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darks,flats,bias with different scopes and cameras ??


iwols

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hi just wondered if you need to retake the above when you change a camera on your scope or you change the scope your using your camera with if that makes sense,i have two scopes with two different camera i swap between thanks

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The purpose of darks and bias is to identify issues with the sensor so you might get away with having a set of darks and bias for a specific camera - irrespective of the scope thats attached to it.

The purpose of flats is to identify issues with the optical train - any time you change or move or even disturb anything you will have to take a fresh set of flats - its takes very little to move a dust speck!

For the time it takes I would take a fresh set of all 3 every time unless you have a obsy mounted rig than never gets touched.

 

 

 

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23 minutes ago, iwols said:

thanks peter so once i have a dark and flats library i can use that with either scope for the same camera but i need to take seperate bias  frames for each setup i have ?

No. Other way round. You need to take flats each time you use either scope whatever the camera as it will help eliminate defects in the image train like dust. Darks and bias can be used again as long as the conditions are similar i.e temperature.

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I don't agree that darks and bias should be re-done after a change of scope because, if there were any difference between them after this change, it would be because they were affected by light leakage and no good anyway! The best way to do darks and bias is off the scope with an absolutely perfect seal to prevent light ingress. Many camera makers include a screw-on metal chip cover for just this purpose. When I compared darks done this way with darks done on the scope, with every effort to exclude light, I found a perceptible difference because excluding light entirely is a lot harder than you might think.

Flats record the projected light through a specific optical train at a specific orientation onto a specific chip, so they must be done after any change and at the focus position used for the lights.

Olly

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Since getting cooled cameras, I create a dark library at frequently used exposures with the camera shut off from light, by placing a cap over the camera, and cooling it to the set point I prefer (generally -10 Celsius). There can be reused until the chip degrades for some reason (pixels can become defective), or I decide to use a different temperature. I make flats at the start or end of every session, as I have to build up the rig every time (no obsy (yet))

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