Which mono camera for my 80mm triplet.

[Crushellon]

Hey guys,

So I'm looking into getting a mono cam for my 80mm triplet. Originally I was just going to get one of the asi1600 packages with the wheel and filters but I'm not sure if it's what I'm after. It will be used mostly for narrowband imaging with the main aim of capturing the dusty background regions around objects. My main concern is with the short imaging times commonly used with the asi1600 and if it will capture what I'm looking to get with those short subs. I'm used to and prefer long exposures and less subs as my mount will easily handle 15min and upwards exposure times with this focal length and it's a lot easier to process 20x15min subs than it is to process 60x5min subs. Any suggestions as to an alternative? Is this camera capable of doing what mono CCD's can do with long subs? I was considering maybe another KAF8300 camera as I always dither every sub and drizzle anyway.. I'm not sure, just looking for some more input. Price range is around $3K with filters, doesn't matter if I go second hand to get what I need at that price.

Thanks, Tim

[glend]

Tim I don't know where your getting your information from, the ASI1600MM-C is a fantastic narrowband camera. The flexability of the camera means it can fulfill different roles. Most of what i shoot is narrowband, and the 1600's remarkable smoothness enhances these images. The ability to adjust gain and offset allow you to shoot narriwband in different ways if you wish, fast narrowband can be done with 90 sec subs and gain setting of 200, changw the settings and you can shoot 5 min plus subs at gain139 or lower ( max well depth is at gain 76). With many narrowband targets 15min subs are just not required. Processing makes no difference, the files are the same size.

[gregbradley]

Dusty background regions would require lots of luminance imaging rather than narrowband which picks up the gases.

So keep that in mind.
Atik and QHY now offer all in one KAF8300 camera similar to the QSI 683 WSG 8.

If I could get one for that sort of price second hand the QSI would be the go as its the proven performer with many superb images around and excellent OAG setup and it uses the smaller filters which are less expensive. But 2nd hand on Astromart they seem to go now for around US$3000.

The QHY and Atik versions may be closer to your budget.

Greg.

[Atmos]

With the ASI1600/QHY163 at its 12-bit gain setting you’ll be looking at 10 minute subs in narrowband.

[Slawomir]

Atik will release next month their version of Asi1600/QHY163, will be interesting to see if it will offer any improvements/advantages.

As far as I know KAF-8300 should be more sensitive than ASI1600 with the same telescope due to having larger pixels and similar QE, and files will be smaller in terms of MB, but data will be somehow under-sampled (can be rectified with drizzle to a degree).

I would personally look primarily into matching pixel size with focal length to suit my needs, and as Greg mentioned, having FW-OAG-camera as a complete package that is rock solid would be very important for me as well.

[Camelopardalis]

Lower noise and higher resolution of the 1600 would be an advantage at short focal length. No amount of dithering is ever going to make up for real resolution.

[Slawomir]

Very true, but 80mm aperture is not necessarily optimal for high resolution imaging.

Assuming 80mm f/6 telescope, imaging with 3.8micron pixels might be a bit below a diffraction limit for such instrument, so gain in resolution over using 5.4 micron pixels might not be as significant as we might believe. Moreover, with 5.4 micron pixels we can get data more quickly (important for time-poor astronomers) due to higher sensitivity of larger pixels, and still recover some detail by drizzling. That is why I would be quite tempted to pair a KAF-8300 in a reliable camera with 80mm aperture.

But everyone's priorities can vary, and with certainty ASI1600 or similar would be a very nice choice as well.

[Camelopardalis]

The Dawes limit for a 80mm f/6 approximates to that of the pixel resolution with 3.8 micron pixels, so you'd see the difference between a good night and a duff one. I can certainly notice the difference on my Esprit 100. With larger pixels you're just oblivious to it.

I believe the Panasonic sensor has higher QE than the 8300 too, but that's largely anecdotal. One thing it does have in its favour is the read noise at high dynamic range is ~2e. It's generous to quote the 8300 at 8e, so even software binning the data from the 1600 the read noise is no worse...and surely, if 5.4 micron pixels are better than 3.8 micron pixels, 7.6 micron pixels must be better :shrug:

And we have to get over the stigma of newcomers folks :P In the same time that I've been imaging with my ZWO without a hitch, I've heard of several accounts of premium cameras suffering electrical faults, condensation, poor repairs from the OEM...what gives?

[Slawomir]

Glad to hear your camera works very well :thumbsup:

Perhaps I am a bit conservative, but at this stage, I would rather get a nice KAF-8300 based camera for a small fast refractor, for the reasons I mentioned in my earlier post :)

As for being fault free and well thought-out design, this solution to preventing dew forming on the cover glass indicates, well, I will let everyone make own judgement ;) : https://astronomy-imaging-camera.com/products/accessories/anti-dew-heater/

In the end, I hope that this discussion will be somehow useful for Tim in terms of making the best choice for his next camera :thumbsup:

[Camelopardalis]

Ha ha yeah that’s a pretty “interesting” solution, but to be fair, I’ve not had dew or internal condensation using mine with a refractor. Maybe with an open tube reflector it’s more of a problem? They’ve subsequently redesigned the camera and the “solution” isn’t necessary.

When it comes to well thought out design, I just can’t get past a certain company that sells astro cameras but doesn’t moisture protect the circuit boards, which then rust and fail. Certainly wouldn’t be happy paying extra for that, lifetime warranty or not.

This will no doubt come up again and again, and I’ll always be here to troll the traditionalists...technological advancements wait for no one ;)

[glend]

I read everything related to the 1600, including the user forum, and can only recall a couple of version one owners in the USA reporting condensation inside the sensor compartment of a 1600, and they received prompt service from ZWO. Those stick on heaters were brought out more in response to the rapidly evolving competition from late comer QHY who introduced a heated window in their version. New 1600s incorporate a new design in that area, and no further condensation problems have been reported.
My version one 1600 has never had a condensation issue, and it is used on five different scopes, open and closed tube designs of various focal lengths.

I almost bought a KAF-8300 in early 2016, glad now that i didn't.

[Slawomir]

Thank you for clarifying that Glen. Good news indeed.

[Shiraz]

another vote for the ASI1600/QHY163 Tim. You don't have to run these cameras in low noise mode if you don't want to and can happily make one work just like a very low noise 8300 (with 16mpix) by choosing zero gain. There will be somewhat lower signal than an 8300 due to the smaller pixels, but on the upside there will be a significant improvement in resolution if your scope is good enough quality.

FWIW, my 1600 has worked perfectly since the initial software wobbles (interacting with SGPro) were sorted. Agree with Glen that the dew heater was a fix for a non-problem - marketing.

Seems to me that we have entered the era where the astro camera has become a lowish cost consumer commodity - sounds too good to be true, but this particular CMOS chip really does provide better performance at a much lower cost - has to be a good thing.

[dpastern]

Another vote for the ZWO ASI 1600 camera (I'm about to lash out on getting one myself after a LOT of research).

Image quality from the ZWO camera is outstanding, every single bit as good as that from KAF 8300 based cameras.

From my reading, I've seen a few people recommend keeping the gain/bias lower,; with bias @ 21 and gain between 100 and 139.

Do lots of short sub exposures - 2-3 minutes max. 2-300 subs for each channel.

The ZWO can do longer imaging subs, but it is better suited to shorter (and lots of them) subs. The KAF 8300 are the opposite (less subs, but longer, as a rule).

I've just bought an Esprit 80 (queenslanders can think me for all the wet weather we've been having lol!) and will be mating it with the 1600 because the FOV matches what I want, and the arc seconds per pixel are in the 1-2 sweet spot.

I would agree with Ray's comments that the CMOS cameras are offering better performance at a lower cost. I give CCD cameras 5 years max before they become extinct in astro imaging. The same thing happened to DSLRs years ago now (and CCD was dead in under 2 years in that instance).

I've seen a lot of snobs hating on the ZWO cmos camera, simply because they are snobs. The same thing happens with other types of gear sadly, both in this hobby, and in other hobbies.

Cheers,

Dave

[dpastern]

Oh, and Tim, there's a used ZWO 1600 up on Astromart, with filter wheel and filters, for USD $1200. It only has the mini EFW though, and LRGB filters...may or not may be suitable for you. As usual, caveat emptor, and I have no association with the seller.

[lazjen]

I've got the ZWO ASI 1600MM and while I think it's great, I think your statement here about CCD being extinct in 5 years for astro imaging is not correct. So far there's no real replacement in CMOS cameras for large pixel mono CCD cameras. Until that time there's zero chance CMOS will replace CCD.

[dpastern]

I base my comment on how quickly CMOS killed CCD in the DSLR market. I personally think that in terms of outright IQ (at least with terrestrial imaging), CCD is better than CMOS. CMOS is more convenient. It's a bit like LPs vs CDS - LPs offer far better sound quality, but CDs offer convenience for the masses ;-)

edit: rumours are that ZWO is already well into development of a full frame mono camera. Larger frame sensors are so expensive it isn't funny...only the wealthy can play with them...

[Crushellon]

Thanks for the replies, there's some interesting points to consider there.
I don't understand the short exposures though, if the 1600 can do long exposures at neutral gain settings why are they commonly used for short subs and lots of them? What's the benefit to it? Surely longer exposures are better for NB imaging, or does it not matter so much because the background has a low noise level with the 1600?
Also, if used at low gain settings, are you just holding back the capabilities of the camera unnecessarily? As in, if I did 20x600subs at low gain and 20x90sec subs at a higher gain, would the resulting amount of signal captured be the same? Therefore making the longer subs redundant? Or would you have to do 130x90sec subs to match the amount of signal as the 20x600sec subs?
I'm just trying to get a better idea of why they are "generally" used for sort subs and lots of them to make up integration time rather than fewer long subs. The main reason I'm trying to figure this out specifically is because the idea of capturing and processing 100's of subs does not sound desirable to me at all. Measuring weights, registration, local normalisation, integration, then at the end something didn't work out right and you have to go back and find the issue within 100's of subs... uggh makes me shudder, lol.
But in saying that, if lots of short subs is the best way to get results with the camera (even if it is capable of longer subs), then that's just how it is.

[dpastern]

I'm not best placed to technically answer this (I still have my L plates on!), but hopefully this thread on CN helps:

https://www.cloudynights.com/topic/559771-asi1600mm-c-cheat-sheet-no-math/

[RickS]

To get the best SNR in the shortest total time you need to take subs long enough that read noise is swamped by shot noise from the detected signal. If you have a sensor with low read noise, e.g. ASI1600, then you can take shorter subs and still be in this magical goldilocks zone. With a KAF-8300 you'll need to take longer subs which requires better guiding, results in more data loss if a cloud wanders through your FOV, and probably gives you detail that's a little less sharp. On the plus side, you'll need less CPU grunt to calibrate, register and integrate the data.

You can get good results with CMOS or with CCD. It's a matter of using either sensor to best advantage.

If terms like read noise, shot noise and quantum efficiency mean nothing to you, then you really should do a little reading. The Handbook of Astro Image Processing book by Berry and Burnell is very good or try the signal to noise articles by Craig Stark: http://www.stark-labs.com/craig/articles/articles.html

You'll hear a lot of opinions about this stuff but many of them are uninformed. It's a good idea to learn a little. The maths behind this stuff isn't terribly difficult and intuition will often lead you astray.

PS. Ray (Shiraz) is one of the folks that does understand the maths. You can generally believe what he says :thumbsup:

Cheers,
Rick.

[dpastern]

Rick - you are a very bad man! I had not heard of The Handbook of Astro Image Processing before and now you are making me want to buy it...when I am trying to stop buying stuff!

I read Craig's article and it is excellent. The maths isn't hard, but I have worsening concentration issues, so for me it was a difficult read. But yes, I would agree, it's well worth the OP reading Craig's insights on SNR etc.

[RickS]

Sorry, Dave, but it is a good book and not difficult to read :) I think every serious imager would benefit from an understanding of the basic concepts. It would save a lot of pointless arguments :lol:

[dpastern]

All good. I actually have always enjoyed reading, but as I've gotten older, my eyesight has degraded (just presbyopia, nothing serious) and my attention span (suspected adult ADHD amongst other things) has severely worsened. I hate it, cos it makes reading difficult for me, and I used to love reading well into my late 20s. Frustrating as hell...

All good re: book - will buy it cos it looks worthwhile. May take me a while to read through it and even longer to digest the information inside of it (that's another thing that's gotten severely worse for me as I've gotten older - information retainment).

[Shiraz]

there are some advantages to short subs - eg:
- better resolution and star shape due to ability to remove transient bursts of poor seeing by rejecting a small percentage of the subs
- easier guiding/better resolution by keeping exposures well within mount PE periods .. normal PA errors and guide scope drift are immaterial
- less data lost to transient events such as clouds
- more effective non-linear rejection of transient noise such as cosmic rays

however, if you don't want to take advantage of the above, then there is no major penalty to running the 1600 camera at zero gain and using "normal" long subs for broadband imaging. Provided you use long enough subs to overcome read noise, the total exposure time is what matters - 10x5 minutes = 50x1 minute. As far as I can tell, the CCD equivalent mode of the chip is at zero gain even though it seems to be widely assumed that "unity gain" has some inherent significance.

Narrowband imaging is a different kettle of fish altogether. The 8300 will be severely limited by read noise for all practical sub lengths under dark sky, whereas the 1600 at high gain can give genuine shot noise limited imaging - ie, the 1600 final result will not include ~any read noise, whereas the 8300 result will still have a significant read noise component. Thus, the 1600 will go deeper (possibly by quite a bit). Of course the 1600 will require quite long narrowband subs to get to sky-limited performance under dark sky, but at least it can do it. There are quantisation effects from the 12/16 bit conversion (not hidden by read noise), but FWIW, I have not found this to be an issue. Suggest that you ignore any advice that says that you should always use short subs for narrowband 1600 - sometimes worthwhile, but not always so. http://www.iceinspace.com.au/forum/showthread.php?t=155908 may possibly be useful if you haven't already read it.

The other thing that might be worth considering is the very fast download rate of the 1600. A full res download takes ~ 1 second or less and once you have done a 9 step full frame focus run in under 1 minute, it is very painful to go back to a CCD camera (I tried).

[Crushellon]

Thanks guys. All very clear now. I'll have to have a look at that book Rick :thumbsup:

Anyhow, looks like the 1600/variant will be the go then.

[graham.hobart]

looks like my FLI 8300 mono is being overtaken in the slow lane !!.
Interesting thread folks, and as always, good information backed by experience and objective data. I personally think, mainly because of the members willingness to share and also to experiment, this is the best astro forum.
Every one pat yourselves on the back and buy a new filter!!

:thanx::thumbsup:

[Camelopardalis]

I wouldn't say that at all...they're still mighty effective photon collectors, that hasn't changed.

The CMOS revolution has been coming for years...Sony announced several years back that development (but not production) of their CCD range had ceased, leaving the excellent 674/694 sensors as their last hurrah.

With the CMOS sensors, their primary purpose for production is something else, so we're just benefiting from the economies of scale, which in turn makes them a more accessible entry into astrophotography...which is a Good Thing(tm) IMO.