Comparison between e2v and 618 sensors - Jupiter

[budski]

Hi Guys, in response to Neil's question regarding a comparison between the IDS e2v NIR and DMK21.618 sensors.

I came home a bit late on Saturday night (i.e. the wee hours of Sunday morning) but started an imaging run at about 2.40am.

By then the seeing was visibly deteriorating but I managed to get a reasonable set of RGB's from each camera. All the .avi's were processed in AS2, AviStack and WinJUPOS. I tried to keep the processing as even as possible for both sets of images.

The left image is from the DMK and the right from the IDS.

Tell me what you think - there's a 16 minute gap between them (note the GRS's movement) so the DMK might have suffered a tad on account of the declining seeing. A truly accurate comparison would be to run both cameras at the same time on identical 'scopes - but I think Mrs. Bud would have something to say about another C11 out there!

Cheers.

Bud

PS: If you're good with crossing your eyes - these two make a reasonable 3D pair when viewed side-by-side.

[bus_ter]

There's more detail in the 2nd image, but they're both very similar. They could easily be two runs from the same camera.

I don't know anything about this e2v sensor. Do you have a link?

How's the low light sensitivity and frame rate compare to the DMK?

[bus_ter]

ok I've just been googling.. another new CMOS sensor. We were just talking about the move to CMOS sensors in another thread. I wonder how this compares to the equivalent Micron sensors?

I found this QE graph online, on paper it looks good compared to the older CCD sensors.

[bus_ter]

There's a UK site here that sells a camera with this sensor. They don't seem to have prices listed.

http://www.lambdaphoto.co.uk/products/120.125

[JamesF]

The second image is definitely sharper, but I'd agree there's nothing to split them on the basis of those images given the potential variation in seeing.

James

[neil phillips]

I agree with James Bud hard to tell any advantage or disadvantage with the short comparison. What it might be showing me is the cmos sensor does appear to be doing a good job, as the 618 ccd is no slouch.

I think a extended period of time is needed with the cmos sensor to really see its potential.

Just as a aside ( would like to let my imagination run for a bit hope you dont mind Bud )

The xiQ series talks about frame rates up to 600 fps. One thinks of a monster dobsonian lets say a 22" tracking included. shooting at maybe f15 f20 at 600 FPS wow can you imagine a 9 sequence 1 min RGB run. I am not seriously suggesting this would work, Exposure would be impossibly low, but i wonder how far you could go with a monster dob at only f20 Whats the largest commercial dob with tracking in production in the uk ? If the full frame rate was possible with HUGE primary, that would be a whopping 324000 frames over 9 mins using winjupos. Damm i wonder how long it would take to process. The mind boggles. Can you imagine 1000 astronomers starting a planetary project with £100 each invested. £100.000 would get such a crazy idea off the ground. A permanent site somewhere nice ( one thinks barbados ) Hmmm i am wondering about any super rich astronomers who would fund such a crazy idea ? I know Brians likely got a bit. oooooooo

[riklaunim]

Very fast framerates are useless as it would require very short exposures (to short) producing rather unusable frames And stacking a lot of very bad underexposed frames won't give you a good stack.

The e2v sensors are getting quite popular. Airylab is testing them too. They got very good results. Direct comparison with another cam won't rather show much as both DMK21AU618 and that IDS camera can give perfect images.

[sologuitarist61]

Like the second best but both great

[Cath]

I too prefer the image from the e2v sensor, It has more contrast without extra noise. No idea if that was due to the seeing or not though.

[Space Cowboy]

Very impressive result from the new cam! How do prices compare?

Neil's monster Dob idea sounds a winner to me. If the location was Barbados and as I have experience imaging with a Dob I therefore volunteer to be the on-site operator!

[neil phillips]

Yes i know Rik ,but i do talk about lowish f numbers and huge primarys. how much light could be gained with a even bigger primary say 60" ? had to say. i know you have a C14 but its a far cry from say a 60 " i do wonder the maximum usable frame rate. with monster optics ?

[neil phillips]

Very impressive result from the new cam! How do prices compare?

Neil's monster Dob idea sounds a winner to me. If the location was Barbados and as I have experience imaging with a Dob I therefore volunteer to be the on-site operator!

Yep you would be in the driving seat Stuart, I dont like heights anyway.

Going back to the topic yes i wonder what the price comparisons are too Stuart.

[JamesF]

Very impressive result from the new cam! How do prices compare?

I've not been able to find any pricing information myself so it would be interesting to know, if Bud is willing to divulge the depth of his pockets. My suspicion is however that the e2v camera is more expensive than the DFK21.

James

[JamesF]

Yes i know Rik ,but i do talk about lowish f numbers and huge primarys. how much light could be gained with a even bigger primary say 60" ? had to say. i know you have a C14 but its a far cry from say a 60 " i do wonder the maximum usable frame rate. with monster optics ?

I was thinking about this last night and wondering if there's a simple relationship between them. For example, if you need N photons per unit time to trigger the sensor for a pixel at a useful level, could you simply double the area of the primary to get 2N photons per unit time and then half the exposure time to get back to where you were?

So, for example, if 1/50 sec is a good exposure time for a 10" primary, if you moved up to a 14" scope (twice the primary area) with the same focal ratio could you then go to 1/100 sec exposures and still get the same result?

My understanding of these things is inadequate to make a guess an an answer...

James

[neil phillips]

I was thinking about this last night and wondering if there's a simple relationship between them. For example, if you need N photons per unit time to trigger the sensor for a pixel at a useful level, could you simply double the area of the primary to get 2N photons per unit time and then half the exposure time to get back to where you were?

So, for example, if 1/50 sec is a good exposure time for a 10" primary, if you moved up to a 14" scope (twice the primary area) with the same focal ratio could you then go to 1/100 sec exposures and still get the same result?

My understanding of these things is inadequate to make a guess an an answer...

James

Me too James i am not sure either, but sounds plausable doesnt it. What ever way you look at it massive optics would allow much faster exposures and hence frame rates though i have no idea of the limit even with massive optics

[budski]

Hi Guys, let me see if I can provide you with all the technical and financial details regarding this camera:

Tech stuff: The sensor is a monochrome EV76c661 Near Infra Red device, 1280x1024 pixels housed in a very small 28mm aluminium cube with a c-mount lens fitting. It weighs 43 grams - a lot less than the USB3 cable that needs to be attached to it.

The pixel size is 5.3um (much the same as the DMK devices) but its low light sensitivity appears to be better than the x618. It produces a bright f20 image at 60fps in its native mode of 1280x1024 but can easily go to 90 fps in its ROI option of 640x480. I've tried maxing it out at 125fps but I think that's probably asking too much of the UK weather. I examined the individual frames of that 125fps .avi to find that nothing was sharp or clear making me think that maybe the camera is faster than the seeing - if that makes sense. Just as a little aside - when I was collimating the C11 (via the usual Airy Rings procedure on a laptop) I noticed how much visible turbulence my fingers were generating as I was adjusting the knobs. This has now made me wonder if using the dew heater on the 'scope degrades the image at this time of year.

I think the camera will produce better results when the weather stabilises and we get a few really dry cold nights to allow the camera to dissipate its own heat quickly. Another point worth mentioning is that the noise level and the 'ringing' artefacts disappear when using this camera in its 16 bit, RAW, Rolling shutter mode. Correspondingly, the .ser file sizes are bigger: - a 45 second run producing 4050 frames at 640x480 was 2.4 Gigabytes in size for each filter i.e. 7.2 Gb's for an RGB set.

As yet I'm not sure I can capitalise on this improved signal2noise ratio because I don't know enough about how Auto Stakkert (AS2) works and whether the fundamental process behind Wavelets needs to be reviewed. This could be another can of worms - I dunno.

Finally the cost: The camera and USB3 cable cost £700 from Stemmer Imaging ... yes, I know, you could buy two DMK.618's for that money. My justification (and a fair amount of faith, I have to say) is that I'm a researcher/engineer looking to improve the tools avaiable to us. If you've read my article in last month's (November) issue of Astronomy Now, you'll see what motivates me.

Finally, I'm currently in dialogue with Framos (of SkyNyx fame) to see what they're doing with the new emerging technologies.

Thank you for your constructive comments - always much appreciated because I can forward them to the people who manufacture these things.

Kindest regards

Bud

[neil phillips]

Hi Guys, let me see if I can provide you with all the technical and financial details regarding this camera:

Tech stuff: The sensor is a monochrome EV76c661 Near Infra Red device, 1280x1024 pixels housed in a very small 28mm aluminium cube with a c-mount lens fitting. It weighs 43 grams - a lot less than the USB3 cable that needs to be attached to it.

The pixel size is 5.3um (much the same as the DMK devices) but its low light sensitivity appears to be better than the x618. It produces a bright f20 image at 60fps in its native mode of 1280x1024 but can easily go to 90 fps in its ROI option of 640x480. I've tried maxing it out at 125fps but I think that's probably asking too much of the UK weather. I examined the individual frames of that 125fps .avi to find that nothing was sharp or clear making me think that maybe the camera is faster than the seeing - if that makes sense. Just as a little aside - when I was collimating the C11 (via the usual Airy Rings procedure on a laptop) I noticed how much visible turbulence my fingers were generating as I was adjusting the knobs. This has now made me wonder if using the dew heater on the 'scope degrades the image at this time of year.

I think the camera will produce better results when the weather stabilises and we get a few really dry cold nights to allow the camera to dissipate its own heat quickly. Another point worth mentioning is that the noise level and the 'ringing' artefacts disappear when using this camera in its 16 bit, RAW, Rolling shutter mode. Correspondingly, the .ser file sizes are bigger: - a 45 second run producing 4050 frames at 640x480 was 2.4 Gigabytes in size for each filter i.e. 7.2 Gb's for an RGB set.

As yet I'm not sure I can capitalise on this improved signal2noise ratio because I don't know enough about how Auto Stakkert (AS2) works and whether the fundamental process behind Wavelets needs to be reviewed. This could be another can of worms - I dunno.

Finally the cost: The camera and USB3 cable cost £700 from Stemmer Imaging ... yes, I know, you could buy two DMK.618's for that money. My justification (and a fair amount of faith, I have to say) is that I'm a researcher/engineer looking to improve the tools avaiable to us. If you've read my article in last month's (November) issue of Astronomy Now, you'll see what motivates me.

Finally, I'm currently in dialogue with Framos (of SkyNyx fame) to see what they're doing with the new emerging technologies.

Thank you for your constructive comments - always much appreciated because I can forward them to the people who manufacture these things.

Kindest regards

Bud

Thanks for all the extra information Bud. I am always interested in new ccd chips, they do sometimes have a way of finding them selves in cheaper cameras as time moves on. So yes its something we all should be interested in. Thank you for sharing what your finding out.

£700 is over my budget. But as mentioned prices sometimes fall as new chips get in some more commercial cameras like imaging source. Certainly worth watching. And for those with bigger budgets that want the most sensetivety. Looks like it would be a great lunar cam Bud something we havent discussed.

Apologys for going off track. All this talk of sensetivety and high frame rates got me thinking was the reason. Hope you didnt mind

[JamesF]

Thanks for posting all the details, Bud. It's very interesting, even if such a camera is way beyond my pocket

James

[budski]

Hi Neil & James, .... Neil has a point about the cost of these sensors coming down in price once they've become established. Every early-adopter has paid a premium to be at the leading edge of technology then seeing the cost drop rapidly a few months later. I was shown a sensor at the Stemmer Open Day that can virtually 'see' in the dark. It's still in it's development phase and the price tag was (pardon the pun) astronomical - we're talking about six-figure numbers here - MoD budgets... at the moment.

It's an interesting thought regarding the relationship between high frame rates / aperture and where there might be a limiting factor. Even from my own (admittedly unscientific) appraisal I couldn't see any real difference between images I took at 60fps and those at 125fps. My observing location is far from ideal so that might influence the results - but in any case my situation is much the same as the rest of the astro community.

Anyway, it's great being able to share my thoughts with you guys - especially on such a dreary, wet day. Whoever mentioned Barbados has my vote!

Bud

PS: The initial Lunar images look stunning - but I've not done anything with them yet .

[Space Cowboy]

Thanks for the info Bud! I will wait till Santa's Xmas list 2013 I think.

[riklaunim]

Yes i know Rik ,but i do talk about lowish f numbers and huge primarys. how much light could be gained with a even bigger primary say 60" ? had to say. i know you have a C14 but its a far cry from say a 60 " i do wonder the maximum usable frame rate. with monster optics ?

There is no scope size effect. 100" or 10" imaging on f/20 will use the same exposure times to get the same histogram fill. Only resolution will differ. Of course very big scope doesn't have to do f/20 to get a big planet. It can go on faster framerate (but why - if you can use the f/20).

If the air wouldn't move we would be using DS cameras for planetary imaging and catching like 20 frames per channel at few sec exposures. Decreasing exposures time and increasing gain lowers signal to noise ratio as well as brings read noise and read artifacts as a major problem (grainy noise is the weakest effect of them). Thats why we should use short exposures for planetary imaging - but as short as needed, not as short as possible. Lower gain than lower exposures time is in general better.

[JamesF]

There is no scope size effect. 100" or 10" imaging on f/20 will use the same exposure times to get the same histogram fill. Only resolution will differ. Of course very big scope doesn't have to do f/20 to get a big planet. It can go on faster framerate (but why - if you can use the f/20).

Of course! You are quite right. I clearly didn't have my thinking head on this morning. Presumably if the aperture were increased you'd be wanting to keep the focal length the same to give a faster focal ratio and hence increase the arrival rate of photos on each pixel of the sensor? How that changes the game, I'm not sure. I think it might become impractical very rapidly unless you fancied building very fast, big mirrors.

James

[bus_ter]

Sorry slightly off topic, but in regard to sensors.

What about back illuminated sensors? These are starting to do the rounds in consumer compact cameras and even Smart phones. So they must be mass produced and very cheap. The wiki article (below) suggests they were first used in Astronomy sensors because of their low light performance before they became widely available. Anyone know anymore?

http://en.wikipedia.org/wiki/Back-illuminated_sensor

[riklaunim]

Sorry slightly off topic, but in regard to sensors.

What about back illuminated sensors?

A lot of CMOS is now BSI, but still none of them is in the right category for Solar System imaging. BSI is now used for sensors with very small pixels - around 1-2 micrometers and alike. For sensors with sane pixel size it's not used.

Presumably if the aperture were increased you'd be wanting to keep the focal length the same to give a faster focal ratio and hence increase the arrival rate of photos on each pixel of the sensor?

Thats a solution. If the seeing isn't best and you can oversize the aperture then using faster f-ratio may allow better imaging than smaller scope on max f-ratio.

[Cath]

A lot of CMOS is now BSI, but still none of them is in the right category for Solar System imaging. BSI is now used for sensors with very small pixels - around 1-2 micrometers and alike. For sensors with sane pixel size it's not used.

Shame

Back illuminated CMOS sensors allow the active area (the bit that collects the photons) to be increased (normally a CMOS sensor has small active pixel area compared to the total pixel size) due to moving each pixel pre-amp off the front of the sensor and to the back of each pixel.

It ort to be done for all CMOS sensors these days I think. Once a sensor is in mass production the costs come down a great deal, so that's not a real problem.