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Arduino to make light screen for flats!


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#1 gasman

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Posted 27 July 2013 - 06:39 PM

Hi folks
I`ve been thinking of a way to make a light panel to create flats using my 120mm refractor. I have an arduino uno board with quite a few components and led`s and wondering if I can utilize this to create a light panel?. I`d like to use quite a few led`s to cover a 120mm diameter area so maybe 13 or so to get an even light and I`d also like to make it dimmable to aim for 1/2 to 1/3 full well lumination. These led`s would be behind a diffuse cover of some sort.
I`ve found some basic code but that will only control 3 led`s, is this doable with an Arduino uno board please?. I`ve also got a raspberry pi knocking about somewhere but maybe the Arduino would be easier to set up?.
Thanks
Steve

 

Ps maybe get away with less than 13 led`s?


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#2 Starlock

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Posted 31 July 2013 - 10:36 PM

I have no experience of Raspberry Pi's or the like but I think a matrix of LED's would work nicely behind a panel without all that even. I'm trying to work out why you need a processor? I have been using a much more simplified version of this (in a way). Just using a LED torch with an array of about 9 LED's. I simply shine this at a distance onto a white baby grow stretched over the aperture of my scope. Works a treat and I should have really done this on my last imagine session thats for sure :) Can't you just use a stream of white Xmas tree LED's and lay them uniformely behind a uniformely white translucent plastic cover.

 

Please feel free to dish out the dunce cap if I've missed the point :D

 

Chris 



#3 gasman

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Posted 01 August 2013 - 06:47 PM

Hi Chris

Yes I did wonder if I was being a bit OTT. I gather with a 16bit camera like mine the max well level is 65536 so for flats I should be aiming for about 20000 to 30000 average pixel value and I thought I could get a more even and accurate light screen using  something like the Arduino and as its been gathering dust on a shelf I thought it could be put to good use. I have tried your method using a led torch and white t towel with not much success either too bright or not bright enough, maybe have to pinch one of my grandkids onesy`s ;) .

 

Steve



#4 todd8137

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Posted 03 August 2013 - 01:25 PM

I am yet to find something that is great
"atoms are mainly empty space.matter is composed chiefly of nothing,
The absence of evidence ,is not the evidence of absence
Tibshelf Astronomy group founder-Founded March 2013C gem on astrotec pier in my shedC9.25, Acenssion127mm edt cf,80mm apo (guide scope)Qhy5,dmk21mono ,cannon modded 10d/600dFilters idas hutech2",neo,oiii,uhc s,ir740 ,uvirCelestron x-cel lx 7-12-18-25Barlows tal x 2,3 vixenx2 roll of obsy lots of cables adapters
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#5 Starlock

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Posted 04 August 2013 - 08:13 PM

 I have tried your method using a led torch and white t towel with not much success either too bright or not bright enough, maybe have to pinch one of my grandkids onesy`s ;) .

 

Steve

Hi Steve, you're totally right about it being either too bright or dim, I take a number of flats at different exposure lengths and just pick the best ones when I get them up on the laptop for closer inspection. I was doing this last night with a white t-shirt but I do think the baby grows are better, they seem to fit the aperture of my scopes better and my little trick is to double up on the material which seems to give a more uniform illumination.

 

Chris 



#6 DENEB

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Posted 28 August 2013 - 10:06 PM

Buy a Gerd Neumann, the spectrum on his foils are good....



#7 todd8137

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Posted 07 September 2013 - 11:12 AM

I have no experience of Raspberry Pi's or the like but I think a matrix of LED's would work nicely behind a panel without all that even. I'm trying to work out why you need a processor? I have been using a much more simplified version of this (in a way). Just using a LED torch with an array of about 9 LED's. I simply shine this at a distance onto a white baby grow stretched over the aperture of my scope. Works a treat and I should have really done this on my last imagine session thats for sure :) Can't you just use a stream of white Xmas tree LED's and lay them uniformely behind a uniformely white translucent plastic cover.
 
Please feel free to dish out the dunce cap if I've missed the point :D
 
Chris


Baby grow lol i use my daughters white school shirt over the end of the scope and a torch
Pat
"atoms are mainly empty space.matter is composed chiefly of nothing,
The absence of evidence ,is not the evidence of absence
Tibshelf Astronomy group founder-Founded March 2013C gem on astrotec pier in my shedC9.25, Acenssion127mm edt cf,80mm apo (guide scope)Qhy5,dmk21mono ,cannon modded 10d/600dFilters idas hutech2",neo,oiii,uhc s,ir740 ,uvirCelestron x-cel lx 7-12-18-25Barlows tal x 2,3 vixenx2 roll of obsy lots of cables adapters
http://www.tag.binhoster.com/

#8 todd8137

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Posted 07 September 2013 - 11:13 AM

Do you need to remove filter when doing this a feel this is what is killing mine
Pat
"atoms are mainly empty space.matter is composed chiefly of nothing,
The absence of evidence ,is not the evidence of absence
Tibshelf Astronomy group founder-Founded March 2013C gem on astrotec pier in my shedC9.25, Acenssion127mm edt cf,80mm apo (guide scope)Qhy5,dmk21mono ,cannon modded 10d/600dFilters idas hutech2",neo,oiii,uhc s,ir740 ,uvirCelestron x-cel lx 7-12-18-25Barlows tal x 2,3 vixenx2 roll of obsy lots of cables adapters
http://www.tag.binhoster.com/

#9 Neil

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Posted 10 September 2013 - 06:41 PM

The solution is very simple and no ardinuo is required. 

 

You just need a three position swtich to change the resistance of the array of LED's , then by carefully calculating the resistance you can have 3 different intensity levels, that should put you in the ball park where a minor adjustment of the CCD shutter speed will give you the desired 20,000 to 30,000 ADU for a 60,000 ADU CCD sensor.

 

If you need a circuit diagram just let me know!

 

Clear Skies

 

 

Neil.



#10 todd8137

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Posted 10 September 2013 - 07:01 PM

Send me one ! Diagram that is
Pat
"atoms are mainly empty space.matter is composed chiefly of nothing,
The absence of evidence ,is not the evidence of absence
Tibshelf Astronomy group founder-Founded March 2013C gem on astrotec pier in my shedC9.25, Acenssion127mm edt cf,80mm apo (guide scope)Qhy5,dmk21mono ,cannon modded 10d/600dFilters idas hutech2",neo,oiii,uhc s,ir740 ,uvirCelestron x-cel lx 7-12-18-25Barlows tal x 2,3 vixenx2 roll of obsy lots of cables adapters
http://www.tag.binhoster.com/

#11 gasman

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Posted 10 September 2013 - 07:20 PM

A diagram would be useful Neil thanks ;)

Steve


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#12 Neil

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Posted 10 September 2013 - 07:36 PM

Don't laugh, here it is...

The resistors need to be calculated based upon the selected LED's and voltage source.

Controlling the current allowed through the resistor will control the intensity.

image.jpg

image.jpg

#13 gasman

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Posted 14 November 2013 - 11:23 PM

Sorry Neil only just noticed your reply to this post, very useful thanks for that ;)

Best

Steve



#14 duskchaser

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Posted 18 November 2013 - 07:43 PM

I've been looking around at ideas for a flat screen for my 6" refractor.

Here's an idea I'm trying:

 

http://blog.timesuni...WVquotation.jpg

 

It's a site that has a image of a laptop with a white screen, you just click the image once to make it full screen and voila!

I unplugged the power lead to my laptop then that reduces the brightness of the screen.

Maybe a piece of white perspex or similar would be needed to diffuse the light or dim it some more depending on the length of your flat exposures.

I'll be trying it out when I get a star to focus on. ;)


Doug.

 

6" Helios Refractor+Monorail focuser+ ST80 Guidescope+Baader guide rings.

Pier mounted NEQ6+EQMOD+Astrotortilla+CDC+Maxim DL 5+'V' filtered SBIG ST 7ME nabg.

Roll off obsy+warm room.

Photometry of Pre-Main Sequence + CV variable stars.


#15 dave_galera

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Posted 18 January 2014 - 07:43 PM

Try http://www.earlsmann.co.uk they make electroluminescent panels, I use one and have never had a problem with flats.

Dave

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#16 RickS

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Posted 19 January 2014 - 11:37 PM

I've been looking around at ideas for a flat screen for my 6" refractor.

Here's an idea I'm trying:

 

http://blog.timesuni...WVquotation.jpg

 

It's a site that has a image of a laptop with a white screen, you just click the image once to make it full screen and voila!

I unplugged the power lead to my laptop then that reduces the brightness of the screen.

Maybe a piece of white perspex or similar would be needed to diffuse the light or dim it some more depending on the length of your flat exposures.

I'll be trying it out when I get a star to focus on. ;)

 

Unless you have a high-end monitor (Eizo or similar) you're likely to find some significant variations in brightness across the screen.  Some sort of diffuser might help.

 

An easy way to check if your flats are any good is to use your master flat to calibrate another flat taken at 90 degrees rotation.  The result should be flat and featureless.

 

Cheers,
Rick.