David's Astronomy Pages CCD Image Notes - Session 95 (2005-09-30)

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Sky Condition Graph

Sky Conditions Chart (S95)

Notice  1) Generally poor seeing (FWHM < 5 arc secs) 2) Patch of dark thin cloud of lower light transmissibility at around 20:55 h UT

See explanation of these graphs

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Optical Artifact Analysis

An image of bright star Gamma Draconis was examined in additional detail, as it shows an optical artefact which I commonly see associated with glare from bright stars.   Examination of older frames, shows that it was present even before using filters.

Image of Gamma Draconis shown with four different black-white ranges

CCD  Image  20s exposure, C filter 2005-09-30 21:11h UT (#95019)

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False Plate Solution Matches

Two images gave false matches 95068 & 95069 (these also gave incorrect Scale & Incorrect Angle - 308 deg !). Both images where rich star fields images of M37 taken through B filter and 60sec exposure length.  Errors were produced using GSC catalog and returned matches based on 8 stars.  Matching on UCAC2 catalog produced normal match (based on 80 stars).

One of two images that produce false match using GSC catalog

CCD Image  60s exposure, B filter 2005-09-30 22:30h UT (#95068)

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M37 Mosaic Attempt

Two attempts were made to acquire mosaic sets over M37 and surrounding area. Both times the attempt was aborted due to bad star trailing.  
The reason appeared to be due to buffetting of the scope by gusts of wind.  (The target was positioned farily low in Eastern sky and other potential reasons such as poor RA drive response due to poorly balanced scope can not be completely ruled out,  however since it was possible to record a CBVR set of centre of M37 ok, this would seem unlikely). 

Aborted attempt of Mosaic over M37

CCD Image Mosaic (3x4) 30sec exposure, R Filter 2004-09-30 (#95057-63)

Analysis of one of trailed images from mosaic attempt

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Variable Star Patrol Tool

3 NSV star fields were re-imaged during the session, and compared against baseline images taken during a previous observing session.
Sky transparency was poor, this can be seen below by comparing the image of NSV 13384 starfield (left) with its baseline image (right). Despite this the power of the Excel tool for comparing instrumental magnitudes from two images is shown in the graph. The red diamond 'anomoly' with 0.5 mag difference from baseline is a false alarm and is due to the star being right at the edge of the frame in new image, thus giving an invalid magntitude. The patrol sequence was aborted because cloud began to develop.   

New Image - 2005-09-30		Reference Image - 2005-09-18
30s, C Filter 2005-09-30  22:49h UT (# 95092)		30s, C Filter   (# 94019)

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