B&W cameras and filter wheels

[aerobrake (Michael)]

HI everyone,

I've been using my trusty toucam 740 as my planetary imager and want to upgrade. It seems that the black and white cameras are the way to go now from my search of the web.

Question is to get a colour image I have to obviously use a filter wheel and shoot thru different colours one at a time, so does this mean that I would need to take a longer sequence of shots so I get a reasonable number of stackable images thru each colour? Also would the planets rotation then not become a factor?

Any info from you gurus outh there are more than welcome.

Cheers
Mike

[Stephen65]

With the better quality firewire cameras I think you can shoot at higher fps without losing data to compression, this lets you compensate for needing to take a shot through each filter.

[bird (Anthony Wesley)]

Mike, a monochrome firewire camera + filter wheel is the way to go, but be sure and get narrowband (dichroic) filters for the best result.

I'm using Astronomik RGB filters, and on Jupiter I record about 60 seconds through each filter at 40fps uncompressed. This gives me about 2400 frames in each colour to play with and the rotation artifacts after 3 minutes are still very small.

I'm using a Dragonfly Express camera from www.ptgrey.com

regards, Bird

[aerobrake (Michael)]

Thanks for the info guys. I'll start hunting down a suitable camera.

Is higher resolution better for planetary, I'm thinking the higher the res the smaller the pic so maybe 640x480 is plenty???

Cheers
Mike

PS Bird do you have a pic of your setup or a link to web page if you have one, cheers.

[Stephen65]

I've drooled over Bird's setup before:

http://www.acquerra.com.au/astro/lexx.html

[rat156]

Hi Mike,

It's a tough choice really. If you buy one of the nice mono firewire cams it's a pretty large investment, then add on filters and a wheel of some sort. Or you could do what I just did, use the toucam for the colour and the mono for the luminance. Seems to work pretty well.

Now I have a mono SBig and CFW for deep sky stuff, and you quickly learn that all the detail is in the luminance channel. Many astroimagers bin their colour subs 2x2 with no drop in image quality. So why not for planetary? The SPC900NC Toucam uses the same chip as the DMK21AF04, with a bayer matrix over the top, so image scale is the same as well.

Good luck.

Stuart

[aerobrake (Michael)]

Thanks chaps,

Hi Stuart, yeah I still like my toucam 740 (same chip as the 900NC by the way) and I have flashed the ROM so it uses the latest codec as the 900NC so basically the same cameras. Interesting what you say about using a mono for luminance, I havent much experience in doing so but now certainly will.

Cheers
Mike

[bird (Anthony Wesley)]

Mike, my web page is www.acquerra.com.au/astro

There's a page about my scope as well: www.acquerra.com.au/astro/lexx.html

regards, Bird

[Stephen65]

On a related subject - am I right in thinking that 1024x768 cameras have no real advantage over 640x480 cameras for planetary imaging because the limiting factor on fine detail is your telescope's resolution and not the number of pixels in a 640x480 display? FPS seems to be more important than extra pixels for planetary.

However, when it comes to lunar I've noticed that some very good lunar pics are taken with higher resolution cameras.

[bird (Anthony Wesley)]

The camera has to be considered in context with the rest of your scope, it only forms one part of the imaging system - the other bits of your scope form the rest of the system. You have to match the pixel size of the camera to the focal length of your scope to be sure that images are at an appropriate size, and also you have to match the sensitivity of the camera to the f/ratio of your scope to make sure that images are bright enough to capture.

So, I don't think there's one ideal camera that will suit everyone...

cheers, Bird

[Rigel003 (Graeme)]

Originally Posted by rat156

The SPC900NC Toucam uses the same chip as the DMK21AF04, with a bayer matrix over the top...
Stuart

I wouldn't have guessed this. Is that really the case?

[rat156]

The SPC900NC uses the ICX098BQ chip, the DMK uses the ICX098BL.

Specs for the BL
http://www.theimagingsource.com/prod...s/icx098bl.pdf

specs for the BQ
http://www.theimagingsource.com/prod...s/icx098bq.pdf

The second page of each shows the differences, essentially the Bayer matrix.

Cheers
Stuart