ZWO ASI178MM Sensor analysis.

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Neil
Posts: 18
Joined: Tue Feb 14, 2017 8:00 pm
Location: Cardiff, UK.

ZWO ASI178MM Sensor analysis.

#1

Post by Neil »

Hi,

I have been trying to run a sensor analysis on my 178MM for a while now, and despite altering the brightness to suit the beginning of the process, towards the end it tells me to reduce the brightness because the minimum exposure has been reached. I have tried several methods of uniform lighting but I cannot get a level that suits both ends of the process.

Sharpcap version 3.2.6480.0 - 17/2/2021

Can you help?

Regards,

Neil Springate.
barnold84
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Joined: Thu Apr 08, 2021 6:44 am

Re: ZWO ASI178MM Sensor analysis.

#2

Post by barnold84 »

Hi Neil,

What I did to analyse my AA183M is to take an iPad as light source. I placed the camera directly on the screen. To be able to play with the intensities, I created a few gray scale images (100%, 50% and 25% luminance) and if I had to reduce brightness even further, I placed one or two sheets of usual white printer paper on top of the iPad screen. Fine tuning was done with the brightness setting of the iPad.

Cheers,
Björn
Neil
Posts: 18
Joined: Tue Feb 14, 2017 8:00 pm
Location: Cardiff, UK.

Re: ZWO ASI178MM Sensor analysis.

#3

Post by Neil »

Hi Björn,

That's exactly what I have been doing, I have a flat-screen panel that I use for taking flats. When I start the sensor analysis it tells me too bright/dim and I adjust the lighting until the process starts, it then runs for a few minutes quite happily until it gets to a point where it says the light is too bright because minimum exposure is reached. I do not seem to be able to set a light level to keep both ends of the process happy.

Cheers,

Neil.
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admin
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Re: ZWO ASI178MM Sensor analysis.

#4

Post by admin »

Hi Neil,

you shouldn't normally run into the minimum exposure issue unless the brightness changes during the run. Unfortunately iPad/Phone screens can be really bad for sensor analysis as by default they change brightness in response to ambient light levels. If the iPad is near the computer monitor (which will change brightness during the testing), this can feed back into the iPad brightness.

My preferred approach to analysis involves using a 25mm CS thread lens with adjustable aperture (available from about £12 on ebay if you are prepared to wait for them to come from China, more if you want them quicker). Failing that, I uncover the sensor (no lens) and point the camera into a dark corner behind my monitor, adjusting the shadow level to get the recommended exposure. Normal domestic lighting is fine (if you don't move around and shadow the area during the run). Daylight is also fine on a clear or overcast day, but beware if the day is one with sunny/cloudy spells!

cheers,

Robin
Neil
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Joined: Tue Feb 14, 2017 8:00 pm
Location: Cardiff, UK.

Re: ZWO ASI178MM Sensor analysis.

#5

Post by Neil »

Thanks Robin, once again.

I'll keep your reply for future reference.

Pondering this, I suddenly thought of the Quantum Mechanic's Double slit experiment, where light can behave as either a particle or a wave depending on whether or not it is being observed. So I started the run again, and went downstairs, only sneaking back into the room to remove/replace the lens cap as quickly as I could, before the kit or software knew I was there. And it worked. I now have a full analysis.

That's my theory, and I'm sticking to it. It was either Quantum Mechanics or my human Kirlian Aura that messed things up. Or my nylon shirt.

Going for a stiff drink and a lie down.

Thanks again,

Neil.
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Re: ZWO ASI178MM Sensor analysis.

#6

Post by admin »

Hi Neil,

glad you got it to work - certainly moving around while the 'light' phases of the analysis is running can have an impact, so hiding downstairs may be a good idea :)

Robin
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