3rd-4th Oct 2005 - A SERIES OF IMAGES REQUESTED BY ADULT EDUCATION CLASS STUDENTS

5th Sept 2005 - FLAT FIELD CORRECTION

The Bradford Telescope Galaxy camera suffers from vignetting of the field as can be seen in this stretched image. This is normally corrected in processing by dividing the image by a flat field (an image of an evenly illuminated area) Currently however there is no means of taking a flat field. I was fortunate however that for one of my jobs the telescope took an image of what I presume was a cloudy sky in error. This proved to be a reasonably good flat field as can be seen in the corrected image below.

The flat field was rather noisy so it was filtered before applying it. This means that the small dirt specks are not corrected for but the severe radial gradient is well compensated for with only a slight linear gradient left.

The raw flat field FITS file (zipped) can be downloaded for your own use by right clicking on the link below.

RAW FLAT

Completion Time

23:33 on Wed 15 June 2005

NGC 6946 with supernova sn2004et marked.

A much better image than previously with good focus in this unfiltered image. Some sign of star trailing. Brightness of the supernova was measured at +16.4 in this image (CCD unfiltered using AAVSO comparison star V magnitudes)

Completion Time

00:24 Thursday 16 June 2005

An additional unfiltered frame was taken and combined with the RGB frames to make an LRGB image. The L exposure was deliberately kept short to minimise the effect of tracking errors. Other than combining and histogram adjustments, no further processing has been done. The smearing on the brighter stars is caused by leakage into adjacent pixels. (This is because the CCD camera does not have antiblooming so it has good linearity for photometric work)

Completion Time

04:12 Wednesday 15 June 2005

 M27 the Dumbell Nebula. 3 separate red green and blue images were taken and combined. The blue and green were adjusted to produce a teal blue colour of the OIII region and the red increased to bring out the H alpha regions (Red +10% Green-15% Blue+15%) You can see an image of this object taken with my telescope here

The pointing and focus problems appears to have been solved. There is some star trailing caused by a tracking error in RA (approx 6 pixels in 3mins) Vignetting is still apparent. (A flat field correction is needed). The in focus black marks are still present. Some are common to all three colours, others are different.

 Original Red, Green and Blue images 25% original size but otherwise unchanged from the original FITS file

Completion Time

00:17 on Tuesday 7 June 2005

This is of Galaxy NGC6946 home to supernova sn2004et which exploded September 2004. (marked) It has faded considerably since then and is approximately mag +16.5 in this image. South is up in this image. You can see an image taken with my own telescope here

This image was taken before a summer service of the telescope which took place 12th June 2005

Pointing error was approximately 5 arcmin in RA. The telescope was suffering from focussing problems at the time. A colour image was taken (converted to greyscale) as the focus was reported better in this configuration but it was still an obvious problem. Other problems are vignetting and strange black marks which appear to be in focus.