Sat Feb 1 23:56:23 BRST 2014 Observation and Magnitude Determination For Nova Centauri 2013 1) Photo-taking: - Set my GEP approximately along the N/S axis (used Ulysse Gizmos running on Monica's Nexus4); - Very rough estimation; - Also didn't check leveling; - Turned on my Canon SD1400IS; Loaded CHDK and set intervalometer for 10 sec intervals; Set "P" mode, configured Long Exposure, set for 15 secs; set focus to infinite; set initial delay to 2 secs; - Put Camera on mini-tripod (which, by the way, sucked: could not point camera ~51d up without holding the front leg of the tripod down with my hand, otherwise it would fall: legs are too "elastic", won't stay the way they are bent); Set mini-tripod on top of the GEP; - Turned on the GEP, moved to start, started tracking; - Pressed the start button, took a few pictures of the Crux and Alpha/Beta Centauri region with Zoom 1 - Put zoom at max (4x on this camera), pointed it to Beta Centauri area, took as many pictures as I could before running both camera batteries down. 2) Image processing: - Mounted camera's SD card on the computer; - Used imageviewer to inspect each picture manually, and discarded the worst ones (usually due to blurred stars, ie, vibration/movement when photo was being taken). - Moved all no-zoom pictures to ./zoom_1, ditto all max-zoom pictures to ./zoom_4; Examined and selected best picture (rounder stars, etc): it's IMG_8606.jpg; loaded it in GIMP; - Took a GPS Time Reference picture of the camera (using Ulysse Gizmos on my Nexus4); Saved it to ./GPS_Clock_Reference_-_IMG_8615.JPG; used exiftool to set all pictures to correct, GPS-adjusted time (see my Google Doc https://docs.google.com/document/d/1lNhh43CX5ozU_nFPaHgkjKoZ32WGwYknFB-T8yfGia0/edit, paragraph starting with 'td="-=HH:MM:SS";' - Set the Mint_Maya_13 VM to the Stellarium snapshot; started it; - Updated Stellarium with all additional star catalogs (stars_5 to stars_8); - Enabled the "Bright Nova" plugin in Stellarium; Also, updated its catalog (by clicking on the "Update Now" in the plugin's "Configure" screen). - Searched (Control-F) for Nova Centauri 2013; - Set the picture to maximum zoom (1:1) on GIMP; - Rotated the picture in GIMP until its orientation coincided with the Stellarium display; - Adjusted the picture's Contrast/Brightness in GIMP by: (a) setting contrast to the maximum (127), and (b) setting brightness high enough to show as much as possible stars (when compared to the Stellarium screen), but low enough to highlight as little as possible of the camera's noise. 3) Obtaining Magnitude comparison data: - Accessed http://www.aavso.org/data/lcg, filled form with: Name: "Nova Cen 2013" Limit: 5 days End Date: (clicked on the javascript link); - The light curve graph is rendered; I click on the "Create star chart for NOVA CEN 2013" link. - The star chart is shown; unfortunately it's completely useless: field is too small, and comparison stars are much too faint in relation to NovaCen2013. - I post a topic on the AAVSO forum describing the issue and asking how to proceed: see http://www.aavso.org/v1369-nova-centauri-2013-magnitude-estimate-comparison-stars - Got a response instructing me to plot a chart with other parameters: Field Of View: 700 arcmins Limiting Mag: 9 Binocular chart option: marked -> Did it, also set "North is up" and "East is Right" to coincide with my picture's orientation. - New chart is rendered; clicked on the "Photometry Table for this Chart" link; - Photometry table page is show; By examining picture in GIMP and comparing it to random (ie, non-AAVSO comparison-sanctioned) stars in Stellarium, I estimate NovaCen2013 mag to be between 5 and 6, so I got the coordinates for the stars 52, 54, 56, 59 (BTW, about the same that the responder to my post indicated he was using) and then searched for them in SIMBAD (http://simbad.u-strasbg.fr), using the "Coordinate search" function. -> Asked at the same AAVSO topic above whether there was an easier method; no response yet. - Got HIP catalog ID for the star from SIMBAD and searched for it in Stellarium; matched the Stellarium screen with that star highlighted to my picture in GIMP, then copied a square around the star and pasted it to a separate file (./20140201_-_Magnitude_Determination_For_Nova_Cen_2013.png); Finally, copy/pasted NovaCen2013 itself to this file, then ordered them by apparent (ie, diffraction disc) size. - NovaCen2013 size is between 56 and 59, but much closer to 59; therefore, I interpolate it as 57 (ie, magnitude 5.7). - Posted it to AAVSO at http://www.aavso.org/webobs/individual; Unfortunately the "Comments" field tops at less than a line, so I entered this on my website at http://durval.com/astronomia/20140201064803UTC_NovaCen2013_AAVSO_Obs_Comment.txt Took many pictures with my unmodified Canon SD-1400IS point-and-shoot camera (digital, but not SLR) which does not accept any filters (that's why I entered "Filter" above as "Unfiltered with V Zeropoint"). Used ISO 400 and 15s exposures, loaded CHDK and used its intervalometer script to take pictures continuously for about 5 mins (took around 30 pics). Camera was on a tripod on top of an tracking equatorial platform to avoid star tracks. Set focus to infinite and optical zoom to maximum (4X). In post processing, selected the best picture (rounder stars, lowest noise, etc), then loaded it into GIMP and maxed contrast (127) and turned brightness up as much as possible without getting too much noise. Selected comparison stars (initially had difficulty given the default star chart returned by AAVSO VSP for this star, see my topic post at http://www.aavso.org/v1369-nova-centauri-2013-magnitude-estimate-comparison-stars), but finally got it right and compared NovaCen2013 difraction disk to the comparison stars': found it was a little larger than star 56 and significantly smaller than star 59, so I interpolated NovaCen2013 magnitude as 5.7). =Eof= -> This observation can be seen at http://www.aavso.org/webobs/edit/1263905652 (must be logged in as "durval" for URL to work). =Eof=