Re: ATM New to list

[akelly@ghgcorp.com (Albert F. Kelly)]

>I am new, and have enjoyed reading your posts the last 24 hrs.  I have
>entered into this hobby, quite by accident.  While attending a garage sale I
>noticed a telescope for sale and decided to buy it on impulse.  The owner
>happens to be my employer and had bought the telescope 20 years ago for her
>husband's birthday.
>
>The scope is made by Edmund Scientific and is a 4.25" Newtonian Reflector.
> It is mounted on a solid equatorial mount with a clock drive.  Eyepieces
>included are 1" Kellner, 1/2" Ramsden, and a 2-3X Achromatic Barlow (-47mm
>f.l.).  There is also a finder scope mounted.  For $75 I couldn't pass it up.
> I figured the optics were worth at least that, and the mount is very heavy
>and sturdy.

>I live in a rural area with a clear view of the southern hemisphere from my
>deck (northwestern part of Illinois).  Is this enough telescope for starting
>out?  Since the scope is 20 years old, are there any suggested optics that
>would enhance its performance.  Eventually, Can I convert it to a 6 or 8 "
>reflector, using many of the existing components?

Hello Craig,
        Welcome to the world of amateur astronomy!  The scope you bought
sounds like a great starter outfit for you.  I would have given my eyeteeth
for such a scope about 40 years ago when I was starting out.  You have an
optical instrument that has an "eye" that is 17 times the diameter of your
own dark-adapted eye, allowing you to gather 289 times as much light.
Assuming that your 4.25" mirror has a focal ratio of f10 (42.5" focal
length), your Kellner and Ramsden eyepieces will allow you to magnify those
bright images 42.5 and 85 times, respectively.  You will have a lot of fun!
        There are a couple things you need to check, the quality of the
aluminum coating on the surface of the mirror and the alignment of the
optical elements ("collimation").  If the scope has been kept indoors and
covered when not in use, the coating is probably still OK for beginning use.
Just look closely at the front surface of the mirror to see if it is
"blotchy" looking and/or seems to allow much light through from the backside
(some is to be expected).  You can shine a flashlight onto the back of the
mirror and look to see how well that light can be seen from the front.  If
the coating still has sufficient integrity to keep all but 25-30% of the
light from coming through you are OK for now.  Collimation is a fine art and
members of your local astronomy club (look them up!) can help you.  For now,
just take the eyepiece out and look into the focuser of your telescope so
that you can see the secondary (flat diagonal) mirror and the reflection of
the primary mirror in it.  Put your eye close enough to the focuser (and
rack the focuser in, if necessary) to allow you to see the whole primary
mirror within the secondary mirror.  Try to keep your eye centered in the
focuser.  If the edge of the primary mirror seems reasonably concentric
within the  secondary mirror and the reflection of the secondary mirror
seems reasonably centered in the primary, then you ought to take the scope
right out and use it!  Fine tuning is for later.
        If the scope can't pass these tests, within reason, then write us
all about it and get in touch with that local club.

>Also, the setting cirles have a rubber grommet fitting.  They are a tight
>fit, but can be turned by hand.  I'm not sure what the fixed settings should
>be for R.A. and declination?  Help!

        The declination setting circle will have a fixed setting and should
remain unmoved after proper adjustment, which it may now need since it
sounds as though you have turned it...:)...!  The RA circle or its pointer
should be adjustable so that it can be set at the beginning of each
evening's observing session.  
        After aligning the RA axis so that it is parallel with the axis of
the Earth ("polar alignment"), the RA setting is accomplished by centering a
star with a known RA coordinate in the eyepiece and setting the RA pointer
to that coordinate.  As long as your RA drive motor is running, this setting
should not have to be changed.
        I just sort of zoomed through "polar alignment," didn't I?  This is
mandatory if you are really going to use those setting circles.  It really
is not much of a black art when you have done it a couple times and I once
again highly recommend those local club members.  Let me know if you want an
e-mail dissertation, but in person is better!
        Your declination setting circle should read 90 degrees (actually
89.2) when the mount is polar aligned and the north star (Polaris) is in the
center of the eyepiece view.

        If the scope will give you a decent image of a distant tree right
now just take it out and start using it without worrying too much with all
the above at first.  Right now, Jupiter is bright and beautiful in the SSE
sky as soon as the sun goes down!

Al Kelly