Background stars or noise?

[deadfraggle]

Anyone know the best ISO and shutter speed setting for a starfield picture with a digital camera? The longest time I can set on my GE T145 is 30 seconds, though the camera tends to go wonky at that setting. (Perhaps my batteries were low...)

Here are two pictures I took using ISO 1600 (the highest available to me). The first is 15s, and the second is a 20s exposure. Did I capture background stars, or is that mostly noise?

Edit: There seems to be a red halo near the top of the image. Could this be caused by the red indicator light on the camera itself?

[Keiran]

The problem you have is with such a low exposure time, you will have to up the ISO but this creates alot of noise in the photo. Have you got the camera on a tracking mount?

I would maybe try iso 800 and take a large number of shots and stack them in DSS.

What lense are you using too? Keep the F stop low (Ignor this if you are using a telescope )

That halo at the top could be from a camera light, or other light leaking in to the lense (street light, house light etc)

If it is the light on the camera then just stick a piece of black elecy tape over it

Hope that helps

[skygazer]

Setting the ISO higher will increase noise in the picture. Have a play at different ISO levels and see how high you can go before the noise becomes too high.

Paul

Sent from my Google Nexus One

[deadfraggle]

Nothing as fancy as a tracking mount, just a tripod. Lens? Whatever is built in the digital camera, and no other can be attached. I will try several lower ISO images as you suggested then try stacking them. Black tape too.

Personally, I didn't think I would be able to capture anything with an $70 camera. Am now encouraged to save up for better equipment.

[RikM]

Take a picture at the same settings but with the dust cap on. Any dots you capture there will be noise. Compare it to these frames and see if the patern is the same. That would indicate hot pixels and could be removed in stacking by subtracting darks (images with the dust cap on) from the light frames.

To me it looks like there is a bit of noise in the background, but nothing that wouldn't be dealt with by taking a bunch of them (30+) and stacking them up.

[Spikey]

There are a lot of stars in that shot fraggle.

Try lowering to ISO800 and shooting 20 or 30 lots of 15 second shots - these are your light frames. Then, as Rik suggest, put the dust cap on the lens and shoot exactly the same with the dust cap in place - these are your dark frames.

Try a stacking program like Deep Sky stacker and put all your lights and darks into it, DSS will stack and calibrate these for you and the results should hopefully be a much improved image to work with.

[deadfraggle]

The camera does not have a revolvable dust cover. It opens automatically when the camera is powered up and the lens extends. Could I use a jar cover instead?

Can I take 20 to 30 fifteen second exposure shots without star trails becoming a problem? (A tracking mount seems to be logical next purchase or build.) The camera has 'continuous shot' but not sure how to use it. The options are Unlimited, 3 shots, 3 shots(last), and Timelapse with 30 seconds being the lowest setting. Or I could just keep pressing the button...

The red bleeding may in fact be the 'Auto Focus assist beam'. Will make sure it's off next time. That the camera does not manual focus is a pain. Auto Focus only has two settings - Single mode and Multi.

So not the best camera for AP, but neat to see what I can squeeze out of it. How should the following be set?

Expo Metering: Spot, Center, or AiAE

WB (white balance?): Auto, daylight, cloudy, fluorescent, fluorescent CWF, incandescent, or manual. Manual just allows you pick one of the other choices when the shutter button is pressed.

Color: Auto, Vivid, Black & White, or Sepia.

Size & Quality set to highest, 14m and Best.

Here's some numbers on the front of the camera lens - 5 x 6.3 - 31.5mm 1:30-4.7

[skygazer]

Use electrical tape over the lens and make sure its black to cut out all the light

Paul

Sent from my A500 using Tapatalk 2

[Spikey]

The camera does not have a revolvable dust cover. It opens automatically when the camera is powered up and the lens extends. Could I use a jar cover instead?

Can I take 20 to 30 fifteen second exposure shots without star trails becoming a problem? (A tracking mount seems to be logical next purchase or build.) The camera has 'continuous shot' but not sure how to use it. The options are Unlimited, 3 shots, 3 shots(last), and Timelapse with 30 seconds being the lowest setting. Or I could just keep pressing the button...

The red bleeding may in fact be the 'Auto Focus assist beam'. Will make sure it's off next time. That the camera does not manual focus is a pain. Auto Focus only has two settings - Single mode and Multi.

So not the best camera for AP, but neat to see what I can squeeze out of it. How should the following be set?

Expo Metering: Spot, Center, or AiAE

WB (white balance?): Auto, daylight, cloudy, fluorescent, fluorescent CWF, incandescent, or manual. Manual just allows you pick one of the other choices when the shutter button is pressed.

Color: Auto, Vivid, Black & White, or Sepia.

Size & Quality set to highest, 14m and Best.

Here's some numbers on the front of the camera lens - 5 x 6.3 - 31.5mm 1:30-4.7

The stacking software should take care of any slight shift in between images so don't worry about it too much, they should come out OK.

Don't bother with darks for now then, just do the lights and see how it turns out. You should be pleasantly surprised

[deadfraggle]

Thanks for the advice. This forum is great! Taking these pictures is fun and educational. The camera picked up that Mizar in the tail of Ursa Major has a companion Alcor. Never noticed that before with the naked eye. I see myself taking pictures, inspecting, then revisting areas of interest with the bins that will soon be delivered.

Stoopid weather right now though.

[Spikey]

Thanks for the advice. This forum is great! Taking these pictures is fun and educational. The camera picked up that Mizar in the tail of Ursa Major has a companion Alcor. Never noticed that before with the naked eye. I see myself taking pictures, inspecting, then revisting areas of interest with the bins that will soon be delivered.

Stoopid weather right now though.

Mizar & Alcor collectively sometimes called the Horse & Rider.

I like using Mizar as an alignment star if imaging in that area because it's so easy to see I have the right one

[deadfraggle]

Supposed to be clear skies tonight so I might have the opportunity to practice, but it will be a cold -8 degrees Celsius. Many people in the forum talk about climatizing their scopes. Should I do the same with my camera and bins?

[deadfraggle]

So the digital camera I'm using resets the shutter speed to default after every picture. This makes taking multiple long exposes impracticable, since you have to fumble through the menu each time to set it up. There's a 'macro' feature, but it's for closeup shots, not for recording key presses.

Anyhow, I still took various single shots at different settings. Wish I could tell you what I used for these two shots, but I wasn't paying much attention after my game plan went south. Most likely these were ISO 800, 15 to 25 second exposure.

The first photo shows the constellation Cygnus quite well. The second has Aquila on the left, most of Ophiuchus on the right, and you can just make out some of the Milky Way.