Darks

[jaygpoo]

I have taken darks before using my cannon camera but I have just sat down to take my first darks using my QHY8L CCD. In EZcap the planner has a box to tick if you are taking darks and a message pops up saying that the shutter will not open if you take darks. Strange as I see no shutter on the camera but I guess its right. Anyway I took some 180sec darks but the screen view after the shot has been taken shows an almost white screen?   Is this right or am I doing something silly. I know the camera works as I was imaging M31 only last night.   Jay

[Thalestris24]

Hi

Not sure what that EZCap message is... It might be Chinglish for making sure the lens cap is on... I find it better to use APT for lights and for taking darks/bias/flats. One thing about darks is, especially if you take them during the day, make sure you have no light leeks! Also, make sure the cooling temperature is stable. I have made a library of calibration frames - shouldn't need to redo them unless I change something. Presumably you have only recently acquired the qhy8l? Don't forget to set the gain and offset as per the manual Not sure why you have a white screen image after taking a dark, lol. Make sure you have the most up to date driver - there were driver problems with the camera (overscan, then amp glow) but they have been sorted now.

Hth

Louise

[jaygpoo]

Thanks for reply, Had the ccd sometime. Was taking them this evening so it was dark/had lens cap on. will check for software update. Had temp at -20 and steady. Now I did not set gain or offset . Will try to find out what they are?

[Thalestris24]

Hi

They are settings to set the camera for maximum dynamic range without saturation - there's an old thread on it here: http://stargazerslounge.com/topic/135633-gain-and-offset-for-qhy8l/

But it's explained in the user guide.

Louise

Edit: they are a one-of setting - once set you leave them alone

[lensman57]

I have taken darks before using my cannon camera but I have just sat down to take my first darks using my QHY8L CCD. In EZcap the planner has a box to tick if you are taking darks and a message pops up saying that the shutter will not open if you take darks. Strange as I see no shutter on the camera but I guess its right. Anyway I took some 180sec darks but the screen view after the shot has been taken shows an almost white screen?   Is this right or am I doing something silly. I know the camera works as I was imaging M31 only last night.   Jay

Hi Jay,

I am not familiar with EZ cap but taking darks is just as easy as putting the lens cap on and making sure that you have no light leaks . I can only think that thicking a box for Darks is to mark the files as darks or imbed them as darks so the stacking software could recognise  them and make your life a little easier.

A.G

[Earl]

EZcap will cover the camera options that QHY have hence the shutter option as the QHY9 has a shutter.

[jaygpoo]

Thanks one and all. I downloaded the manual as the info I had was not that good. I calibrated the gain and offset and tried again and bingo darks appeared.  So one laat question. do I keep the 30 odd darks for each exposure to put in DSS or do I put them in DSS and come up with a master one that I use. ?? 

[Thalestris24]

Hi

You can create master darks and just use those. I was going to say before that if you are taking bias and flat frames then you may not need darks for short exposures (like 180s). But they are a good idea for 300s+. With 900s+ you may see some amp glow appear in the darks.

Hth

Louise

[Earl]

I use 101 darks to make my master. I keep them all on my astro images hdd as backup

[jaygpoo]

Thanks again but no one is telling me how to make that master copy? do you use DSS to stack them or some other method?  As in both cases you really have no image for DSS to really sort through.

[lensman57]

Thanks again but no one is telling me how to make that master copy? do you use DSS to stack them or some other method?  As in both cases you really have no image for DSS to really sort through.

Depending on the software you use a master dark, master bias file will be created and so named. With DSS these are clearly marked as such and are kept in the same folder as your reference subs default along with the relevant text file so you can use these as masters in the stack. I do not advocate using mater flats as my set up is mobile but i know that other imagers with fixed set ups and clean optics are using master flats per scope and filter combination. just run the stacking routine normally once and then save the files.

A.G