Go Back   IceInSpace > Equipment > Software and Computers

Reply
 
Thread Tools Rate Thread
  #1  
Old 21-05-2017, 09:41 AM
skogpingvin's Avatar
skogpingvin (Bill)
Registered User

skogpingvin is offline
 
Join Date: Mar 2017
Location: Kew East, Melbourne
Posts: 75
PHD2 drift graph - some sort of colinearity?

Hi all, Bill here

I'm still pretty new to this, and there are lots of things I don't understand, but like all the other noobs, I'm ploughing through anyway.

Last night I set up my NEQ6 in the back yard, and only after I'd levelled it carefully did I find that a tree had grown slightly and was obscuring Sigma Oct. Bummer. Well, rather than move and re-level I thought I'd try drift alignment using the PHD2 tool.

It seemed to go OK, and I got reasonable tracking afterwards (well, reasonable for a tripod set into soft dirt), but one of the graphs I got during the operation interested me. From memory I was adjusting the altitude, looking west, but not terribly close to the horizon as there's a house in the way.

As you can see I hadn't quite nailed the adjustment yet, 'cos the red line is trending down, but that wasn't the bit that was weird. There's clearly some negative relationship between Dec and RA in the graph. I suspect that it's multicollinearity (that is, a third factor causing the two lines to move in an apparent relationship).

Does anyone know what might be the cause? It might be the fact that I was sighting high (prob 30 deg) over the west horizon, so not in the ideal spot, meaning that the star drift was diagonal rather than perpendicular to the axis - if you know what I mean?

(also, the graph is telling me I had a polar alignment error of 3.75. Is that arc minutes? While that wasn't the end of my drift alignment exercise, what is considered good for a portable setup?)

Thanks!
Attached Thumbnails
Click for full-size image (drift.JPG)
47.9 KB82 views
Reply With Quote
  #2  
Old 21-05-2017, 09:49 AM
skogpingvin's Avatar
skogpingvin (Bill)
Registered User

skogpingvin is offline
 
Join Date: Mar 2017
Location: Kew East, Melbourne
Posts: 75
By the way, is there a forum where people can submit PHD2 log and find out from the experts what it's telling them?
Reply With Quote
  #3  
Old 21-05-2017, 11:59 AM
tlgerdes's Avatar
tlgerdes (Trevor)
Love the moonless nights!

tlgerdes is offline
 
Join Date: Mar 2009
Location: Sydney
Posts: 2,284
I haven't every played with PHD2 (I only use PHD1) but the principle is the same, ignore the blue line during drift alignment!

The blue line means absolutely nothing to the drift alignment process.
Reply With Quote
  #4  
Old 21-05-2017, 03:10 PM
AndrewJ
Watch me post!

AndrewJ is offline
 
Join Date: Mar 2006
Location: Melbourne
Posts: 1,905
Gday Bill
You really need to post the raw logs when asking things like this
as they contain a lot more data.
The colinearity you see can occur if the camera isnt at a perfect
0,90,180,270 deg orientation, and you didnt run a full calibrate before drifting.
Sooooooooo, did you do a calibrate????

Andrew
Reply With Quote
  #5  
Old 16-06-2017, 09:59 PM
skogpingvin's Avatar
skogpingvin (Bill)
Registered User

skogpingvin is offline
 
Join Date: Mar 2017
Location: Kew East, Melbourne
Posts: 75
Sorry it's taken me so long to get back to you on this.

I've probably got the log on disk, but it was more of an interest question rather than anything needing accurate analysis. I think the suggestion of the camera being out of alignment with the axis of the mount might be credible.

At the moment the learning curve is very steep and I'm struggling with a number of different things, the most depressing is the fact that I haven't got any dew straps (they're in the snail mail from Dew-Not in the US), so imaging is out of the question at the moment.

Thanks for the suggestions!
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 03:02 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Advertisement
Bintel
Advertisement
Testar
Advertisement