CCD Imaging

[poltabs]

I have decided to ditch the DSLR and go down the CCD route.

I have a Nexstar 8 GPS scope with wedge.

I have been looking about and have looked at the specs and seen that most of the CCD cameras give a very small file size due to a very small chip (640x480 etc) and want to go for a larger CCD chip in the camera.

I would love a Large Format type CCD but being realistic one is nowhere near my budget but have come across the SAC 10, a 3.3mp Sony chip camera.

So does anyone use one, have any info on them (real user report) or can recommend an alternate option?

Many thanks and look forward to hearing from you

Cheers

Kevin

[narrowbandpaul]

i have seen the Artemis 4000, with the same chip as the H16 from Starlight Express, it comes in at £1500, which is good considering the size of chip

There are a number of things to consider...

what focal length do u plan on using, and particularly the maximum you are likely to use.

what focal ratio do u plan on using

do u want mono or a colour chip

how much u intend on spending

filter wheels or LRGB or narrowband imaging

I hope i can help in your choice.

PS u can get the artemis 11002 (same chip as STL11002) witha grade 2 chip for £2600 approx...dont know if thats in your budget

best wishes

Paul

[Eddie]

The best value for money cooled CCD I know of is the QHY8, its a APS-c size sensor.

http://www.modernastronomy.com/camerasQHY.htm#qhy8

This is the camera I had before I had the artemis11002. Its one shot colour but uses a sony CCD that has the unique property of being usable with narrowband filters.

[narrowbandpaul]

if single shot colour is what ure after, then that QHY8 looks very good, really good infact. And a great price

Paul

[iancandler]

I too looked at the sac 10, the 3.3 MP sensor seemed quite tempting.. then I did a bit of reading on image scale etc and checked the sac's pixel size, its tiny, I think around 3.5 microns.

I ended up ditching the idea for now as I cant afford a QHY8 which would be my ideal camera, though I have heard that their budget model the QHY6 can produce good results..

Why not give Bern a ring at modern astronomy and get his opinion?

[Eddie]

The QHY6 does indeed produce great results! 8)

Eddie

[narrowbandpaul]

the 3.5 micron pixels are tiny, and gather only a very low flux. The resolution with the Celestron is too small the atmosphere in the UK to support.

[Eddie]

Doesn't the SAC 10 use the same sensor as the Starlight express SXV-M8c? Would not touch it with a barge pole, with the loss of resolution that you get from a OSC, you need to have larger pixels and more of them (like the QHY8!)

Eddie

[narrowbandpaul]

i dont agree with OSC CCD's, due to the loss of resolution. Plus mono chips are far more flexible

[Eddie]

Have you used one Paul?

Eddie

[narrowbandpaul]

no, only used mono. But due to the CFA across the chip, you only have a 1/3 of the total available pixels per colour channel. Well dont they use RGGB, so 1/2 chip is green, 1/4 red 1/4 blue. Plus the filters dont have 100% throughput, so they impinge on sensitivity.

I take it you have used one eddie, if so did you like it

I wasnt implying that OSC's are carp, just that I think mono is more flexible and sensitive over its OSC cousin

Paul

[Helen]

Paul,

Take a look at any of SteveL's recent photos - taken with a QHY8 and stunning

Helen

[narrowbandpaul]

i was just putting forward an opinion. And steves stuff is excellent, but when I buy one I'll be looking at mono even though OSC is tempting. i dont want any arguements

[Eddie]

Yep, was the first one in the UK to get the QHY8. Awesome camera. One shot cameras are no way near as bad as they used to be, but you do need the higher resolution ones like the QHY8 (6 MP) But ultimately I am like you Paul and prefer the mono cameras.

Eddie

[narrowbandpaul]

thanks eddie, I was agreeing with your assesment earlier. Im not trying to imply that they are bad, but they have limitations...enough to put me off

cheers eddie

ps you have an 8"f4 APO/astrograph...can i have details...sounds awesome

[Eddie]

If I sounded defensive, its because there seems to be a lot of folk out there that don't appreciate OSC's of today are not like the ones of old!

I see you have a 10" APO too! It's just a play on words, it's a 8" f/4 corrected newt. When you think about it mirrors are perfectly corrected, in terms of colour, across the field. The newt in question is the GSO 8" f/f that Bern at Modern Astronomy sells. It copes with the 35mm frame of the Art11002.

Eddie

[narrowbandpaul]

yes the perfect apo, yeeeaaahhh!!!

what flattener do u us.We...built in custom made from the sounds. It sounds amazing...

Genuinely not trying to be derogatory of OSC, i type before I think. Which is not going down well here. Its always been a problem of mine

Its gotten to the stage where I almost cant reply for fear of a complaint...dont mean your post neccessarily. I just offer my opinion, but not in the best way

U off to kielder

Paul

[Eddie]

Amazingly, I use a MPCC. Only problem with this is that it does cause some vignetting with the Art11002. Might get a Paracorr at some point.

Not off to kielder, to far to go far skies that are the same as mine! Will be going to kelling though.

Eddie

[narrowbandpaul]

shame,

at least you have some dark skies...or were you referencing the cloud...;-)

Paul

[Eddie]

Yep, some of the darkest clouds in the UK!

Eddie

[MartinB]

Kevin, your simple question raises a lot of issues and there is no right or wrong answer. It can get really confusing and give you a headache.

My first advice would be don't aim for a once and for all purchase, the chances are you will want to change it within 2 years! Get a camera with a good track record, capable of producing stunning images but which isn't fussy about equipment used or challenging to get good results.

Large format chips come with a whole set of problems - to get the most out of the chip size you need optics that will deliver good illumination over a wide field and in addition be capable of focusing the image over the whole of the field - no mean feat. Large chips are slow to download their data to the computer. That's not a problem if you are running long exposures but is a pain with the shorter exposures you often need in the UK, you end up loosing valuable exposure time. Finally processing these big files is tedious, even on a fast computer you can spend a lot of time thumb twiddling waiting for the computer to do it's stuff.

One shot colour is another controversial subject. As far as I'm concerned the main advantage of OSC is that it does away with the need for a filter wheel (truly relaxed LRGB imaging requires a motorised filter wheel which are a bit pricy), beyond that the advantages lie with mono but as Eddie has suggested, differences aren't that great. For someone starting out I would strongly recommend mono - this is slightly more sensitive so you will get better data in a short time, processing is more straight forward and sooner or later (probably sooner with our light polluted skies) you are likely to want to use narrow band filters such as Ha. The OSC cameras such as the QHY8 and H9C do a pretty good job with Ha but they aren't on a par with mono.

In the UK we are faced with problems of poor climate, light pollution and often mediocre seeing. We can't accumulate the imaging hours that many people around the world are able to. We need a chip that is sensitive (poor climate), good for narrow band imaging (good if you have light pollution) and works well at short focal lengths (for when the seeing is poor)

This is a long winded way of suggesting that you go for a camera with a Sony 285 chip. This might be an Atik, QHY or SXV. The cameras vary somewhat but the heart of the system is the chip. The 285 was the largest mono CCD Sony produced before they moved onto CMOS chips. The QHY8 is also another brilliant Sony chip (I wish they'd left the bayer matrix off!).

Reasons for recommending this chip

- big enough to be capable of framing most targets especially using short focal lengths (this chip excels with the sort of small refractors which you will want to consider piggybacking to your NS8

- small enough to avoid vignetting and problems with field curvature - using the NS8 with a 6.3 reducer works very well. You won't need to faff around with flats to remove vignetting (although you will still want to do flats eventually)

- very sensitive, a max quantum efficiency of 65% is superb for a non blooming camera and, very important, this sensitivity is carried into the Ha wavelength. The 285 is an Ha imaging demon.

- very low dark current so no need to use dark frames.

- USB2 camera take little more than a second to download images

- Stacking and processing is reasonably rapid

- Small pixels means you can get decent resolution at short focal lengths. Nik Syzmanek has produced some stunning images using and SXV H9 with a little ZS66 and 0.67 reducer - focal length <300.

The development of CCD cameras has been such that you are unlikely to be disappointed whatever you get but I think a 285 chip will do you very nicely.

Sorry to have waffled on!

[markcol]

Martin, that is an extremely well argued & written piece of advice to Kevin. Obviously infomed by much experience.

As someone who has just been through this dilemma and is in the process of acquiring a SXV-H9, it is also immensely reassuring!

Mark

[dogfish]

Martin

Waffle away. I found this really helpful as someone just on the verge of my imaging career. How about editing it and adding it as a primer?

Just a thought, Martin

[FLO]

.... an extremely well argued & written piece of advice to Kevin. Obviously informed by much experience.

.... I found this really helpful as someone just on the verge of my imaging career.

Nice one Martin

Its pinned to the office wall, along with your summary of CCD manufacturers :thumbleft:

[narrowbandpaul]

i take it that was the sony ICX285 you were refering to. if so that really is a great chip, we have used the mono version. The thing practically drinks Ha

Paul

wish sony had made a 6MP version, but they've moved on to the world of CMOS