oversampling ...

[Somnium (Aidan)]

Originally Posted by gregbradley

But the advantage of the 4.54 micron pixels is 2x2 binning gives 9 microns plus more than 77% QE as its now binned. You would not lose anything there but gain. On a night of good seeing you could go back to 1x1 binning.
You could also do that with the 16200 and get 12 micron pixels and higher QE and with 16mp you have plenty of pixels still. You would be bang on 1 arc second per pixel at 2x2 with the 16200.


Greg.

yeah that was my thoughts too, by having the 16200, you have enough pixels to play with binning. i might go down this path and get the 16200, maybe look into the reducer down the track. ultimately my other options are the 16803 (a lot more pricey) and the 6303 (problems with blooming). the 16200 might be a bit more versatile.

[Somnium (Aidan)]

Originally Posted by loc46south

Hi Aidan - I did the sums and I chose the 12.5 to go with the ST10XME - it gives a native resolution of 0.67 arc sec pixel which fits right in with my seeing. Plus the ST10 has excellent QE and well depth.

Cheers
Geof

Thanks Geof

the 16200 at .5 is probably pushing, unless anyone wants to sell their second hand FL 16803 then i might have see how that goes. i cant justify the extra $7K +

[Atmos (Colin)]

I just did a very quick calculation comparing the 964 against the 16200, they come in near identical in at 700nm (red). Just to give some of my methodology for scrutiny, I have used some numbers that I have taken from my own imaging system last full moon.

A month ago I took 23x900s frames of Ha from my suburban backyard, these ranged with me being sky limited from 60-120 seconds, 90 being the average stacked from all 23. I am sky limited at ~1860 ADU when imaging at 1.5"/pix. My QHY9 has a gain of 0.389 and a read noise of 8.5e-. The methodology is as follows.

1860 ADU for 90 minutes equates to 20.67 ADU per minute or 53.114e-/min.
The 8300 has a QE of 30% at Ha so theoretically there should be 177e- that were actually there. At 1.5"/pix I can therefore say that I am through my 3nm Ha filter I have a sky background of 78.71e-/arcsec^2/min.

Taking all of the figures from the FLI Microline stats page, the 964 chip would be seeing 125e- but only detecting 75.22e-. With a gain of 0.282 it would get 21.21 ADU per minute and it is sky background limited at 319 ADU so it would take 15 (903s) minutes to be sky limited under these conditions (full moon in suburban Melbourne).
Following the same calculations the 16200 would detect 87.58e- or 52.11225 ADU. It is sky limited at 823.5 ADU or 15.8 minutes (948s).
As a comparison, the 16803 would only need 130s!! Larger pixels (massive pixel surface area) and deep wells so high gain, even with a higher read noise.
The MLx814 comes in at 17.5 minutes (1049s). Although only having a read noise of 2e- it has a very small pixel surface area, lower QE than the 964 and even smaller wells (gain of 0.228). Given the extremely low read noise it only need 175 ADU to be sky limited BUT due to tiny pixels and very low gain, it takes a lot more time to get to that small ADU.

The importance of all this comes down to subframe length, the shorter your frames need to be to become sky limited the more you can take. The more subs you get the better your rejection becomes and higher SNR. But in short, the 16803 is the best of the lot, followed by the 16200. Although the 16200 took marginally longer, you're getting a MUCH larger FOV.

[Shiraz (Ray)]

Originally Posted by Atmos

I just did a very quick calculation comparing the 964 against the 16200, they come in near identical in at 700nm (red). Just to give some of my methodology for scrutiny, I have used some numbers that I have taken from my own imaging system last full moon.

A month ago I took 23x900s frames of Ha from my suburban backyard, these ranged with me being sky limited from 60-120 seconds, 90 being the average stacked from all 23. I am sky limited at ~1860 ADU when imaging at 1.5"/pix. My QHY9 has a gain of 0.389 and a read noise of 8.5e-. The methodology is as follows.

1860 ADU for 90 minutes equates to 20.67 ADU per minute or 53.114e-/min.
The 8300 has a QE of 30% at Ha so theoretically there should be 177e- that were actually there. At 1.5"/pix I can therefore say that I am through my 3nm Ha filter I have a sky background of 78.71e-/arcsec^2/min.

Taking all of the figures from the FLI Microline stats page, the 964 chip would be seeing 125e- but only detecting 75.22e-. With a gain of 0.282 it would get 21.21 ADU per minute and it is sky background limited at 319 ADU so it would take 15 (903s) minutes to be sky limited under these conditions (full moon in suburban Melbourne).
Following the same calculations the 16200 would detect 87.58e- or 52.11225 ADU. It is sky limited at 823.5 ADU or 15.8 minutes (948s).
As a comparison, the 16803 would only need 130s!! Larger pixels (massive pixel surface area) and deep wells so high gain, even with a higher read noise.
The MLx814 comes in at 17.5 minutes (1049s). Although only having a read noise of 2e- it has a very small pixel surface area, lower QE than the 964 and even smaller wells (gain of 0.228). Given the extremely low read noise it only need 175 ADU to be sky limited BUT due to tiny pixels and very low gain, it takes a lot more time to get to that small ADU.

The importance of all this comes down to subframe length, the shorter your frames need to be to become sky limited the more you can take. The more subs you get the better your rejection becomes and higher SNR. But in short, the 16803 is the best of the lot, followed by the 16200. Although the 16200 took marginally longer, you're getting a MUCH larger FOV.

Colin, thanks for posting your methodology. Couple of quick questions, have you used inverse gain (electrons/ADU) as is commonly (perversely) called "gain" by the chip makers, or have you taken the quoted figure to be a gain in ADU/electron? were your subs 15 minutes or 90 minutes?

regards Ray

[Atmos (Colin)]

Originally Posted by Shiraz

Colin, thanks for posting your methodology. Couple of quick questions, have you used inverse gain (electrons/ADU) as is commonly (perversely) called "gain" by the chip makers, or have you taken the quoted figure to be a gain in ADU/electron? were your subs 15 minutes or 90 minutes?

regards Ray

Trying to actually track down all of the actual gain figures takes far too long so I am doing the straight calculation as (well depth)/65535. With my QHY9 I got my gain setting to the point where full saturation (ADU) happens when the well fills so it is actually at 0.389. I have been using e-/ADU as the conversion so the 16803 is the only one in that list that has above 1e-/ADU.

My subs were 15 minutes long but from that I could calculate that they wouldn't be sky limited until I hit 90 minutes (as an average of the night).

[Shiraz (Ray)]

thanks for that Colin.

you quoted "1860 ADU for 90 minutes equates to 20.67 ADU per minute or 53.114e-/min" - shouldn't that be "20.67 ADU per minute or 8.04 e/min" (ie each electron generates more than 2 ADU if the inverse gain is 0.389e/ADU, so you should have fewer electrons than ADU), or have I completely misunderstood what you are doing?

[Atmos (Colin)]

Originally Posted by Shiraz

thanks for that Colin.

you quoted "1860 ADU for 90 minutes equates to 20.67 ADU per minute or 53.114e-/min" - shouldn't that be "20.67 ADU per minute or 8.04 e/min" (ie each electron generates more than 2 ADU if the inverse gain is 0.389e/ADU, so you should have fewer electrons than ADU), or have I completely misunderstood what you are doing?

Nope, you are correct, I am just a sleep deprived idiot living on coffee today It made perfect sense while I was driving from job to job today, now it just looks stupid

[Shiraz (Ray)]

Originally Posted by Atmos

Nope, you are correct, I am just a sleep deprived idiot living on coffee today It made perfect sense while I was driving from job to job today, now it just looks stupid

happens a lot to me as well , but I am old, so that's my excuse.

[Atmos (Colin)]

Well it makes more sense in that regards.
33 min for the 16893, 7ish for 964 and 6 for the 814 and 36 min for the 16200.