Flat Field Panel recommendation query

[ronson]

Hi all,


Lately I've been looking at options to replace my current setup I use for taking flats. Currently, I use an LED tracing panel + sheets of paper to darken the brightness when required. This is not optimal and the scope setup + the sheer size of the panel (A3) requires me to be holding it with one hand while operating the acquisition app at the same time. Not convenient, plus I suspect the LED panel's uniformity and color are not great.


So, I went on a search of what is out there. Been reading astro forums, review websites, watching videos etc. In short, there are multiple options, but mainly the divider is the light technology used, either LED or EL. GN Aurora, Primaluce Giotto, Geoptik, Deep Sky Dad, Alnitak, Ellumiglow, DIY etc.



The requirements I've set for myself are:

• No automation required i.e., no open/close mechanism required.
• No permanent attachment to the scope required. It's a portable setup.
• Be able to control the brightness level manually e.g., via a dimmer switch on the device.
• Power either via batteries (AA, 9V etc) or 12V DC.
• To be suitable for both OSC and mono (LRGBSHO filters).
• Good uniformity, 1% or less.
• Preference for something that can be secured to the front of scope rather than just sit on top e.g., nylon screws. But this is not essential.

Looking for something that can work with refactors between 60-80mm in diameter.


Budget: max $400-500, but the less the better


So, if you are still reading, the reason for this post is to reach out to the forum and ask for some advice what would fit my requirements.


Thank you in advance.

[ronson]

So far I've shortlisted the following:

1. GEOPTIK FLAT FIELD GENERATOR SMALL 164, https://www.testar.com.au/products/g...f3ecac1e&_ss=r
2. GIOTTO 120 SMART FLAT FIELD GENERATOR, https://www.testar.com.au/products/g...f3ecac1e&_ss=r

Can't find any reviews on either, but at least on paper seem to cover most of the requirements. If anyone has used them, hope to hear your feedback.


A compromise, if the first two don't work out, is the GN Aurora Flatfield Panel, D100 or D160: https://www.gerdneumann.net/english/...-overview.html. But really rather have an easier way to control the brightness

[Atmos (Colin)]

I used to use a smaller version of this (would have been 8"):
https://www.teleskop-express.de/shop...-Lighting.html

Found it to work very well, since I've been imaging at 10" I've been doing sky flats which have their disadvantages. I'm often packing up before dawn and not always set up early enough for twilight. I just haven't bothered getting around to getting another flat field.

[AnakChan (Sean)]

If you don't need it to be secured (yes I read that it's desired but understood it to be not a necessity), I have the Hercules Optica flat panel. It's not fancy but it's decently priced and it's manual. They go from USD $70 -> USD$150 ex shipping.

Note though with these (and I guess with other astro flat panels), one could have quite a long duration for 3nm NB filters (in my case up to 40 sec per sub through an Sii filter, 25 sec with Ha, and 6.5sec with Oiii with my F10 scope).

I assume it'll be the same with other flatfield panels.

[AstroViking (Steve)]

Have a word with Ekfos(?), as he is usually advertising flat panels in the 'For Sale' section.

I have one, and it's a box that fits over the end of your scope and can be supplied with a dimmer. It works well, but I had to add a couple of layers of white paper to dim it enough to get flat exposures of reasonable length.

Cheers,
V

[ronson]

Thank you all for your recommendations. It's tougher than I thought to choose the right one Will do some more research.

[ronson]

Just a quick update - I ended up buying the Giotto 120 panel. I am not using ASCOM/USB, so it's really handy to be able to adjust it via wifi using the browser on my mobile.


Did couple of quick tests on the uniformity following the instructions on CN from John Upton (https://www.cloudynights.com/topic/8...#entry11849571) and the results I got were 0.8% and 1.17% non-uniformity. Used different brightness and exposure between the two tests, so this might explain the difference. Will do some more testing down the track. But pretty happy with the results.

[Drac0 (Mark)]

Originally Posted by ronson

Just a quick update - I ended up buying the Giotto 120 panel. I am not using ASCOM/USB, so it's really handy to be able to adjust it via wifi using the browser on my mobile.


Did couple of quick tests on the uniformity following the instructions on CN from John Upton (https://www.cloudynights.com/topic/8...#entry11849571) and the results I got were 0.8% and 1.17% uniformity. Used different brightness and exposure between the two tests, so this might explain the difference. Will do some more testing down the track. But pretty happy with the results.

Be sure to let us know how it goes. I'm currently considering options for a future upgrade to the A4 tracing panel I currently use.

Cheers,
Mark

[ronson]

No worries, Mark, will update once I run some more tests.

For comparison, here are some non-uniformity numbers for other panels: https://www.astroworldcreations.com/...t3-conclusions, Non-uniformity section.

The build quality of the Giotto seems fine. Looks like a 3d printed shell, but pretty sturdy.

Something I noticed, my 5.5mm 2.5 and 2.1 DC 12v cables did not fit the power socket. I tried with my cables as the included one has a cigarette lighter on one end and I prefer both ends to be 5.5mm DC. There are adapters with female cigarette lighter sockets to DC, so this might be an option. Not an issue really, my cables might be picky

In terms of brightness, it’s plenty. A 3nm narrowband filter at f/6.4 and gain 100 gets me an ADU of about 28k (this is close to the optimal for my setup) with a 2 sec exposure at 2/3 brightness of the panel. This is pretty good as I was worried it might take minutes for the narrowband flats, based on people’s experience with other panels.

[Drac0 (Mark)]

Originally Posted by ronson

No worries, Mark, will update once I run some more tests.

For comparison, here are some non-uniformity numbers for other panels: https://www.astroworldcreations.com/...t3-conclusions, Non-uniformity section.

The build quality of the Giotto seems fine. Looks like a 3d printed shell, but pretty sturdy.

Something I noticed, my 5.5mm 2.5 and 2.1 DC 12v cables did not fit the power socket. I tried with my cables as the included one has a cigarette lighter on one end and I prefer both ends to be 5.5mm DC. There are adapters with female cigarette lighter sockets to DC, so this might be an option. Not an issue really, my cables might be picky

In terms of brightness, it’s plenty. A 3nm narrowband filter at f/6.4 gets me an ADU of about 28k with a 2 sec exposure at 2/3 brightness of the panel. This is pretty good as I was worried it might take minutes for the narrowband flats, based on people’s experience with other panels.

Sounds good. Interesting read. I try & get exposures between 3 & 4 seconds so knowing it will get down there even with 3nm filters is a plus. The power cable isn't an issue, I'll just make my own if needed.

Cheers,
Mark

[ronson]

Originally Posted by Drac0

Sounds good. Interesting read. I try & get exposures between 3 & 4 seconds so knowing it will get down there even with 3nm filters is a plus. The power cable isn't an issue, I'll just make my own if needed.

Cheers,
Mark

I tested with 2s exposures as that was enough to cover all filters: LRGB + SHO. I then, just adjusted the panel brightness per filter to get me to the desired ADU. 2s for L meant I dropped the brightness of the panel pretty low. It was at level 8/100. Having the same exposure is really a convenience for me as this way I only need one set of dark flats You can go the other way as well, where you keep the brightness fixed and let the acquisition software determined the best exposure for each filter.



Certainly there is plenty of latitude with the panel brightness to cover comfortably faster and slower setups with all filters .