Astrophotography - DSLR or webcam?

[RedByName]

Hello. Newbie signing in.

I just got my first scope - a Celestron NextStar 127SLT - a couple of days ago (Christmas present from my lady wife!), and I'd like to take the opportunity to try and get some great pictures: both planets and DSOs, given the chance.

Now I already have a DSLR (Canon EOS 450D) and know that I could get an eyepiece adapter and T-ring for not too much money, but my wife (who's reading up more than I am, to be fair) is telling me I should be getting a webcam to link it to our PC and use software to build up an image.

But I'm having difficulty coming to terms with the idea that a little VGA webcam's output is going to get better results than a 12MP 'proper' camera taking a long exposure.

Are webcams just a way of producing images without having to fork out several hundred pounds for a camera? Or do they genuinely produce better results?

Thanks.

[Afro Boy]

Welcome RedByName!

Now I'm no expert but here are some thoughts from what I have seen ...

Simple webcams are generally used for planetary photography. They can gather thousands of frames quickly which you can stack with software and produce a reasonable image from.

DSLR cameras (I used a 450D like you) are great and I see them used a lot for deep space objects. The thing I like about a DSLR is that you don't have to rely on a computer out in the field to be taking your shots. A cheap intervalometer to fire off multiple shots and an adapter is all you need.

CCDs are the next level up and can get very expensive. These are essentially webcams but of a very high quality. Some of the best imagery comes from these (but not exclusively either).

I've been using my 450D and love it. It's portable and I don't need to worry about the computer frying up in the middle of taking shots. One less variable to worry about. I've tried one of the cheaper modified Philips webcams and whilst they work well, it's not my favourite.

If I were you, I'd get the adapters for the DSLR and go with that to start with. You'll be pleasantly surprised with what you capture.

Cheers,

Af.

[E621Keith]

Webcam will be better for you.

The biggest problem with planetary imaging is atmospheric turbulence. Like Af said, webcam take thousands of images discard the bad ones. Then the good ones are stacked together to average out the distortion caused by the turbulence. If you take thousand of frames with a DSLR very quickly and then apply the same process, you can achieve similar results provided you use a large telescope to compensate for the large chip area. However in practice, the high megapixel count, memory requirement, large sensor size and limited computational power means this is not possible with a DSLR.

DSLR performs better in long exposure DSO imaging. Long exposure required very accurate tracking to minimise movement of stars in the image. As such it requires a good equatorial mount. Your SLT mount is not suitable for this type of imaging. The minimum mount for this type of photography is a HEQ5.

[Demonperformer]

I would agree, except to say that the SLT mount is good enough to give you a taste of DSO imaging, but you have to pick your targets. Open clusters are good. Using 20 second subs (that's what we call each individual exposure) you can capture all of the Messier objects using a canon at 1600 ISO. Accurate alignment is the key - what is good enough for visual is not necessarily good enough for a 20s sub! NOT that that is the end of the story. To get a good picture, it would be necessary to take loads and loads of subs at 20s and stack them using a free program called Deep Sky Stacker (DSS), together with dark and flat frames. I often use the canon on my 102SLT as a visual-aid. Take a 10s exposure and view the screen rather than at the eyepiece (but that is largely due to the impressive array of streetlights I have overlooking my front garden!).

OK, got into a bit more detail than I intended to there, but what I am saying is that you can experiment on bright DSOs using a SLT mount.

[Luke]

Hi,

Welcome to SGL!

Just to add to Af's post, planets are very bright so only need short exposures, but you want lots of them, partly because planets require high magnification, where the planet will drift in and out of focus due I think to turbulence in the atmosphere that is very apparent at high magnification.

The blurry frames are discarded by the stacking software and only the sharper frames are kept. By stacking hundreds of the sharper frames, you get an image that is much better than any of the individual frames.

Even if you do use a DSLR for planets, you won't benefit from its greater number of pixels because the planet will only cover a tiny peanut of the size of the full DSLR frame, so you might as well use a webcam that will keep the filesize much more compact and will use much more of the frame. You are wasting acres of space with a DSLR.

With deep sky objects, the needs are very different. Normally you are not zoomed in so much as with planets, and the DSO is much fainter, so you need much longer exposures ideally, such as five minutes per shot. Most webcams can't do long exposures, so you need a DSLR or CCD ideally, which also has the benefit of more pixels than a webcam that can come into play as you don't typically get the oodles of wasted space as with planets.

However, for long exposure DSO's you ideally want an equatorial mount or a wedge. You are likely to get star trails when doing long exposures on your current setup.

Sometimes it's amazing what can be done with lots of short exposures, no harm trying especially on things like clusters, but personally I would focus on webcam and planets with your gear.

[Demonperformer]

it's amazing what can be done with lots of short exposures

Some time back there was an image posted on here of the horsehead nebula taken with 2 second (I think) subs ... did a quick search, but could not locate it. Will look further and if I find it will post the link.

[RedByName]

Thanks for the comments - all very useful. Sounds like the correct answer is "Both!"

I think I'll go with a webcam at first - it has the advantage that we can view the scope's output from the warmth of indoors (which was a key selling point in my wife's opinion!). But it's nice to know that the DSLR has potential too.

[Rihard]

Hello

Expert people might find me wrong (please correct me in this case ) but this is the story from my POV:

- you probably have a 10" and 25" eyepieces. Average webcams, with their small sensor, when connected to a scope, will act as a 10" (or actually smaller, I am not good with numbers) eyepiece, giving you high magnifications.

Thus, planets will look fairly sized and detailed, and as other people said, you can record a movie with a webcam (i.e. 30 or 60 fps) and some of those 30 frames per second will look good enough, without atmospheric or shaky-scope errors, and when stacked all together will provide better definition.

- An SLR sensor, instead, will act as a wide view eyepiece, I don't know the numbers, but I guess something like a 30" or 40" eyepiece. In the huge, high resolution image you'll get, you'll see a very wide field, and a planet will be just like a small dot without details, even if you try to enlarge the picture. This will be, however, a good choice for starfields and other DSOs.

So, from my little personal experience, the real difference is like the difference between a high magnification eye-piece (like a 10") and a low-mag eyepiece (like a 25").

So:

- use a webcam for targets like moon and planets and some smaller DSO (with the advantage of taking a lot of FPS into a not too big AVI video).

or

- use a SLR if you need to take widefields and very faint objects like galaxies and nebulas that might require long exposures and more accurate colour and light gain.

With the scope and tripod you own, I believe you can do a better job with a webcam: the Mak's focal lenght should be good for planets. The AZ mount of your scope, not only will be too shaky with the added weight of a SLR, but is not designed to keep up with earth's rotation, limitating your pics to very short exposures times, this isn't the best option for DSOs. Of course, if you are very patient and want to spend some time with it, you can give it a try with DSOs, But the field of view might be pretty small and the light gathering not enough: this way you may not be able to fit a whole M42 on your FOV or it might look kind of darker.

Best advice: get the SLR adapters and a 10 bucks store webcam to play with and experience the difference yourself.

Regards,

TziuRiky

[RogerTheDodger]

Another thing to think about is video astronomy - there are a bunch of guys on here that are doing some great stuff, have a look in this section Video Astronomy - Stargazers Lounge

[RedByName]

- you probably have a 10" and 25" eyepieces. Average webcams, with their small sensor, when connected to a scope, will act as a 10" (or actually smaller, I am not good with numbers) eyepiece, giving you high magnifications.

Thus, planets will look fairly sized and detailed, and as other people said, you can record a movie with a webcam (i.e. 30 or 60 fps) and some of those 30 frames per second will look good enough, without atmospheric or shaky-scope errors, and when stacked all together will provide better definition.

- An SLR sensor, instead, will act as a wide view eyepiece, I don't know the numbers, but I guess something like a 30" or 40" eyepiece. In the huge, high resolution image you'll get, you'll see a very wide field, and a planet will be just like a small dot without details, even if you try to enlarge the picture. This will be, however, a good choice for starfields and other DSOs.

Not far off - I've got 9mm and 25mm eps.

I hadn't realised that the smaller resolution sensor would effectively work as a higher magnification eyepiece. In fact, that also answers the question I had about what the absence of an optical eyepiece would mean for the image.

Thanks for your comments.

[Jannis]

Hi, and welcome!

The thing is that the sensor itself of the webcam is a lot smaller (physically, it have nothing to do with the resolution). It's this wich gives you the extra magnification. personally, with my 550d, i have this 640*480 crop video recording. this only used the center of the sensor and therefor gives a similar effect as a webcam sensor. but in your case, i dont think your camera have it.

So basically, this means, for planetary, and close up lunar pics, use a webcam. for the whole moon, and other deep sky objects, use the canon. you Can do deep sky with your setup too, like mentiond before, so don't let it limit you. you will be restricted to shorter exposures, but don't worry, many targets don't need very long exposures. like M42, the orion nebula, can give great results with just many many 10 sec exposures at high ISO put together to lower the high ISO noise and to drag out the fainter details..