LtE in CMO #244

From   Edward A GRAFTON


@. . . . . . This image was taken 5/10 at 8:21 UT from Houston Texas

 

http://www.kwasan.kyoto-u.ac.jp/~cmo/cmons/EGf10May01.jpg

 

MARS IMAGE : May 10, 2001  08:21 UT

Ed Grafton, Houston Texas  ST6 CCD 14 inch f/11 Celestron SCT

Eyepiece Projection @ f/60

 Integration Times:

                 1 BLUE  + IR rejection, .5 seconds, Edmunds filters

                 1 GREEN + IR rejection, .5 seconds, Edmunds filters

                 1 RED + IR rejection, .5 seconds, Edmunds filters

                 10 CLEAR+ IR rejection, .5 seconds, Edmunds filters

             Seeing variable, fair-good  4-7/10, transparency hazy 4/10, wind calm, moderate dew.

             Elysium orographic clouds appear to be broken into two nearly equal parts.

(10 May 2001 email)

 

@. . . . . . . . . . This image was taken 5/14 at 9:22 UT from Houston Texas

 

http://www.kwasan.kyoto-u.ac.jp/~cmo/cmons/EGf14May01.jpg

 

MARS IMAGE : May 14, 2001  9:22  UT

Ed Grafton, Houston Texas  ST6 CCD 14 inch f/11 Celestron SCT

Eyepiece Projection @ f/60

Integration Times:

                 4 BLUE     + IR rejection, .5 seconds, Edmunds filters

                 1 GREEN    + IR rejection, .5 seconds, Edmunds filters

                 1 RED         + IR rejection, .5 seconds, Edmunds filters

                 14 Magenta + No IR,        .1 seconds, Edmunds filter (luminance channel)

           Seeing variable, fair-good, slow undulating waves 4-7/10, transparency very hazy 3/10, wind calm, moderate dew.

Hazy conditions with thin cirrus passing through.

(15 May 2001 email)

 

@. . . . . . . . . . Please note that my Mars observations from 5/10 and 5/14 were incorrectly labeled for UT. The 5/10/01 image was labeled as 9:21 UT and should have been 8:21 UT. The 5/14/01 image was labeled as 10:22 UT and should have been 9:22 UT. The image files have been corrected. It seems that I was still operating on CST instead of CDT.

PS: The surgeon general has determined that working all day and imaging all night is hazardous to you brain! Sorry for the confusion

    (16 May 2001 email)

 

@. . . . . . . . . . I am very pleased that you find my images worthy of your publication "Communications in Mars Observations". Please feel free to use them as you wish. It is also fine to make a hyper-linkage to my web from your site. Please note that the UT on the original images was incorrect. I have corrected this and the UT is now correct on both image files. Each was off by one hour due to the shift to day light saving time which I did not take into account. The 5/14/01 image was actually taken at 9:22 UT instead of 10:22 UT and the 5/10 image was actually taken at 8:21 UT instead of 9:21 UT. The image files have been corrected and are at the same URL as before.

http://www.kwasan.kyoto-u.ac.jp/~cmo/cmons/EGf14May01.jpg

 

http://www.kwasan.kyoto-u.ac.jp/~cmo/cmons/EGf10May01.jpg

 

If you need anything from me let me know. Regards

(17 May 2001 email)

 

@. . . . . . . . . . This image was taken 05/19/01 at 8:32 UT from Houston, Texas.

 

http://www.kwasan.kyoto-u.ac.jp/~cmo/cmons/EGf19May01.jpg

 

MARS IMAGE : May 19 2001  08:32  UT

 Ed Grafton, Houston Texas  ST6 CCD 14 inch f/11 Celestron SCT

 Eyepiece Projection @ f/60

Integration Times:

                 4 BLUE  + IR rejection, .5 seconds, Edmunds filters

                 1 GREEN + IR rejection, .5 seconds, Edmunds filters

                 1 RED      + IR rejection, .5 seconds, Edmunds filters

                 10 Magenta, No IR       .1 seconds, Edmunds filters (luminance)

           Seeing variable, fair-good  4-7/10, transparency hazy 6/10, wind calm, heavy dew.

Occasional low clouds blowing through. A Dusky "Collar" is noted along the entire length of northern borders of Mare Sirenum and Mare Cimmerium.      

(20 May 2001 email)

 

@. . . . . . . . . . The seeing here is good in the summer but not really any better than most favorable locations. It is a real struggle to get the sky to cooperate with Mars being only 35 degrees altitude here in Houston. I refer to the upper air currents to determine where the jet stream is located which provides some indication as to when the sky is stable at high altitudes. See:

 

http://virga.sfsu.edu/crws/jetstream.html

 

 The C14 is collimated well. I use the standard method of looking at the diffraction pattern of a star at high magnification to keep the optics aligned.

 The images are produced using a method called LRGB (as opposed to RGB). The Luminance channel for the images is created separately from the color channels. This allows one to take shorter exposures since the L channel does not require any filters (although I have used a magenta filter to gather the L channel information on the last couple of images). The color data is derived in the standard way with RGB filters and an IR blocking filter. The color data in this method tends to be weak but the L channel is stronger. The image processing is done mainly on the L channel images as the RGB data has low S/N since I have gathered little data for the color channels. I usually capture one red, one green and four blue and 40 L images in a few minutes time. I can get four data sets of the RGBs and L images during about 90 minutes (with focusing and adjusting the scope etc). I only have 90 minutes of visibility of Mars per night as it passes between two trees located in my neighbors yard. I examine to see which of the four data sets have the best images and choose that set for processing. If I am lucky I can use 10 and so of the L images out of the 40 that were taken for the best data set. Processing is done on the L images first using CCDOPS (SBIG CCD software). The images are sharpened using the bipolar filter (hard) and then smoothed (soft) and then sharpened again (hard) in CCDOPS. I save the images and then use Megafix software to average the 10 or so L channel images. This results in a high S/N L image that are made up of 10 or so low S/N images but they only have required 0.1 seconds exposure each so the atmosphere and the tracking problems are at a minimum. The averaged image is then sharpened again in the megafix software. The L is then aligned with the RGBs and a color image is produced. The image is saved and opened in Photoshop where a mild unsharp mask is applied.・・

 (22 May 2001 email)

 

@. . . . . . . . . . Yes..please feel free to use the information however you wish. If one can improve their technique from my experience then I am pleased.

 You have understood exactly. The RGBs are only to give a reasonable color balance and most of the detail is in the non-filtered (or magenta filtered images). These are my first attempts to image Mars although I have imaged Jupiter and Saturn before. Unlike Jupiter, I noticed that Mars had high contrast in the infrared so I altered my technique to include IR in the L channel. This had the effect of gathering more light per time unit and allowed me to shorten the exposure times and cope better with the atmosphere. The exposure times had already been shortened by the application of the LRGB technique since the whole image did not have to be constructed from just the filtered and IR blocked RGBs. The RGBs were shot with the IR in place to give proper color balance.

 I used the Magenta and no IR filter for the L channel with the idea that all the albedo feature contrast was in the red and IR. I wanted to try and capture the cloud features also so using the magenta picked up the blue also. There may be better combinations of filters that can be applied but since this is my first attempt to image Mars I have not experimented much. I do not know if my magenta filter is open to the UV but have wanted to include data down to 300nm and see if that helped to enhance the cloud features. The QE of the CCD chip is getting very low at that wavelength though. Here in Houston Texas USA, Jupiter was very high in the sky last year and the seeing was excellent on a couple of nights. Please see:

 

http://www.egrafton.com/juphr.jpg

 

I will send the following unless you let me know differently. The uncompressed but processed files are in .tif format 5/10/01  red.tif, blue.tif, integrated.tif 5/14/01 and 5/19/01  red.tif, blue.tif, magenta+IR.tif

 I will send the images tomorrow as now I have house guest and do not want to appear rude with self interest.

(23 May 2001 email)

 

@. . . . . . . . . . Attached are the images that I said I would send in yesterdays email.

 I hope that you can make use of them.

(23 May 2001 email)

 

@. . . . . . . . . . I would be very pleased to receive the printed version of the CMO. I will send you all observations that I get.

(25 May 2001 email)

 


 Ed GRAFTON (Texas, USA)


 Back to the LtE Home Page

 Jump to the LtE Archives