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Inexpensive Flat Frame Panel?

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#1 StevenBellavia

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Posted 07 April 2020 - 06:34 PM

Hi,

 

I just tried this last night: An inexpensive artists LED tracing panel.

I don't think the light is 100% uniform over the surface, but I also think it was "good enough" to do the job.

 

Note, that I was using this on a C6 HyperStar, so at its dimmest setting, it was still too bright, so I added one layer of combination CTO / ND film and then a layer of 1/8" HDPE plastic.  That got me to a 0.4 second exposure with 50% histogram.

 

I like that it is powered by a USB cable.

I also like that it is larger than I need.  I will make an enclosure for it, as I have done for my other panels, so I can use it at a dark sky site.

It's also a good back-up.  My Gerd Neumann, with those dainty wires, is on its lasts legs, after many years of use and repeated repairs.

 

Steve

 

*CTO = Color Temperature Orange

*ND = Neutral Density

 

I don't remember but I am pretty sure it was 3420 or 3407 Roscosun Cinegel ND/CTO. (About $7 for a 20" x 24" sheet)

LED is very blue so the CTO helps if doing RGB or a one-shot-color camera. I will try to see how spread out the three peaks in the histogram are.

 

 

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#2 Cfreerksen

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Posted 07 April 2020 - 06:48 PM

I have never heard of this. I see they come in varying types 3/4, 1/2 and others. what would you recommend to try first? I use a similar panel and yes it is very blue. It would be helpful to get the peaks better aligned.

 

Yes they are not very flat. I have a light meter for verifying monitor intensity for medical use and did a few checks. It was about 10 to 15% different from center to edge. I have a SCT so the middle is obstructed and I have a panel A4 so I don't use it to the edges. It works well and soooo much less expensive than dedicated panels.

 

Chris



#3 ismosi

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Posted 07 April 2020 - 06:48 PM

I started using something similar a couple of years ago. I'm sure it's not perfect but seems to get the job done, and, it was only about 20 bucks. It's not very large so I can only use it on my smaller scopes.

 

I pad mine with tracing paper to get the exposure time to at least one second. Mine has three brightness settings but I've only ever used the lowest intensity.



#4 richorn

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Posted 07 April 2020 - 06:55 PM

You might want to try 1/8 inch frosted (white) Plexiglas in addition to your ND/CTO.  Might take you a bit below 50%. but should help with the uneven intensity.

 

Not something I have tried for astro, but do this kind of thing in the studio for product shots here and there. I am a big fan of white Plexiglas ;-)



#5 Cfreerksen

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Posted 07 April 2020 - 06:59 PM

You might want to try 1/8 inch frosted (white) Plexiglas in addition to your ND/CTO.  Might take you a bit below 50%. but should help with the uneven intensity.

 

Not something I have tried for astro, but do this kind of thing in the studio for product shots here and there. I am a big fan of white Plexiglas ;-)

I noticed the same company had frosted too. https://www.amazon.c...50&sr=8-2-fkmr0

 

Would the plexiglass be better in you estimation. do you have an example that works for you?

 

Chris



#6 richorn

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Posted 07 April 2020 - 07:07 PM

I use primarily 4'x8'x1/4" sheets for product photography, but use smaller sheets of 1/8" and 1/4" for disunion in close.

 

In your case, I would use the 1/8" sheets, and double up if needed.  You can put the ND/CTO in between the layers as that might help disperse the light even more.

 

This looks similar to the stuff we got for the studio:

 

https://www.amazon.c...,aps,203&sr=8-1

 

 

EDIT:  Wait, you said better.  Better than what?  The idea is to add the Plexiglas to the tracing panel to reduce and diffuse the light. The only thing you don't use is the "t-shirt".  Also, once you get the setup right, you can build the frame and this all becomes self -contained.


Edited by richorn, 07 April 2020 - 07:10 PM.


#7 S.Boerner

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Posted 07 April 2020 - 07:10 PM

From personal experience be really careful of where the USB plug goes into the tablet.  I had one break at the tablet and it ended up in the junk.

 

If you want to check if the tablet has even illumination take two images with identical exposure information, flipping the panel between shots.  Do pixel math on them by adding a few hundred ADU to each and then subtracting one from the other.  That should help you locate the problem areas.  


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#8 ekallgren

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Posted 07 April 2020 - 07:13 PM

The Plexiglas is much cheaper from here.

https://www.usplasti...23681&catid=442


Edited by ekallgren, 07 April 2020 - 07:28 PM.


#9 ntph

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Posted 07 April 2020 - 09:13 PM

For an enclosure, I used the box the panel came in. Use whatever packing came with it, or some suitably sized styrofoam, cardboard, whatever is handy, to hold the panel firmly in position when you close the box. Cut out an appropriate sized circle to fit over your dew shield, a port for the power cable to come out and an opening for you to hit the power button. Tape the whole thing together with postal packaging tape or whatever you like. Lightweight, fits securely on the end of your OTA, doesn't leak light anywhere (as long as you turn it off and on while it's in place). Works a charm and costs nothing. 

 

 

 


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#10 dswtan

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Posted 07 April 2020 - 09:54 PM

Some good tips on using these here - see post 22, but the whole thread is useful: 
https://www.cloudyni...-vs-flat-panel/


Edited by dswtan, 07 April 2020 - 09:56 PM.


#11 PeteM

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Posted 08 April 2020 - 09:22 PM

I used the thread(below) to modify one of these types of tracing panels off amazon for my flat field target. Works great with SGP where I can set the brightness over 255 different brightness levels. So with my Lum filter I can be around 1-2s or crank it up for my narrowband filters for 10-15s. (with a 8" f/8 RC)

 

https://www.cloudyni... panel arduino


Edited by PeteM, 08 April 2020 - 09:23 PM.

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#12 Cfreerksen

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Posted 08 April 2020 - 09:29 PM

I used the thread(below) to modify one of these types of tracing panels off amazon for my flat field target. Works great with SGP where I can set the brightness over 255 different brightness levels. So with my Lum filter I can be around 1-2s or crank it up for my narrowband filters for 10-15s. (with a 8" f/8 RC)

 

https://www.cloudyni... panel arduino

This is brilliant. I may be able to incorporate this into my scope shed.

 

Thanks,

 

Chris 




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