Were am I going wrong ?

[johnb]

Well im not giving up (yet) im using a Sony A350 on a fixed tripod and ive experimented alot with exposure time and ISO given my light pollution etc and settled on exposure of 20 seconds and an ISO of 1600.

Well I took ten exposures and 5 darks DSS registers but they simply wont stack, i guess because it cant really define the stars properly they seem very porly defined and enlarged ?

here is a link to a single exposure (converted in photoshop for the web) the stars seem to large ?, the lens is spotless, any clues as to were im going wrong ?

http://i294.photobucket.com/albums/mm105/johnb_001/1-frame.gif

Regards

John B

[brendant]

John, you are certainly on the right track in what you are doing capture wise.

Examining your image the stars are not sharp and slightly out of focus which is why DSS will not stack them. As you have probably found out by now, focus through a camera lens in the dark is much harder than in daylight, take a series of images and take care to examine carefully until your stars are just pinpricks before comencing capture. 20 seconds may also cause the images to trail but that is dependant upon the focal length of the lens, wider is better in terms of exposure length / time.

Brendan

[johnb]

Thanks for that, I thought it might be focus related, yes getting focus in the dark is a nightmare. i will try again tonight and take a series of 20 second exposures adjusting the focus as i go

Regards

John B

[johnb]

Thanks for the pointers, i can now focus, what a difference.

Here is a single image

http://i294.photobucket.com/albums/mm105/johnb_001/singleframefor-frame.gif

Regards

John B

[themos]

DSS has a slide control that determines how hard the software should look for stars.

Adjusting the star detection thresholdThe star detection threshold is 10% by default (10% of the maximum luminance).

You can modify this threshold in the Advanced tab of the Register Settings dialog. If you decrease the threshold DeepSkyStacker will detect fainter stars. On the other hand if you increase the threshold only brighter stars will be detected.

To help you finding the best threshold for your light frames you can compute the number of stars that will be detected. To do this, DeepSkyStacker is using the first checked light frame and is activating temporarily the hot pixel detection.

You should note that this number is only a hint and that the real number of detected stars may vary if you have checked dark, offset and flat frames.