#1  
Old 31-12-2010, 12:24 PM
kustard's Avatar
kustard (Simon)
Great Sage == Heaven

kustard is offline
 
Join Date: Sep 2009
Location: Melbourne, Australia
Posts: 734
Observation Report - 30/12/2010

I am loathe to call this an observation report as I didn't really have any set objects to view, I was more than happy to just have the scope out and I didn't really record anything with great detail.

Anyway, here is the link and comments appreciated as usual

http://astronomy.kustard.org/?Astronomy_Blog:20101230
Reply With Quote
  #2  
Old 01-01-2011, 01:29 AM
ngcles's Avatar
ngcles
The Observologist

ngcles is offline
 
Join Date: Dec 2006
Location: Billimari, NSW Central West
Posts: 1,664
Hi Simone & All,

Yep, Fomalhaut was too close to Zenith to align on early in the evening. Using the 'scope in Alt az mode, aligning on anything close to zenith is a likely to produce pointing errors. If using an Equatorial, aligning near the SCP is similarly a bad idea for the same reasons.

All these systems use optical encoders that have a certain number of ticks per revolution. What I want you to do is imagine these ticks on the aximuth axis projected out into the world -- out to the horizon. See how far apart they are spaced? Probably about one tick per few arc-minutes.

Now imagine in your minds-eye every one of these ticks at the horizon has a line connecting it to the Zenithal point. In your minds-eye again, do you see these lines converging as their altitude approaches zenith ? Near zenith they get very, very close to each other (only arc-seconds apart) and then finally converge. If you align on an object near zenith, the 'scope can move through perhaps a three dozen ticks on the az encoders with the object only moving a few arc-minutes in the eyepiece. Trace those 3 dozen ticks back in the direction of the horizon and you can see they diverge till they are in total maybe a couple of degrees apart -- this is probably a large slice of the error you saw.

Which ever system you are using in Alt-Az mode (or Eq mode for that matter), use two stars that are as far apart in azimuth as practicable -- at least 40-odd degrees, better 80-120 if possible. At 8.30pm (15-odd metres from you on the Argo Navis), I used Canopus and Hamal (Alpha Aretis) -- 90-odd degrees apart. Both were well above the horizon without being close to zenith (air-mass refraction error is therefore negligible -- zenithal error therefore negligible) -- and they are at quite different altitudes above the horizon. This means your alignment could be described as "well-sampled" and more likely to produce better accuracy. I didn't need to re-align all night. For me, every object landed comfortably inside a 12mm TII Nagler field (27 arc-mins). If you've picked an area of the sky to concentrate on (for example say Vela, Puppis, Canis Major, Lepus Orion etc) then alignment stars one on either side of this area will work particularly well -- like Canopus and Hamal for example.

Yours will do the same I'm sure -- just follow the advice above. If someone else is reading this and has a Eq mount, just substitute Dec and RA for Alt and Az


Best,

Les D
Reply With Quote
  #3  
Old 01-01-2011, 07:29 AM
kustard's Avatar
kustard (Simon)
Great Sage == Heaven

kustard is offline
 
Join Date: Sep 2009
Location: Melbourne, Australia
Posts: 734
Yeah makes sense Les, I would say the program that I used to give me best pairs for alignment isn't taking that into account, just giving you which has the best figures then it leaves it up to you to decide which to use.

I was going to start to observe in specific areas so you suggestion of alignment stars either side of your area of interest is a good idea.



ps: I'll get you for that 'e'
Reply With Quote
  #4  
Old 01-01-2011, 08:19 PM
Paddy's Avatar
Paddy (Patrick)
Canis Minor

Paddy is offline
 
Join Date: Jun 2007
Location: Strangways, Vic
Posts: 2,214
Not having an observing list doesn't seem to have stopped you collecting some good observations. A very interesting read. Shame about the batteries in your recorder. I've had that happen and felt quite flat footed.

Sorry to hear about your back problem - it's very good that it's resolved but these things can be quite scary. Good to see you posting reports again.
Reply With Quote
  #5  
Old 05-01-2011, 10:01 AM
ngcles's Avatar
ngcles
The Observologist

ngcles is offline
 
Join Date: Dec 2006
Location: Billimari, NSW Central West
Posts: 1,664
Missing NGC 2298 ...?

Hi Simon,

Just re-read your report and you are missing NGC 2298 (I remember looking at it through your 'scope) G.C in Puppis.

Just though you ought to know.


Best,

Les D
Reply With Quote
  #6  
Old 05-01-2011, 04:04 PM
kustard's Avatar
kustard (Simon)
Great Sage == Heaven

kustard is offline
 
Join Date: Sep 2009
Location: Melbourne, Australia
Posts: 734
Thanks Les, I knew there was a globular in Puppis we were looking at but couldn't remember it
Reply With Quote
  #7  
Old 06-01-2011, 10:33 PM
michaellxv's Avatar
michaellxv (Michael)
Registered User

michaellxv is offline
 
Join Date: Oct 2009
Location: Adelaide, Australia
Posts: 1,581
Sounds like you had a great night.
Thanks for the alignment lesson too, makes perfect sense when it's explained properly.
Reply With Quote
  #8  
Old 07-01-2011, 12:38 AM
Suzy's Avatar
Suzy
Searching for Travolta...

Suzy is offline
 
Join Date: Jan 2010
Location: Brisbane, Australia.
Posts: 3,700
Thanks for sharing your report with us, Simon. Sounds like you had a great night with that bag of "goodies". Take care of that back and I hope you have a quick recovery.
Oh, and thanks to your post, I now note to myself: When I start to use my new voice recorder, have spare batteries with me!
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 12:25 AM.

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