Bubble in Ha (Atik 16ic)

[Aza]

Hi

This is a few hours worth of 15 minute subs.

8" Newt with Atik 16ic.

I hope to get some OIII next

Thanks for looking.

[daneel]

Beautiful image Aza - looks like a magnifying glass has been put in front of the nebula. What difference does the OIII filter make?

[Parallax]

Excellent!

Steve

[CELESCOPE]

Very good image Aza, well controlled in the bubble , excellent stuff

Rog

[barkis]

Very Nice Arran. The Bubble is very prominent in your Image. Nice Indeed sir.

Ron.

[Aza]

Thanks guys

What difference does the OIII filter make?

When I grab some OIII data I can then start to combine them to make a colour image.

[narrowbandpaul]

nice image.

the O[iII] filter will pick out the higher energy emission rom nearer the wolf rayet star. The bubble itself comes out well in O[iII]

[Psychobilly]

Hmmmm...

Nice first stage in the process

My bank manager is asking will you please all stop posting these amazing narrow band images ...

Billy...

[narrowbandpaul]

billy

I just sent you an email to webmaster@.....

Paul

[Aza]

Thanks guys

I really want to upgrade to a better camera as I dont think I can get much more detail with this one. Something with a 285 chip perhaps

I was trying to sharpen it a bit, but couldnt get a result I was happy with.

[narrowbandpaul]

i generally find sharpening difficult?

its the 285 we use for our narrowband stuff.

its superb really,

exceptionally low noise (darks arent neccessary even for 30min exposures, as long as you have a few for averaging)

0.55 QE peak, with 0.5 Ha and 0.55O[iII]

it really is a great sensor!

a joy to use

[Aza]

Which 285 do you use?

I have been looking at the Atik 16HR, Atik 314L and the QHY2, but to be honest I dont know much about the varying specs.

Cheers Paul

[narrowbandpaul]

SXV H9

if they are all the same chip (guess theyre not) then the performance should be similar. The only thing the camera manufacturer builds is the cooling.

I'll take a look.

Do you have any absolute requirements (size, QE dark current etc)

Paul

[Aza]

Cheers man

I am a beginner with no knowledge of all the specs and stuff.

But I hear good things of this 285 chip and the price is in the range I would hope to spend.

So then its really what makes one cam better than another when they use the same chip.

Maybe its the QHY2 then, if its based on the cooling. Plus I think its the cheapest of the ones I have been looking at.

[Whippy]

Nice image Arran .

Tony..

[jonbarr87]

I must note that all of you DSO imagers especially, are true artists! You all downplay EVERY photo..... I mean work of art. Which to me I must say are ALL AMAZING!!!

Aza- Very well done sir. It looks almost Zen-like.

[narrowbandpaul]

hi aza,

i have had a look at the 3 cameras you have mentioned.

basically the full well depth of a pixel is goiverned by the physical size of the pixel. The 6.45um pixels offered here have a relatively low well capacity of 27500e-, according to specs I read on the internet. This value seems to produce decent numbers when I have analysed the read noise and dark current.

The important ability for a camera, particularly for a sensitive camera like these, is to have a high dynamic range. Dynamic range is a measure of the fainest and brightest sugnals that can be imaged simultaneously. The brightest signal is equivalent to the well depth 27500e-, and the faintet signal is the read noise, which varies from camera to camera.

The read noise originates from fluctuations primarily in the output amplifier (which creates a voltage proportioanl to the number of electrons in each pixel) and the ADC (analogue to digital converter), which converts the voltage to a didgital number (DN) based on the resolution of the ADC. All cameras feature a 16 bit ADC, hence full well should occur at 2^16 or 65535. Reducing read noise is importnat to maximise the dynamic range, and is obtained by reading the camera slower, although other techniques are employed, enabling fast read out and stable digitisation.

So what of the cameras then.

QHY2....claims a microlens covering the pixel to help focus light, boosting QE to 62%Ha. if this really is the case, then this is a very good QE for a front illuminated sensor incorporating antiblooming. The read noise they state at 6-8e- RMS, equating to a dynmamic range of around 4000. It also has a 2 stage TEC cooler reducing the temp to-50 below ambient. CCD dark current halves for every 6 degree drop in temp, so a temp of -50 should really kill dark current. Most importantly this temp is settable, and controllable, meaning accurate dark frames can be acquired, either during the imaging session or the next day, as long as the sensor is at the same physical temerature.

if these claims are true, then it really ought be be fantastic. It would have virtually no dark noise, plenty of signal, so a high SNR should be achieved fast.

ATIK314L....same sensor, but no microlensing, so QE reduced to 50% Ha (as per our camera), but that is still good. They claim a lower read noise of 4e- RMS. A single TEC cooler is employed, but it doesnt regulate its temperature. Its either on or off. Darks need to be acquired during the imaging session. This can be annoying if you are using 20 min subs and it 4am!

So reduced QE, but better dynamic range around 7000

ATIK 16HR same as above but with 8e- RMS, imapcting heavily on dynnamic range. Again -25 cooling but not controllable.

So, from the manufacturers specs, I would say the QHY2 would offer the best performance...basically during long exposures, you are limited by dark noise, as this dominates the read noise, the fact that cooling to -50 is possible might infact mean that you are read noise limited ver a certain range of intensities, resulting in a SNR that is proportional to (signal level)^0.5

Interseting, during long exposures with the SXV h9 (ATIK 314L...i think) we have reached saturation for some brighter nebula...the crescent was one. We were over exposed after 20mins at f4. This is a consequence of sensitivity and lower well depth, but there was plenty of background signal, so i dont think the dynamic range is a limiting factor.

I have conducted some test of our sensor and have produced the following data...

4.1 e- RMS read noise

0.015e-/pix/sec (obtained from a 20min exposure)

the average signal due to dark current afetr 20 minutes was 18 electrons, and the noise was 4.8 electrons, roughly obeying Poissonian statistics as expected

I hope this gives you an idea of the performance of the Sony 285 sensor, and the different cameras you were looking at.

Good luck

paul

[Aza]

Thanks for all your time and input Paul, most appreciated

To be honest I dont understand much of what you said, I am still at the beginning of this learning curve, but it does seem like the QHY2 is the best bet.

I was thinking this also, but only based on cooling and price!

Thanks again man

[FLO]

Arran, I have also been looking into the various Sony 285 based cameras, for FLO and for myself. After speaking to owners, manufacturers and other dealers one thing really stands out, they all like the Sony 285 chip 8)

As for which camera, that isn't quite as clear cut. Whilst it is generally accepted that pretty-much anything with a 285 chip will work well, the design and manufacture of the camera (case, cooling, placement and quality of components) varies considerably and has a very real impact on its ability to deliver the quoted specifications. Don't be persuaded that they are all equal simply because they have the same 285 sensor and a cooler.

In a nutshell, a camera's performance is reflected in its price (no surprise there I guess) so buy the best you can afford, and enjoy it

[Aza]

Hi Steve

So whats your impressions of the various 285 cameras? What would you buy with your money?

Cheers

[FLO]

For FLO we chose the Atik 314L and Starlight Xpress SXVF-H9, for myself I settled on the SXVF-H9. If your budget doesn't stretch to an Atik or Starlight then look at either the QHY or Opticstar, the Sony 285 chip itself should ensure they are capable performers.

Also, try sending a PM or two to owners, the more experienced ones are a mine of useful information

HTH

[Aza]

Thanks for the info Steve.

But what was it that made you choose those, over the others?

[FLO]

Partly because FLO has only just begun supplying imaging kit so we have a preference for 'safe' brands with established reputations and service-centres.

[Aza]

Ah right fair enough

[MartinB]

Great close up Bubble Aran. A wonderful thing about the 285 is it's size. It's big enough to be really useful but not so big as to be difficult to avoid vignetting and field curvature. Very easy to match it with any scope. What's more, it's small pixels give good resolution with small refractors. This means you can get a big field of view and decent resolution with a fast refractor and a light weight set up. Imaging heaven. Why have I sold mine????