CCD Camera decisions - Mono vs OSC, FOV, Filter wheel etc...

[Zakalwe]

@Zakalwe - I had also contacted Bern about reserving a QHY8L. I haven't pulled the trigger (can't yet) and I look forward to your first (and second, third, et. al) reports

Best,

Mike

fo'schnizzle, as (apparently) the kids say... That, translated into English means "certainly, my good Sir, there will be multiple posts in this fine forum about my latest purchase"

He is out of stock at the moment, and awaiting an order from QHY. I'm hoping for this week, though knowing my luck.....

[ncjunk]

Nice thread!

I picked up an Artemis285, cameras and use that. I have recently picked up a qhy8l and aim on sticking that on the ed80 with the art285 on a c11.

As for which camera i would go for between the two...it would be a 314+L with an HA.

I would then do mono imaging and HA imaging. The file size of the 285 captures is just easier to deal with/copy/store/process.

Then get a filter wheel when funds allow.

But i've done all that already and know have the qhy as well to put together whatbi hope will be an entertaining setup....if my machinist will just complete the bracket for piggybacking the ed80 on the c11...hes suffering from spanish mañana syndrome!

[ncjunk]

If you can cope without sp cooling then pick up a art285 for 500/600 and an ha filter.

Still a fine camera i love mine...but cleaning the dust off the lens is a pain

[AndyUK]

Cheers Neil - Thanks for the confirmation...

It looks as though these 285-chipped cameras are rarer than rocking horse do-do on the 2nd hand market, so although I'd prefer to buy second hand (for obvious reasons), I know my impatience will get to me... in addition to which I don't want to risk my "finance director" deciding to reduce, or withdraw, funds in the meantime...! I wish I could afford the lot in one go, but it will have to be just the camera and Ha filter for now (and maybe I can add some RGB data from the DSLR using Registar in the interim?)

[PortableAstronomer]

I could go for an OSC but this is what makes me nervous. On the left, OSC. On the right, Ha (from our mono camera) plus OSC.

That is an interesting demo of like-for-like OSC vs mono which I assume the CCD sensors are otherwise "equivalent" (i.e. same manufacurer, same internal technology etc), which is no big surprise. But then again, not many people would choose a OSC with a Kodak CCD.

It would be more interesting to compare a Sony OSC (e.g. SXV 25-C or QHY8) with one of the Kodak 8300 mono sensors. It is that sort of comparison that will show how much bang you get for your buck.

I have owned a 285-based mono sony sensor (the 314L) which are known for their sensitivity, but also own a Sony OSC (QHY8), and borrowed a Kodak 8300 based CCD. To my amazement, the biggest surprise in "ooh that's not very sensitive" was *not* going from the 314L to the QHY8; it was actually comparing the 314L to the Atik 383. Of course I was "expecting" the OSC to be less sensitive, so that I am sure had something to do with it, but because the Sony OSC in the QHY8 had *so* little noise, I am not having to take so many subs.

Still not convinced? You could try looking here : http://stargazerslounge.com/imaging-widefield-special-events-comets/79020-cygnus-milky-way-widefield.html , a post from 2 years ago which shows a *single* 10 minute sub on the QHY8. It would be great to see what a KAF8300-based mono sensor could do for a single 10 min sub of the same region. It might be more sensitive, or you might be surprised. The KAF8300 would certainly be a bit more noisy, and certainly not so wide.

It's just a shame that the flourescent street lighting in my neighbourhood goes through OIII and HA, so even narrowband is not very satisfying, but I cannot blame the equipment for that!

So (for instance) the QHY8 with a 6 megapixel sensor would be using approx 1.5 mega pixels in narrowband, versus the 285 chipped CCDs which have also 1.5 megapixels?

Of course, the mono CCD will have more sensitive pixels.

With a like-for-like sensor ( e.g. kodak 8300 colour vs kodak 8300 mono) then you'd still expect the mono to be more efficient because even if the red pixels in the bayer matrix on the OSC has a good HA transmission, it would not be 100%, more like 90% or maybe lower (?); so in theory the mono would be more efficient even if you add a OSC sensor with 6 million pixels leaving 1.5 million useful pixels for HA capture. But you've also got to factor in the larger pixel size of the Sony OSC CCD compared with the KAF8300-based chips, which is a plus for the large format OSCs.

[MikeWilson]

....( e.g. kodak 8300 colour vs kodak 8300 mono) then you'd still expect the mono to be more efficient because even if the red pixels in the bayer matrix on the OSC has a good HA transmission, it would not be 100%, more like 90% or maybe lower (?); so in theory the mono would be more efficient even if you add a OSC sensor with 6 million pixels leaving 1.5 million useful pixels for HA capture. But you've also got to factor in the larger pixel size of the Sony OSC CCD compared with the KAF8300-based chips, which is a plus for the large format OSCs.

Good evenin'

Comparing the 1000D DSLR with the QHY8L CCD, the CCD is about the same size (although slightly less pixels), about twice as sensitive (akin to having a faster scope), far less noise (and what remains is easily removed using dark frames) and a larger bit depth (dynamic range between brightest and darkest pixels).

It's also a lot more expensive than the 1000D.

Compared with the next nearest CCD in terms of price, the ubiquitous Atik 314L+ - the QHY8L is somewhat less sensitive (due to the Bayer matrix), but this can be easily resolved by taking a slightly (10%?) longer exposure. Whilst the QHY8L captures much more data than the 314L+, it does so over a much wider area meaning that the 314L+ captures a higher resolution image than the QHY8L.

The QHY8L is also cheaper than the 314L+ and doesn't require additional RGB filters.

I've been very impressed with my first Ha test with the QHY8L even though my coma corrector is over 20mm out of place:

The differences are worth thinking about - not in terms of either or (mono VS OSC), but as complimentary/different cameras for different purposes.

Mike

[AndyUK]

Hi Mike

The differences are worth thinking about - not in terms of either or (mono VS OSC), but as complimentary/different cameras for different purposes

I think I'm coming to the same conclusion... Like you, I'm happy with my decision, but feel that (one day!) it would be very nice to have an OSC as well (but I'm not going to tell the wife that - I know she'll need a new car first!)

[Deneb]

Personally If i was deciding on a colour camera, just save the cash & buy a modded dslr again & use registar to combine the images... between the two...

Nadeem.

[PortableAstronomer]

I nearly went on the modded DSLR route.

At the time, if you wanted a decent modded DSLR with a good viewing screen, modded IR filter/removal, you'd be paying 700 pounds or so. For just a little more, I could get a full-frame OSC CCD camera to get the 16-bit well depth, more sensitivity, less noise & TEC cooling. If you're out in the field without a laptop then a DSLR has its merits. Otherwise the choice of OSC CCD or modded DSLR would be a no-brainer.

It was still quite recently when the ICX285-based sensors (Atik 314L or SXV-H9) really rules the imaging world. The Sony SuperHAD technology in those chips are still unsurpassed to this day, in terms of sensitivity and low noise. What many imagers didn't realise when they rushed out to get the larger format mono chips, was they were 'trading-in' the sensitivity for a larger sensor size (even staying on mono), and in the case of the KAF8300 it is still not a particularly large chip anyway.

With the large OSC CCDs like the SXV-25C or QHY8 you get to keep the Super-HAD ultra-low-noise sensor technology used in the ICX285 based chips, but the trade off is just having the bayer matrix; a trade-off with sensitivity that you are going to have *anyway* by moving from a mono ICX285-based (Atik 314L etc..) to a mono KAF8300 (Atik 383 etc..).

[fatwoul]

So for the price of a KAF8300-based camera and filters, a person could buy an ICX285-based camera like the 314, smaller filters, and probably have enough money left over to get a modded DSLR as well, giving them the in-the-field versatility and widefield capability of an SLR, and the sensitivity and narrowband capabilities of an astro CCD. Choices, choices...

[PortableAstronomer]

...and get more sensitivity and less noise with the ICX285-based CCD.

[Deneb]

So for the price of a KAF8300-based camera and filters, a person could buy an ICX285-based camera like the 314, smaller filters, and probably have enough money left over to get a modded DSLR as well, giving them the in-the-field versatility and widefield capability of an SLR, and the sensitivity and narrowband capabilities of an astro CCD. Choices, choices...

Why do think I went for a 314L+, i could have gone for the 383L+ & 2" filters with ease; That was my plan, This way I can get a modded dslr also with a reducer for the scopes i have...also having a low noise clean ccd chip ..

Nadeem.

[RobH]

Whilst the QHY8L captures much more data than the 314L+, it does so over a much wider area meaning that the 314L+ captures a higher resolution image than the QHY8L.

Actually, the area covered has nothing whatsoever to do with the resolution.

Resolution (assuming all other things to be equal) is down to pixel size, and obviously the bayer matrix too when comparing a mono vs OSC.

My 8300 chipped SX H18 has 5.4 micron pixels, and my 16HR has 6.4 micron pixels. The 8300 chip is much bigger than the 285 chip, but theoretically has greater resolution due to the smaller pixel size.

The QHY8L has pixels of 7.8 microns, plus a bayer matrix, so yes, it is of lower resolution than the 285 chipped 314L, but not because of the chip size.

Rob

[fatwoul]

And what about the pixel size? 7.4 v 5.4. Either seems like luxury after my D3 (which I think I worked out as somewhere around 10?), but is the 5.4 not a consideration? The Titan I just bought is 7.4, and I'm already impressed with it (but oh dear lord that chip is small...)

EDIT: Typed this one too slow, and the person before me kinda answered the question before I clicked "post quick reply".

[Deneb]

It will be a very small area it covers on your MN190 ! Have you tried using it on your 80ED, as some objects might be better suited for it through your 80mm.

Nadeem.

[fatwoul]

Oh yes, I've only tried it on my 80. I won't even bother putting it on the MN190 unless I want to fill the frame with M57!

[MikeWilson]

Resolution comparison of the 1000D, QHY8L OSC CCD, and 314L mono CCD on a 6", 750mm Newt:

*made using Ron Wodaski's CCD Calculator

Ergo, an image made using a 314L to the equivalent size of the QHY8L (i.e. the whole of M42) will result in a higher resolution final image. However, a 314L will also take longer than the QHY8L OSC and require a mosaic to be made...

[Whippy]

Resolution comparison of the 1000D, QHY8L OSC CCD, and 314L mono CCD on a 6", 750mm Newt:

[ATTACH]59837[/ATTACH]

*made using Ron Wodaski's CCD Calculator

Ergo, an image made using a 314L to the equivalent size of the QHY8L (i.e. the whole of M42) will result in a higher resolution final image. However, a 314L will also take longer than the QHY8L OSC and require a mosaic to be made...

Erm, that's a field of view comparison, the resolution would be measured in arc secs per pixel. I also can't see how the QHY8 would be quicker than the 314 to create an image, from what I've read mono with RGB takes about the same length of time as OSC.

Tony..

[MikeWilson]

Erm, that's a field of view comparison, the resolution would be measured in arc secs per pixel.

Yes, you're right although my point still stands - in comparing the 314L with the QHY8L OSC - it is quicker to create an image of M42 using the QHY8L but the resulting image will have a higher resolution in the 314L. Right? Or am I missing something here..?

I also can't see how the QHY8 would be quicker than the 314 to create an image, from what I've read mono with RGB takes about the same length of time as OSC.

"an image made using a 314L to the equivalent size of the QHY8L (i.e. the whole of M42) will result in a higher resolution final image. However, a 314L will also take longer than the QHY8L OSC and require a mosaic to be made..."

My understanding is that while the QHY8L can fit the entirity of M42 within it's frame, the 314L would require a mosaic of at least four frames. Ergo, the larger field of view is quicker to image the target although at a lower resolution...

Please somebody interject this thread with a c-c-c-combo breaker!

Clear skies,

Mike

[Whippy]

Ah, I see what you're saying now. The QHY8 has a larger chip and so a larger FOV therefore, it's quicker than a 314 because the 314 has to mosiac'd to get the same FOV as the QHY8.

That's true if you're basing it purely on how much sky you want to cover, and you can't argue with that if you're looking at the larger objects like M42, M31, NGC 1499 etc etc but for everything else it's a bit of a moot point IMO. Even M33 fits easily onto the 314's chip with a small refractor like the Zenithstar 66 (although of course, the resolution won't be particularly high with such a short focal length), in this case there's no real difference, especially when you're going for smaller objects like M51 where FOV isn't an issue because it's only about 11 arcmins wide.

Tony..

[MikeWilson]

Ah, I see what you're saying now. The QHY8 has a larger chip and so a larger FOV therefore, it's quicker than a 314 because the 314 has to mosiac'd to get the same FOV as the QHY8.

That's true if you're basing it purely on how much sky you want to cover, and you can't argue with that if you're looking at the larger objects like M42, M31, NGC 1499 etc etc but for everything else it's a bit of a moot point IMO. Even M33 fits easily onto the 314's chip with a small refractor like the Zenithstar 66 (although of course, the resolution won't be particularly high with such a short focal length), in this case there's no real difference, especially when you're going for smaller objects like M51 where FOV isn't an issue because it's only about 11 arcmins wide.

Tony..

Hi Tony,

You make a very good point there.

There's one other thing to consider - cost & value for money. Moving from modded DSLR to something like the QHY8L gives you the benefits of TEC and a huge sensitivity boost at a lower price than a 314L+ & filters.

I had to make a similar decision to Andy and went for the OSC given my lack of time although the moment I can get a pier set up I think I'll want to move to a mono CCD too.

Clear skies,

Mike

[Whippy]

TBH Mike, It's swings and roundabouts really, sensitivity or size? I'd still argue that you'd need to budget for a flattener with a large chipped camera with a QHY8 whereas I've only used a flattener with my atik because it's also a reducer plus you can't get away with 1.25" filters..... Anyway, there's no denying that the chip in the QHY8/SX M25 does a great job and in an ideal world, Sony would make a chip that has the sensitivity of the 314's with the size of the QHY8's, we'd all be winners then!

Tony..

[MikeWilson]

TBH Mike, It's swings and roundabouts really, sensitivity or size? I'd still argue that you'd need to budget for a flattener with a large chipped camera with a QHY8 whereas I've only used a flattener with my atik because it's also a reducer plus you can't get away with 1.25" filters..... Anyway, there's no denying that the chip in the QHY8/SX M25 does a great job and in an ideal world, Sony would make a chip that has the sensitivity of the 314's with the size of the QHY8's, we'd all be winners then!

Tony..

Mind if I ask what the deal with the 383 is? I thought it was what you suggest in your ideal world scenario - the 314 quality at the APS-C size of the QHY8/DSLR.

I'm earmarking either the Atik 383, or (more likely) the QHY9 as my 'next' camera - probably a long way down the line...

Mike

[RobH]

The 8300 chip is considerably less sensitive than the 285, but has great resolution on a short FL scope due to the pixel size. On a larger. longer FL scope, binning 2x2 still gives you pixels small enough for good resolution in our seeing conditions, and it becomes very sensitive.

I used my H18 (8300) binned 2x2 at F10 on my 11 inch edge, and it more than made up for the slow F-ratio.

[Whippy]

TBH Mike, I haven't given the cameras with the 8300 chip (383/QHY9/H18 etc etc) a huge amount of thought as I'm not really considering a new camera right now. Purely on anecdotal evidence, I've heard of one or two issues with the shutter in relation to flats and the colour one has has a bit of bad press, other than that I don't really know.

I don't think it's as sensitive as the 285 chip (314L, H9 etc), and I know you need darks with it plus it's not as big as the QHY8's chip so it's a bit of a half-way house in that respect. An APS-C size chip with the 285's charecteristics would do nicely .

I think like with any new(ish) bit of kit, there's a bit of playing around needed to get the best out of it and working methods made up, it looks good on paper so I guess in time we'll see how good it can be.

EDIT: Rob's post covered it nicely!

Tony..