: Night sky 60 second exposures
« Reply #2 on: 31 / January / 2008, 07:58:52 »
Thanks Posco, I've never seen the Southern Cross, never been in that far away place you call Southern Hemisphere but someday I will.

Your Orion nebula is awesome, I wonder if you did took the photo or downladed it from the NASA site.

I also have the bulky S3 and sometimes think about buying a Axxx. Keep experimenting with your telescope!
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Offline Posco

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Re: Night sky 60 second exposures
« Reply #3 on: 31 / January / 2008, 15:03:07 »
Thanks for your kind comments - yes, it really was taken by me, it did take a little work in Photoshop to bring out the detail that was there but the amazing point is, that it was there all the same!
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Offline PhyrePhoX

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Re: Night sky 60 second exposures
« Reply #4 on: 01 / February / 2008, 04:58:39 »
at what ISO setting did you take the shots?
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Offline Posco

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Re: Night sky 60 second exposures
« Reply #5 on: 04 / February / 2008, 15:13:30 »
Sorry for the delay in reply. The photos were taken at ISO 100 to minimise noise. I probably should have tried a higher ISO to see how much more signal I could record in 60 seconds but this will have to wait until the next opportunity.

The apeture was set to F3.2



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Offline chuckheron

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Re: Night sky 60 second exposures
« Reply #6 on: 19 / February / 2008, 13:45:07 »
Cool photos!
I've been doing the same, mounting my s3 on an LX90.
I'm also playing with ideas about how to center the weight and lighten it up a little.
I posted a Long Exposure Intervalometer script in the user script area:
UBASIC/Scripts:Long Exposure Intervalometer - CHDK Wiki

I'm still processing/stacking, but I've also gotten some nice photos of the orion nebula. I'll try and post them when I'm done..

Clear Skys
-chuck
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Offline thunderstorm

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Re: Night sky 60 second exposures
« Reply #7 on: 09 / April / 2008, 17:53:59 »
Try next time to set the aperture to the largest F number possible (Probably F8.0), since you photograph the infinity, and compensate for the lesser light by doing more 60 sec shoots and combine them together.
You'll get much sharper results.
Now with CHDK you can apply higher stop numbers, and as written in the comparsion table, some Axxx cameras not only lighter by weight, but can get higher over-ride shutter F-numbers.

Good luck :)
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Offline Barney Fife

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Re: Night sky 60 second exposures
« Reply #8 on: 09 / April / 2008, 19:51:32 »
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« Last Edit: 22 / April / 2008, 17:07:26 by Barney Fife »
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Offline thunderstorm

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Re: Night sky 60 second exposures
« Reply #9 on: 10 / April / 2008, 15:12:41 »
Quote from: Barney Fife on 09 / April / 2008, 19:51:32
Higher f-numbers (smaller apertures) means more edge softness due to pronounced diffraction effects. This is less apparent in P&S cameras as opposed to larger sensor and film cameras due to the shorter distance of aperture edges to the recording media, but it still has some effect to reduce image clarity.



I partly agree... and correct me if i'm wrong.
I've experienced much sharper night pictures (at long shutter) by using F8.0 instead of F2.8 . The street lights and other far city lights were sharp, and those at F2.8 looked like i needed glasses. They seemed like out of focus a bit and soft :)
I know that the narrower the shutter and thus the light "hole", the more sharp would be the picture appearing on the sensor.
I didn't look at the edges, and it makes sense that those would become a bit darkened, but the center, which is the "heart" of the picture, will be very sharp and live.
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