POLAR ALIGNMENT TIP AND ETX-70AT FINDERSCOPE THOUGHTS Last updated: 19 Janaury 2003

Sent:	Sunday, January 19, 2003 5:27:48
From:	AlanM@peoplepc.com (Alan McDonald)
I saw your question on the finderscope, and thought I'd offer some
thoughts on it.  I have both an ETX60 and a 125.  I bought the 60 first,
and then added the finderscope to it, and I must say it made using the
scope a heck of a lot easier, at least until I learned how to align it
easily.  Now I pretty much only need to use the finder scope only for
terrestrial viewing - but since I have it, I still use it for set up.

Why you don't need the viewfinder on the ETX60/70:
The 60/70 is very easy to get into home position for alt az viewing
because the field of view is so wide.  To do so accurately and quickly I
do the following:
1) I make sure the base is level before I start the process (I do this
with the tripod base before I even mount the scope).
2) Then I find Polaris by aiming the tube to the right altitude using
the setting circle on the altitude axis (make sure that it is set
correctly - it should read zero when the tube is level) and lock the Alt
axis, then swing the scope in azimuth to find Polaris - all this takes
just a few seconds.
3) Then I lock the Az clamp and use the Autostar to place Polaris
correctly in the field of view to get the scope aimed dead north (see
Clay's "Kochab's Clock" at
http://www.weasner.com/etx/ref_guides/polar_align.html, and place
Polaris about 1/4 of the way into the FOV with the 25/26mm eyepiece per
the proper orientation - remember things are reversed left to right).  I
then slew the scope down and check for level.
4) This, coupled with having your exact latitude and longitude
(http://www.geocode.com/modules.php?name=TestDrive_Eagle) and the exact
time (http://nist.time.gov/timezone.cgi?Eastern/d/-5/java) keyed into
the Autostar, and the alignment stars will pop up almost dead center in
the 25/26mm eyepiece every time.  No need for a view finder!

Why the viewfinder is nice on the ETX 60/70:
1) If the viewfinder is correctly aligned to the scope, it is even
easier to properly place the scope due North by checking this handy web
based feature before I begin - itsa.ucsf.edu/~rpb/finder.html -
If you make your viewfinder look like the picture on this site, you'll
be done in no time.
2) It is also nice for quick viewing where you don't want to bother with
alignment - like the moon in early evening before dark.  I find it in
the viewfinder, and use a higher power eyepiece, and either fake
alignment first to keep it close, or just manually track the scope.
3) Manually tracking satellites - since it is such a pain to update
satellite data in the 494 autostar, I would use my ETX60 to see the ISS
manually (find opportunities through http://www.heavens-above.com/), and
the viewfinder is key to this.  I use the higher power eyepiece (I use
the Series 4000 6.4mm) with a barlow, and I lightly clamp both drive
axis so that the scope will stay put when left alone, but can be moved
easily by hand.  I then find the ISS in the viewfinder and place move
the scope so that the ISS will drift through the eyepiece, and then move
to the eyepiece to watch it float through the eyepiece.  I then go back
to the viewfinder and repeat.  It works pretty well! (Note: I now use my
125 for this in automatic tracking due to the ease of preparation and
the higher resolving power - I could never bring myself to pay for the
506 cable).

The best "viewfinder" for the ETX 60/70:
Since I also have an ETX 125, I bought the 40mm eyepiece for the bigger
scope.  Out of curiosity, I put it in the ETX 60, and was blown away by
the view!  This turns the scope into an awesome viewfinder for itself!. 
With the 40mm eyepiece, it is basically an 8.75 x 60 (70 in your case)
optical instrument with a 4.9 degree FOV - that blows away the dinky
5x25, 8 degree viewfinder (there is no crosshair, but you are looking
through the actual scope anyways, so the center is the center).  Meade
states that the 32 and 40mm eyepieces are not to be used in the scope,
but I think they are wrong (they probably just say it due to the low
power - I can focus my scope just fine with the 40mm Series 4000).  The
40mm is not parfocal with the other eyepieces, so you'll need to
refocus, but I think it is worth the effort.

The Meade 5x25 viewfinder is really only good for centering objects -
the optics are pretty poor, and everything more than a quarter of the
way out from the center is blurry (true in both of my viewfinders).  But
the 40mm is crisp to the edge of the almost 5 degree field of view. 
Having both items is clearly best, but with what I know now (plus I knew
I would get a long focal length scope to complement the short focal
ETX60 someday), I think the money is better spent on the eyepiece than
the viewfinder - you won't spend much time "enjoying" the view in the
viewfinder, but you probably will in the 40mm eyepiece.  Unless you plan
to do much terrestrial viewing, or manually track satellites, the 40mm
is probably the best way to go.  Orion's sword is awesome in this set up
- you can see the whole thing!  There is a lot to be said for wide field
viewing, and these scopes are pretty good at it.

By the way, watch e-Bay for these kind of items - I've bought almost all
of my accesories this way, have saved a bundle (40mm eyepiece for $70
shipped vs $105 new), and have always been satisfied.

I think that page is great for either polar or Alt-Az alignment, as it
shows how far off north the "north star" really is.  The 55 arcmins is a
total disaster in the ETX60/70, but it is killer in the ETX 125 (that is
wider than the whole field of view with the 40mm eyepiece!).

I find that when I take great care in setting up the home position with
the ETX60, I don't even have to bother finding additional alignment
stars when one is blocked by a tree (I'm surrounded by them at my house
- love it during the day, but not at night).  Just finding one of them,
which is usually dead center, is enough for perfect alignment with the
wide FOVs of that scope  It is a whole other matter in the 125, as
higher power eyepieces yield FOVs less than 25 arcmins across.

By the way, I now have a 497 autostar for my 60 - I bought it for $70
shipped off e-bay (slightly used), which is only $30 more than the 506
cable.  I rationalized it as a backup for my 125, with immediate use in
the 60, and it is so nice to have a common interface with both scopes. 
It is nice to have instant access to any slew speed, and it is really
nice to be able to enter those Messier numbers directly.

I am amazed at how much more I appreciate the 60 now that I have the 125
- the big scope takes planning to use, due to cool down times and all,
but I can pretty much grab the 60 and go out in the cold (I'm in
Michigan) with only a few minutes needed for reasonable cool down (the
objective cools pretty fast, and there is no large primary buried in the
tube holding all that heat).  I just wish it had the added light grasp
of the 70!

Alan

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