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which flat would you choose


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testing different ways of capturing flats with nina,which would you choose 1 top left then right stretched then second bottom left then to the right stretched thanks both within adu values

 

 

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Posted (edited)

im using a tracing panel light for the top one and a dedicated geoptic light panel for the bottom using nina flat frame wizard on both ,its just that the bottom one looks more even to me after i have stretched them both?

Edited by iwols
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I would choose ones that work. :D

You can always try flat/flat calibration to see if you have proper set of flats.

Take one set of flats at certain exposure level - say 30-40% histogram peak, and other set at twice exposure length 60-80% histogram peak (no need to be precise about it as long as you don't have clipping and have different exposures).

If two calibrate out properly - you have good flats (meaning you divide one master with other and you get perfectly flat noisy image).

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16 hours ago, Stuart1971 said:

If it’s a CMOS camera, then you need flats between about 3-5 seconds, any shorter and they can cause issues….

I have flats of <1s with the 1600mm pro and it has never been a problem. I know the 294 can be temperamental but I think it does depend on the camera.

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16 hours ago, Stuart1971 said:

If it’s a CMOS camera, then you need flats between about 3-5 seconds, any shorter and they can cause issues….

I think it depends on the camera. On my 071 MC Pro the auto flats on the ASI Air Pro typically come in at around 30 milliseconds when I use a UV/IR filter, and around 300 milliseconds if I use the L-Enhance filter. They seem to work just fine.

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1 hour ago, Clarkey said:

I have flats of <1s with the 1600mm pro and it has never been a problem. I know the 294 can be temperamental but I think it does depend on the camera.

I did say, CAN cause issues….👍🏼

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1 minute ago, Stuart1971 said:

Ok, so,it’s a CCD, different story…..any length flats you like, as @vlaiv says use the ones that work…..👍🏼

Actually with some CCDs - long flats are mandatory :D

If flat has mechanical shutter - then using short flats can record shutter motion and create gradient due to shutter motion (CCD will be still exposing while shutter is closing).

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As Vlaiv says, the only flat that's any good is one that works. If you think you can decide this from theory, then may the force be with you. I've had flats which worked, flats which didn't,  flats taken with a method that worked and then stopped working, with no change that anybody could identiffy...

When you stretch data as we do, you render it incredibly sensitive to initial conditions. You may think you are doing exactly what you did last time but you may not be.

On the plus side, flats which work are (in my experience) very durable. I've used the same luminance flat on all filters for up to 9 months because it worked. I couldn't care less whether or not it ought to have worked. It did so I used it.

Olly

Edited by ollypenrice
typo
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3 hours ago, vlaiv said:

Actually with some CCDs - long flats are mandatory :D

If flat has mechanical shutter - then using short flats can record shutter motion and create gradient due to shutter motion (CCD will be still exposing while shutter is closing).

Ok….Dr Vlaiv…👍🏼

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