Which are better - SKY FLATS or flats shot using a FLAT PANEL for astrophotography?

[@jml7916]

I run the flats as part of setup and framing. Basically, send the scope to zenith, use flat wizard with a cheap LCD panel from amazon with paper taped to it to make it less bright, then acquire my target and start the imaging night. Usually all of this is done a before astronomical night starts. I hate getting up early so this works best for me. I can also do them anytime the next day really. Even in full sunlight.

[@dmintz88]

Another solid video! Thanks, Kamil 🙏🏼

[@ma9x795]

Another great video. I have a very portable setup, usually with DSLR/zoomable lens, and living in an apartment in a city means I can't image at home. I used to use a tablet as a light generator, but I found that pointing the camera up and placing the heavy tablet on top would change the zoom. The same problem is caused when trying to put a t-shirt over the end and get all the wrinkles out. So now I've worked out my own way to do flats. I have picked up an embroidery ring, used to keep material taut and stretched 2 plain white handkerchiefs across it. That way it always remains flat without any fiddling about. I put a USB powered light pad on top of that and take my flats and dark flats right after my imaging session. The ring and pad are light enough no to affect the zoom of the lens, but still stay perfectly flat. It's quicker and less fiddly to do flats now than it is to just put the lens cap on to do darks!

[@kamilkp]

An easy fix for lens creep when you put weight on top is to tape the zoom ring to the lens barrel with electrical tape or gaff tape

[@ma9x795]

@@kamilkp Yes, I always do that anyway, but sometimes I still saw afterwards in Bridge that it's dropped a couple of mm. I'm not sure how much difference a couple of mm would make though. It was a very heavy 10" tablet :D

[@radioastronomy2001]

Very good video, thank you for posting. I think you should compare both flats the artificial and natural ones with no filters. I suspect that the backlight on the iPad is not continuous (to preserve battery) which may affect flats if they are taken using short exposure. Also, the displays may have some imperfections now visible to human eye. I always try to take sky flats in the morning. Once I used a white plastic IKEA lamp (with an energy efficient lightbulb) for my small WO telescope. It worked well.

[@kamilkp]

Thanks! The exposure times were around 1-1.5 seconds so screen flicker was not an issue

[@radioastronomy2001]

@@kamilkp Hi Kamil, Thank you for your reply. I am not saying that the flickering of the display was an issue but in fact nobody knows how the display works when "nobody is watching". I know that Samsung phones and tablets actually follow user's face and can determine if they are in use and they adjust settings accordingly. It would be nice to try:1. flats with no filters in place 2. take a series of very short exposures to catch the flickering, if any is there. I hope this makes sense.

[@Kevin.kistermann]

Hey Kamil, can you do also a comparison for normal lenses. Because when I read through the web some many people have problems with flatframes. I will try the white t-shirt method on the week ✌🏻

[@ЛеонідТкачук-ж9я]

Determining the difference by comparing photos is the wrong method. Astronomical image processing programs allow you to use pixel math. In addition, it is worth trying to check whether the result will differ when choosing different areas of the sky and different orientations of the ipad.

[@woody5109]

To much computer time, I’m in my sixties and it’s the computer time that discourages me.

[@anata5127]

Uncallibrated images looks pretty bad. Where from comes this awful unevenness. I have the same camera; and it doesn’t have it.