Tips for using Webcams?

[lw24]

Hi all,

I've just placed my order for the 'famous' Pre Flashed SPC880 webcam bundle from Morgan Computers, and am eager to get started capturing images when it arrives. I have a few queries however.

Firstly, how much data should I capture to get a decent image (in terms of minutes)?

What frames per second should I let the webcam record at?

What software can I use to combine AVI's? (I have an Alt-Az mount, so will need to combine a series of short recordings before I stack)

Are there any useful tips on getting a nice crisp image? (Such as specific options to choose on Registax etc)

I would just like to get a pretty decent first picture (not just end up with a blurry mess) that I can show to my family, who are interested in my progress with my telescope.

Cheers all!!

[Bizibilder]

I suggest you time an object across the field of view (the camera will seem "like" a 6mm eyepiece) and then work out around three quarters of that time to run your avi.

Run at 10fps.

Use Sharpcap to capture the image (dead easy to use with the SPC900 - set the exposure just "too dark" and use the gain slider to get it "dead right").

Combine the avi's in Registax. - there are some good video tutorials to get you started on: Astronomy Shed UK Astronomy Forum • View topic - Registax Planetary Tutorial

(along with some others that will be of interest).

Crisp image - focus, focus and focus! Spend as much time as you need to get this right - you cannot "improve" an image that is out of focus to start with.

Hope this helps.

[lw24]

So do you focus by looking at the image on sharpcap on your laptop?

[Bizibilder]

Yes - it will shimmer and move about a bit so you have to take your time. At first you will think it impossible to get anything from the image on the screen but, be assured, you will!

[lw24]

Alright, so it's all in the focus then

Can I combine AVIs in Registax?

[Bizibilder]

I'm likely to be told otherwise but I don't believe you can.

[lw24]

Combine the avi's in Registax.

Oh, you said you could?..

[Bizibilder]

Sorry! I misunderstood! I thought you meant combine several different avi's!

Yes - You combine all the frames of a single avi in Registax

[lw24]

I think I've confused you here.

I want to combine several separate AVI files.

[MorningMajor]

One point to note is that the cam has a vey narrow field of view, equivalent to a 6mm EP - so make sure you align your target in the scope as accurately as possible, otherwise, you'll pop your webcam on and find you can see nothing - very frustrating!

[the_laughing_crow]

to combine several avi's download and use virtual dub. the software will also allow you to re-save the avi's as an "old format avi" which seems to get round some problems with registax and normal avi's

[lw24]

Ok, thanks guys

[JamesF]

I'll re-iterate that it is not simple to do this and that you cannot expect brilliant results immediately. Be prepared to go back and start all over again a few times, and keep plenty of notes on what you're doing. Don't be surprised if it takes weeks or even months before you get an image that you actually feel happy with.

Not that I want to put you off, but it's not as easy as just dropping a webcam in the diagonal and all of a sudden you have lovely pictures of Saturn on your screen.

James

[lw24]

So much for the famous saying "How hard can it be..."

[JamesF]

Well, yes But just consider the number of variables involved...

You need a night when the seeing is fairly good to start with, and if you have school or work the next day then your hours are likely to be very limited at the moment except for the weekends and even then I reckon you'll have little more than three hours when it's dark and Saturn is clear. For me at least, genuinely good imaging nights were almost non-existent in April too, so you could be waiting a long time between opportunities.

Then there are all the different variables with camera setup, which can change if you add a barlow and/or an extension. Some settings may mean you get a better image, some may mean you don't get a usable image at all and others will just leave you with something that looks right, but isn't really what you were after. Getting a decent focus can take an age too, so despite perhaps taking half a dozen five minute subs over the course of an hour, you might eventually discard all but two because in the cold light of day they just aren't good enough.

Aligning and stacking doesn't seem to painful, but the rest of the post-processing has so many variables that you can spend ages trying stuff out, deciding you're not happy and going back to the start to try again. And if at this point you decide that your original images aren't up to snuff, you're waiting for the next decent night's seeing before you can try anything else.

I'm not trying to put anyone off, because when you see your work improve it's a great feeling, but I think there's a good reason that you see people posting images here with comments like "I've been working on my imaging for a year and now I feel I might be getting somewhere". Since I got my 127 Mak I've probably put in forty or fifty hours of imaging time (capturing, processing or just trying to learn my way around the various bits of software, not to mention doing a fair bit of reading) and I feel I'm still very near the bottom of the learning curve.

That said, I think it's a load of fun and I get as much enjoyment from it as I do from finding a new Messier object after spending an hour looking for it, so go for it.

James

[lw24]

I've heard that a webcam is the same as a 6mm eyepiece. Bearing this in mind, i will get an image of Saturn at 100x magnification in my telescope. Is this enough?

I could put it in a 2x Barlow, to take it up to 200x, but would this be too much?

Cheers

[JamesF]

The 6mm thing is often repeated and I have no specific cause to doubt that the image size in a 6mm eyepiece is similar to the image size in a webcam, but I don't know where the idea originally came from nor at what point the similarity starts to break down (if at all).

There are a number of images in this thread:

http://stargazerslounge.com/imaging-planetary/140984-saturn-2-5-2011-skymax-127-mak.html

showing what's been done with 127 Maks in various configurations (so not a huge amount different in aperture from your scope), but they do have a focal length of about twice that of your ST120 and you may find that you need a barlow to get anywhere close to that as fast refractors aren't the ideal for planetary imaging.

I have to admit that it hadn't even occurred to me to try planetary imaging with my ST120. Next time I'm out (unlikely to be before the start of next week by the looks of the current weather forecast) I'll try to remember to give it a go and post the results.

James

[lw24]

I have just downloaded Sharpcap, for recording AVIs on my webcam, and have noticed a problem. From what I can see there is no 'gain' control, which is constantly discussed on this forum.

The only explanation I have for this is that I have not plugged my webcam into my laptop (I dont have my webcam yet).

Cheers

[Bizibilder]

Once you load the driver for the SPC900 you will see the gain control appear (It only appears for webcams where you can manually vary the gain).

To comment on James' post - you will get a planetary or Lunar image with a webcam quite easily.......Getting a GOOD image.....Well!!! (But it is fun trying ).

[TheThing]

A webcam can be similar to anything between a 10mm and 6mm EP, depending on your set up.

Webcams are more sensitive than the human eye, so it is often possible to push the boundaries with them. Whilst most people recommend not more than 200x for visual, you can use much higher mags with a webcam, if the seeing is good.

I have been known to dabble with 300 - 500x on the moon, on ocassion...

[lw24]

I have a Baader Fringe Killer for my telescope, should I use this with the webcam to gain some contrast?

[bm1980]

Well, yes But just consider the number of variables involved...

You need a night when the seeing is fairly good to start with, and if you have school or work the next day then your hours are likely to be very limited at the moment except for the weekends and even then I reckon you'll have little more than three hours when it's dark and Saturn is clear. For me at least, genuinely good imaging nights were almost non-existent in April too, so you could be waiting a long time between opportunities.

Then there are all the different variables with camera setup, which can change if you add a barlow and/or an extension. Some settings may mean you get a better image, some may mean you don't get a usable image at all and others will just leave you with something that looks right, but isn't really what you were after. Getting a decent focus can take an age too, so despite perhaps taking half a dozen five minute subs over the course of an hour, you might eventually discard all but two because in the cold light of day they just aren't good enough.

Aligning and stacking doesn't seem to painful, but the rest of the post-processing has so many variables that you can spend ages trying stuff out, deciding you're not happy and going back to the start to try again. And if at this point you decide that your original images aren't up to snuff, you're waiting for the next decent night's seeing before you can try anything else.

I'm not trying to put anyone off, because when you see your work improve it's a great feeling, but I think there's a good reason that you see people posting images here with comments like "I've been working on my imaging for a year and now I feel I might be getting somewhere". Since I got my 127 Mak I've probably put in forty or fifty hours of imaging time (capturing, processing or just trying to learn my way around the various bits of software, not to mention doing a fair bit of reading) and I feel I'm still very near the bottom of the learning curve.

That said, I think it's a load of fun and I get as much enjoyment from it as I do from finding a new Messier object after spending an hour looking for it, so go for it.

James

i agree with James, sounds like you have a lot of questions to ask but dont try to hard to get the best image you can straight away because you wont, the main thing to do is go out and enjoy it and learn from your mistakes, You may fall into the trap of over complicating things if you dont . I have found myself falling into the same trap you will just get very frustrated. I am sure your familly wont be too critical about your first astro images if they dont look like they were captured by the hubble space telescope.

Regards

Ben

[lw24]

My webcam arrived! Woohoo

One small issue. After watching a Sharpcap tutorial on AstronomyShed, the guy reccommends leaving the exposure setting on 0 - 2. My exposure setting bar only allows me to go from -14 to -4.

What do I do???

[JamesF]

I'm not certain about this, but I believe -4 is 1/25 sec, -3 is 1/33 sec, -2 is 1/50 sec and so on, so you'll probably be wanting to keep the setting on -4 or -3.

James

[Bizibilder]

Ignore the numbers - when you are looking for your target set the exposure to the far right (ie "max") and the gain about mid way between centre and far right. The screen will look terrible! but you can soon see your target! When the target is centered put the gain in the middle (32 I think - having said ignore numbers!) and then move the exposure to get a good, but slightly dim, image. Then move the gain to the right (just a little at a time) to get the image "right" (takes some practice!).

If your target is the Moon set the exposure with the Moon a "bit dim" and then move the gain as far as you dare WITHOUT "whiting out" any highlights. You can always process a dim image but you can't get anything out of a "blown" one.