Why Webcams over DSLR

[SionR25]

Hi everyone,

Just reading through the talks about planetary and lunar imaging and was wondering, why do people prefer to film with webcams and software rather than film with DSLRs and software. Are the better sensors of DSLRs not more suited to it.

Just wondering if I am missing something? Sorry if it sounds silly

[Alanmads]

I too am a little confused re this matter. Specially considering i have now received my new canon 350D for xmas based on advice given. Im wondering if it may be preference? Does anyone know what the best software i should be using would be?

Cheers

Alan

[Ags]

The webcam can shoot 10 or more frames a second and then you can stack hundreds of these images to subtract the effects of bad seeing.

[Ags]

Steppenwolf posted a thread recently where he used software to capture the camera's live view as a video stream - that might be the way to do planetary imaging with a DSLR.

[Black Knight]

That's the main reason, yes. Although it seems counter-intuitive at first glance, high frame-rate cameras can effectively negate the effects of bad seeing by recording many, many frames in a movie file. The best frames from the movie are stacked to improve the signal using Registax or Avistack. If you were to try shooting with a DSLR, you would be very unlikely to capture an image during those rare moments of seeing clarity.

The other reason is simply sensor size. A planet would look tiny given the FOV or most DSLRs.

Edit: I was referring to Ags' first post!

[badgers]

Check out Eos Movie Rec:

EOS Camera Movie Record

Allows you to record direct (20-30fps) from Canon Eos live view, either whole sensor or a 5x zoomed portion at webcam resolution.

Works just like a webcam and best of both worlds in my opinion.

Downside is still that the DSLR is much heavier than a small webcam, so stability may be more of an issue.

Badgers.

** The AVI files it generates are a little strange, you might need to run them through VirtualDub before Registax will load them.

[brantuk]

Planets are bright so short exposure webcams are great for capturing them. And because of the frame rate you have more chance of grabbing a good frame during those elusive moments of perfect seeing when the atmosphere is otherwise making a mess of the view.

Dso's on the other hand are really dim so you need longer exposures to capture good images and dslr's lend themselves very nicely to that. You can leave the shutter open 5 or 10 mins at a time then stack all the sub frames together to build a complete picture of the object.

It's not so much "a preference" as it is "the right tool for the right job"

[asterix]

Is it easy to add a webcam to a Tal1 telescope?

[Mark Scott]

Is it easy to add a webcam to a Tal1 telescope?

Yes, you need A webcam 1.25 adaptor (around £10). Remove the front lens and screw in the adaptor. I'd post a link but I'm not sure it would work from the mobile phone app.

[todd8137]

Get both if ya can

[jgs001]

The sensor size is another key factor (alongside the frame rate). I'm going to use the crop factor ratio's to give examples of this, as it provides a fairly good framework for envisaging what's going on... Based on a 35mm camera exposure being a full size frame, the 350d has a 1.6x crop factor. That means, for the FOV, you multiple the focal length by 1.6. A webcam, on the other hand, has a sensor with an approximate crop factor of 8.5x.... Therefore,

Sensor Crop EQ Focal Length (mm)

35mm 1 1000

350d 1.6 1600

webcam 8.5 8500

This means, that to get the same FOV with an SLR as with a webcam, you have to use a (approx) 5x barlow (or equivalent), with the subsequent change in exposure times etc... when what you actually want is to use a barlow with the webcam to get in even closer.

I hope that makes sense.

[Alanmads]

Perfect sense. Thankyou Badgers and jgs001.

Brantuk, you keep popping up with pearls of wisdom and put in across in a way that is clear and concise. Thanyou. So, decision on whether to use DSLR or webcam depends solely on what i am trying to view, as you said Brantuk, its about using the right tool for the job.

Jgs001...........crystal clear and simple to understand explanation. Thanks once again everyone.

[lukebl]

Although I use webcams and dedicated planetary cams for planetary imaging, I am amazed at what is possible with a DSLR, like this image and video of Jupiter captured with a Canon 500d, EOSmovrec software and a 200mm Newtonian by Michael Vlasov in Israel.

[Macavity]

There is, of course, another option... VIDEO astronomy. Splitting the difference between the (sometime) disappointment of "Planetary" Webcams and the skill (financial investment) requirements of more conventional, large-chip, imaging?

But it can provide "family access" - the "Holiday snaps" (IMO more than that!) of Messier objects? You can develop the more sophisticated imaging techniques - stacking, darks, flats etc. too. Unfortunately still MODESTLY expensive, but...