g__day
29-10-2007, 12:19 AM
By hook or by crook - house blocking East and dome roof obscuring straight up - I was determined to improve polar alignment better than 30 arc minutes!
So with PHD running from a Meade DSI plugged into a Megrez 80mm I managed a fair bit of success - by the end of the night I was getting a 2 pixel drift in 6 minute shots! Maxpoint on a 42 star model showed elevation was 3 arc minutes low after doing the elevation drift align. The mount was 20 arc minutes West of the SCP too according to this model.
With the camera aligned so that West <-> East movement (RA) was horizontal and North <-> South (DEC) was vertical I realised you could simply run PHD uncalibrated as a star monitor.
By this I mean select a star and click on it. A box appears around the star and you get an X, Y readout like 234.5 545.6, updated every second. With my seeing stars could jump +/- 0.5 pixel so I simply averaged things out this run.
So without enabling autoguiding and ignoring the X (RA) movement) I simply took the Y co-ord to give me real time DEC. Using DSLR Shutter as a stop watch I set it for 240 second shots. Into Excel, I simply keyed in starting and ending RA and DEC and tracked their differences. After each run I'd adjust the mount, re-centre the star and try again until DEC drift was minimal.
Even with seeing limiting the accuracy of the tuning - this finally got me to the point where both shots about 30 degrees above the Eastern horizon and secondly shots high up - showed very little drift in DEC.
I ended up then turning guiding on and snapped Orion and the Tarantella for up to 9 minute runs - guided. Pointing, tracking and guiding was great. I finished at 5am - else I would have re-calibrated my ending position in MaxPoint to see see how well it though I'd captured alignment.
I was going to re-calibrate my sky model tonight - but a power cycle showed me my UPS has a flat lead battery - and it won't start without a charged battery - so its bed for me (and a new battery and a 1000VA UPS $212 from Jaycar) until hopefully tomorrow when I'm back in action.
My August order from BinTel Losmandy dovetail side saddle bars and plates should arrive next weekend (hope it attaches easily to my mount) - then I'll really be in action!
So with PHD running from a Meade DSI plugged into a Megrez 80mm I managed a fair bit of success - by the end of the night I was getting a 2 pixel drift in 6 minute shots! Maxpoint on a 42 star model showed elevation was 3 arc minutes low after doing the elevation drift align. The mount was 20 arc minutes West of the SCP too according to this model.
With the camera aligned so that West <-> East movement (RA) was horizontal and North <-> South (DEC) was vertical I realised you could simply run PHD uncalibrated as a star monitor.
By this I mean select a star and click on it. A box appears around the star and you get an X, Y readout like 234.5 545.6, updated every second. With my seeing stars could jump +/- 0.5 pixel so I simply averaged things out this run.
So without enabling autoguiding and ignoring the X (RA) movement) I simply took the Y co-ord to give me real time DEC. Using DSLR Shutter as a stop watch I set it for 240 second shots. Into Excel, I simply keyed in starting and ending RA and DEC and tracked their differences. After each run I'd adjust the mount, re-centre the star and try again until DEC drift was minimal.
Even with seeing limiting the accuracy of the tuning - this finally got me to the point where both shots about 30 degrees above the Eastern horizon and secondly shots high up - showed very little drift in DEC.
I ended up then turning guiding on and snapped Orion and the Tarantella for up to 9 minute runs - guided. Pointing, tracking and guiding was great. I finished at 5am - else I would have re-calibrated my ending position in MaxPoint to see see how well it though I'd captured alignment.
I was going to re-calibrate my sky model tonight - but a power cycle showed me my UPS has a flat lead battery - and it won't start without a charged battery - so its bed for me (and a new battery and a 1000VA UPS $212 from Jaycar) until hopefully tomorrow when I'm back in action.
My August order from BinTel Losmandy dovetail side saddle bars and plates should arrive next weekend (hope it attaches easily to my mount) - then I'll really be in action!