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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 ё50-ё100 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 ё119, when you
can get an equal or better quality 70mm refractor by buying the ordinary
70mm Skylux for ё39.99, 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
aol.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 ё50-ё100 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 ё119, when you can get an equal or better quality 70mm refractor by buying the ordinary 70mm Skylux for ё39.99, 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
