DSO's with the ToUcam

Screwdriverone (Chris) · #1 01-07-2008, 02:10 PM

Hi Everyone,

Essay for the day starts.......now!

I am after a bit of advice as to where to start attempting some pics using my webcam which is long exposure modded to capture some Nebulae, Open Clusters and Globulars etc.

I know I dont have the ideal imaging rig, but I would like to try getting some decent pics of say Eta Carinae, Jewel Box, Omega Centauri etc, and to date seem to be heading nowhere.

My tracking at the moment seems to be woeful because even short exposures of bright stars are trailing and no good. I can use the K3CCDtools reticle to check the drift aligment and have been practicing this so I will put that to the side as something important overall, but off topic here.

My scope in a dark site can see quite well DSO's like M104 and NGC5128 (Centaurus A) as well as M8 etc, so I would like to start somewhere easier and get some practice. I am comfortable for the moment with planets, but baulk a little when it comes to DSO.

I use K3CCDtools and the Philips ToUCam PCVC840K with long exposure mod to capture the images.

Can anyone please provide some basics to get me started?

Like:
Shutter speed (not sure how to set this to an exact number - there is only a slider)
Length of exposure
Number of exposures
How to take a "dark" and do I need one
How to take a "flat" ditto ^
(I think I know what to do once I have these, just unsure of what to do to get them)
What is the best application for gathering data for this and any other variables I need to consider. (without mortgaging the house)

I am hoping that the setup is capable of something worthwhile, I am confident I can navigate most applications but havent seen too many "how to's" related to DSO using a webcam.

I would really appreciate any help offered.

Thanks

Chris

renormalised (Carl) · #2 01-07-2008, 07:54 PM

Chris, that will be an interesting DSO setup

Your shutter speed adjustment is just a slider with no scale?? What you will have to do there then, is, knowing the range of shutter speeds your camera has, to "eyeball" the approximate value along the shutter slider. However, you'd be better off finding software which will allow you to enter the value for the shutter speed. Your length of exposure depends on many things, as you'd be aware of, but the general rule is the fainter the object, the longer the exposure. However, taking more, shorter length exposures and then stacking them works as well... which having a modded webcam will be the way to go. Some go to great lengths to make masks and such to cover their scopes to negate the light, but it's just as easy to place the cap over the end of your scope and take an exposure for the darks....make sure they of the same length of your exposures, and taken under the same conditions of exposure, otherwise you may introduce artifacts instead of removing them. Flats... you could make yourself a lightbox to produce them, but it's probably easier just to get yourself a whitish T-shirt and making a cover for the end of your scope out of it. Then taking the flat by pointing it towards zenith in an afternoon sky. That way, you try to assure that the sky is evenly illuminated but not too bright. As with the darks, try to take an exposure of the same length as you intend to take your main pics with. You may have to make subs for both then combine them into a master flat and dark frame.

Hope that helps.

kinetic (Steve) · #3 02-07-2008, 05:46 AM

Hi Chris,

Using the default Toucam control sliders (and the SPC900 later model)
can be a pain in the ... without knowing exact values for the settings
that you can write down and repeat another time.

I use a great program from Martin Burri called WcCtrl:
http://www.burri-web.org/bm98/soft/wcctrl/

It runs in tandem with K3ccdtools and is basically a settings uploader
and saver/ driver utility.
It makes all of your camera settings numeric sliders and you can save
settings in 'slots', such as 'good moon settings', Jupiter with 3x barlow etc.

I can't get it to work reliably though in a Windows ME platform, but it works
fine on XP.

I will trawl through some of my better results and suggest some slider settings that work for me in a later post.

regards,
Steve B.

Screwdriverone (Chris) · #4 03-07-2008, 10:52 PM

Hey thanks Renormalised and Steve,

This helps a lot!

I thought that was the method for taking darks but the flats I had no idea. What do you do with the flats by the way? I assume that the darks bring out more details by reducing the background noise once subtracted from the images stacked. Will this also remove the hot pixels I get when the camera is in Long Exposure mode?

I will give the program Steve suggested a try, it seems to be what I need alright. I now have an XP work laptop so this should fix things up a bit.

Any other suggestions for favourite exposure lengths for certain objects or other software that kicks butt for DSO or ToUcam driving?

Thanks

Chris

p.s just whack me upside the head and point me to the post if this is covered elsewhere in IIS please.

renormalised (Carl) · #5 03-07-2008, 11:32 PM

Chris, try here...picked this up on here earlier this week...

http://www.noao.edu/outreach/kpvc/im...-software.html

Flats are used to remove such things as vignetting, dust bunnies and such. They provide a flat (and hopefully evenly illuminated) field that compensates for noise within the pictures you take. The noise is generated by uneven sensitivity across the pixels within the chip in your camera and the flat basically helps to cancel it out.

When you image DSO's, the best one's to start out with are the brighter, more prominent ones, such as Omega Centauri, M31, M8, Eta Carina, LMC/Tarantula Nebula etc. The brighter ones are easier to image (or should be). You still have to make up a series of subframes and then stack them, but you'll find them easier to handle than going to objects like PN's and smaller, dimmer galaxies etc. Your 840K will take upto 60fps, so if you wanted to get a good shot of, say, Omega Centauri, I would take a 1 hour avi of the glob and then crop out the best pics in the bunch. Try to strive to get 300-400 stills or more. 800 is even better. Then you can calibrate and stack them using Registax, perform preprocessing and then export the subsequent file to your IP software for further work.

Know what....have a talk with the Icemeister... I'm sure Mike would give you few good tips and advice. He's the webcam king