CCD v CMOS

[Gina]

I know this has been discussed before but a new thread seems appropriate for my particular situation.

Looking at my imaging results from years ago, it seems I was getting better results than more recently.  Now there may be several reasons for this including age but I'm wondering now if I did right in selling my Atik 460EX mono CCD cameras and buying ZWO ASI1600MM-Cool instead.  The FLO website shows the Atik cameras being a lot more expensive that the ZWO and I have always had the feeling that you get what you pay for but guess this is not always so.  I can't remember now what my reasons were for doing this as I sold used and bought new.  I am now wondering if I did the right thing.  Maybe I should have kept one 460EX particularly for the smaller DSOs but I could have needed the money.

I would appreciate your thoughts on this.  TIA.

 

Edited September 29, 2019 by Gina

[Adam J]

16 minutes ago, Gina said:

I know this has been discussed before but a new thread seems appropriate for my particular situation.

Looking at my imaging results from years ago, it seems I was getting better results than more recently.  Now there may be several reasons for this including age but I'm wondering now if I did right in selling my Atik 460EX mono CCD cameras and buying ZWO ASI1600MM-Cool instead.  The FLO website shows the Atik cameras being a lot more expensive that the ZWO and I have always had the feeling that you get what you pay for but guess this is not always so.  I can't remember now what my reasons were for doing this as I sold used and bought new.  I am now wondering if I did the right thing.  Maybe I should have kept one 460EX particularly for the smaller DSOs but I could have needed the money.

I would appreciate your thoughts on this.  TIA.

 

I am not sure on that one but what I am sure on is that the ATIK460ex now sells second hand for around 900 - 1000 pounds on ABS and here. The ASI1600mm pro will sell second hand for around 800 - 900 pounds. Recent examples on here and ABS being one of £900 and one for £999 people have tried selling them for £1100 but they have not sold.

So in the case of the ATIK460ex its selling for around 45% of its new price. On the other hand the ASI1600mm pro is selling for 65% of its new price (about the standard for astro equipment). So that tells me that the ASI1600mm pro is currently a more in demand camera by far than a Atik 460ex when sold second hand despite the apparent bargain prices that are coming up.

Adam

[Stub Mandrel]

22 minutes ago, Gina said:

I would appreciate your thoughts on this.  TIA.

 

I've only been doing imaging since 2015, but I've picked up that most people feel recent years have been cloudier with fewer opportunities for imaging.

Plus, you've only got back into imaging actively quite recently - Iooking at my own images the results are all over the place and better gear doesn't always mean better pictures. Better skies always help!

Now the nights are drawing in I suspect you just need a few runs of clear evenings to get you hand in?

[DougM43]

As the owner of both ccd (Starlight express SVX-M25c) and an as yet unused Zwo ASI1600mm-cool I am going to follow this thread closely, 

what I can say is there’s some absolutely stunning images taken with the  Zwo ASI 1600 camera so I don’t think you made a bad choice, I think it may just be a case of learning and understanding how to get the best from an as yet unfamiliar camera.

Doug. 

[alan potts]

I have to say with me I want a large chip and the 071 or indeed the 1600 were just more affordable without being stabbed by the wife. I liked the look of an Atik model 16200 and still believe they are better quality. I would have liked their camera with APS H sized sensor, but at near to 3.5 grand I could hear knives being sharpened, then one of the members on site sold one for about half price the day after i bought the 071.

Alan

[Davey-T]

I've resisted all the hype about CMOS cameras ( not like me ) and am sticking with my various CCD cameras which are plug and play with no worrying about amp glow, sensor cover reflections and gain settings, got enough stuff to think about.

As far as I can see the only advantage they have, apart from larger sensors being cheaper, is their short exposure capability which makes deep sky imaging possible with a less than perfect mount.

Dave

[Gina]

Thank you everyone - very interesting.  More thoughts on this most welcome.

It's certainly true that I need to get "up to speed" again both due to not imaging for some time and the new hardware and software.  I think my mount is not only good kit but well set up too and the shorter exposures mean I can get away without guiding for a lot of my imaging, which simplifies matters.

[Adam J]

3 minutes ago, Davey-T said:

I've resisted all the hype about CMOS cameras ( not like me ) and am sticking with my various CCD cameras which are plug and play with no worrying about amp glow, sensor cover reflections and gain settings, got enough stuff to think about.

As far as I can see the only advantage they have, apart from larger sensors being cheaper, is their short exposure capability which makes deep sky imaging possible with a less than perfect mount.

Dave

Yet the larger sensor is a huge advantage. Nothing is faster if you need to take two panels to cover your target. For smaller objects though its makes more sense to want to go with the smaller sensor.

[Davey-T]

Just now, Gina said:

I can get away without guiding for a lot of my imaging, which simplifies matters.

Me too, 30 minutes unguided

Dave

[Gina]

My exposures are unlikely to be over 2m maybe 5m for dimmer DSOs.  The lower read noise permits shorter exposures at higher gain

Quote

Very low read noise - 1.2e @30db gain

I shall need to experiment to find the best balance between full well capability and gain/sensitivity.  For my very wide angle images I have been using 60dB gain (the maximum) but may find longer exposures and lower gain give more image depth.  At least the high sensitivity of the ASI makes focussing and plate solving easier/quicker.

Yes, lots of experimenting and practice needed to get the best out of the camera and the new software, though I did use PixInsight before, it was some time ago and I need to get back into it.  Still learning KStars/Ekos/INDI.  I like the control the Open Source INDI drivers give me - I can change them to control practically everything. 

I think the problem I'm having with distrusting my decisions is probably all due to this terrible weather and not being able to actually capture images!

Thank you for your encouraging comments

[Gina]

Seems I was using the ZWO camera and PI in my earlier imaging and getting fairly good results so I now need to get back into it all.

Ah the sun's come out - shades of "Hello mother, hello father" 🤣

Here's a copy of a post a couple of years ago.  Seems I had pretty much got to grips with PI then...

On 22/01/2017 at 16:31, Gina said:

This is an experiment in filtering.  Ha 3nm and OIII 3nm but NII obtained by subtracting Ha 3nm from Ha 5nm. 

28mm f3.5 Super Takumar lens with ASI1600MM-Cool camera.  98 3nm Ha, 98 5nm Ha and 123 OIII 3nm subs all 60s with gain of 600 and -30C sensor temperature.  All processing in PixInsight then saved in PNG format for upload.  Calibrated with bias and dark master frames but no flats as there was no vignetting with this lens and no dust bunnies seen. 

StarAlignment used to register each set and then to register sets with each other.  DynamicCrop and DBE applied.  NII created by using PixelMath to subtract 3nm Ha from 5nm Ha - I have never tried this before.  PixelMath was then used to create the colour image using Red=H, Green=OIII*2-0.055 and and Blue=N.  Then CurvesTransformation used to pull out the nebulosity and calm the background and stars.

The Rosette Nebula can be seen in the top of the image.  Other DSOs - Barnard's Loop, Angelfish, M42/43, Running Man, Flame and Horse's Head with hydrogen nebulosity.

Edited September 29, 2019 by Gina

[Stub Mandrel]

2 hours ago, Davey-T said:

Me too, 30 minutes unguided

Dave

Yes, but not many of us image with pinhole cameras 🙂

[Starflyer]

9 hours ago, Adam J said:

I am not sure on that one but what I am sure on is that the ATIK460ex now sells second hand for around 900 - 1000 pounds on ABS and here. The ASI1600mm pro will sell second hand for around 800 - 900 pounds. Recent examples on here and ABS being one of £900 and one for £999 people have tried selling them for £1100 but they have not sold.

So in the case of the ATIK460ex its selling for around 45% of its new price. On the other hand the ASI1600mm pro is selling for 65% of its new price (about the standard for astro equipment). So that tells me that the ASI1600mm pro is currently a more in demand camera by far than a Atik 460ex when sold second hand despite the apparent bargain prices that are coming up.

Adam

That's driven by the current fad for CMOS cameras surely? It doesn't mean they're better than CCDs. I haven't been dragged in by the hype, the amp glow problems and the need to faff around with settings puts me right off. Why go for CMOS when CCDs are plug and play?

A 460EX at under £1000 is a true bargain!

[newbie alert]

I'd have a 460ex in a heartbeat and currently saving up for either a 460 or 490..I've looked at others with the same sensors but you know where you stand with a Atik..

Various cmos issues stop me from considering  them until the issues are resolved, so I'd be happier with a ccd at the mo..

There are some awesome pictures out there taken with the 1600

[Adam J]

1 hour ago, newbie alert said:

I'd have a 460ex in a heartbeat and currently saving up for either a 460 or 490..I've looked at others with the same sensors but you know where you stand with a Atik..

Various cmos issues stop me from considering  them until the issues are resolved, so I'd be happier with a ccd at the mo..

There are some awesome pictures out there taken with the 1600

I have recommended the 460EX to a number of people recently, but the amp glow on the ASI1600mm pro is one of those things that makes people fear until you own one and realize its no problem at all is certainly not the reason to chose the 460EX over a 1600. The real reason to do that is the micro lens diffraction issue. The big reason to chose the ASI1600mm pro over the 460Ex is purely sensor area. Sensor area is more important than people think  sometimes because it means that you can use a larger aperture at the same f-ratio while maintaining field of view. So a 80mm scope at F5.5 with a ATIK460EX has about the same FOV as a 110mm scope at F5.5 with a ASI1600mm pro as a result you can down sample the image on the ASI1600mm pro image by a factor of 1.66 to the same image scale as the 80mm and ATIK460ex combo gaining significant signal improvement at the same FOV.

Edited September 29, 2019 by Adam J

[newbie alert]

55 minutes ago, Adam J said:

The real reason to do that is the micro lens diffraction issue

Yep, my main reason for not wanting one..

Also a friend has a 1600 and a 183, he creates superb images with both but his 1600 has stopped working, and repairers say there's nothing wrong with it..

He has a terabyte of data on 1 target..!

[DaveS]

I found the amp-glow on the 1600 to be manageable with good darks and can be cropped without losing much frame, but the 183 drove me nuts with it's horrendous amp glow which covers so much of the sensor as to be virtually un-cropable. The only good image I got out of it was taken with meridian flips and dithering in addition to the darks, sigma stacking then saw the amp-glow spikes as artifacts and eliminated them. Otherwise just trying to use darks it proved impossible to calibrate out.

My next camera which I have incoming is a CCD, a Moravian G3 16200 mk1, which also has a bigger sensor than just about all the CMOS cameras on the market.

[andrew s]

I don't think all CCD or CMOS chips can be discussed effectively by category.  You have to consider each one and how it is packaged individually. I know of one CCD that added fringes to high resolution spectra but not others. Some CMOS cameras have more amp glow but I recall the days when CCD cameras had the same issue.

CMOS is where the research and development money is going so consumer CCD will be a thing of the past in a few years. Even NASA is using a CMOS camera on one of its solar missions.

Look at each offering and how you want to use it objectively then decide.

Regards Andrew 

 

[jimjam11]

I dont think any of this matters. If you have either of these cameras they will not be the limiting factor; a million other things will...

The asi1600 exposure tables on CN are a great resource, exposures should be surprisingly short in most conditions...

https://www.cloudynights.com/topic/573886-sub-exposure-tables-for-asi-1600-and-maybe-qhy163/#

 

[Adam J]

14 hours ago, DaveS said:

I found the amp-glow on the 1600 to be manageable with good darks and can be cropped without losing much frame, but the 183 drove me nuts with it's horrendous amp glow which covers so much of the sensor as to be virtually un-cropable. The only good image I got out of it was taken with meridian flips and dithering in addition to the darks, sigma stacking then saw the amp-glow spikes as artifacts and eliminated them. Otherwise just trying to use darks it proved impossible to calibrate out.

My next camera which I have incoming is a CCD, a Moravian G3 16200 mk1, which also has a bigger sensor than just about all the CMOS cameras on the market.

If you need to crop it out after calibration you are calibrating incorrectly. 

[DaveS]

44 minutes ago, jimjam11 said:

I dont think any of this matters. If you have either of these cameras they will not be the limiting factor; a million other things will...

The asi1600 exposure tables on CN are a great resource, exposures should be surprisingly short in most conditions...

https://www.cloudynights.com/topic/573886-sub-exposure-tables-for-asi-1600-and-maybe-qhy163/#

 

Useful tables, thanks.

[DaveS]

39 minutes ago, Adam J said:

If you need to crop it out after calibration you are calibrating incorrectly. 

I should have made it clear that under normal circumstances I don't have to crop any 1600 images as I Calibrate with darks, It's just on odd occasions when I haven't had an up to date dark library to hand.

The 183 images are still a pain to calibrate out.

[Adam J]

3 hours ago, DaveS said:

I should have made it clear that under normal circumstances I don't have to crop any 1600 images as I Calibrate with darks, It's just on odd occasions when I haven't had an up to date dark library to hand.

The 183 images are still a pain to calibrate out.

Guess i am confused by this as I took a set of darks about two years ago and have never had to take another. 

[Rodd]

I have an STT-8300 and the ASI-1600.  I find the results are very comparable.  The big difference is the acquisition approach (many shorter subs vs fewer longer subs).  That is really the only difference I see (note below)...and it can be a big one, especially if you want to dither all your subs.  A dither movement of, say 15 sec, combined with a dither recovery period of , say 30 sec, represents an additional 45 seconds that must be added to the exposure time for each sub.  When your subs are 60 sec long, this represents a 75% increases in the amount of time you need--or, and this sounds worse, you can only collect 15% of the data you would get if you didn't dither.   When your subs are 10 min long, an additional 45sec is not nearly as expensive from a "imaging time" perspective. 

But there are benefits to shorter subs.  In  10 min sub, there might be 1m2m3 or more good minutes in there that would make decent subs if they weren't part of a 10 min duration.  You have to either use the 10 min sub, or not use it.  If you collect 10 1 minute subs with a CMOS, or even 5 2min subs, you might very well be able to keep some of those 10 minutes that you have to throw away with a CCD.

The other benefit with this [particular camera is the filter wheel, guide cam and main camera can all run off the same USB connection--which is in my case a powered USB hub on the tripod.  I actually have 0 cables from the scope to the computer.   Cable management is still a pain though, even with 0 cables to the computer.

Note: As far as data quality--there is one possible thing that I have noticed at times that I did not see with the STT-8300.  Sometimes I get uneven distribution of chroma in an image.  For example the red channel may impart a patchy, or mottled chroma to an image.  So upon zoom you see the red areas to be patchy--or speckled (a patch of pixels red, a neighboring patch not red and so on at a pretty small scale).  It does not happen for all targets, and it only happens when I bump up saturation--even a little.  But this could be caused by something other than sensor issues.

Rodd

[kens]

On 29/09/2019 at 21:54, Gina said:

My exposures are unlikely to be over 2m maybe 5m for dimmer DSOs.  The lower read noise permits shorter exposures at higher gain

I shall need to experiment to find the best balance between full well capability and gain/sensitivity.  For my very wide angle images I have been using 60dB gain (the maximum) but may find longer exposures and lower gain give more image depth.  At least the high sensitivity of the ASI makes focussing and plate solving easier/quicker.

Yes, lots of experimenting and practice needed to get the best out of the camera and the new software, though I did use PixInsight before, it was some time ago and I need to get back into it.  Still learning KStars/Ekos/INDI.  I like the control the Open Source INDI drivers give me - I can change them to control practically everything. 

I think the problem I'm having with distrusting my decisions is probably all due to this terrible weather and not being able to actually capture images!

Thank you for your encouraging comments

60dB gain (gain 600) is way too high. You have less than 4 stops of dynamic range there. I keep the gain at 200 (20dB) or lower where the dynamic range is a bit less than 10 stops.

Typically I use gain 75 for luminance,  139 (unity) for RGB and 200 for narrowband unless I an get a reasonable exposure at 139.