AltairAstro 269c PRO TEC Gain settings

[bluemoonjim]

hi
I have recently been in contact with Altair Astro regarding sensor analysis read out for my 269c pro tec camera which shows the noise 'drop' occurring around gain 2000 rather than around 200, which was the expected figure according to info on the Altair Astro and TS Optics websites. The following is the reply from AltairAstro tech support:
....It would help to run through the various settings and with SharpCap technical support as there are "gain autoswitch points" for each camera built into the software and settings must be correct for it to work. You can also try using HCG and Ultra mode switched on and asking SharpCap for advice on their latest version as to where the "gain autoswitch level" is for this camera. Also try using the ASCOM driver to compare.
I have now read a similar message on this forum about the sensor analysis and have seen your reasons for the gain settings appearing as they do on the graph. Is this something you might revisit in future updates of SharpCap?
Kind regards
John

[admin]

Hi,

this was a deliberate decision on my part - when I tested out the 269C, there was a significant amount of banding noise visible in HCG mode (and not in LCG mode). My impression was that this, combined with the fact that the read noise drop from changing to HCG is smaller on the 269 sensor than on other models, meant that best results were likely to be obtained on LCG.

I have just had a chat with Altair and they say that the camera circuitry has been tweaked to deal with the banding noise issue since the early pre-production model I had, so I can change the code in SharpCap to alter the HCG start point.

cheers,

Robin

[bluemoonjim]

Thank you for the quick response Robin and for your great work with SharpCap.
All the best
John

[Chiefsmith]

John I hope you are still there!

My AltairAstro 269c PRO TEC will be delivered in about 3-hours. I am not smart like the rest of you so I need a lot of help with setting things up. In this case, there are no graphics on the Altair website for this camera like ZWO provides for their cameras.

I do not know how to figure these things out for myself so would you be kind enough to provide default settings for bin, gain, and offset?

This will give you an idea of where I am with all of this:

https://aptforum.com/phpbb/viewtopic.ph ... 0b5#p45754

Thank you in advance for your courtesies responding to this request,
Chiefsmith

[Robertjohn]

This thread seems out of date by a few years - Robin mentions a possible change in his comment - so as a new owner of the Altair 269c I'm going to risk raising the issue again. Am I correct in thinking that as things stand currently I need to set gain to 282+ in SCpro in order to get the best performance (i.e. in high gain/low noise)?

I have run a sensor analysis this morning and noticed a couple of things:
The tabulated data is on a relatively course scale (e.g. compared to screenshots shown in earlier forum posts and in Stacey Downton's YouTube guide) and that makes discerning unity gain difficult.
My best guess value from the data displayed is actually ~562, so very different to the oft-quoted 282 value.

Any advice/clarification would be greatly appreciated. Thank you, Bob.

P.s. I also ran the sensor analysis tool on my 533c (best guess from the course data was 310 gain) and on my 174m (best guess 910).

[admin]

Hi,

with current versions of SharpCap, the switchover into HCG mode should occur at these gain values for Altair cameras:

* IMX294/IMX492 based : 900
* IMX571 based (Altair 26C/M) : 300
* IMX269 based : 200
* Altair 24C/M : 500
* IMX533 based : 300
* IMX585 based : 1365

You should see a cliff fall in the read noise at these points if you run the sensor analysis with a measurement taken each side of the cliff (ie at 299 and 300 for IMX533 based cameras). In most cases it is a good idea to be on the low side of the cliff fall in read noise, particularly if you are not guiding or your guiding/tracking is not 100% reliable, as it allows shorter exposures.

Note that this all assumes that the new(ish) option to take manual control of the LCG/HCG changeover for Altair cameras (in the Cameras settings page) is *NOT* turned on.

cheers,

Robin

[Robertjohn]

Thank you Robin, this is much appreciated. I love SharpCap - it's been the making of my post-retirement astrophotography hobby. However, this was a confusing issue for me, especially in light of the conflicting numbers published online - including those on the Altair help site. It is now evident that I ought to be at a gain of 200+ for my 269c and 300+ for my 533c.
Thanks again, Bob.

P.s. Returning to the step size in the analysis, the attached is what I got for the 269c - I confess that I found it hard to identify step- changes ...

[admin]

Hi Bob,

glad that you are enjoying using SharpCap

I think there is a step drop there with the 269, but it just isn't very big. If you look at the red crosses, the first three points on the left form the start of one curve and then the rest to the right make up a different curve that doesn't join up with the first. Mind you with the drop only being from about 3.4 to 3.0 on the read noise, it isn't as compelling to be beyond it as on (for example) the IMX533 cameras.

cheers,

Robin

[Robertjohn]

Thank you - I really do appreciate your time