Advice regarding a process for “perfect” flats - Forums

Would the following make sense?

I am thinking about either buying or making a flatpanel where I can control the strength, so that I could always make flats that are eg. 2 seconds with perfect exposure and distribution on the histogram.

Then I would be able to have a library with dark frames that I could use again and again, thereby saving time.

Anyone else doing this??

If I were to buy a flatpanel - what would you suggest?
I have looked at the products from Gerd Neumann, but they don’t seem to be dimmable?

I use an Artesky flat field generator. It's dimmable and has an option to control it through your computer as well as a manual control option. They're a little pricey, but what isn't in this hobby? It comes in 2 sizes: 250mm and 500mm. They seem hard to come by now…….I think they're no longer manufactured as Artesky may have gone out of business. However, you might find a used one on cloudynights or astromart.

An Italian company makes a series of flat field generators. Check out PrimaLuceLab Their Giotto series. I've not used one but they look pretty cool and should work well.

CS

Patrick

I own a Pegasus Astro FlatMaster 150 (the old version based on EL panel) and a Gerd Neumann Aurora 315.

The Aurora came with a very basic hardware dimmer switch. There is no software control. You can purchase ND filters in varying degrees (sold by Gerd cut to fit to whichever panel you buy). If you're looking for a software solution, this isn't the panel for you.

The Pegasus is completely controllable via software. Both the Pegasus-provided Unity platform and ASCOM/Indigo drivers will allow you to control the brightness dynamically. Works out really nicely with NINA's flat wizard. Just set the mode to dynamic brightness and give your exposure time. It'll adjust the panel's brightness to meet that exposure time.

Some have complained about banding on the FlatMaster. I definitely see it when using low brightness settings and fast exposures. Since I always targeted 5 second flats, the banding was never really an issue for me.

I use Alnitak panels available through Optec Inc. Again a little pricey but completely controllable with ASCOM drivers for whatever software you happen to use. I have had a great experience with them making flats very easy. Let me throw this out about the "Flip-Flat" option that Alnitak and other companies make. It's a novel idea and works perfectly. Problem is they are like attaching a small sail to the end of your scope to catch every little breeze. I would not recommend those unless your setup is completely protected from the wind. I also have had poor experiences with CMOS flats shorter than around 5 sec as mentioned in an earlier comment. I personally target 6 sec for broadband filters and 15 sec for narrow band filters. Just adjust the panel brightest to get the desired ADU values at those exposure lengths.
CS,
Jeff

I've been doing sky flats in NINA and never had satisfactory results. I have a cheap tracing panel that works great for <100mm apertures, but has uneven lighting at the edges and will not suffice for the 8" scope. I'll be paying close attention to this thread as I am growing weary of every little item in this hobby being another couple days' wages.

Thank you all for your input - I will investigate the different panels and update this thread when I move ahead with a panel.

Currently I’m om an ASIAIR pro which works sooo smooth - but I can also read that NINA has a whole lot of very interesting features and considerably better planning capabilities than the ASIAIR - so maybe that might be worth a try as well 🤣🤣

All comments are more than welcome.

Diffusor screen on the aperture + dusk sky and Bob's your uncle. I have been taking dusk flats for as long as I remember (so more than 20 years) and as certain as day follows the night I am not to pay the astonishingly high price most of the companies mentioned in this thread are asking for.

Yes I have a this flat panel and the USB based controller that does just what you say. The driver remembers the exposure and strength settings for each filter.

https://wa-chur-ed.com/ab-light-flat-calibration-panel/

https://wa-chur-ed.com/adim-controller/

Kevin

I find Willem's series of blog posts very useful. He does a deep dive into the topic and not only compares different flat panels but also presents some interesting experiments.

Am a huge fan of the deepskydad flatpanels have both a wall mounted version and a custom flap panel for my little refractor. They are dimmable and have quite a range. It achieves the aim of getting flats at set times e.g. all my LRGB flats at 0.5s and Narrowband at 1.25s which means I can reuse the darks that go with it. Believe you could probably DIY this yourself however I am lazy and to me they are worth it https://shop.deepskydad.com/product-category/flat-panels/

I find Willem's series of blog posts very useful. He does a deep dive into the topic and not only compares different flat panels but also presents some interesting experiments.
Part I: Gain Matching
Part II: Flat Panels Compared
Part III: Conclusions

Thank you Y, and glad you find my posts useful.
After all the testing I settled on the DeepSkyDad panels. Best control over brightness (4000 levels, linear), decent uniformity, no banding, good maximum brightness and all this for a reasonable price.

@Christian, if you decide to go with a non-dimmable panel, you can still apply your method of one set of darks, e.g. bias or short dark. It is not perfect, but not bad either. Many people use biases with current CMOS cameras. In the posts you can see the effects.

I also use the Optec Alnitak. I would suggest you think in terms of exposure lengths /ADU 1for each filter and not a constant 2 seconds.
Set the flat illuminator at a consistent setting. Adjust the exposure times for each filter to acheive a desired ADU. Some software will generate this automatically, such as SGP. Save the exposure time settings.

If you do this in day time, check for light leaks. Filter wheel USB ports or terrible about letting light in.

Lynn K.1

I find Willem's series of blog posts very useful. He does a deep dive into the topic and not only compares different flat panels but also presents some interesting experiments.
Part I: Gain Matching
Part II: Flat Panels Compared
Part III: Conclusions

Thank you - these are awesome 🙏🙏

Willem Jan Drijfhout:
I find Willem's series of blog posts very useful. He does a deep dive into the topic and not only compares different flat panels but also presents some interesting experiments.
Part I: Gain Matching
Part II: Flat Panels Compared
Part III: Conclusions

Thank you Y, and glad you find my posts useful.
After all the testing I settled on the DeepSkyDad panels. Best control over brightness (4000 levels, linear), decent uniformity, no banding, good maximum brightness and all this for a reasonable price.

@Christian, if you decide to go with a non-dimmable panel, you can still apply your method of one set of darks, e.g. bias or short dark. It is not perfect, but not bad either. Many people use biases with current CMOS cameras. In the posts you can see the effects.

@Willem Jan Drijfhout - you da’ flat maiin 💪🏻💪🏻💪🏻
Fantastic blog posts.

Nick Grundy:
I bought this light a bit ago and it's worked great. https://www.bhphotovideo.com/c/product/1459186-REG/viltrox_vl_500t_vl500t_professional_photography_led.html/?ap=y&ap=y&smp=y&smp=y&smpm=ba_f2_lar&lsft=BI%3A514&gclid=CjwKCAjw2K6lBhBXEiwA5RjtCSKkP1WVrE4mm2MiRodNg-G0ETBaKY-2lDJEYAhq4ETYE6PskdVU0xoCMQsQAvD_BwE

It runs on 12v DC with a 5521 connector, so if I want to use it in the field I can. (hasn't happened yet)

I did need another sheet to get exposure time up to 2s-6s https://www.amazon.com/gp/product/B08TZSP1DH/ref=sw_img_1?smid=A1J202IJKBIAGN&psc=1

This looks fantastic! I think I'm going to pick one of these up. Thanks!

I went ahead and got myself a flatpanel from Artesky in Italy.
It will arrive next week…more to come.

Jeff Reitzel:
I use Alnitak panels available through Optec Inc. Again a little pricey but completely controllable with ASCOM drivers for whatever software you happen to use. I have had a great experience with them making flats very easy. Let me throw this out about the "Flip-Flat" option that Alnitak and other companies make. It's a novel idea and works perfectly. Problem is they are like attaching a small sail to the end of your scope to catch every little breeze. I would not recommend those unless your setup is completely protected from the wind. I also have had poor experiences with CMOS flats shorter than around 5 sec as mentioned in an earlier comment. I personally target 6 sec for broadband filters and 15 sec for narrow band filters. Just adjust the panel brightest to get the desired ADU values at those exposure lengths.
CS,
Jeff

I recently developed an alnitak upgrade that allows 270 degree rotation of the panel. I've been working with optec to modify the firmware and driver for compatibility and just got that yesterday. So it's ready to go. I'm partnering with optec to offer the upgrade to existing customers and have shared the design with them for a future upgrade on their product line.

The only detail i may or may not need to iron out is circuit board compatibility. They used several generations of circuit boards over the years and some have larger lamp transformers, etc so I'm testing this as I go. If anything it's a tiny modification to the design.

I've also developed a ring mounting system to replace the zip style mount. You can see it here: https://www.overcastobservatory.com/product/alnitak-270-case/

Sean van Drogen:
Am a huge fan of the deepskydad flatpanels have both a wall mounted version and a custom flap panel for my little refractor. They are dimmable and have quite a range. It achieves the aim of getting flats at set times e.g. all my LRGB flats at 0.5s and Narrowband at 1.25s which means I can reuse the darks that go with it. Believe you could probably DIY this yourself however I am lazy and to me they are worth it https://shop.deepskydad.com/product-category/flat-panels/

This looks awesome. Too bad it can't be controlled with ASIAIR.

Robert Žibreg:
Sean van Drogen:
Am a huge fan of the deepskydad flatpanels have both a wall mounted version and a custom flap panel for my little refractor. They are dimmable and have quite a range. It achieves the aim of getting flats at set times e.g. all my LRGB flats at 0.5s and Narrowband at 1.25s which means I can reuse the darks that go with it. Believe you could probably DIY this yourself however I am lazy and to me they are worth it https://shop.deepskydad.com/product-category/flat-panels/

This looks awesome. Too bad it can't be controlled with ASIAIR.

Have you tested it with ASIAIR? I am using the DSD panels with KStars/Ekos via INDI and have full control over them. If I'm not mistaken, ASIAIR software is heavily relying on this INDI platform (clone?), and therefore benefits from many INDI drivers being developed. Of course they are only copied over if ZWO allows you to use them, but since there are no competing flat panel products in the ZWO product line, it would make sense to be available?

Robert Žibreg:
Sean van Drogen:
Am a huge fan of the deepskydad flatpanels have both a wall mounted version and a custom flap panel for my little refractor. They are dimmable and have quite a range. It achieves the aim of getting flats at set times e.g. all my LRGB flats at 0.5s and Narrowband at 1.25s which means I can reuse the darks that go with it. Believe you could probably DIY this yourself however I am lazy and to me they are worth it https://shop.deepskydad.com/product-category/flat-panels/

This looks awesome. Too bad it can't be controlled with ASIAIR.

Yeah this was one of the reason for me to switch to NINA as ZWO (ASIAIR) does not have a rotator nor flatpanel control on their exosystem at the moment.

A cautionary note I just discovered this week…watch out for some of the light panels you use and make sure they are "pure white".

I've been going along happily with my flat solution happily calibrating mono frames for the past year. Turns out one of my lights isn't pure white and produces some interesting calibrations with OSC. Does anyone know of a software trick around this?

I haven't shot OSC in about a year and never thought much about the colorization in the calibration frames until now.

Nick Grundy:
A cautionary note I just discovered this week...watch out for some of the light panels you use and make sure they are "pure white".

I've been going along happily with my flat solution happily calibrating mono frames for the past year. Turns out one of my lights isn't pure white and produces some interesting calibrations with OSC. Does anyone know of a software trick around this?

I haven't shot OSC in about a year and never thought much about the colorization in the calibration frames until now.

That is correct, not every panel that looks white, is white. With the exception of some panels that may have very narrow emission lines, as long as you have good illumination across the spectrum you should be fine. Your OSC camera itself is also not very 'white' in its response, with twice as many green pixels than either blue or red. Flat calibration is just for correcting brightness variations across the frame (vignetting, donuts, etc). The overall response at each color will later be corrected when you do colorcalibration in processing.
What kind of abnormalities do you see in your OSC images?

Willem Jan Drijfhout:
What kind of abnormalities do you see in your OSC images?

ive been processing in mono for so long, I don't remember any specific to OSC. the flats seemed to have the right correction in terms of vignetting, but i figured that reddish hue was over the top

I use a simple artists' tracing LED panel. I have a C925, 9.25" or 240 mm aperture so use a larger size, A3 LED panel. Just go to Amazon or search anywhere online and you can find them. They are really inexpensive, you can find them for less than $40 US. For a smaller telescope you could use a smaller A4 panel. Works great, easy to find one with brightness controls, and it works well for me with an OSC and no problem with narrow band filters, I have had no issues. Mine plugs into a USB port for power, so no adapters needed.

I was a bit confused about your comment on having a library of flats?. You can do that for darks for sure. For flats I can run for weeks to months with the same flats, but to do this I do not take my image train apart. I keep everything the same. And if you change anything at all in your image train, like a filter, or rotate your camera, or clean your filter, you must do new flats.

CS
Rick