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Kevin Phillips

Sep 26, 2021, 2:07:36 PM9/26/21
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This photo of M39 was taken from Kennely. I used 4 inch refractor f/9. Eq5 mount on a pillar. I used zwoISA294 cooled to -15. 1 min exposure x140. Also flats,dark flats and flats. Guided using Altair 130m mono camera guding was less than  0.40 second. There was a lot of dew so after 140 frames we finished. Thank you Willlam for helping out with the guiding. 


William Bottaci

Oct 6, 2021, 6:45:01 AM10/6/21
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Hello Kevin, so this came out well. Nice small stars, well focused, no tracking errors, and against the backdrop of the Milky Way.
There was exceptional dew, we had to use the hair dryer part way through, but on other nights it's been more or less dry. The dew shield is a foot long as can be seen in the photograph but that only went so far on such a damp night.

Lights, Darks from library, Flats, Dark Flats. No Bias frames as this is a CMOS sensor, not CCD.

The trick to good guiding is good focusing, as PHD2 expects stars to be tiny. Also, whilst PHD2 is easy to use once set up, there is some initial calibration that should not be skipped; that's the other trick.

Apart from that it was all your own work. I did a bit of guider focusing; oh, and the hairdryer bit...

Another detail of possible interest, you used a Bahtinov mask for focusing the telescope. It gives assurance and saves time. Trying to focus when the image updates every 2 seconds and you have to wait for it to be acquired and the telescope to settle, going back and forth (you have to defocus to see if the focus was actually good - not productive :).

As Tim has said, it's worth going back to processing as there are lots of options, none easily identified as optimal - a witches brew. Star colours are not well pronounced, but that is just one of many processing options so can be revisited; the important thing is that the images are of good quality.

Well done, and thanks for sharing, William
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