more planetary camera musings/questions

[Robert_T]

Hi Guys, looking about at the firewire cameras from imaging source (DMK - mono, and DFK's - colour) I notice they also have DBK's "BAYER" - does anyone know what this means and what these do? The specifications seem pretty well identical, same chip and all that?

One other thing that struck me was that if I could get a chip with smaller pixel size then I could achieve better resolution as the same size image on the chip would be covered by or cover off more pixels. On this I see that they also have larger chips (1028x768) firewire cameras that have 4.6micron pixels as opposed to the 5.6micron pixel size on the 640 by 480 chips of the toucam's neximage and DMK/DFK's of this size. The downside is these only have a top frame rate of 30fps versus 60fps for the 640x480 DMK/DFK cameras.

What think you guys - you think the pixel size reduction may be worth it?

cheers,

[Dennis]

Hi Robert

I think that when you see the term Bayer, it usually translates to INFERIOR resolution compared to black & white.

If I understand correctly, all ccds are B&W and to obtain one-shot colour, 4 pixels are "grouped" together to capture R, G & B (via micro-lenses) to then form the final colour image.

I think that CMOS may be different, although still suffers from inferior resolution due to the chip or circuit design in an attempt to obtain one shot colour.

That's about all I recall on the topic.

Edit: just found a useful link: http://www.licha.de/astro_article_ccd_camera_bayer_matr ix.php

Cheers

Dennis

[Robert_T]

Thanks Dennis - I think I can now understand the difference between the Bayer and the Mono cameras, but wonder how the Colour version differs (there are thre varieties Mono, COlour and Bayer). I thought the colour versions work the way the Bayer stuff below is described:shrug:

[Dennis]

Hi Robert

I think that there are astrophotographers who de-bayer their images from the raw capture mode to preserve the equivalent B&W resolution, but then they seem to end up with a B&W image with a grid pattern overlaying the image, which is the bayer grid.

Image processing can somehow either minimise or remove these artifacts from what I understand.

As far as I know, the only colour ccd that can "match" a B&W ccd is where there are 3 stacked, separate physical layers than register R, G & B so that resolution is not lost. They are very rare and expensive.

Hopefully someone who has a clearer and deeper understanding of the specific issues you have asked about can provide more details, as my knowledge is a little piece meal from casual reading.

Cheers

Dennis

[Robert_T]

Thanks Dennis you've already boosted my understanding a few notches, but if anyone else can add... especially on the issue of pixel size I'm all eyes:P

[davidpretorius]

wheres bird when you need him???

Yes the need for extra detail is required, but at least 30 fps would be a beauty, BUT, the laptop is quickly becoming the weak link!!! THe hard drive has to be able to handle this data wizzing its way!!!

Rumples has newish Dell and I think still has the odd freeze during capture at 30 fps.

60 fps may be a few years away for us to have hardware to make use of the speed.

Damian Peach has just gone for this beauty

http://www.lumenera.com/astro/docs/SKYnyx-ProductOverview.pdf

to quote

"Here are some images from last night. The usual seeing down at low altitude. The bright oval ahead of the GRS is well seen. A new Lumenera Skynx camera was used. This is excellent with a notably smoother image than the 075M and all free of any artifacts."

[davidpretorius]

http://www.astrovid.com/products.php?cat=175

[Robert_T]

I'm salivating - me want! DO you know which model he has the colour or mono, I assume it's the 2.0 model? They reckon these work with K3CCD Tools too:D

[iceman]

He has the mono. You want a mono Robert, simple as that. If you're going to go the next step up, get a mono. I know Lester bought a colour, and Astroman is looking at colour as well, but that's probably because they want the extra hassle of changing filters etc.

I've seen some people with the DMK 1024x768 mono as well, great images with huge image scale. Though For lunar stuff it's just what you want. For planetary it wouldn't make too much difference because the image scale you're working at isn't usually that large anyway.

I reckon you're all set up with your 925, and the next scope will be your beast newt. To go to the next level, you want a better camera.

60fps isn't really a concern at our level. To use 60fps, you'd need to be either imaging a very bright object (like the moon), or have an 18" scope to let enough light in.

Almost every top imager is using 30fps as far as I know. Some cameras have hardware ROI (region of interest) as opposed to software ROI. That way, you can draw a box around what you want to capture and not have to pull down the full 640x480 each frame - if imaging a smaller object like Mars, you can draw a smaller box around it and use a higher fps. Again though, you'll need enough light coming in.

and a fast enough computer to keep up.

30fps is 6 times faster than what I use now.. In theory, I should be able to get 6 times more frames than what I do now. I lose some due changing filters/dampening, and I lose some because i'm not capturing for the full 2 minutes in each colour, but if I can capture 30 seconds of each colour, and allow 30 seconds for changing filters and dampening, I'll end up with 900 frames of each colour channel. That should be plenty enough to find 200 good frames.

[Robert_T]

Thanks Mike, you just about got me convinced, though I'm railing at the outrageously high prices of motorised filter wheels. How can they possibly justify more for a simple wheel with a stepper than what you'd pay for a full Got To telescope mount. The mind boggles. Reckon I'll get the ATIK. We need someone talented to come up with a motor add on.

cheers,

[Lester]

Go Robert,

and if it works I may do the same if the colour DFK doesn't perform.

[iceman]

The cheapest motorised filter wheel is the Andy Homeyer one, which is still US$499 (more than the DMK camera). He may have availability problems though.

Then you still need to buy RGB filters. I'm getting the baader ones at the budget price of AU$170. I simply can't justify spending any more than that on filters. I hope the wavelength cutoffs are the same.

The Atik does look like it could be motorised by someone with DIY skills.