Recommendations on my next imaging Camera after years with modded DSLRs?

[glend (Glen)]

If your night sky is polluted then narrowband will be more satisfying, but the filters and filter wheel need to be factored in to your budget. There are sales now and then from Cyclops Optics in Hong Kong on QHY filter wheels, i got the small 5 position 36mm usb wheel from them at a very nice price. Baader NB filters are nicely priced from Tekeskop-Express if you buy the three filter set and they are good filters and all parafocal.
Of course NB means longer subs, and a camera capable of fast narrow band is a real bonus. The ASI1600MM-C is producing very nice NB images with subs of 300 seconds, much shorter than traditional narrowband with less sensitive cameras.
Also short sub broadband can be done, here i mean 30 second subs, to escape skyglow effect, but you need to shoot more subs obviously. Be prepared for a learning curve.

[multiweb (Marc)]

With the british pound dropping like a stone I'd be looking at a starlight xpress.

[glend (Glen)]

Originally Posted by multiweb

With the british pound dropping like a stone I'd be looking at a starlight xpress.

And if bought from the EU you get the 19% VAT removed for export to Australia.

The Starlight Express filter wheels are export priced from 310-325 euro from Teleskop-Express, depending on size of filter you want to use and number of positions, this equares to $456-480 Aud.

The ZWO electronic 5 position 31mm filter wheel just developed for the ASI1600 is $199 usd ($261 aud ) direct from ZWO Optical and is available bundled with the camera if you wish. Check the ZWO Optical website for details.

[Slawomir (Suavi)]

Originally Posted by glend

The ASI1600MM-C is producing very nice NB images with subs of 300 seconds, much shorter than traditional narrowband with less sensitive cameras.

To my knowledge sensitivity is not only affected by low noise, but also by QE and pixel size - not entirely sure whether the chip used in 1600MM sets a benchmark for sensitivity

[Atmos (Colin)]

Originally Posted by glend

Of course NB means longer subs, and a camera capable of fast narrow band is a real bonus. The ASI1600MM-C is producing very nice NB images with subs of 300 seconds, much shorter than traditional narrowband with less sensitive cameras.
Also short sub broadband can be done, here i mean 30 second subs, to escape skyglow effect, but you need to shoot more subs obviously. Be prepared for a learning curve.

Read noise doesn't directly have anything to do with "sensitivity". The 1600 is a fraction higher than the 8300 and very similar to the 16803 and 16200 over most of the spectrum, little stronger towards the blue though.

Short subs also gain no benefit in "escaping skyglow". The sky glow sets a limiting factor on the length of each sub but has no effect on beating light pollution.

[gregbradley]

Originally Posted by Slawomir

Also, Atik claims they will release their camera with 16200 chip in early December, and they promise it will be similarly priced to QHY with the same chip. It will have nice 50 C below ambient cooling, but read noise most likely not as low as in the FLI...

That is a main reason I got the FLI, read noise is probably a class leading 6 electrons or less. It certainly seems cleaner than other cameras I have used from FLI which are already very clean. That plus FLI reliability and attention to detail. FLI are the Astrophysics of cameras.

Greg.

[gregbradley]

Really? Maybe SBIG put the wrong values on their website then... https://www.sbig.com/products/cameras/stxl/stxl-16200/

And QHY are quoting 10e!

"clean" like a Sony sensor...ICX674/694 family are generally ~4e (QSI quote better). Just presenting the facts according to the interweb...[/QUOTE]

I am talking about the FLI Microline 16 which is 6 electrons or better. The 694 is around 5 so hardly any difference and to my eye they look much the same. The Sony a touch cleaner. What other manufacturers get out of their electronics may be a different story. Just like QSI seems to extract more out of the KAF8300 than anyone else.

As far as RBI goes I have not noticed this on this and rarely on my 16803 for that matter. I believe these KAF sensors do have RBI but it must be a fairly slight issue as only rarely have I seen it impact an actual image.
Usually something super bright like a plane flying through the frame and you can see the lines of the bright lights for a few subs afterwards until it fades out to nothing again.

Not something I would concern myself as to whether or not to get a particular camera or not. Hardly an issue.

The things that matter are field of view, pixel size to match your focal length, F ratio and seeing, QE and well depth.

Well depth of this sensor is 39,000 electrons. which is quite adequate.

20,000 is starting to get a bit too skinny in my experience.

Greg.

[gregbradley]

Originally Posted by glend

If your night sky is polluted then narrowband will be more satisfying, but the filters and filter wheel need to be factored in to your budget. There are sales now and then from Cyclops Optics in Hong Kong on QHY filter wheels, i got the small 5 position 36mm usb wheel from them at a very nice price. Baader NB filters are nicely priced from Tekeskop-Express if you buy the three filter set and they are good filters and all parafocal.
Of course NB means longer subs, and a camera capable of fast narrow band is a real bonus. The ASI1600MM-C is producing very nice NB images with subs of 300 seconds, much shorter than traditional narrowband with less sensitive cameras.
Also short sub broadband can be done, here i mean 30 second subs, to escape skyglow effect, but you need to shoot more subs obviously. Be prepared for a learning curve.

I find it hard to believe a one shot colour camera is good for narrowband. The colour filter array means only one pixel in 4 is really getting any signal from each of the usual narrowband filters. Typically a mono sensor leaves a one shot colour sensor in the dust for this sort of imaging.

It may seem OK until you saw an equivalent exposure from a mono camera and the difference would be more apparent.

Greg.

[gregbradley]

Originally Posted by billdan

I have no experience with NB imaging so I trust what you say Ray. However the CMOS chips with very low read noise also have very low full well capacity, so I think that is more important for going deep and getting mag20+ objects.

Bill

EDIT: I forgot about anti-blooming so there probably is no difference - plus dynamic range = full well / read noise, which for the ASI 1600 is 20,000/3.8 and the 16200 is 60,000/10 slightly better.

The KAF16200 full well is 39,000 electrons and read noise obviously varies with manufacturer but can be as low as 6 or less. FLI is that and I think Moravian is good too.

Greg.

[glend (Glen)]

Originally Posted by gregbradley

I find it hard to believe a one shot colour camera is good for narrowband. The colour filter array means only one pixel in 4 is really getting any signal from each of the usual narrowband filters. Typically a mono sensor leaves a one shot colour sensor in the dust for this sort of imaging.

It may seem OK until you saw an equivalent exposure from a mono camera and the difference would be more apparent.

Greg.

Greg, the ASI1600MM-C is a mono camera.

My point in relation the advice i provide to the OP, is that he can probably get the ASI1600MM-C, plus the filter wheel, and a set of narrowband and broadband filters for less than $3K, and that equates to an entry level cheap much noisier KAF-8300 (Atik) alone. He is of course free to spend his money as he choses.

[Retrograde (Pete)]

This is a great thread full of useful information. Although I'm a long way off making the jump to a dedicated astro-camera myself it's a fantastic resource for the future. Thanks to the OP and all who have contributed so far.

Originally Posted by Shiraz

An alternative would be to use a ZWO1600 with software binning, but you would end up with only 4m of 7.6micron pixels - still plenty for many DSOs, but not all. In other aspects, a software binned ZWO would be better than alternatives, with lower read noise, slightly better QE (possibly) and much better dynamic range.

What pros and cons are there between software and hardware binning? Presumably CMOS can only do SW binning because of the underlying HW but are there practical differences in the results you would achieve with each?

[RickS (Rick)]

Originally Posted by Retrograde

What pros and cons are there between software and hardware binning? Presumably CMOS can only do SW binning because of the underlying HW but are there practical differences in the results you would achieve with each?

Pete,

The only advantage of hardware binning is that you may get a reduction in read noise. The ideal situation is that you get the same amount of read noise reading 2x2 pixels as you do reading a single pixel. In practice it doesn't work perfectly and some sensors get a partial improvement and some get very little (like most of the Kodak/Trusense sensors.)

With software binning you don't get a read noise improvement but you have more flexibility, e.g. you can extract lum from your RGB data and add it to your normal luminance if you image LRGB unbinned. If you do unbinned L and binned RGB as some people do that option isn't available.

If you have the luxury of doing sky limited subs then read noise is irrelevant and HW binning has no value. It may have some utility for NB imaging especially for slow optical systems under dark skies.

Cheers,
Rick.

[Retrograde (Pete)]

Thanks Rick

[Slawomir (Suavi)]

Originally Posted by Atmos

Read noise doesn't directly have anything to do with "sensitivity".

On the contrary, I think when assessing sensitivity of any camera, we must consider not only sensor's QE but also noise injected by the camera. Sensitivity determines the achievable SNR which is of key importance in astrophotography, and SNR depends on the camera's capacity to have the signal stand out from the surrounding noise. All else being equal, a camera with higher read noise will have a lesser capacity to detect wanted signal (lower sensitivity), as opposed to a camera with a low read noise that will readily capture faint signal (higher sensitivity). That's how I see it anyway

[Atmos (Colin)]

Originally Posted by Slawomir

On the contrary, I think when assessing sensitivity of any camera, we must consider not only sensor's QE but also noise injected by the camera. Sensitivity determines the achievable SNR which is of key importance in astrophotography, and SNR depends on the camera's capacity to have the signal stand out from the surrounding noise. All else being equal, a camera with higher read noise will have a lesser capacity to detect wanted signal (lower sensitivity), as opposed to a camera with a low read noise that will readily capture faint signal (higher sensitivity). That's how I see it anyway

This is only true if you don't overcome read noise. Take the 16803 which has a very similar QE to the ASI1600 but a RN of 8e- compared to the variable RN of the 1600. As long as they both overcome the read noise, their sensitivity is more or less identical. The 16803 will have to do longer subs to reach that point but it has MASSIVE wells to be able to accomodate for that.

[glend (Glen)]

Originally Posted by Atmos

This is only true if you don't overcome read noise. Take the 16803 which has a very similar QE to the ASI1600 but a RN of 8e- compared to the variable RN of the 1600. As long as they both overcome the read noise, their sensitivity is more or less identical. The 16803 will have to do longer subs to reach that point but it has MASSIVE wells to be able to accomodate for that.

I believe people adapt their techniques to work to the strengths of their equipment. For example, with the ASI1600, owners are experimenting with short sub imaging and running large numbers of them, also using the varible gain feature to shoot short NB. With broadband subs of 30-60 secs not uncommon, but hundreds of them. This makes the mount and guiding much less of an issue. Deep wells are not really an issue for a camera with very low noise and short sub capability. Max depth on the 1600 is at Gain 70, but many of us shoot at Unity (Gain 139) and just shoot more subs, we gain our depth through stacking, not sub open shutter duration. As 50 subs at 300" is equal to 300 subs at 50 secs in terms of data acquired. Short subs also are less likely to be sky limited.

Have a look at Ray's Optimum Broadband Sub Length Chart, which shows maximum electron count (after stack) for various Gain settings and suggested sub lengths for those Gain settings.

[Slawomir (Suavi)]

Originally Posted by Atmos

This is only true if you don't overcome read noise. Take the 16803 which has a very similar QE to the ASI1600 but a RN of 8e- compared to the variable RN of the 1600. As long as they both overcome the read noise, their sensitivity is more or less identical. The 16803 will have to do longer subs to reach that point but it has MASSIVE wells to be able to accomodate for that.

More time needed to reach the same SNR = lower sensitivity

[billdan (Bill)]

I think my old PC would die of a heart attack if it had to stack 300 subs.

[Shiraz (Ray)]

Originally Posted by RickS

Pete,


With software binning you don't get a read noise improvement but you have more flexibility, e.g. you can extract lum from your RGB data and add it to your normal luminance if you image LRGB unbinned. If you do unbinned L and binned RGB as some people do that option isn't available.


Cheers,
Rick.

Rick, I think that you do get a signal-to-read-noise advantage from software binning. With 2x2, the signal goes up by 4x, but the read noise adds in quadrature and only goes up by 2x, so you get a 2x improvement in SNR - probably works out about the same as hardware binning with many chips, except that you also get the full 4x effective well depth (most hardware binning only gives about 2x).

[Atmos (Colin)]

Originally Posted by glend

I believe people adapt their techniques to work to the strengths of their equipment. For example, with the ASI1600, owners are experimenting with short sub imaging and running large numbers of them, also using the varible gain feature to shoot short NB. With broadband subs of 30-60 secs not uncommon, but hundreds of them. This makes the mount and guiding much less of an issue. Deep wells are not really an issue for a camera with very low noise and short sub capability. Max depth on the 1600 is at Gain 70, but many of us shoot at Unity (Gain 139) and just shoot more subs, we gain our depth through stacking, not sub open shutter duration. As 50 subs at 300" is equal to 300 subs at 50 secs in terms of data acquired. Short subs also are less likely to be sky limited.

Have a look at Ray's Optimum Broadband Sub Length Chart, which shows maximum electron count (after stack) for various Gain settings and suggested sub lengths for those Gain settings.

It does certainly make it a LOT easier on the mechanical side of things doing 30-60s broadband but you also lose considerably more time with dithering, guider/mount settling and the like. With the download speed of the 1600 that becomes irrelevant however.

Deep wells are still of importance because your well depth drops faster than the read noise does. As you increase the Gain the dynamic range also drops so well depth is still most certainly a consideration. You may only need 30s but you can blow out parts of an image with 30s as the well depth drops considerably.

The being sky limited is purely having the sky background (the amount of photos emitted by the sky) being brighter than the read noise of the camera. With my QHY22 that happens in about three minutes at my dark site at 4.7e-, with a lower read noise it just hits the required level faster. If I did 10x180s and you did 30x60s it is likely that the results will be more or less identical. On the same telescope theoretically my QHY22 will be deeper as it has a 30% higher QE than the ASI1600.

Originally Posted by Slawomir

More time needed to reach the same SNR = lower sensitivity

It takes more time to get over the read noise but 10x300s is the same as 30x100s as long as on both accounts they are sky limited. Under both instances there are the same number of captured photons above noise so the SNR will be very similar.