14 replies to this topic

[MELeslie67]

Here is my delima, I switched from OSC to Mono and now I am having issues getting my Flat exposure to ~1 sec.  Equiptment:  QHY Minicam8M (love the images),  Svbony SV555 122mm f/7 reducer/flattener 0.80x.  I take my subframes using N.I.N.A.  with Gain=74 & Offset=12 (calculated with Sharpcap Smart Histogram).   Using Flat Wizard with Dynamic Exposure, LED Panel, and TeeShirt method,  I cannot ~1 second flats without either changing the brightness of the LED panel (making Flat Wizard useless) or having different Gain for each filter (is this wise).  Ascom  flat panels a expense (as most astrophotography is).  Maybe I could build my own Ascom flat panel, does anyone have concise parts list and instructions to do this?  I love the detail I am getting from Mono over OSC, but but things like this make it flustrating.

[Dynan]

Go ahead and brighten your LED panel. I use minimum brightness for LRGB and max brightness for SHO. It's repeatable since it's a known setting for the panel for each set/run. I use one sheet of regular printer paper for diffusion.

[MELeslie67]

With my LRGB with LED at it's dimmest using gain=74 my L exposure time is less than .1 sec and the others range from .7 to 3 sec.  that is with 4layes of tee shirt and 2 to 3 pieces of heavy white paper

Edited by MELeslie67, 14 May 2025 - 05:00 PM.

[TXLS99]

Are the flats causing any issues?   If the flats work then dont worry about matching exactly what the program says you need.

[fewayne]

Why do you care about 1" exposures? If the peak's in the sensor's linear range, the exposure is immaterial unless you've a cam that wigs out on short exposures (e.g. ASI1600).

[MELeslie67]

If flats are not at least ~1 sec you get banding from LED panel  and that cause issues

Edited by MELeslie67, 14 May 2025 - 05:20 PM.

[archiebald]

If flats are not at least you get banding from LED panel ~1 sec 

In order to get banding, you'd need to be down in the range of 1/30th or 1/60th second or at the PWM frequency that the dimmer might be using.  Anything over around 0.2 second is considered pretty safe, and 0.5 second and onward is just overkill.

 

As long as I have the ADU at about 30-40% on the histogram and an exposure time of 0.3 second and up, then I get perfect flats.

 

And I'm not sure why you are assuming that changing the flat panels brightness makes the Flat Wizard useless??

[Dynan]

If flats are not at least ~1 sec you get banding from LED panel  and that cause issues

Can you upload and link a SINGLE FLAT (.fit)? (One that you think may be troublesome.)

Edited by Dynan, 14 May 2025 - 06:10 PM.

[AstroFromHome]

Maybe you should get a LED drawing board from Amazon. Those usually have three brightness levels. Just add one, two, three sheets of paper if the Lovestory brightness setting is still to bright.

 

Those LED boards used to start as of $15.

[Alex McConahay]

Here is my delima, I switched from OSC to Mono and now I am having issues getting my Flat exposure to ~1 sec.  Equiptment:  QHY Minicam8M (love the images),  Svbony SV555 122mm f/7 reducer/flattener 0.80x.  I take my subframes using N.I.N.A.  with Gain=74 & Offset=12 (calculated with Sharpcap Smart Histogram).   Using Flat Wizard with Dynamic Exposure, LED Panel, and TeeShirt method,  I cannot ~1 second flats without either changing the brightness of the LED panel (making Flat Wizard useless) or having different Gain for each filter (is this wise).  Ascom  flat panels a expense (as most astrophotography is).  Maybe I could build my own Ascom flat panel, does anyone have concise parts list and instructions to do this?  I love the detail I am getting from Mono over OSC, but but things like this make it flustrating.

Maybe I misunderstand something, but you say:

 

>>>>>>>changing the brightness of the LED panel (making Flat Wizard useless)

 

Why does NINA's flat wizard become useless?

 

I take LRGB flats with it regularly (although I have not been using it for more than a few months). It seems to change to a filter, select an appropriate exposure (after a series of tests) and then captures as many flats as I specify. Then changes to the next filter and does the same. Each filter requires a different exposure, but they all get done with my light panel at the same setting. 

 

If I increase intensity of the light panel, the flat wizard chooses a shorter exposure, and proceeds.  

If I decrease the intensity, the wizard chooses a longer exposure, and proceeds. 

 

In either case, it still does what it does. 

 

 

Then you ask:

 

>>>>>>>>or having different Gain for each filter (is this wise)

 

I would rather keep the gain, offset, and so forth, the same for all calibration shots because part of the process is to make conditions the same for the calibration and the light frames. However, I think it would be hard to notice the difference between flats taken at different exposure settings.. (As long as they are exposed to the same extent. (That is, the resulting median ADU is about the same.) 

 

In another post, you say:

 

>>>>>>>>>L exposure time is less than .1 sec and the others range from .7 to 3 sec.  that is with 4layes of tee shirt and 2 to 3 pieces of heavy white paper

 

Yeah, that sounds too short for me. And it sounds like you already know to just add more t-shirts and stuff. But, add some more. Or change the light source to a dimmer bulb or whatever. 

 

I may have missed it, but if the full well of your system is 65K, what are you looking for in the way of median exposure in your flats?

 

The bottom line, incidentally, is not whether you are getting .1 second or six second exposures. It is------do the flats work to calibrate the lights properly?

 

Alex

[AstroFromHome]

No dimmable LED Panel makes the Flat Wizard useless. FW still control the exposure time to reach the desired median brightness level that you are aiming at.

With a panel that only has one, two, three brightness levels you will in most cases not just reach a good median brightness of the flat files. Mostly you will have to set it to higher brightness and dim it down using T-shirt or paper. NINA FW will then measure in iterations what is the appropriate exposure time.

 

If you want a LED panel that always delivers the appropriate brightness for a fixed exposure time then you need an ASCOM compatible FP for $350-$400.

If you do not have a 294 color or monochrome camera it does not really matter if your flat were taken with 0.1 or 5 seconds exposure time.

 

I have taken my flats for years with a sketching LED panel with three brightness levels and a couple sheets of paper. In the FW I set 0.5 to 2 seconds of exposure time and let it run to find the correct exposure time.

That's one of the reasons for FW as you can define the median value and the software tried to achieve it.

 

It is an either or decision. Manual dimming or spend a few hundred $.

[gsaramet]

There is a second option, if the panel supports it: a LED PWM. I use a 4 EURO unit purchased from an electronics store. Works nicely, with the caveat that for broadband you need a really light touch on the button. I understand it costs a bit (but not much) more to get somebody to build an ASCOM arduino PWM unit. 

[archiebald]

No dimmable LED Panel makes the Flat Wizard useless. FW still control the exposure time to reach the desired median brightness level that you are aiming at.

With a panel that only has one, two, three brightness levels you will in most cases not just reach a good median brightness of the flat files. Mostly you will have to set it to higher brightness and dim it down using T-shirt or paper. NINA FW will then measure in iterations what is the appropriate exposure time.

 

If you want a LED panel that always delivers the appropriate brightness for a fixed exposure time then you need an ASCOM compatible FP for $350-$400.

If you do not have a 294 color or monochrome camera it does not really matter if your flat were taken with 0.1 or 5 seconds exposure time.

 

I have taken my flats for years with a sketching LED panel with three brightness levels and a couple sheets of paper. In the FW I set 0.5 to 2 seconds of exposure time and let it run to find the correct exposure time.

That's one of the reasons for FW as you can define the median value and the software tried to achieve it.

 

It is an either or decision. Manual dimming or spend a few hundred $.

There are many other options, here's a good one....

 

https://www.youtube....h?v=POvcBwyBBEU

[Arcueid]

You should get a LED drawing board or panel light.

 

I've been using a LED light panel that costs less than $10 equivalent and have no issue with flats with exposure from 0.005s to 0.02s.

[AstroFromHome]

There are many other options, here's a good one....

 

https://www.youtube....h?v=POvcBwyBBEU

Sure that is an option. But not everyone has owns a 3d printer, is able to design the 3d model for it or knowledgeable to set up the Ardiuno. So it is just an option for a few.

 

You should get a LED drawing board or panel light.

 

I've been using a LED light panel that costs less than $10 equivalent and have no issue with flats with exposure from 0.005s to 0.02s.

That's also my recommendation to get one of these. I still have mine for the large telescopes. The smaller ones I am step by step equipping with controlable flat panels.