Anyone taken startrails photo in singapore before?

Arsenal07 · Post by **Arsenal07** » Mon Jan 25, 2010 1:50 pm

If so...any recommendation where? I'm gg to vietnam in May and I think i shd be able to get nice startrails there...just that i need some practice before that. That's y i want to know any places in sg. lol. Btw do u guys recommend stacking methos or using ND filter to take startrails? I do have a ND110 but not a timer control though.

I'm new to this forum..so nice to meet all of you!

Post by **weixing** » Mon Jan 25, 2010 5:52 pm

Hi,
Beach facing east and south-east should be your best bet in Singapore. Not so sure which method is the best for star trail. Anyway, you can do a test to see the noise different between this two method.

By the way, welcome to SingAstro!! [smilie=hi.gif]

Have a nice day.

kayheem · Post by **kayheem** » Mon Jan 25, 2010 6:46 pm

Err...I think Singapore has too much light pollution (LP)

If you are looking for really long exposures e.g. several hours, the star trails may be obscured by LP and/or clouds.

:-(

jiahao1986 · Post by **jiahao1986** » Mon Jan 25, 2010 7:15 pm

Hi,

For taking startrails, you can use stacking method. With stacking, you can even get nice startrail shots in urban conditions like Singapore. You can use a software called "Startrails" to create startrail shots at ease, available free of charge from http://www.startrails.de/html/software.html

1). Focus properly; then, depending on sky brightness, choose suitable exposure time, aperture and ISOs. Normally for stacking, 30s exposure is enough. If you are under dark skies, set aperture wide open and high ISO; if you are in urban area, set to smaller aperture and lower ISO. As soon as you get proper exposed single frame, neither underexposed nor overexposed, you can move on to step 2.

2). Say you want a 1-hr startrail, simply take 120 photos using the same settings. For Canon 450, if you want to take 120 photos continuously without manual efforts, you'll need to purchase a timer remote control, or simply use a laptop to control. One point to note, the more photos you stack, the higher the signal to noise ratio.

3). Before or after you take all the single frames, put on the lens cap, take one more frame at same settings. This is called a "dark frame". By stacking this frame afterwards, the hot pixels will be killed.

4). Upon finishing taking all the neccessary frames. Import the light frames into the Startrail software, and import the dark frame also. Then press the startrail icon, stacking process begins; soon enough you'll get your result. Very easy.

Hope this helps.

Best regards,
Jia Hao

jiahao1986 · Post by **jiahao1986** » Mon Jan 25, 2010 7:17 pm

BTW if ground lights are too bright for you, you can try using a GND filter. A timer control is recommended if you use canon, though you can do the same thing with your camera connected to your laptop.

Post by **weixing** » Mon Jan 25, 2010 10:08 pm

Hi,

jiahao1986 wrote: One point to note, the more photos you stack, the higher the signal to noise ratio.

Hmm... IMHO, I don't think this is applicable to star trail photo as the noise will add together when you add all the frames to create the star trails. The question is will the noise of multiple shorter exposure more than a single long exposure??

Have a nice day.

jiahao1986 · Post by **jiahao1986** » Mon Jan 25, 2010 11:07 pm

weixing wrote:Hi,
jiahao1986 wrote: One point to note, the more photos you stack, the higher the signal to noise ratio.
Hmm... IMHO, I don't think this is applicable to star trail photo as the noise will add together when you add all the frames to create the star trails. The question is will the noise of multiple shorter exposure more than a single long exposure??

Have a nice day.

It is similar to Registax for planetary imaging. Stacking will average the foreground since noise is random.

Post by **weixing** » Mon Jan 25, 2010 11:16 pm

Hi,

jiahao1986 wrote: It is similar to Registax for planetary imaging. Stacking will average the foreground since noise is random.

Hmm... you can't do the normal stacking for star trails... remember the stars moves in every frame. As a result, the star trails will be in different position in every frame (like random noise)... so if you do the normal stacking operation, the star trails will gradually disappear like noise did.

Have a nice day.

jiahao1986 · Post by **jiahao1986** » Mon Jan 25, 2010 11:26 pm

weixing wrote:Hi,
jiahao1986 wrote: It is similar to Registax for planetary imaging. Stacking will average the foreground since noise is random.
Hmm... you can't do the normal stacking for star trails... remember the stars moves in every frame. As a result, the star trails will be in different position in every frame (like random noise)... so if you do the normal stacking operation, the star trails will gradually disappear like noise did.

Have a nice day.

Well for stacking startrail photos, the machanism is the same as the Photoshop layer blending option "lighten", which compares the two layers pixel for pixel and uses the lightest pixel value. Since the stars are much brighter than adjecent background pixels, the stars remain. I have a few recent photos using the stacking method stated above:

Post by **weixing** » Tue Jan 26, 2010 12:52 am

Hi,

jiahao1986 wrote: Well for stacking startrail photos, the machanism is the same as the Photoshop layer blending option "lighten", which compares the two layers pixel for pixel and uses the lightest pixel value. Since the stars are much brighter than adjecent background pixels, the stars remain.

That's why I said it's not the normal stacking we usually use for astrophoto. So, I'm not sure whether this method of stacking does improve signal-to-noise ratio, but it'll be better than normal "add" operation.

By the way, IMHO, it's better to do your own noise reduction instead of using the star trails software noise reduction as it's use a colour dark frame which IMHO, is not very effective.

Have a nice day.