Shoot mode question.

What mode should I be in? I have tried taking simple practice sky shots in my backyard and I have found that a 30 sec exposure at 800 ISO and f/5.6 in blub mode and the same specs in av mode render me completely different results. In bulb it seems to gather a lot more light than in av. Is there something I am missing?

Bulb mode means that the shutter will stay open as long as you are fully depressing the shutter release button...so, if you push it and let up, your shutter will be really short; if you push and hold, your shutter will be really long (until you let up). In Av mode, the camera sets the shutter speed, so you're not actually getting a 30s exposure there. That's why the Bulb shot is gathering more light; the shutter is open a lot longer.

By specs being the same I mean everything was exactly the same including a 30 sec exposure.

In Bulb you are totally in control of all settings as where in AV mode you only control a portion and the rest is AUTO . SO even tho you say the same specs the camera settings in AV mode will still have some different settings as the Bulb mode . Best way to tell is bring up the Histogram and see what the ISO , F/Stop and Exposure time is compared to your Bulb settings .

You can't specify f-stop AND shutter speed in Av mode; nor can you set a specific shutter speed in Bulb mode. So, how are you going about setting the "exact same" settings in both modes to do the comparison?

Oh hmm then it must not have been a 30 sec expo in av. I guess I was lying Anyways what mode should I be in? Or does it not matter as long as I can get a 30 sec exposure?

Use whichever mode is easiest to shoot in with the settings you are trying to get. If your primary concern is getting a 30 second shutter speed, Tv or M are going to be your "go to" modes; you can specify 30s in either one. In Tv, the camera will adjust the aperture for you (which may/may not actually give you what you're looking for right off the bat) and in M you also have to specify your own aperture, but you need to understand what the meter is showing you in order to choose the right one.

Snydremark wrote in post #13344678
Use whichever mode is easiest to shoot in with the settings you are trying to get. If your primary concern is getting a 30 second shutter speed, Tv or M are going to be your "go to" modes; you can specify 30s in either one. In Tv, the camera will adjust the aperture for you (which may/may not actually give you what you're looking for right off the bat) and in M you also have to specify your own aperture, but you need to understand what the meter is showing you in order to choose the right one.

Yes, also given the fact that the OP is shooting "sky" shots then having the aperture wide open seems to be the best option.

In manual mode choose your 30" shutter, then aperture and ISO, take some shots and adjust if required.

Thank you guys! I will try your suggestions tonight!

You may not have been lying. If it's really dark in Av mode, the camera would have selected the longest shutter time it has available, which would be 30 sec (it can't do bulb by itself). Try it with the lens cap on.
If the camera comes up with something less than 30sec, cover the viewfinder with your thumb.

MrJack787 wrote in post #13345004
Thank you guys! I will try your suggestions tonight!

Since your testing sometimes when i shoot horizon night shots i'll use the "No-Flash" setting in the "Auto-Mode" side . It's exposes as long as it needs to pick up a certain amount of light without using a flash . You'll be surprised what quality of images you'll get !!

I just always shoot manual, typically 15-30 sec depending on how bright my target is. Sometimes longer (60 - 120 sec) if I happened to get a good polar alignment on my mount. I control the camera with BackyardEOS (www.backyardeos.com).

archer1960 wrote in post #13348873
I just always shoot manual, typically 15-30 sec depending on how bright my target is. Sometimes longer (60 - 120 sec) if I happened to get a good polar alignment on my mount. I control the camera with BackyardEOS (www.backyardeos.com).

Thanks for your input. I just got the backyardEOS trial and it looks really cool. Is there a good tutorial out there for it?

MrJack787 wrote in post #13349930
Thanks for your input. I just got the backyardEOS trial and it looks really cool. Is there a good tutorial out there for it?

I don't know; I haven't looked for one. It's fairly intuitive to get the basics going, and the author is very quick responding to questions on the yahoo group.