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Notes (S98) |
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Notes (S100) |
Notes from CCD Session 99 (S00099) Sky Condition Graph RR Lyrae Photometric Analysis Altair - glare vs focus relationship Star Elongation Analysis Computer Crashes >
Sky Conditions Chart (S99) |
Notice Analysis of previous session (S98) shown that poor
attempts at refocussing had |
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The main part of session 99 examined the variation in RR Lyrae over a 5.7 hour interval, during which 366 images were taken in each of B and V filters. The comparison star method was used to produce calibrated magnitude estimates for the variable. As per previous session, a distinct brightening of RR Lyrae over an interval of less than 2 hours was observed, with gradual dimming thereafter. Data seems to be consistent with the 'standard' period of 0.56686776 days.
Data / Data QC |
Calibrated V mag and B Mag data are plotted against time in
the graphs below, along with control star magnitude (shifted to fit on
graph). Zero Point values determined from reference star measurements that
lie above a threshold level are used to distinguish higher quality data.
Analysis of QC Plots below show that the RR Lyrae brightening is real (far greater than variation in control star brightness). Quality of magnitude data is slightly compromised on occasions due to temporary formation of dew on the front lens of the LX200 scope. |
Magnitude Data (B & V Filters) |
V mag, B mag and B-V data is plotted here against time. The high quality data points (passing QC) are highlighted. |
Magnitude / Colour Analysis including comparison with previous sessions |
V mag and B-V data was combined with data from previous sessions & plotted against phase, assuming the catalog period length for RR Lyr. |
[Prior Sessions : Data/Analysis from 2005-10-08 ] |
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Bright stars have been noticed to produce off-centered
glare anomalies when contrast is turned up to show dim stars. Anomaly
comprises off-centered glare around the star, together with an off-centred
mirror reflection/diffraction pattern. To investigate how the pattern changed
with focus position a set of images of Altair were taken, moving from
before-focus, through focus, to after-focus. It was noticed that the position of
the secondary light circle moves close or further to the star.
It is thought that this off-centered glare is a result of mis-collimination of
the telescope, as it appears to mimic the bias in donut light pattern
shown by out-of-focus dimmer stars.
Altair (Aquila) |
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CCD Image (false colour) 20 sec exposure, C Filter Square root brightness scaling , 275-1000 ADU, 2005-10-13 19:07 h UT (#99003-20) |
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Examination of the distribution in star elongation direction from all images in session S89, shows that there is a preferred direction of elongation towards theta=40 deg. This corresponds to the orientation of the offset-centered anomaly noticed during analysis of images of Alair (see above)
Elongation Direction Analysis |
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Analysis of elongation data from previous session also
shows an elongation bias towards theta= ~ 40 deg |
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Two computer crashes occurred earlier in session (seems related to hardware/driver in someway). Connection between TheSky and LX200 telescope was lost on two occasions and USB mouse also lost connection at one stage. Lasts 4 hour of session went smoothly.
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This Web Page: | CCD Image Notes - (2005-10-13) |
Last Updated : | 2015-05-16 |
Site Owner : | David Richards |
Home Page : | David's Astronomy Web Site |