h-alpha flat box?

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FlankerOneTwo
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h-alpha flat box?

Post by FlankerOneTwo »

Hi,

Has anyone tried building an h-alpha flat box using 656nm LEDs for illumination? I'm thinking of something like these. They are quite inexpensive but I'm not sure how many of them one would need to be sufficiently bright to be usable for flats. I'm sure it would be an easy project for someone with electronics experience (i.e. probably not me) - would you just need something like a prototyping breadboard and an LED driver for each bulb connected to a power supply?

http://www.newark.com/osram/lhcpdp-3t4t ... dp/28W1874


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Re: h-alpha flat box?

Post by rsfoto »

Hi,

Interesting idea and how many do you want to arrange on a board ?

Another question is how do you want to get an even illumination across the whole telescope entrance ?

Now one thing that might be a problem is the spacing which could make that you get many hotspot eg. one from each LED and for that you would need to arrange them and test it.

Yes, they are not expensive but difficult to solder and you need a thermal release underneath. If I understood correctly they need 0.35Amp of current at 2.1V. quite high and according to what I read 0.4W power ...

Making a special PCB would solve the problem and this would be a US $ 30.00 investment additionally.


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Re: h-alpha flat box?

Post by marktownley »

Interesting idea. Someone needs to give it a try!


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Re: h-alpha flat box?

Post by rsfoto »

marktownley wrote: Sun Jan 21, 2018 4:40 pm Interesting idea. Someone needs to give it a try!
I am keen to get some but still do not know how to solve the problem of heat dissipation

:idea: :!:


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Re: h-alpha flat box?

Post by rsfoto »

Hi,

I was just going to order 10 of them cost US $ 14,50 plus 16% VAT tax into Mexico but then a surprise and this was US $ 20.00 charge for shipping costs ...

My Tinkerer love does not get that far ...

Forget it :lol:


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Re: h-alpha flat box?

Post by FlankerOneTwo »

Ouch, that's quite a shipping charge!


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Re: h-alpha flat box?

Post by Merlin66 »

Ohhh, that's nothing! You want to see some of the eBay items marked "free shipping" only to find that's within the US....$40 to Australia!!


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Re: h-alpha flat box?

Post by Montana »

Wow! that shipping is very cheap :shock:


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Re: h-alpha flat box?

Post by PDB »

I really like the idea, it is very difficult to make flats when large part (or whole) sun is in the fov. So if someone can do this it would be a great help. Unfortunately it probably will require a very bright light source. Some months ago I did some tests with a one of these 500W Halogen lamps and still needed around 1 minute of exposore to get a decent histogram for flats. Then I gave up the idea of a "solar" flat-box. Maybe these leds give better results because of red emitted light. A challenge.

Regards,

Paul


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Re: h-alpha flat box?

Post by danpro1 »

If the goal is to do a flat, during the day time, wouldn't a simple semi-transparent clear piece of glass in front of the objective do the trick?


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Re: h-alpha flat box?

Post by FlankerOneTwo »

The bag / glass / defocus flats don't work well for full-disk images, or if the solar limb is in the frame. Works OK if the disk completely covers the sensor.


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Re: h-alpha flat box?

Post by Ibbo »

Would be interested in progress on this.


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Re: h-alpha flat box?

Post by pedro »

Me too


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Re: h-alpha flat box?

Post by FlankerOneTwo »

I haven't done anything further re: red LEDs, however I did notice that the "100W equivalent" (14W actual) Utilitech warm white (2700K) LED floodlights that I use in my house are bright enough at Ha that I can produce a flat with the bulb stuck in the end of the dewshield. The bulb is slightly larger than the dewshield, so it does completely block the end of the OTA (LS80). I do have to crank gain and exposure way up still and I see some significant offset vignetting which I'm not sure whether it's due to non-uniformity of the bulb, possibly not having it aimed straight down the OTA, or the optics proper. The LED of course doesn't generate anywhere near the radiant heat of an incandescent bulb.

Sylvania produces a 3000K LED floodlight, the Ultra 250 PAR38, that is twice as bright at 2400 lumens that might work better, either set on top of the tube, or aimed at a diffuser set on top of the OTA. I'm thinking to pick one up, as well as a lamp where I can aim it a bit more precisely (I had an old desk lamp tottering on a pile of books).

I haven't found any companies that make a bright 656nm bulb, the closest I found were 633nm; waiting to hear back on the spectral width on these LEDs.


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Re: h-alpha flat box?

Post by KingKong852 »

I ordered a red LED before. Before that, I still didn't think how expensive the shipping cost was. I only understood after ordering. https://www.allicdata.com/list.html?category_id=1961


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