My Flats!

[turfpit]

Dale

For flats it is all about setting the histogram to around 50% by adjusting exposure. See below for some ideas. There are no 'standards' only 'guidelines'.

colour-flat.JPG (59.66 KiB) Viewed 1755 times

mono-flat.JPG (58.79 KiB) Viewed 1755 times

If the flat is captured in FITS format then expect the mean value to be around 30,000 (29,000 - 31,000 range is ok as long as the histogram does not touch either the left hand or right hand sides.) as shown in FITS Liberator.

colour-camera-flat-frame-in-FITS-Liberator.JPG (145.83 KiB) Viewed 1755 times

Dave

[dalepenkala]

Thank you Dave, This helps me a bit. I do adjust my exposures so that my White is at the 50-60% range then make sure the other 3 channels are within the 20-80% range before taking the exposures. Can you tell me what is that Libirator program is for? Is it just a flat frame analyzer some other software you use in your setup?

Dale

[turfpit]

Dale

FITS Liberator software download https://www.spacetelescope.org/projects ... load_v301/

FITS Liberator user guide https://www.spacetelescope.org/static/p ... rguide.pdf

Best to read the user guide to fully appreciate the functionality. FITS Liberator can be used to view and manipulate images stored in the FITS format (the most widely used standard format for storing astronomical data). Output can be in TIFF for further manipulation by software such as GIMP/Photoshop.

I use it FITS Liberator to analyse single exposures prior to imaging (rather than waste a night). It can be used with lights/darks/flats/bias frames. Some ideas for how I use the software are contained in viewtopic.php?f=35&t=2552.

There are other programs which can view FITS files.

Dave

[oopfan]

Hi Dale,

Here are two master flats. One for luminance and the other for a Wratten #12 filter. I used an EL panel which emits a lot of blue light. The Wratten #12 exposure was a rather long 1.3 seconds due to the fact that filter cuts blue. The luminance exposure was 0.4 seconds. Each master is a stack of 50 frames.

Notice the two small circular defects. Those are on the sensor window. The larger defects are the respective filter.

Question, the one image you shared at the beginning of this thread, is that the master or an individual frame? Is it stretched? I ask because to me that is a very clean flat; I would be happy to own that! Can you share a calibrated light frame? If you can't supply a single calibrated frame, how about the stack? You suggested that the flat didn't do its job during calibration.

Brian

[dalepenkala]

Dale

FITS Liberator software download https://www.spacetelescope.org/projects ... load_v301/

FITS Liberator user guide https://www.spacetelescope.org/static/p ... rguide.pdf

Best to read the user guide to fully appreciate the functionality. FITS Liberator can be used to view and manipulate images stored in the FITS format (the most widely used standard format for storing astronomical data). Output can be in TIFF for further manipulation by software such as GIMP/Photoshop.

I use it FITS Liberator to analyse single exposures prior to imaging (rather than waste a night). It can be used with lights/darks/flats/bias frames. Some ideas for how I use the software are contained in viewtopic.php?f=35&t=2552.

There are other programs which can view FITS files.

Dave

Thank you so much Dave! I’ve heard of this software but I’m just so new at all this tech stuff I’m honestly lost. I can get around a computer fairly well but a lot of this stuff is well over my head and trying to understand it a bit. Unfortunately for ALL you guys I have to ask stupid questions!

I will look at the links and software more and see if I can figure it out to help me with my flats.

Thanks again Dave!

Dale

[turfpit]

Dale

4 years ago I was where you are now. Read my doc - it will save you 3 years - but you wont get it in one reading.

Dave

[dalepenkala]

Hi Dale,

Here are two master flats. One for luminance and the other for a Wratten #12 filter. I used an EL panel which emits a lot of blue light. The Wratten #12 exposure was a rather long 1.3 seconds due to the fact that filter cuts blue. The luminance exposure was 0.4 seconds. Each master is a stack of 50 frames.

Notice the two small circular defects. Those are on the sensor window. The larger defects are the respective filter.

Question, the one image you shared at the beginning of this thread, is that the master or an individual frame? Is it stretched? I ask because to me that is a very clean flat; I would be happy to own that! Can you share a calibrated light frame? If you can't supply a single calibrated frame, how about the stack? You suggested that the flat didn't do its job during calibration.

Brian

Hello Brian

The flat that I shared at the beginning of my thread is what I believe to be my master flat. This is the file that SC is using in the software to I guess subtract out of my images.
Stretched? Ok I don’t understand this stretched thing. So sorry for my ignorance but that is over my head. What do you mean by stretched? Also “calibrated light frame? “ what is the difference and how would I create a Calibrated one? Is it something I really need?
Gosh I feel so stupid with these questions!
Back to the original point of me asking about this flat frame thing, My camera sensor, protective screen, etc is extremly clean. I have always been careful with storage and handling it. I have ordered replacement dececant tablets per a suggestion instead of just recharging them. I get this goffy looking pattern in all my images in the location of the spots you see in my master flat. This is why I’m trying to figure out if its my flat that is giving me the issue or if its my camera, processing etc... I’m at a loss and just tying to figure out why my images look the way they do. I’ll see if I can post an image with this blotchy pattern I’m referring to later tonight or tomorrow.

Thanks for all your help!

Dale

[dalepenkala]

Dale

4 years ago I was where you are now. Read my doc - it will save you 3 years - but you wont get it in one reading.

Dave

Hello Dave
I will do that but what is doc? I assume its a document or article???

Dale

[turfpit]

viewtopic.php?f=35&t=2552