DMK mono which model to go for

[IanL]

Guys DMK mono USB flav. Is their much benefit of going for the larger chip size or is it swings and round abouts.

I am looking to do planetary stuff also moon shots. But I see a lot of folk with these camera with a lower resolution.

This is a real headache for me choosing.

I am looking for clean image low noise and as many frames a second as USB2 could handle. I know that I could be asking a lot but I don’t really know as in-depth as some of the folk on here about these cameras. I have around 700 bucks to play with. Could anyone suggest what model would be best?


Many thanks,
Ian

[Dennis]

Hi Ian

Here are the specs of the DMK21 & DMK31 from the Imaging Source website.

DMK 21AU04.AS

• The ICX098BL is a diagonal 4.5mm (Type 1/4) interline CCD solid-state image sensor with a square pixel array.
• Chip size: 4.60mm (H) × 3.97mm (V)
• Unit cell size: 5.6μm (H) × 5.6μm (V)
• Video formats @ Frame rate 640 x 480, Y800 @ 60, 30, 15, 7.5, 3.75 fps

DMK 31AU04.AS

• The ICX204AL is a diagonal 6mm (Type 1/3) interline CCD solid-state image sensor with a square pixel array.
• Chip size: 5.80mm (H) × 4.92mm (V)
• Unit cell size: 4.65μm (H) × 4.65μm (V)
• Video formats @ Frame rate 1024 x 768, Y800 @ 30, 15, 7.5, 3.75 fps

It looks like the DMK31 has smaller pixels 4.65μm than the DMK21 5.6μm and as a general rule, smaller pixels tend to be less sensitive (smaller photo sites = smaller collecting area) and I think that this worsens the Signal to Noise Ratio (SNR) – by how much I’m not sure? Or, would it be even noticeable in real a world application?

The DMK31 can only run at 30fps whereas the DMK21 can operate at 60fps – this could be important when doing LRGB of Jupiter as you would get 1800 frames in a 30 sec avi with the DMK21 as opposed to a meager 900 with the DMK31.

For the Moon, I would say the DMK31 is the way to go 1024x768 – lots of Real Estate to play with meaning less need to do mosaics to cover larger areas.

For planets, the DMK21 will be fine as you are unlikely to be able to image at a scale larger than 640x480?

Some food for thought eh?

Cheers

Dennis

[beren]

You could use this software for mosic capture .... http://eq-mod.sourceforge.net/mosaic/..... with the DMK21 and have the higher frame rate and sensitivity

[iceman (Mike)]

Check out the review I did of the Astrovid Voyager X - it's the same chip as the DMK31. The results I had, showed the DMK21 was more sensitive but it didn't take into account any possible chipset improvements in the DMK, or the faster framerate (I could only get 15fps with the Astrovid).

I'd probably get the DMK21.

[IanL]

Thanks guys. I think it will be the DMK21 then.


Many thanks
Ian

[Dennis]

Probably a good choice Ian, as 1024x768 data streaming to the PC may be quite a heavy workload for all parts of the imaging/data capture system, as well as generating much larger file sizes.

Also, processing 640x480 AVI’s should be less onerous too.

Cheers

Dennis

[rumples riot]

All this really depends on what you want to use it for.

For the moon the larger format camera will be better. I can say that Alan Friedman uses the larger format and his images are superb. You can still use the larger format for planetary, you will need to take slightly more frames in better seeing though, but being mindful of rotation.

The smaller format is best suited for planetary imaging but means that you have to do mosaics if you want to capture large areas on the moon. There is more work involved in doing this over the larger format.

For capture, try to buy an external hard drive with 7200rpm. This will allieviate most of the problems. I can capture at 53 frames per second on the moon and sun. For the planets I am limited to 43 fps. Although if you have a modest aperture your rates will be less. It also pays to get more RAM for your machine if you don't already have a gig or more.

So really horses for courses. If you see yourself doing a lot of moon work, then go for the DMK31. If you see yourself doing more planetary then the DMK21. The smaller pixels really does not come into play a lot. Alan Friedmans images on the moon and sun contain a lot of data and are almost flawless.

[IanL]

Thanks for that Paul. 8 out 10 i will probably be imaging the planets and less of the moon. I did have the toucam which was superb but with my new laptop running vista it just dies of death. The new laptop should be ok 1G video ram and 2G system ram bus speed is about 2.2G HDD is up thier as well.
I also tried registax on the new laptop. What takes 40seconds now takes about 10.
So hopefully it should all be good.

Cheers
Ian

[rumples riot]

All the software will run in Vista. I am running all those and they are fine. I still recommend an external drive with the 7200rpm speed.

I have a HP Pavillion Laptop from this year. Very fast machine, but I still need to have the drive. That will enable high speed data transfer.