Wed, 09/25/2019 - 21:02
We at American Public University System (APUS) have a remotely-operated 24-inch Planewave CDK telescope where it's really tough to get flat field calibration frames.
What are our options to mount a screen inside the dome so we can point the scope at the screen and get our flat fields? I looked at Gerd Neumann's Aurora page, and I don't think that's what we're looking for.
Thanks,
Dave Syndergaard; assistant professor of astronomy and space studies
Anyone who knows the answer to this, please post--I know several people who need larger ( > 16") flat-field panels.
(I've always been amazed that large-scope vendors haven't figured out that they should bundle a $2000 panel with every $50,000 scope. Their buyers will all need one.)
Perhaps we were lucky enough to buy a 30" Optec Flatman for our CDK 24 some years ago before they were discontinued and it has worked flawlessly. I have it mounted on the dome wall about 18" from the end of the scope using a re-inforced flat-panel TV mount. The automation software automatically points to and controls the panel when taking flats.
Dave, Director, Burke-Gaffney Obs.
Hi:
At the 2014 SAS, James Vail gave some useful guidance on designing & making flat sources. His design using styrofoam in transmission seemed to work well. The paper is available on the SAS website (SocAstroSci.org) -- go the the "Publications" tab, select "Proceedings" and find 2014. His paper is on p. 23 of the document.
The video of his presentation is at
https://www.youtube.com/watch?v=mfJ6R_Fo_SA&feature=youtu.be
Cheers,
Bob B.
For APASS, we started with grain-of-wheat bulbs and hard foam insulating panels; see the article by Tom Smith in the SAS proceedings. We eventually moved over to KPNO-paint panels, kindly painted by Donn Starkey for us. For the Mittelman Observatory, we are using high color rendition LEDs and insulating panels (a slide or two will be in my AAVSO presentation). The system was designed by Alan Sliski, Aaron Sliski and myself. It is one of the reasons that Alan and I proposed to the AAVSO several months ago that they should start an instrumentation section, as finding this kind of information is difficult - it would be great to have it in one place. The problem has been to find a section leader - everyone is too busy!
Arne
Hi, all: You can find the article that Arne refers to at the SAS website (SocAstroSci.org) -- go to the Publications tab, then Proceedings, then click on the 2011 Proceedings. Tom Smith's article is on page 121.
The video of Tom's presentation of this work is at
https://www.youtube.com/watch?v=2dSEu-fZl4s&feature=youtu.be
Cheers,
Bob B.
We don't have to make our own OTAs, mounts, piers, focusers, filters, filter wheels, CCD cameras, focal reducers, dew shields, dew heaters, or software. We choose and buy and connect them. Done.
As things are now, should my own light panel break, I couldn't do photometry so I would be selling all my equipment and closing my observing program. It's nice that there's info out there to make my own panel, but I couldn't be less interested in finding scattered documents, watching videos, designing and building a light panels system, through many iterations of trial and error. I'm not good at it and don't want to be. There must be someone out there who is.
So what in the world is wrong with these vendors that they refuse to make and sell larger light panels at any price, and have even bought out and promptly closed the major suppier who did? This situation is just ridiculous.
My vague understanding is the manufactuer (Alnitak/Optec) was having reliability problems either with the panels or the high voltage drivers (or even sourcing the drivers). This meant long lead times or early failures, warrantee work, failures after warrantee, etc. You can't sell a product that is crap and keep your good reputation.
I think it is unfair just think the "industry" is going to build every gadget you think you need and it to be commercially viable at the same time. I am sure, the makers of these things sell lots of the small ones and very, very few of the large ones and if half of the large ones fail to work over the long term nobody is happy.
There is more than one way to do this. Prior to about 10 years ago, there were NO commercial flat panels, but somehow we got by with sky flats, white-t-shirt flats, dome flats, etc. With my home observatory (C14) I made a wooden flat board painted with flat white paint, illumuninated with two incandescent lamps. It is mounted to an adjustable TV mount and adjusted so that the panel is square to the end of the scope.
--- Dave LDJ
ps. and as to whether these panels are any better or worse than simpler solutions, maybe they are, maybe their aren't. Our 30-inch panel is far from flat to the eye or by measuring the light output (which I did at various points in the panel). Just because you pay $2k for a panel doesn't mean it is any better than a $50 home made solution!
I had my smallish LED flat panel custom made by https://photoglow.com/
The panels offered by sources supplying the AP community are, IMO, very difficient on the infrared end. So I searched for custom manufactoring company. Photoglow was able to include IR LED bulbs in the mix, making Ic flats quick and easy.. I have no idea if they would make large panels, nor to I know the costs, but it would be worth check with them.
Ed