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Old 22-06-2019, 11:41 AM
Startrek (Martin)
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PHD2 Guiding Troubles

First night of imaging in Sydney since the recent spell of rain and cloudy nights over the past few weeks
Fitted new primary mirror springs to my 6” f6 newt plus cleaned both mirrors.The original GSO springs finally gave in after only 2 years. I bought the new springs custom made from Better Springs ( small business) at Winston Hills Sydney , wow what a difference they make

Anyway picked a nice easy target NGC 5139 Omega Centauri up nice and high to capture before the moon got up to high later in the evening
Started PHD2 guiding which has been set on Auto Calibration for the past 8 months and has been working really well in all sorts of conditions
Guiding started off ok at 1.20 arc sec error but after a minute or two kept getting worse 1.50 then 1.90 then 2.20 and so on
Stopped guiding , disconnected , reconnected , chose another guide star then started Guiding again. Went ok for a while then same thing happened 1.40 then 1.80 then 2.30 then 2.60 and so on
I thought what’s going on ?? Sky is clear , Jetstream low , no moon around , no wind , conditions ideal for guiding , stopped guiding again
Ran the Guiding Assistant which took 15 minutes and it said problem with backlash try lower Min Mo settings settings and re calibrate to clear backlash
Then the “penny just dropped” I remember taking the guide camera out of the guide scope to clean the guide scope front lens and broke the golden rule. If you Auto calibrate you can’t move or rotate the guide camera as it affects calibration. Obviously I reinstalled the guide camera not in the exact same position as previously.
So I unchecked “Auto restore calibration” in Guiding ( Brain) performed a normal calibration, guiding started again at 1.20 arc sec error, increased a bit and settled at around 1.35 to 1.40 for the rest of the night
Problem resolved !!
I think from now on I will do a normal calibration when using PHD2 and forget the Auto calibration which worked well for so long but has it’s risks
Anyone experienced the same problem ?
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Old 22-06-2019, 01:46 PM
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The_bluester (Paul)
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I always have it ticked, just you have to remember to recalibrate if you change something.


I have only made that mistake once and found it much the same way, in my case I removed an adapter and the camera was 180 degrees away from where it was previously so it was pretty obvious, pretty quickly.
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