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Old 10-04-2014, 09:57 PM
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Used 314L OSC vs New 314E Mono

Hey guys,

I'm in the market for a CCD. With my (very limited) budget I can currently purchase a used 314L OSC, or a brand new 314E mono. I'd love to get a used 314L mono, but there's none around at the moment.

So, my question is, which of the two would I be better off with? I'm mostly interested in photographing galaxies and to a lesser extent nebula. I live in a reasonably dark area (we have 5 acres near Kilcoy, about 10-15mins drive @100km/hr from the nearest street light).

Thanks,
Lee

[edit]: Forgot to mention, I will be using an Skywatcher BD ED80 600mm F7.5 refractor
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Old 10-04-2014, 11:21 PM
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Hi lee,

How much time do you have for imaging? Remember your mono cam would need separate exposures for red, green, and blue and possible a luminance also. So add 3 filters imaging time, and not to mention the cost of the filters and probably the filter wheel also ( you mentioned limited budget ).
If you have the time, and can extend your budget to cover the filters etc, go the mono. Otherwise the OSC is a safe bet.
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Old 11-04-2014, 05:44 AM
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Thanks Goran :-)

I was thinking if I went the mono route I would just acquire the ccd for now, and get the filter wheel and filters later, as more funds become available. There's much to be said for B&W images anyway, in my opinion :-)

As for imaging time, I've read that a lot of mono enthusiasts believe that they ultimately take the same amount of time. I'm not sure how that works out, unless the monos are more sensitive; I understand the only difference there to be the fact that in one the photons pass through a colour filter array, reducing the resolution by splitting them into four pixels on the sensor - RGGB, whereas the mono just grows straight to the sensor.

To my understanding the difference between these (besides being OSC and mono) is that the OSC has a temperature set point so darks, if I need to take them, would be easier because it would always be the same temperature, whereas the 314E just cools to whatever it can. I understand that darks are likely to be unnecessary with these cameras though, in a lot of cases, so the impact of that seems limited.

The other obvious point of difference between the two is pixel size and FOV. I'd actually prefer the FOV of the 314E, so that's not a problem. Pixel size apparently affects noise as well though, but looking at the specs they both claim the same noise metric.

I think I'll go with the 314E because the only absolute benefit I can see (unless the sensor is vastly better on the OSC) is the temperature control, which doesn't seem to justify the restrictions of OSC and also the lack of warranty I'd get by buying it used.
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Old 11-04-2014, 01:10 PM
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the OSC has much higher quantum efficiency and larger pixels than the mono, so it will be quite sensitive. The downside of the large pixels is that galaxies will be pretty small - great for nebulae though.

The mono has relatively low quantum efficiency, but the small pixels will give you much bigger galaxy images. You will just have to spend longer taking images than with the OSC to overcome the inherently low sensitivity.

You are right not to worry too much about cooling - these chips are very quiet and you will not really need to do darks for most targets.
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Old 11-04-2014, 01:42 PM
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If you're using that mono camera with your refractor you'll need an L CCD filter at least to block IR.
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Old 11-04-2014, 01:52 PM
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Quote:
Originally Posted by kosh View Post
Hi lee,

How much time do you have for imaging? Remember your mono cam would need separate exposures for red, green, and blue and possible a luminance also. So add 3 filters imaging time, and not to mention the cost of the filters and probably the filter wheel also ( you mentioned limited budget ).
If you have the time, and can extend your budget to cover the filters etc, go the mono. Otherwise the OSC is a safe bet.
EXCEPT

With a MONO camera all the light hits all the pixels all the time - thus they are about 3x as sensitive as their OSC equivalents all other things being equal total exposure time for the same SNR will be the same. If you move to LRGB and bin the colour 2x2 you can get more data in less time than with a OSC. And you can use it for NB. The trade off is more processing and more gear.
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Old 11-04-2014, 04:30 PM
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Quote:
Originally Posted by Shiraz View Post
the OSC has much higher quantum efficiency and larger pixels than the mono, so it will be quite sensitive. The downside of the large pixels is that galaxies will be pretty small - great for nebulae though.

The mono has relatively low quantum efficiency, but the small pixels will give you much bigger galaxy images. You will just have to spend longer taking images than with the OSC to overcome the inherently low sensitivity.

You are right not to worry too much about cooling - these chips are very quiet and you will not really need to do darks for most targets.
Ahh, that's interesting. I wonder how that would work out for nebula in terms of exposure length.

Quote:
Originally Posted by pluto View Post
If you're using that mono camera with your refractor you'll need an L CCD filter at least to block IR.
Thanks mate, I'd wondered about this. Just found Sony's documentation on the sensor in questions which confirms the sensitivity to IR which I didn't know initially. I thought that IR was effectively useless for astrophotography so I had made the assumption that these cameras would block that. That's what I get for making assumptions... :-)

Quote:
Originally Posted by JohnH View Post
EXCEPT

With a MONO camera all the light hits all the pixels all the time - thus they are about 3x as sensitive as their OSC equivalents all other things being equal total exposure time for the same SNR will be the same. If you move to LRGB and bin the colour 2x2 you can get more data in less time than with a OSC. And you can use it for NB. The trade off is more processing and more gear.
Wouldn't this just affect the resolution, rather than sensitivity, and thus mean that interpolation is required to make up those missing bits in each colour channel of the OSC? This would suggest that image quality would be improved with a mono, but sensitivity (all else being equal) would remain unchanged. Please correct me if I'm mistaken :-)



- I ended up pulling the trigger on the 314e mono. Time will tell if that was the right choice or not... given how inexpensive they are for a ccd I don't see it as being a high risk investment regardless.
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Old 12-04-2014, 06:39 AM
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Quote:
Originally Posted by Shiraz View Post
the OSC has much higher quantum efficiency and larger pixels than the mono, so it will be quite sensitive. The downside of the large pixels is that galaxies will be pretty small - great for nebulae though.

The mono has relatively low quantum efficiency, but the small pixels will give you much bigger galaxy images. You will just have to spend longer taking images than with the OSC to overcome the inherently low sensitivity.

You are right not to worry too much about cooling - these chips are very quiet and you will not really need to do darks for most targets.


I think you meant the other way round Ray. The OSC is way less QE than the mono which is the case with every OSC sensor I am aware of.

Typical QE for a OSC (not sure what a 314 is, is it the Sony ICX694 chip?) is around 25% or less but mono's are usually 50% -77%.

The bottom line, OSC is good for bright nebula but not for galaxies which are dim. Dim objects in OSC will show a ton of noise which is hard to get rid of especially in the dim areas of the image.

Straight luminance images of galaxies are quite nice even without colour. They are like Ha images.

No doubt at all - mono all the way and add colour later otherwise you will be disappointed for sure.

Greg.
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Old 12-04-2014, 09:10 AM
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I found the data sheets for both of the sensors in question, which give some seemingly interesting numbers. I say seemingly because I don't even know the metric, let alone what the numbers mean, but I can only assume bigger is better:

Sony IX205AL (314e mono):

http://www.sony.net/Products/SC-HP/d.../E98619D7X.pdf
[INDENT]

Sensitivity:
Symbol: S
Min: 360
Typ: 450
Unit: mV
Saturation signal:

Symbol: Vsat
Min: 450
Unit: mV
Dark signal:

Max: 16
Unit: mV
Dark signal shading:

Max: 4
Unit: mV

Sony ICX285AL (314L OSC):

http://www.sony.net/Products/SC-HP/d.../E00Y42B3Z.pdf
[INDENT][INDENT]
Sensitivity 1:
Symbol: S1
Min: 1040
Typ: 1300
Unit: mV

Sensitivity 2:
Symbol: S2
Min: N/A
Typ: 4000
Unit: mV
Saturation signal:

Symbol: Vsat
Min: 850
Unit: mV
Dark signal:

Max: 11
Unit: mV
Dark signal shading:

Max: 4
Unit: mV
The OSC has a more rounded spectral sensitivity curve as well. Assuming I'm correct in that bigger is better, it looks like the OSC is waaaay more sensitive.
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Old 12-04-2014, 01:15 PM
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The ICX285AL (colour) is a newer, better sensor. That's why it's more sensitive. That said, it doesn't change the fact that each pixel will lose ~2/3rds of the signal hitting it because those photons will be of the wrong colour and will be absorbed by the filter sitting above the pixel.

I'm not sure what Ray's saying about galaxies looking bigger with more pixels - I guess you can digitally "zoom" in more with more pixels, but the resolution is set by the diameter of your scope and the image size by the focal length...

One thing not otherwise mentioned here is that the 314L has a physically larger chip, and that means a larger field of view. That will likely make it easier to frame your target and give you more options for things to image without having to take mosaics.

Hope this helps,
Cam
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Old 12-04-2014, 07:17 PM
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Quote:
Originally Posted by gregbradley View Post
I think you meant the other way round Ray. The OSC is way less QE than the mono which is the case with every OSC sensor I am aware of.

Typical QE for a OSC (not sure what a 314 is, is it the Sony ICX694 chip?) is around 25% or less but mono's are usually 50% -77%.

The bottom line, OSC is good for bright nebula but not for galaxies which are dim. Dim objects in OSC will show a ton of noise which is hard to get rid of especially in the dim areas of the image.

Straight luminance images of galaxies are quite nice even without colour. They are like Ha images.

No doubt at all - mono all the way and add colour later otherwise you will be disappointed for sure.

Greg.
Quote:
Originally Posted by codemonkey View Post
I found the data sheets for both of the sensors in question, which give some seemingly interesting numbers. I say seemingly because I don't even know the metric, let alone what the numbers mean, but I can only assume bigger is better:


The OSC has a more rounded spectral sensitivity curve as well. Assuming I'm correct in that bigger is better, it looks like the OSC is waaaay more sensitive.
Quote:
Originally Posted by LightningNZ View Post
The ICX285AL (colour) is a newer, better sensor. That's why it's more sensitive. That said, it doesn't change the fact that each pixel will lose ~2/3rds of the signal hitting it because those photons will be of the wrong colour and will be absorbed by the filter sitting above the pixel.

I'm not sure what Ray's saying about galaxies looking bigger with more pixels - I guess you can digitally "zoom" in more with more pixels, but the resolution is set by the diameter of your scope and the image size by the focal length...

One thing not otherwise mentioned here is that the 314L has a physically larger chip, and that means a larger field of view. That will likely make it easier to frame your target and give you more options for things to image without having to take mosaics.

Hope this helps,
Cam
The cameras have quite different chips Greg. The 205 chip in the 314e has a little over half the QE of the 285 in the 314L. The 205 pixels are just over half the area of those in the 285. Putting these factors together, a mono 314L would be about 3.5 times as sensitive (per pixel) as a mono 314e. 2 out of every 3 photons will be lost through absorption in the Bayer matrix of an OSC 314L, reducing the sensitivity to 1/3 that of a mono version, but it will still detect more photons per pixel than the mono 314e - and it will provide full colour into the bargain. When you add in the time required to get colour data with the mono 314e, you should expect to spend about twice as long as you would with the 314L OSC for similar signal to noise.

Cam, agreed that the scale of the physical image will be determined by the fl of the scope, but the size of an object in an electronic image will depend on the sampling. For example, if a galaxy has an extent of 10 arc seconds and you are sampling it with pixels that are 1 arc second across, the resulting image will be 10 pixels across. If the pixels are larger (eg 2 arc seconds), there will only be 5 pixels across the galaxy (ie it will be smaller in the electronic image). objects taken with the 314e (smaller pixels) will have about twice the area (in pixels) as those taken through an identical scope with the 314L. As an illustration, the attached composite image shows an identical scene taken through the same scope but using three different cameras. The leftmost image is taken using a camera with 5.6 micron pixels and the central one using a camera with 3.75 micron pixels - the fields of view vary with the chip size, but the central insulator is also clearly of different size due to the different pixel sizes in the cameras.

For imaging galaxies, the 314e with its smaller pixels makes sense.
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Old 12-04-2014, 10:04 PM
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I see what you mean Ray, yes, more pixels is good when trying to zoom in on a tiny target.

Perhaps for the Lee's main subject the 314e would be the better camera, though I think for a more general purpose CCD I'd recommend the 314L.
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Old 13-04-2014, 07:42 AM
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Yeah, the "crop factor" was one of the positives in selecting the 314e. Even knowing now that the 314l is so much more sensitive I'm happy with the choice.

Now... does anyone have a used filter wheel for sale? :-)
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Old 15-04-2014, 09:22 PM
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Well, this isn't working out so well at the moment.

I received the camera from Andrews Comms on Monday, after placing the order on Friday (man I love those guys), but that's where the good news ends.

Either I'm retarded, the software doesn't work, or I have a hardware problem.

Attached is the image I get out of nebulosity. Tried using the mac version, the windows version, the windows version with ASCOM drivers and their own Artemis Capture, all with the same, or similar results.

Unless my power source is insufficient (900amp jump starter), I'm thinking the camera is DOA. Any thoughts?
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Old 15-04-2014, 09:41 PM
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Have you got the camera in a telescope Lee?

I had to test mine with a scope rather than with just the cap off to get a picture, the chip is so sensitive and with no lens, an uncapped image of the room i was in did not show anything other than what you are seeing.

I suspect once you have a focused image on the chip, all should be OK.

I used my finder guider to test mine as I had the same result without any scope on it.

Give it a go,

Chris
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Old 15-04-2014, 09:51 PM
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Thanks for your help, Chris :-)

Yes, I do have the camera in my scope. I tried shifting the focus to various points but all gave me the same result, although some darker than others. I also tried various exposures ranging form 0.3/s to 5s.

Would this camera need an extension tube or something to be able to focus? At the moment I have it going directly into the focus tube of my ED80.

The streaks in the image are what concerns me most. On some of the images there were black streaks on the edges. That's not what I'd expect to see if it was simply not in focus.
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Old 15-04-2014, 09:57 PM
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Yep, without a diagonal, your ED80 focus tube would need to be racked all the way out and possibly with an extension tube to reach focus. Try it with the diagonal and see if that helps.

Also, even though the cameras are very quiet, they do show read noise on bright environments without focus, I found that when it was almost pitch black out in my back yard, I could easily see my neighbour's foxtel dish at night time with the camera in the finder guider at focus. It was almost a night vision camera it was sooo good.

Also, make sure that if you are using Artemis Capture, that the cooling is ON, the thermal noise in a 21 degree or more indoor environment with high ambient light will show columns or streaks like you are seeing on the test shot. Turn the cooler on, if possible set the temperature (my 314L+ can) and then focus in the diagonal across the room if possible or as far away as you can indoors and then see if you get something.

Chris
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Old 15-04-2014, 10:00 PM
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Also, try pointing it at the TV when focusing and wind the exposure RIGHT DOWN to 0.001 seconds (or whatever the minimum is) because it will be so bright, you should get to see the changes quickly in brightness as the TV scene changes.
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Old 15-04-2014, 10:58 PM
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Hi Lee,

i just tried this with my 314L+ and the ED80 and found that without the diagonal in, I needed to put in a Bintel camera projection tube which makes the distance between the camera flange (with the 1.25" nozzle removed") and the 1.25" focuser adaptor to be 70mm.

To focus on a light about 16m away in my dining room, or close enough, the focus draw tube was racked out and the distance between the telescope tube and the camera flange was 180mm.

So, you will need an extension tube of similar length 60-70mm in order to reach focus without a diagonal. I have attached a picture.

Cheers

Chris
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Old 16-04-2014, 05:36 AM
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Thanks for going to all that effort Chris, I really appreciate it! :-)

I took it out after I posted last night and tried it outside in the scope with the diagonal. I used Artemis Capture, with cooling turned on.

I tried setting it to "raw" and "luminance" but no matter which I used I got crazy results out of the camera, ranging from smooth linear gradients, smooth partial radial gradients, something that looked like a dense black and white bar chart, but most frequently the resulting images simply looked like high contrast noise.

I noticed towards the end that my power supply was down to low, so I'm hoping that it might be related to that. If it's not that, I'm pretty confident now that it's bricked.

I charged up the jump starter overnight so I'll try it again when I get home tonight and see how I go.

Thanks again for all your help Chris :-)
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