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analogue video with big chip ?


jonstarrysky
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Talking pure video astronomy (camera analogue output fed direct to AV input of monitor), it seems these vid cameras are based on CCTV units. These typically have small 1/2" or 1/3" chips. Means equilavence to a 6mm eyepiece i.e. narrow field.

Contrast that with full blown CCD imaging or dSLR, with their huge chips and big fields.

So has no one developed an astro video camera with a big chip ? Mallincam have their "Universe" that does this. But ....that looks more like an imaging decide for me. Only USB output, and laptop is essential...

Seems like to get the big field, you are forced down the digital route.....

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I think you might have been wise to start "hording" 1/2" chips? :p

As you imagine, availability is driven by the CCTV market.

I.E. "no demand" for sensitive chips bigger than 1/3"? 

There are also manufacturing issues? Some of the chip types...

e.g. "Exview" are quite difficult to manufacture - Chip defects,

vulnerability to cosmic ray damage (hot pixels) etc. :o

Edited by Macavity
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One reason for the lack of large size video sensors is the approx. 640x480 raster of the NTSC/PAL video standards, set in stone in the 1950's. Video cannot benefit from resolution higher than this. On an APS-C sixe sensor, used in standard DSLR's, this would translate into ~36 micron pixels. For comparison, the Lodestar and the Mallincam video cameras, known for their jumbo size pixels, use sensors with 8.4 micron pixels. DSLR cameras have much finer resolution due to using 4.3 micron pixels. The above measurements are the linear sizes of the pixels meaning that the 36 micron "whales", that would be needed for APC-S size video sensors, would have more than 16 times the area of the 8.4 micron "jumbo" pixels. I don't know if it is technologically possible to produce those whale pixels but for one reason or other, they are not made.

One alternative possibility would be to use sensors with "jumbo" pixels in 4x4 binning mode. The Mallincam Universe does have a 4x4 binning mode. But, unfortunately, half of that is achieved by software binning, which does not provide the same low noise feature as hardware binning or larger pixel size. Moreover Mallicam Universe requires a computer, its images cannot be fed directly into a monitor.

To make the long story short, I see two options for you.

If your budget is a couple of hundred dollars, then you could buy an Astro-Video Systems DSO-1 camera with a 2" infocus adapter and a Varioreducer focal reducer. The adapter would allow you to sink your camera inside of the 2" focuser of your Dob and reach focus with aggressive focal reducers. The reducer would increase your FOV and image brightness at the same time. You would have pretty spectacular views of galaxies, planetary nebulae, globular clustes and of moderate size diffusion and emission nebulae (E.g. Trifid, Swan, Bubble, Crescent, Helix, Flame etc.). The required exposure times would be 17 sec or less.

If your budget is a couple of thousands of dollars, then your prime choice would be the Sony A7S full-frame camera for $2500. This can be coupled with a high definition video monitor but only up to 1/4 sec exposures. That would be o.k. for brighter DSO's, star fields and planets. Fainter objects could be viewed as still images using a remote exposure controller at exposure times 30 seconds or less. You could watch these images on the built-in screed of the camera or on an attached monitor. But these would be still images, not TV-like video movies. You would have to wait 30sec, or whatever exposure time you set, for the image to appear on the monitor. If you want to refresh an image, you needed manually press the button on the exposure controller again. It is NOT necessary to use a computer to watch the images taken by the Sony A7S on a large screen.

Another option that has been mentioned in the $2000 range is the Mallincam Universe (MCU). This camera uses an ICX413 sensor that was also used in some Nikon DSLR cameras about a decade ago.  Those cameras have long been discontinued leaving the MCU as the only camera using this legacy sensor. The MCU cannot be used without a computer but it is capable of automatically update its image. The FOV of the APS-C size sensor of the MCU relates to that of the full-size sensor of the Sony A7s as a 27mm eyepiece compared to a 43mm one.

--Dom

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For that money you can get a laptop and decent CCD camera and just use it to make short exposures...Mather just as much light. The universe is essentially a normal CCD camera. If you could stream video out, you would need a very costly screen to show all those pixels! Depends what you are trying to do and how much you don't want to have a PC in the field.

Cheers

Peter

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For that money you can get a laptop and decent CCD camera and just use it to make short exposures...Mather just as much light. The universe is essentially a normal CCD camera. If you could stream video out, you would need a very costly screen to show all those pixels! Depends what you are trying to do and how much you don't want to have a PC in the field.

Cheers

Peter

Peter I suggest you read more and do your home work before you make comment like this "The universe is essentially a normal CCD camera". Some people on these groups SGL and CN make all types of comments and accusations regarding Rock Mallin's cameras and they really should to be contacting Rock direct to get the actual facts to be fair. Spreading incorrect information is never a good thing for all!

Chris A

Astrogate

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