[Aavso-photometry] DSI Pro Photometry text by Arne Henden, published in S&T

Sat Jul 21 18:57:40 EDT 2007

The DSI supports/supported:

* 8 Bit:
  BMP, JPEG, GIF, and TIFF
  -> unusable for photometry due to loss of data

* 16 bit:
  - FITS (separate R, G, and B images)
    upsampled to 640x480 pixel and “squared up” by some kind of interpolation
    -> not recommendable for photometry
  - FITS3p (3 color plane FITS)
    upsampled to 640x480 pixel and “squared up” by some kind of interpolation
    -> not readable by all software for further processing
    -> not recommendable for photometry
  - Raw FITS
    direct save from the camera without upsampling and “square up”
    -> this is what we want for photometry (like with DSLRs !!!)
    -> requires some kind of "debayering" in to R, G, and B images
       for further processing and photometry that couldn't be done by
       all software in the past

Clear skies
 Wolfgang

-- 
Wolfgang Renz, Karlsruhe, Germany
Rz.BAV = WRe.vsnet = RWG.AAVSO

----- Original Message ----- 
From: "Michael Newberry" <mnewberry at ...>
To: "Wolfgang Renz" <w_renz at ...>
Sent: Saturday, July 21, 2007 11:44 PM
Subject: Re: DSI Pro Photometry text by Arne Henden, published in S&T

> I meant to support it for photometry, not for camera control.
> That seems to be what Arne was saying, and that made no
> sense to me.
> 
> Michael
> 
> 
> 
> ----- Original Message ----- 
> From: "Wolfgang Renz" <w_renz at ...>
> To: "Michael Newberry" <mnewberry at ...>
> Cc: "AAVSO-PHOTOMETRY" <aavso-photometry at mira.aavso.org>
> Sent: Saturday, July 21, 2007 2:34 PM
> Subject: Re: DSI Pro Photometry text by Arne Henden, published in S&T
> 
>> Hi Michael
>>
>> It was published in late 2005 so it was written some time earlier
>> using a prototype he got in late 2004.
>> Article:
>>    Sky & Telescope; Oct 2005; 76
>>    Meade DSI Color CCD Camera - Johnny Horne
>> Box:
>>    Sky & Telescope; Oct 2005; 79
>>    And Science Too - Arne A Henden;
>>
>> Its about the DSI I _Color_.
>>
>> A)
>> At that time most image processing packages have just started
>> to support color cameras and DSLRs. They often showed severe
>> errors reading these different formats in the beginning (e.g.
>> AIP4Win V2 came out in July 2005 and it took some time to
>> get rid of all the color related bugs).
>>
>> I don't know which formats the original AutoStarSuite software
>> could save. But I guess something like JPGs, tri-color FITS and
>> monochromized grey FITS.
>>
>> B)
>> In the beginning just the AutoStarSuite could handle DSI cameras
>> for image aquisition.
>> The AutoStarSuite might have some nice features like Drizzling,
>> but not all users are satisfied with its functionality and the user
>> interface.
>>
>>
>> Maybe some who used a DSI camer in 2004/2005 can explain how
>> the situation was in more details.
>>
>>
>> Clear skies
>> Wolfgang
>>
>> -- 
>> Wolfgang Renz, Karlsruhe, Germany
>> Rz.BAV = WRe.vsnet = RWG.AAVSO
>>
>>
>>
>> ----- Original Message ----- 
>> From: "Michael Newberry" <mnewberry at ...>
>> To: "Wolfgang Renz" <w_renz at ...>
>> Sent: Saturday, July 21, 2007 8:55 PM
>> Subject: Re: DSI Pro Photometry text by Arne Henden, published in S&T
>>
>>
>>> Thanks for the article. I don't understand what Arne means by "once other
>>> software packages start supporting it". If the camera software produces a
>>> FITS image, then other software packages already support it, right?
>>>
>>> Michael
>>>
>>>
>>>
>>> ----- Original Message ----- 
>>> From: "Wolfgang Renz" <w_renz at ...>
>>> To: "Michael Newberry" <mnewberry at ...>
>>> Cc: "AAVSO-PHOTOMETRY" <aavso-photometry at mira.aavso.org>
>>> Sent: Saturday, July 21, 2007 11:41 AM
>>> Subject: DSI Pro Photometry text by Arne Henden, published in S&T
>>>
>>>> I found the S&T article inset text (I knew I have it somewhere):
>>>>
>>>> "Preliminary Science Tests of a DSI-Pro
>>>> by Arne A. Henden
>>>>
>>>> I’m continually asked the question “Can I do photometry with a
>>>> brand X CCD?”  I decided about a year ago to pursue the answer
>>>> in a scientific manner, and have gotten one grant and some vendor
>>>> loans of inexpensive CCD cameras. The DSI-Pro was one of these,
>>>> with John Hoot of Software Systems Consulting providing me an
>>>> early prototype late last year.
>>>>
>>>> I have been favorably impressed with this camera. It has low readnoise
>>>> (about 6-7 electrons), very low dark current (2.5electrons/sec/pix at
>>>> 36F), and excellent cosmetic quality.  The prototype had a fair amount
>>>> of amplifier glow that could be subtracted cleanly if a dark frame was
>>>> taken at the same ambient temperature.  The camera gain is set such
>>>> that the system is reasonably linear to 50K ADU.  However, since ABG
>>>> cameras usually become nonlinear about half-well capacity, this gain
>>>> setting means you lose  the top end of the dynamic range in an 
>>>> individual
>>>> exposure; I much prefer the camera gain to be set to reach the pixel
>>>> saturation limit.  Displaying the non-square pixels makes star images
>>>> elongated but this does not affect the photometry.
>>>>
>>>> On-sky tests show excellent blue response (I was able to get U-band
>>>> images).  A 30-second V-band image on the 1.0m telescope had a
>>>> faint limit of V=19.3, not much different from our science cameras.
>>>> A preliminary reduction of a 2-hour time series on my favorite cluster
>>>> (NGC7790) shows 4mmag photometric errors over the entire 245
>>>> frame series, with the delta Scuti NSV 14781 0.1mag light curve
>>>> amplitude easily resolvable.
>>>>
>>>> I would definitely recommend this low-cost camera as an entry into
>>>> astronomical photometry, especially once other software packages
>>>> start supporting it."
>>>>
>>>>
>>>> Other reviews:
>>>> - Cloudy Nights Discussions
>>>>  Dsi Pro for Variable Star Photometry
>>>>
>>>> <http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/577365/>
>>>>  DSI choice: Meade DSI, DSI pro, Orion DSI? which
>>>>
>>>> <http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/1122736/>
>>>> - Jeff Hopkins
>>>>  Astronomical Photometry with a DSI Pro
>>>>  DSI Modifications
>>>>  http://www.hposoft.com/Astro/DSI/DSI.html
>>>>
>>>> Clear skies
>>>>  Wolfgang
>>>>
>>>> -- 
>>>> Wolfgang Renz, Karlsruhe, Germany
>>>> Rz.BAV = WRe.vsnet = RWG.AAVSO
>>
>>
>> 
> 
> 
>