Canopus Photometry Software

Canopus Photometry Software Price
Canopus Photometry Software Online

Photometry: Canopus Plate Solving and Field Curvature Effect after Coma Correction?

#121

Hello! I'm considering building a 10' f3 system with a large coma corrector like type 2 Paracorr using a full frame CMOS sensor using IMX455 chip in order to use for photometry.
I would like to analyze multiple targets within a single image.
There may be residual curvature of field after coma correction. I've asked the folks at Televue for information on how much the Paracorr might correct curvature of field effect, and I'm waiting for their reply.
Arne Hendon at AAVSO suggested that there may be field distortion effect from curvature of field at the edge of an image with such a fast system after coma correction. As a result, star coordinates at the edge might be off if coordinates are plate solved with X:Y coordinates of the CCD. He suggested that alternate plate solving coordinates, like WCS, would not have this problem with such field distortion effect from residual field curvature after coma correction.
A quick question - does Canopus plate solve by X:Y coordinates in the image or does it use an alternative, like the World Coordinate System?
This may be a moot point if there is adequate field flattening with the coma corrector, but I thought I would ask now. Thank you and best regards.
Mike

#122

When Canopus does an Automatch, it inserts WCS info. However, only the first order terms are included. The higher order terms that would help with field curvature are not included. That's on the to-do list which has become the to-do novel.
Save the Lightcurves (alcdef.org)
Brian D. Warner
Center for Solar System Studies - Palmer Divide Station

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On 11/16/2020 07:21, Michael Heald wrote:

Hello! I'm considering building a 10' f3 system with a large coma corrector like type 2 Paracorr using a full frame CMOS sensor using IMX455 chip in order to use for photometry.
I would like to analyze multiple targets within a single image.
There may be residual curvature of field after coma correction. I've asked the folks at Televue for information on how much the Paracorr might correct curvature of field effect, and I'm waiting for their reply.
Arne Hendon at AAVSO suggested that there may be field distortion effect from curvature of field at the edge of an image with such a fast system after coma correction. As a result, star coordinates at the edge might be off if coordinates are plate solved with X:Y coordinates of the CCD. He suggested that alternate plate solving coordinates, like WCS, would not have this problem with such field distortion effect from residual field curvature after coma correction.
A quick question - does Canopus plate solve by X:Y coordinates in the image or does it use an alternative, like the World Coordinate System?
This may be a moot point if there is adequate field flattening with the coma corrector, but I thought I would ask now. Thank you and best regards.
Mike

Custom BVI+C Photometric Filters
for the ST-402ME Camera
Update: June 1, 2006:Thisproduct is now shipping with a
Special Edition of MPO Canopus Software included at no additional charge

MPO Canopus is a full-featured astrometry and photometry program capable of providing high accuracy results in both fields. With just one program you can process and measure your images, do photometric transforms, generate lightcurves, analyze periods and times of minimum, look for new asteroids or new variables, and much more. I have only fiddled with Canopus a couple of times and that was a few years ago. Therefore it would be hard for me to compare others to it. I also found Maxim DL to be very limited particularly since you must have a comparison star to use the photometry tool and the information window aperture tool is not very accurate and is not recommended for.

Precision photometric package for the ST-402ME
(Note: In production models, the carousel is installed with the filters on the side that faces the front of the camera)

Canopus Photometry Software Price

Although priced as an entry level CCD camera, theST-402ME is an exceptionally sensitive and capableinstrument. The KAF-0402ME CCD is a scientific grade full frame sensor with the samequality, quantum efficiency, and performance of sensors used in cameras costing manythousands of dollars more. Except for its size (field of view), the CCDcharacteristics are essentially the same as the main sensors used in the ST-8XME, ST-10XME and STL-6303E. It has very high quantum efficiency,high linear dynamic range, full well capacity of 100,000e-, dark current of 1e- or less at0C, and typical read noise less than 15 e-. The ST-402ME now has an enhanced cooling package and photometric filter wheel option,giving performance similar to our ST-X series but at a significant savings. TheST-402ME also uses a fast USB 2.0 interface with full frame downloads in less than 1second. The ST-402ME is an excellent choice for making high precision photometricmeasurements where its extraordinary sensitivity can be exploited with professionalresults.

Filter Carousel Installs Easily in the ST-402ME

Quantum Efficiency of the KAF-0402ME CCD

The ST-402ME has an internal filter wheel thatwas originally designed with custom RGBC filters for color imaging. When installed,the filter carousel replaces the shutter wheel and acts as both filter wheel andshutter. Due to the filter/shutter wheel design, the filters must be very thin,about 1mm, and only 85mm in diameter. They are also permanently mounted to thecarousel. This means it is not possible to add 'off-the-shelf' photometricfilters to the camera without buying an external filter wheel because most photometricfilters are about 5 mm thick and made for 1.25' filter cells. There is noprovision for adding standard 1.25' filters inside the camera, although if one isusing only one filter, such as a V filter, it can be screwed into the nosepiece for singlecolor measurements.

Previously we have recommended the CFW10 filter wheel with 1.25' filters for multi-bandphotometry with the ST-402ME, or the ST-7XMEI camera (which usesthe same imaging CCD) and CFW8A filter wheel. In either case, the cost of the system, including filters began at about $2800. Inresponse to requests for an easier and lower cost option, we have designed a photometricfilter set permanently mounted on a replacement internal carousel for the ST-402ME. By saving on the cost of an external filter wheel and larger filters we can offer theST-402ME Photometric camera for over $1000 less than the same or similar system withexternal filter wheel.

CFW-402with Filters

Filter Transmission Characteristics

In the 1950's Harold Johnson (Yerkes andMacdonald Observatories) established three photometric bands, the U, B, and V based on thesensitivity of the photomultiplier tube that he used at the time. Later on he establishedred and infrared (R and I) bands using a PMT with enhanced red sensitivity. In themid-1970's, A.W.J. Cousins and John Menzies (South African Astronomical Observatory) useddifferent filters, that when used with a newer, better detector, would reproduce theJohnson bands. Then, in the 1980's CCD detectors were beginning to replace thephotomultipliers so a new set of filters was required that, when used with the CCD's wouldgive the same results as the older filters when used with the PMT. Bessell (Mt. Stromloand Siding Spring Observatories in Australia) did this in 1990 (PASP, 102, 1990, 1181). It is Bessell's filter definitions that are the industry standard today when usingCCD's.

Canopus Photometry Software Online

Based upon the recommendations of Arne Henden,Director of AAVSO, the photometry set designed for the ST-402ME consists of B, V, and Iband filters, and a clear filter. The filters are high quality, parfocal, AR coatedphotometric filters made by Custom Scientific to SBIG's specifications. Because thetypical photometric filter is made from thick glass that absorb the out of band light, acustom curve is necessary for the I filter in order to make this filter set only 1 mmthick for use in the ST-402ME filter wheel and still match the performance of anequivalent CCD and Bessell filter. The B and V filters are identical to the Bessellfilter curves. If one compares the shape of the curve of the custom I filter to thestandard Bessell I filter, the custom filter has a sharper cutoff in the near IR whereasthe Bessell filter continues to pass light well beyond 1000nm. However, when the QEcurve of the camera is taken into account, there is virtually no difference in spectralresponse between the custom I filter and the Bessell filter. This assures that datacollected with the ST-402ME+BVI filters will be consistent with other systems using theBessell standard filter definitions.

System sensitivity with custom I filter and Bessell filter

The clear filter is AR coated andunblocked. The BVI carousel can be easily installed by the user and exchanged with aplain shutter or an RGBC filter carousel at any time. Update June 1,2006: These custom filters are now available and include a free Special Edition of MPO Canopus photometry software.

Note: The filter carousel isdesigned to work only with the ST-402 version of this camera, for
the ST-1603 and ST-3200 an external filter wheel is required due to the size of thesensors.
For pricing of the BVI+C Filter Carousel for ST-402ME
Please see out Current Price List