Flatfield panels

Forums Imaging Flatfield panels

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    Posted by Americo Watkins at 00:49 on 2013 Nov 11

    Would any body like to share their experiences or views on flatfield panels pros or cons.I carry out photometric filter observations of asteroidsI find obtaining suitable sky flats difficult and the observatory is too small to obtain evenly illuminated dome flats.In particular I’m thinking of obtaining one of gerd neumann’s panels.Cheers Eric


    Posted by Robin Leadbeater at 11:46 on 2013 Nov 14

    Hi Eric,I have investigated them for spectroscopy (I know Lothar Schanne who is mentioned on the Gerd Neumann site) but this is a rather different application where spectral content rather than field uniformity is more critical. Talking to Lothar, from the spectral content point of view I would say that they would be ok for BVR (even too bright for normal imaging flats perhaps) but the output is much lower in the I band.CheersRobin


    Posted by Americo Watkins at 15:57 on 2013 Nov 14

    Thanks Robin,that’s useful to know.I will also use some neutral density filters to reduce the brightness as I understand this could be a problem for unfiltered flat exposures.Cheers Eric


    Posted by Robin Leadbeater at 16:31 on 2013 Nov 14

    Hi Eric,This link seems to confirm that I band flats are a problem using an EL panel, though this is a different supplierhttp://www.lightbuckets.com/forums/showthread.php?p=3118CheersRobin


    Posted by Americo Watkins at 17:14 on 2013 Nov 14

    Unlikely to use that range often, it it does present a problem then I would have to consider an alternative method, but it would be only for that one colour at least.. Cheers Eric


    Posted by Eliot Hall at 21:50 on 2013 Nov 16

    Hi Americo,Don’t know if this helps…I’m building my own light box for to be used for photometry. I’m finding it difficult remove all gradient. I’m taking so much care as I think the precision for photometry is much higher than for imaging.I know someone who uses EL panel his only criticism is that you must reduce the luminance by diffusing to extend the expose time. Otherwise the a strobing effect appears in the flats in very short exposures.Cheers,Eliot


    Posted by Americo Watkins at 02:06 on 2013 Nov 17

    Hi Elliot,I have ordered additional neutral density filters to cope with the brightness hopefully which will allow me to use longer flatfield exposures to get past the problems of a mechanical shutter such as I have. Hopefully then any strobing effect shouldn’t present a problem- One hopes.Cheers Eric


    Posted by Eliot Hall at 08:58 on 2013 Nov 17

    It might be worth experimenting with putting some paper/card in front of the EL panel to dim it as well.Inserting extra elements to the light path might add defects (e.g. vignetting, dust on filters, etc.) that weren’t there in the original image.


    Posted by Americo Watkins at 18:48 on 2013 Nov 17

    Yes I shall try that, it seems to be the general recommendation. The ND filters are actually sheets that are placed immediatly in front of the light panel in the same way that the paper and card as you have suggested.Cheers Eric

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