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From: TerryMoselaol.com
Date: Tue, 6 Dec 2005 20:02:46 EST
Subject: Radio, Lectures, Lidl Scopes

Hi all,
 
1.  Next Sunday's (11 Dec) programme in Mary  Mulvihill's new series Left 
Brain/Right Brain on RTE Lyric FM, is  about the Aurora -- featuring solar 
physicist Dr Peter Gallagher and artist Anna  Hill and sound recordings from the 
Cassini craft of an aurora at Saturn,  among other things. More info at: 
www.rte.ie/lyricfm/invisiblethread/. 
 
2.  Don't forget the lecture on Deep Impact at QUB at 7.0 on Wed 7/12,  in 
the Larmor Theatre, Physics Building; and Leo Enright's talk to the IAA  on Wed 
14/12, at 7.30 p.m., Stranmillis College, Belfast.
 
3. Re the Lidl offer on the ETX-70 GoTO telescopes for the March solar  
eclipse: I got this very helpful hint from Dave Grennan.
 
" From owning an ETX 70 I found that if you just  want to track the Sun 
during the daytime (with the usual safety measures in  place of course),  I found 
that the  two or three star align can be done without actually seeing those 
stars.  By lining the 'scope north and level as  accurately as possible, then 
select two or three stars which you know are above  the horizon and go through 
the align process,  Skipping the center star steps.  Once this is done you 
can use it to keep fairly good tracking on the  Sun.  I found that sometimes 
this  would be good enough to keep the Sun in the field for 10 minutes or more.  
This would make the ETX perfect for next  year's eclipse.  I've now sold on my 
 ETX but I still think they are a terrific little scope for  beginners."
 
Dave's tip could be the solution, and what I'll do is print out in  advance 
star charts of the sky as seen from Turkey at, say, 30 minute  intervals, 
before & during the partial stages of the eclipse. We could  establish the azimuths 
on the horizon fairly easily, and then by estimating the  altitude of the 
stars you could do rough alignments, and update them every so  often. That might 
be good enough to keep the Sun in the field of view during  totality - but 
don't blame me if it doesn't! 
   I'll be giving more advice on equipment for observing and  imaging the 
eclipse closer to the time, but if you want to buy the 'scope now,  at that 
bargain price, bear in mind that you might be able to use it OK as Dave  describes. 
Thanks, Dave.
 
   There's also a lot of more technical comment from Brian  Beesley, which 
follows: - It's your choice folks....
 
(Re the ETX) "The main problems appear to be (a) loads and loads of  backlash 
in the drive - 
the worm gear is only about one inch in diameter,  (b) poor contacts in the 
autostar cable (why oh why did they use a telephone  socket type connector) can 
and does cause random glitches where the 'scope heads  off in some random 
direction for what appears to be no reason at  all.
The drive is expensive to run when used with disposable  batteries but 
rechargeables (1.2v rather than 1.5v) don't really have the  voltage required and 
either give unreliable operation or run flat in next to no  time at all.

(Regarding daytime alignment) - Should not be a problem. You  don't actually 
need to complete alignment to view, or track manually, though  obviously "star 
following" needs reasonable alignment.
Actually  as a scope OTA [Optical Tube assembly] it isn't too bad - the worst 
problem  is that the focussing is too coarse for my taste. But I'd highly 
reccomend  detatching the OTA, throwing the mount in the skip and mounting on a 
_really  solid_ camera tripod instead. OK that's only altaz, and a decent 
geared head  (for slow motions) is expensive, but it's much more useable that  way.

However if you just want something to photograph the eclipse with  then I 
think you'd be better off with a 500mm catadioptric camera lens - you  should be 
able to get a decent one for 50-100 on eBay, the Tamron SP 500mm f/8  is 
particularly reccomended and (through adaptors) will fit just about any SLR,  
film or digital.
Regards, Brian Beesley"
 
My comment on that is: "If you don't want the 'GoTo', why pay 119,  when you 
can get an equal or better quality 70mm refractor by buying the  ordinary 
70mm Skylux for 39.99, complete with the equatorial mount and tripod?  ! OK, 
it's a longer tube, so it's less portable, but it is only 61cm (2  feet) long if 
you remove the lens hood, and it breaks down to  only 55cm (22") long if you 
remove the focussing mount (it's just held  in by 3 screws). That's very 
portable, and it's very light, so would easily go  in 'cabin baggage. 
   Also, I've heard that it's very hard to point the ETX any  higher than 
about 45 degrees if you have a camera mounted on it. That could be  awkward, as 
the Sun will be about 54 degrees elevation from S.  Turkey during totality! Any 
comments on that problem with the ETX?

Clear Skies,
 
Terry  Moseley

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