Atik 414ex sensitivity claim

[mbrickley]

Hi

im interested in the 414ex to supplement my larger but smaller pixel cameras for imaging galaxies. I’ve been interested in the line in the Atik blurb which states that this is more sensitive than the kaf3200. The best figure I can find for it’s QE is about 77% which is less than the 80% or more that the 3200 has as a peak QE and furthermore the 3200 is v sensitive in ha.

not in any way knocking the 414... it looks to be a great camera but wonder if anyone knows where the data is that suggests it’s more sensitive than the the 3200 which is just amazing (still) for these small faint targets albeit with lots of problems like horrid dark noise and rbi.

cheers

mark

[robin_astro]

Depends how you define sensitivity.  If you are looking at the ability to detect faint objects then read and thermal noise matters (and those figures are extremely low for the 414)  For example in Christian Buil's comparison of cameras for spectroscopy, even the old 314 matched the KAF3200 cameras in terms of limiting magnitude, despite having a much lower QE at H alpha. (Though the result would likely have been different if the KAF CCD had been cooled to a lower temperature.)

http://www.astrosurf.com/buil/isis/noise/result.htm

Robin

[robin_astro]

In general I tend to take QE measurements with a degree of caution but this reference suggests the Sony ICX674/694 (the ICX825 is probably similar) has a higher QE than the KAF3200 between 370 and 540 nm

http://blog.astrofotky.cz/pavelpech/?p=864

Robin

[mbrickley]

Thanks guys ... 

this looks potentially a good camera for galaxy close ups on a metre or so focal length system 

[ollypenrice]

6 hours ago, mbrickley said:

Thanks guys ... 

this looks potentially a good camera for galaxy close ups on a metre or so focal length system 

Are you sure? The pixels strike me as being on the big side. You'd be working at 1.33"pp with a 414 while a 460 would give you 0.93 and a 490 would give you 0.76. 

I've used the earlier but similar 16HR at around a metre and now use a 460 at a tad over a metre. I certainly resolve more detail in the 460 and sometimes wonder if I shouldn't have gone for the 490. The 460 at 1015 mm FL gives this:

Clicking on the image should let you see it at almost full size.

Olly

[mbrickley]

Hi Olly

fairly sure *but* I should have made my intention clearer in my first post, I have a 460 that I like very much, I tend to use it with a 540mm FL refractor and the image scale and res are great but in this context I was thinking specifically about near real time viewing for fun and ‘live’ observation rather than image quality ... in this context I’m mulling trying to get the fastest usable image I can with a metre or so focal length newt and thus it seems worth trading absolute resolution, ie small arc sec per pixel for sensitivity which the larger pixels will give. Hence also the question about sensitivity...it seems to me the critical factors as to brightness per pixel are pixel size (which governs how many photons hit the overall pixel per unit time given a constant scope setup), qe which governs how many of these get converted to electrical signal and noise esp read noise which governs how much the snr is degraded by noise ... 

[robin_astro]

How about  just in camera 2x2 binning your ATK460 ? This would give you 9um  "pixels" with no increase in read noise per "pixel".  ie half (1/sqrt(4) ) of the read noise/area. This is how I use my similar ATK428 for faint object spectroscopy.

Robin

[mbrickley]

Hi

i was considering that too and will indeed try it before buying anything but the potential problem for NRT is the download time... which could well be several seconds as against 1-2 frames per second with the 414 or infinity... it might not matter at all or be annoying depending on the sub time... otoh I could always also use a subframe and on chip binning to give quite a high speed download and this might work very nicely. Don’t we live at a truly amazing time when there are so many options to observe and image that even 10 years ago would just be complete fantasy, we are really very blessed

[drjolo]

On 6.03.2018 at 22:42, mbrickley said:

fairly sure *but* I should have made my intention clearer in my first post, I have a 460 that I like very much, I tend to use it with a 540mm FL refractor and the image scale and res are great but in this context I was thinking specifically about near real time viewing for fun and ‘live’ observation rather than image quality ... 

If you care much about download times and short exposures, maybe take a look into CMOS cameras. QHY183 mono version may meet your requirements. It has very low read noise, so short exposures is not a problem. Also download time is only limited with your USB port and computer throughput. It also has small pixels, and last but not least is very sensitive - as much as 414EX in G and B, and little bit less in R.