What is wrong with the darks - Forums

Topic starter

Feb 18, 2019

Hi, I did get a replacement ZWO 1600 Pro mono today. Is started to test with taking some darks. The darks are 300sec. Gain 300 Offset 50. The camera is not attached to the telescope it is covered by cap and aluminium foil so no stay lights will reach the sensor.. Could please someone help me to explain the "star" with the surrounding ring in the left bottom part of the image. For me this does not look good.

Dark

Erik

Andrew Burwell

Feb 18, 2019

That is very strange. I would show it to ZWO. I don't have that on mine, and I do 300s frames all the time.

Uwe Deutermann

Feb 18, 2019

Gain 300 and offset 50 is not what I am doing, but that definitely does not look "normal". Did you try 139/20?

Nico Carver

Feb 18, 2019

Can you rotate your camera 90 degrees? If so, I would suggest rotating your camera and see what happens to the location of the "star". That way you could determine if the problem is the camera. If the problem is the camera, I would contact ZWO for another replacement as that does not look normal at all.

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Erik Guneriussen

Topic starter

Feb 18, 2019

Hi and and thanks,

Nico, the camera is not attached to the telescope. The front is covered with the supplied cap, the camera is palced in a dark place, addtionally aluminium foil is covering the front so there there can not be refleks or stray light-

I have not tried other settings than 300/50, that should be OK.

DerPit

Feb 18, 2019

Hmm, the white spot is several pixels in diameter and nicely round. Does look more like something optical, than an electronic/camera error. Could be some 'defect' in the cap that allows infrared to leak through? Do you have some other cap or a lens to cover the camera? Or at least rotate the cap a bit and see if that changes something…

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Erik Guneriussen

Topic starter

Feb 18, 2019

Hi,

I have used to different caps, the rubber cover and the 1.25 nose piece that is supplied with the camera, additionally aluminium foil so it can not be refleks or stray light.

A 300sec. flat with GaIn 129 and offset 20 gives the same spot and ring.

DerPit

Feb 18, 2019

Wow. So I stand corrected - it seems it has to be the camera. Is this with the cooler running? What temperature? Looks like this needs ZWO to solve it

Erik Guneriussen

Topic starter

Feb 19, 2019

I think it obvious that it is the camera that has a "defect". For me it looks that it is an area of hot pixels that is the actual spot while the surrounding ring is caused by the light from the spot being reflected back form the sensor glass. I assume that this is a defect that can not be compensated during calibration because it will instead of event out add "artifact".

Not funny when I after 5 weeks got back a replacement for a camera which had another defect.

Andrew Burwell

Feb 19, 2019

I’ve been lucky to get three good cameras in a row, but after seeing posts here and in other forums it leads me to believe the quality control is really poor. It makes me question future purchases.

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Erik Guneriussen

Topic starter

Feb 19, 2019

You could have been lucky and me just unlucky, I don't know. One thing that I dont like,is it actually legal? is that the Warranty defines and ZWO requires that the customer must pay for return back to China. My first return was estimated by DHL to approx. 150£, I was allowed to send to Germany, I had to pay for that which was approx. 45$. To many defects can be expensive, but the most irritating si to be without a functional camera for many weeks/months.

Gary Plummer

Feb 21, 2019

Probably amp glow particularly at 300 gain, have to question why such a high gain. Your dynamic range will be incredibly low! Regardless of that a good master dark should remove the amp glow. I use 80 darks at the same exposure time, temperature, offset and gain as my lights to create a master dark and that works a treat.
You should try 139 gain and 21 offset with another accompanying master dark at these settings. You can build a dark library at home on cloudy nights. For my bias I use 400 frames at 0.001sec and these can be used for all lights. Personally I don't bother with flats as my image field is flat to the edges and I keep my sensor and filters clean. Flats actually add noise to the image so I'd avoid them unless you have severe vignetting or dust motes.

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Erik Guneriussen

Topic starter

Feb 21, 2019

It is not the bright areas on the edges which amp glow that is the problem. It is as described the bright spot with the halo in the lower left part of the image.

I will us 300/50 for faint nebulas where the dynamic range and signal is low

Adel Kildeev

Feb 21, 2019

Erik, do you connect 1.25 ' adaptor directly to camera or to filter wheel? Some filter wheel are prone to light leak, my friend has learned it by hard way. But ZWO 5 or 8 filters electronic wheel are safe.

Adel Kildeev

Feb 21, 2019

Also I had some strange amp halo problem with ZWO, they changed voltage on the matrix and fixed, by the way ZWO pay be back courier fees for sending camera from Canada, no problemo .

Erik Guneriussen

Topic starter

Feb 21, 2019

Hi Adel,

Only a cap is covering the front so no leakage.

Chris Sullivan

Feb 22, 2019

Can you visibly see anything on the sensor or the glass in front of the sensor? It definitely doesn't look right to me and that's definitely not amp glow… :/

Erik Guneriussen

Topic starter

Feb 22, 2019 · Edited: Feb 22, 2019

I can't see anything on the sensor. ZWO has accepted the camera as "defect" and will replace it.

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