Setting Gain using ASCOM in TheSky

I have been running some quantitative tests on my AC455. The specs are clearly showing the camera is set for gain = low/1 (full well 50442 e- ; read noise ~4e-). I have tried to set the gain to high (3.0 in ASCOM), and I get the same test results.

My assumption is I need to configure the Read0ut mode (p. 40 in user manual) in Maxim DL to high gain.

My question is will the camera remember the readout mode when I move it to ASCOM drivers? The gain setting in the ASCOM parameters do not appear to do anything (I set high = 3 low=1 for test #1; and high =3.0 low - 3.0 for test #2; results were the same.

Also, it would be very useful to set up the Maxim DL Imaging ASCOM drivers to allow the gain to be modified though other software. Is that in the cards?

Regards, Vince

 

I am at NEAF/NEAIC until Tuesday, I can check after I return home.

 

DLAPI 4.0.2.0
DLAPIWrapper 4.0.2.0
ASCOM.DLImaging.Camera Not Installed
Can I assume you have:
TheSky X 10.5.0 daily build 13936 (64-bit)
ASCOM Platform (should be 7 update 2) Yes

Tried a bunch of things, was finally able to get high gain to show up in the sky when setting ascom parameters (had to set in ASCOM program, then I could see the option in the ASCOM options in the sky. It only allows two potions). However that seems to make things pretty weird, I got very low gain and very low full well capacity.

I choose the DL imaging camera 1 when setting up the camera in the sky (Choose "ANy ASCOM Camera" and then DL Imaging camera 1, then options. Not sure how ASCOM DLImaging camera is not installed.

 

I have done some tests using Maxim 7 LT. I am able to change the gain here without confusion, however I have a bigger concern. I still need to sort out how to make this work as an ascom camera in TheSky. The test result is showing alarmingly high read noise for this camera. I used the CCD parameters script in pixinsight which is a pretty standard method. I have a low gain (1) dataset, a high gain set (gain = 5), and a set in the middle (gain =3, which I believe is close to your high gain setting. the results are below:

Gain = 1; readout noise = 7.3 e-



Gain = 3; readout noise = 6.8e-


Gain = 5; readout noise = 3.1e-

 

I agree something is squirrely here. In the original post on this thread, I had used the same method to calculate a full well 50442 e- ; read noise 3.67e-) with data I believe were from a gain = 1 setting. These numbers were much closer to the expected specification. I will try to collect data again tonight.

The calculation is based on the Howell formula.


F = Flat; B = Bias; D=Dark

The calculation requires 2 bias frames (B1, B2); 2 Flat Frames (F1, F2); and 2 dark frames (D1, D2). In the PixInsight script above Darks are used for thermal noise calculations, so are not relevant for this particular discussion.

 

I have reinstalled the drivers (I think they were the same version) and there is no change in behavior. The camera gain does not appear to change when I select high gain in TheSky (using the ASCOM camera, DL Imaging camera selection). I can see a difference in gain, when I use Maxim 7 LT, as measured by an increase in ADUs under constant illumination. I also note that in the FITS header for the Maxim generated images the camera voltage increases from 11.24 to 11.44 V when changing from Low to High gain. Let me know if there is any more information I can provide to help understand this better.

So, It appears that the ASCOM drivers for the DL Imaging cameras cannot change the gain through TheSky camera control. Is this something that can be fixed? Is there a workaround where I can manually set a default gain, to all the camera to work with TheSky?

Also, regarding measurement of gain, well depth and read noise, do you have a preferred method for characterizing read noise vs gain?

Regards,

 

I have reinstalled the drivers.

I can adjust the gain using maxim 7 LT

If I switch to the ASCOM DLImaging camera in TheSky it will remember where I set the read mode and gain form Maxim 7 LT. However, it disregards the settings command to switch between high and low gain, and will stay on the gain the I used in maxim 7 LT. The camera simulator in TheSky works fine and will allow read mode changes. This suggest that the DL imaging ASCOM interface is not correctly handling the read mode selection.

After reviewing several sources, and discussing with users of IMX455 based cameras, the method used in Pixinsight should work for this chip. I also worked the noise calculations by hand using Adam Block's tutorial. These two methods give the same results. The result for my camera shows there is no substantial read noise decrease when switching from low to high gain modes (3.66 e- and 3.30 e- respectively). This is different from the specifications you list (pp 56 in the AC455 user manual) of 3.6 and <2.1 e- for low and high gain modes respectively. Also, the data I get with my camera is different from other vendors IMX455-based cameras, which more closely match the specifications as described in the AC455 manual.

Have you tested the AC455 in your shop? If so, can let me know if you were able to replicate read noise specifications you cite? I would like to try to replicate these data. Is it possible that the increase in read noise in the AC455 vs. other IMX455-based cameras is related to something in the AC455 electronics? For example, the read noise in the FLI 16803 is increase as the readout speed is increase (could slowing the readout speed decrease read noise?).

This is very concerning to me, as the primary reason for purchasing a 455-based camera is to achieve the very low readout noise cited in the specification. I would like to get to the bottom of this.

Also, it would be great if the ASCOM interface worked properly.

Regards,

Vince

 

PS C:\Users\PrimaLuceLab\Documents> .\DLversion.ps1
DL Imaging Version report 1.0
MaxIm DL 7 64-bit: 7.1.4.0
32-bit dlapi: 2.8.0.0
32-bit DLAPIWrapper: 2.8.0.0
32-bit ASCOM Camera: 6.4.23.0
32-bit ASCOM Guider: 6.4.23.0
32-bit ASCOM FilterWheel: 6.4.23.0
64-bit dlapi: 4.0.2.0
64-bit DLAPIWrapper: 4.0.2.0
64-bit ASCOM Camera: 6.4.26.0
64-bit ASCOM Guider: 6.4.26.0
64-bit ASCOM Filter Wheel: 6.4.26.0
Finished.