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Category: Solar Imaging
MonoChrome cameras
Posted on Sep 2, 2011, 2:53 pm Author: Jen Winter
 

Getting started in Monochrome solar Imaging:

We have already talked about how color imaging for H alpha solar is not a good choice.
We know that the DSLR cameras have IR blocking coatings that prohibit H alpha light passing.
We also know that ALL color CCD cameras block red light from 3/4 of their pixels with blue and green dye.
So the best choice will always be a MONOCHROME CHIP camera.
Most color images of Hydrogen alpha are taken in black and white, then color corrected in a program like photoshop.

In an effort to help new imagers, we conducted a number of tests using entry level equipment priced under $1000 to see what recommendations we can offer.   As I'm an avid astronomer, I thought I would check the astro closets for monochrome cameras that other astronomers could also find lying around in their closets.   I found several, but excluded anything which isn't available on the open market or hasn't been made in over 10 years.  

We found and tried imaging with the following:
Orion Star Shoot - autoguider monochrome camera.   (Sells for $269 today)
Supercircuits - PC-164C low light video camera used in occultations.  (Was $180)
Imaging Source - We use this on one of our optical test benches.

First, we tried the Orion Star Shoot.  It had a convenient 1.25" snout and has a capture button in the software. 
With the Star Shoot, we couldn't reduce the exposure very much, as it's a low light, slow exposure camera designed for nighttime pointing.   The slowest shutter speed would only allow us to see prominences.  We were able to catch a couple in single frames. 
They were single frames only, and subject to the boiling daytime seeing.   So they weren't the fantastically sharp images we sometimes see from expert imagers.

Next, we tried the supercircuits video camera.   It generates raw video, so we needed a program and a dongle to convert it into something the laptop could see.   I already had a digitizer and software loaded on the laptop from the AllSkyCam made by Moonglow Technologies.   This would allow us to pipe in the video from the super circuits camera. 
From the software, we could save video or still images.    Again, this camera didn't have any real exposure control.  It was on automatic exposure with no hope of controlling frame rate.   We captured a few single frames that show prominences, but again it was quite frustrating.    It is a really cheap option and is a toy that many nighttime astronomers have in a drawer already.  It will produce some images of surface and limb detail, but the exposures get a little wild.

Finally, we moved on to the DMK 41AU02. As this camera was in-use in our facility, we chose it last because we will now need to replace it for the work it performs.  It also costs the most of our options so we understand customers will have a hard choice with it too.   This camera comes with IC capture from the manufacturer.   This software allows the user to control a lot of components of the exposure.   I plugged this camera in and liked it immediately.  Focus was much much easier, with fixed exposure control.   We also like the wide variety of controls offered in the IC Capture software.   It can save stills and video in compressed or uncompressed formats.  The chip size is pretty big, so we get a 1280x960 image size. 
(( they make a 640x480 version that runs $390 in case this price tag is a bit high))
The only trick we found was that the image size of 1280 x 980, we couldn't use the little net book we originally planned if we plan to view at 100%.  
We imaged surface at settings like 1/500th of a second and Proms at exposures like 1/11th of a second.  These numbers vary from filter to filter, which each have slightly different transmissions.

So after trying those 3 cameras, we stuck with the DMK 41AU02.   I think the only grievance I have with the camera is that it's only 8 bit.  That makes it really tough to pull out faint prominences or to image both surface and proms at the same time.  You really have to hold your tongue right.  I am still waiting to try the new SBIG monochrome planet cam.   They say it will be out this month, but I'm still waiting.

In the end, we can recommend any monochrome camera above any color CCD camera any day.  However, those with an exposure control are vastly better than the automatic exposure cameras hands down.   Check your closets and drawers in the observatory and see what you have laying around in monochrome.  You probably have something that will work.  


Tagged Keywords: ccd, video, h alpha, halpha, monochrome, color, imaging, Solar

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