ASI185MC amp glow reducing

lylver

Always thought amp glow was limitating this camera. An experimented astrophotographer gave me some advices on CCD/CMOS sensors history and I decided to look inside the cam. checking about any cause. (I am a micro-electronic engineer)

I guess :

- one component of the main board is emitting hot or some disturbing emission

- or the sensor needs to dissipate heat better.

Didn't trying thermal paste (lack of it)

Not really found the cause but I managed to reduce a bit the amp glow on mine with two pieces of plastic comming from a card (credit card size is fine), a square of anti-static bag, just missed to put in middle of the sandwich a layer of aluminium but this already enhance a bit the darks

result sample : unity gain, 15s, 19.1°C, no balance adjustment

Temperature is now more stable and highest bit value recorded is lower on all my dark library renewed.

Less frequent banding too. (maybe a Relationship with EM shielding ? http://zwoug.org/viewtopic.php?f=21&t=6429 )

Myriam

Sam@ZWO

the amp-glow is from the sensor itself :)

lylver

Thanks for your response Sam, I know the cam's limits now.

Very nice for planetary use and one of the top for moon in IR (and visual range when seeing permits)

I ordered a specialized color cooled one for generic deep sky imaging and want to thank you for the efforts you made acquiring some sensors to build the IMX071 cooled

xs_man

Hi Lylver,

Hi Sam,

Hi all,

I have the same camera and I'm searching a solution to 'retrofit' it to reduce amp-glow.

I agree for lunar/planetary it works fine, 2.4 Mpixel sensor is 'comfortable'.

But for deep sky with short exposures (1 to 10 seconds) working at high gain to have minimum readout noise, it's not possible to use it correctly. ASCOM drivers may work for long exposure but are not usefull at short exposure and high gain. Dark don't remove properly amp glow even with stable cooling. And a large area of the sensor shows a huge amp glow light which drown the faintest DSO stars or objects.

If anyone have a good idea ?

Best.

Albéric

lylver

Hello Albéric, I have some similar conclusion, DSO use is limited.

I was in town and now stopped taking extra long series, lucky imaging (statistic amelioration) don't work well when you reach the noise level (dark current, amp glow). It works only to find the good seeing window. See under about amp glow limit with a 80mm refractor

I did my best shot recently with this tuning :

APO triplet 80mm f/D=4.5, gain 200, 75x8s, cam temp around 16°, no IR-cut.

Barely extracted the nebula cloud. (see amp glow)

http://atom.lylver.org/AstroSurf/Constellations/MESSIER/pleiades-M45.jpg

About 40x8 for this next that is faint (hard to take, pushed post-processing, for artistic view)

http://atom.lylver.org/AstroSurf/Constellations/MESSIER/flamme-cheval.jpg

http://atom.lylver.org/AstroSurf/Constellations/MESSIER/cheval.jpg

With better light, I mean bigger instrument you can do better : lowering gain, raising exposure time. but don't expect to go further than 30s exposure @gain 50, cam pixel are small for DSO

This next one is 1h10mm total time, a mix between 200 gain and unity gain 148, some exposures at 15s other at 8s, very cold cam temp (5°), taken at Mont Semnoz 1600m with ideal seeing

http://atom.lylver.org/AstroSurf/Orion-M42/M42-Orion-dn-if.jpg

When I raise the gain over 240 at long exposure some artefacts appears : permanent colored lines. Just unpower the sensor to clean it. I guess there is an inherent sensor/driver issue with zeroing some photosites.

Myriam