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I took my first light with the Askar FRA 500 and a 2600MC pro on last weekend . When I tried to take the flats I observed that my flat panel is excessive. At 40% of the histogram the exposure time was 6ms, so far from the 2-5s I wanted to obtain. So my question is if you know a dimmable panel that can dim the light enough to reach that exposure of 2-5 s or at least 1s. Thanks in advance
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I use a flat panel and then put 1 or 2 sheets of white photocopy paper between the panel and the scope, that has the effect of increasing the exposure time.
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I use an Alnitak Flip Flat with mine. All my LRGB and Oiii Flats are 6s exposure targeting ~18-20k ADU. Ha and Sii flats are 15s targeting ~8-10k ADU. That works well for my QHY268M. The Alnitak Panel seems a bit weak in the Red spectrum so my OSC flats are a bit more challenging, especially with dual NB filters, but still easily managed with similar exposure times. I have also heard good things about the Deep Sky Dad panels. CS, Jeff |
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You can also put a neutral density sheet like these https://www.amazon.es/dp/B0CPLPGT1N?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1 |
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No need to expose for so long with flats when using an IMX571 sensor. My flats are 9.3ms at the moment and work perfectly, so you have nothing to worry sbout here. |
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Oskari Nikkinen: *That cannot be stressed enough. There is NO need for these overly long expsoure times! |
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Thank you to all of you for your advise!!!! Great forum |
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Hi my flats for zwo 2600mm and 6200mm 3s , and ADU 24K to 25k with pegasus masterflat note : for LRGBSHO CS, Brian |
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Finally I bought a PWM module at AliExpress. Setting it at 3% in amplitude a s 24Khz freq allows me to obtain flats of 2" at 40% of the histogram.
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You only need long exposure times for a sensor like the asi294 series.
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In any case I obtain histogram's values about 40%. Using the PWM module I can vary all the parameters (amplitude and freq) to play with exposure times maintaining the histogram at the ADUs I want.
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I have an homemade flat panel with few blue LEDS and several incandescent normal car bulbs (all 12V), with many covers of paper and acrillic. The amount of light for my QHY 268M CMOS is really small, but for luminance filter it's huge…I did an experiment with lesser exposure times but even at times <1 second it saturate the sensor. So I tested taking flats with the front of the scope covered (light zero) and discover the sensor still have some signal (!) but the flats were too dark and useless… At last I go the opposite way and give more exposure times, about 2 seconds for luminance, 4—11 sec for red-green-blue filters and about 30 sec for narrowband filters, as an old flat box I made that works well with my last CCD. Today I'm using the times commented here, regardless the saturation (high ADUs) of the sensor, and surprise…these work fine ! Pedro |
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I bought an RGB ceiling light. Pushed it up tight against my Celestron C9.25 and what came out of the rear was dim compared to the brightness at the front. I'm guessing the 90 degree dispersion LEDS in that "panel" don't go down well with an F10 scope. Ho hum - only £20. However, the fact these RGB ceiling lights come with a remote control allowing you to cycle through red, green and blue interested me. Or you can select colour temperature from 3000K - 6800K. But it made me think. I've got LCD screens for computers. I've got an OLED TV. These could all be possible "light panels" staring me in the face. I could just as easily create R/G/B images in Microsoft Paint (free!), display them on the monitor or TV, and use those. I tested my OLED TV + IMX585(colour) camera. I was able to detect infrared 800nm+ I removed the protection filter from the cam for this test. 585 = STARVIS and they should all have good IR response - if allowed to see it… Before you rush out to buy a panel, maybe the one staring you in the face will do. Regards, Ed. |
