Project Polar align - using PHD as a star monitor rather than autoguiding!

[g__day (Matthew)]

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!

[iceman (Mike)]

Great idea, Matthew. I know Paul Russell has used k3ccdtools in the past for drift aligning.

[[1ponders] (Paul)]

It does make drift aligning much easier that is for sure. Sound pretty much the same principle as K3 Matthew, except K3 has a graphical representation as well as a numerical reading of Dec drift in arcsec/pixel.

[g__day (Matthew)]

I think when I last looked at it k3CCDtools was version 2 and it only supported web cams - I might have a new look at version 3 which supports Meade DSI's!

BTW

I plan to swap the DSI for a DSI pro soon - at which point I'll try drift aligning with a CCD on the main 9.25" OTA - versus the 80mm Meg - which probably suffers tube flex given the cheap rings holding it.

What's the best alignment you guys have achieved and what does that relate to in terms of arc seconds off the SCP or pixel drift after a really long shot guys?

Matt

[[1ponders] (Paul)]

Without sounding like I'm tooting my own horn here..... .....I had Gary Kopff help me with my argo navis at Lostock the other year (working out my mount errors using TPAS) and the pointing error in the argo navis was greater than my error in Az and my error in Alt wasn't much worse

Using my Orion ED80 and drifting using a ToUcam I have easily exceeded 10 min with less than 2 pixel drift at around 1.9 arcsec/pixel. The record at home stands at over 2000 sec.

K3 supports a wide range of cameras now from ToUcams, ATiK, Luminara, DSI, and DMK (I think).

[beren]

My August order from BinTel Losmandy dovetail side saddle bars and plates should arrive next weekend

Hope you have enough counterweights, that gear weighs a bit

[leon]

You guys are far to clever for me, that's for sure.

Leon

[g__day (Matthew)]

Originally Posted by beren

Hope you have enough counterweights, that gear weighs a bit

Yeah - I think I'll order another 7.2 Kg White Vixen weight - until then I have two 5kg Skywatcher weights I have re-bored to fit. I reckon the Atlux coul manage 24kg of weight on the bar (which is fairly short) from how its handled 14 kgs so far.

[beren]

Took me about 23 kGs to balance my OTA's {C9.25/90mm refractor} with the DSBS loaded. Tricky to get everything balanced right and a little scary too

[jase (Jason)]

Not sure if you've ever used PEMPro v2 for drift aligning with a camera. Very easy and accurate. My platesolves from PolarAlignMax indicate I'm approx 20 arcsecs Alt. and 30 arcsecs in Az off polar alignment. This took considerable time to get this level of accuracy so would only be worth it for permanent set ups.

[g__day (Matthew)]

Not bad at all Jase!

Well after the other nights effort - a re-run of MaxPoint tells me I', 1 arc minute and 32 arc seconds East of teh SCp amd 49 arc seconds high - so a definite improvement!

PEMPro V2 is on my watch list - but at present I think it only supports webcams or Meade DSI via MaximDL - so while my trial of MaximDL proceeds I may just give it a go!

Looking at the Website PEMPro V2.1 is due out soon - and this should support the Meade DSI - might wait a few weeks more.

Meanwhile I stacked 4 by 480 second shots and 2 by 960 second shots with a 6 minute dark frame to get this:

[JohnH]

Hi G,

Looks like the alignment and tracking are good - you might benefit from improving the focusing though as the image looks a little soft to me, could be the processing though.

BTW For guiding/aligning you might want to check out Guidemaster (http://www.guidemaster.de/index_en.asp)- it's free - shows you real time drift graphically and has Polar Align routines buit in too...

[g__day (Matthew)]

Agree on the focusing - I haven't refocused for 6 months!

Guidemaster seems to be for webcams only - not Meade DSI from the documentation?

[JohnH]

Sorry missed that response, Guidemaster supports more than webcams, the QHY5 that I use is a usb2 ccd and works as do many others however the Meade DSI is not on the list yet (unless there is a DirectX or VfW driver for it) - sorry!