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Why analog?

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#1 Gavin Bray

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Posted 04 January 2008 - 06:20 AM

Why do Mallincams/Stellacams output analog video rather than digital? Is this simply a by-product of their origin as CCTV cameras or is there some advantage in sticking with analog?

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#2 ccs_hello

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Posted 04 January 2008 - 07:53 AM

IMHO, they started as security camera/CCTV thus stays that way (analog). Digital output to a digital capable monitor would be nicer, but such arrangement is considered as the professional/studio grade. I.e., $$$. In that case, better go for the astroCCD + laptop direction: mature and less costly, e.g., DSI like astroCCD + a laptop.

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#3 jayscheuerle

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Posted 04 January 2008 - 03:51 PM

You could think of it as the premier choice for assisted visual observing since everything WE observe starts with analog information (photons). Going digital would just add another conversion process.

There's nothing inherently "bad" about analog, other than it's not as easily duplicated as digital (see complaints about images not doing the scene on the screen justice). - j

#4 Chris Schroeder

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Posted 04 January 2008 - 07:21 PM

Right you are, we live in an analog world. While I'm a geek and enjoy the benefits of digital stuff, it just seems to lack something compared to good analog stuff.

#5 ccs_hello

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Posted 05 January 2008 - 11:18 AM

Beyond theoretical exercise, when tasks are performed in analog domain, e.g., processing, transmission, modulation, receiving, rendering, etc., analog methods tend to let noise in easily unless extreme ($$$) measures are in place.

Digital method can allow lossless during compression and transmission. It is also possible to allow better sampling in discrete pixel boundaries. With (heavy duty) computer processing, after all just a lot of algorithms running in a computer, e.g., 3D (add time domain) processing, noise control, etc.

Just my 0.02.

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#6 rolandskythree

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Posted 05 January 2008 - 07:46 PM

Going digital for these cameras will occur someday but probably not real soon at the price range that is reachable for a typical observer. I used to study trends in a previous life, but the earmarks of change for this little type of camera have to equate to enough technical advancement without a relative increase in cost...still be able to fit in the same little cubic space...still be able to be cooled with minimal power...must be constrained to use the most advanced chip that fits the price category for the market...AND must be able to work without an external computer. When the sum total of these constraints yield a digital solution that matches a schedule for the vendors to introduce a new product, then you can bet it will happen. Meanwhile, better get the analog solution, because--as one poster said--it's delivering the goods and can be manipulated pretty easy.

Roland

#7 ccs_hello

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Posted 05 January 2008 - 11:35 PM

Sorry for the info for the purist (either the Analog purist or the digital purist):

A lot of these cams are using an in-house designe or SONY's "digital signal processing (DSP) chipset"...

- CCD output is analog.

- A timing pattern generator IC generates all timing pulses for CCD readout as well as for DSP IC.

- within the DSP IC: after S/H peforming CDS and AGC (still analog functions)
then immediately A/D (typically 9-bit or 10-bit) converted into digital form. From this point on it's all digital processing. The final result is sent out thru a 8-bit digital bus (format unknown), or performed within the IC: NTSC encoding to send out analog composite and Y/C signals.

- For long exposure longer than 1/60 sec (since interlaced-field read out mode, only one field is valid for the LE duration), a digital memory is connected to the 8-bit bus to serve as the digital field buffer. The content is (after valid field frozen) read the same field every 1/60 second to be usable as video signal by a NTSC (analog) encoder.

One sentence summary: a lot of functions are done in the digital form.

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#8 Bowmoreman

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Posted 06 January 2008 - 09:01 PM

Right you are, we live in an analog world. While I'm a geek and enjoy the benefits of digital stuff, it just seems to lack something compared to good analog stuff.


Don't even GET ME STARTED on why LPs (on a good turntable with a good tonearm/cartridge, etc.) are STILL more realistic than CDs - and yes I can demonstrate it...

More on topic, given that the origin of these devices was in the purely analog realm... adding conversions will only add noise and reduce information in the signal... Any signal will only (ever) be as good as it starts out... you can't re-create that which is lost...

Given the use-case of these devices, I don't see analog as an issue; and the fact that you can get a top-end MCHP for $1200 truly amazes me...

Once the underlying technology (digital) matures to the point where the CCDs are available at decent price points, things will then enter the faster, better, cheaper race... which can only make this situation even better.

Look how long it took for digital photography to finally equal the best of "analog" (i.e. Kodachrome 64/25)... but it did finally (well almost!) get there...

So, give in to the analog-lover within! Life is analog! Love is analog! Food! Wine! Sound! Light! Digital is only (ever) an approximation... sometimes a very, VERY good one; and for many things that which is lost via approximation is less important than those things that are gained...

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#9 ccs_hello

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Posted 06 January 2008 - 11:26 PM

Many signal processing steps degrade signal quality as more stages are going through.
It is designers' experience decide how to control their design's repeatability and noise immunity.

I'll make two points:
1) These DSP based cameras (including some most talked about ones in this forum) are basically mainly depending on processing in digital domain
(I described their design two posts above. They are not analog except for the
- input: CCD, and
- output: NTSC analog signal.)

2) These camera when doing long exposure, a field buffer must be used to replay the same field over and over to satisfy NTSC specifications. They are using digital memories. There is no A/D conversion that can be avoided. When the field content is played out, they have to be converted back to analog NTSC format which calls for D/A conversion.

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