RASC Hamilton Beginner Tips: Computerized Mounts - How-To Primer -Celestron (and others)

[Rick]

Hi Gary,

 

That's a very good write up with an abundance of information.

 

Rick

 

  _____  

From: astronomers [mailto:astronomers-bounces at hamiltonrasc.ca] On Behalf Of
Gary Bennett
Sent: Monday, March 24, 2014 9:55 AM
To: astronomers at hamiltonrasc.ca
Subject: RASC Hamilton Beginner Tips: Computerized Mounts - How-To Primer
-Celestron (and others)

 

Unfortunately I won't be able to be at the Telescope night - on Monday,
March 24th. If weather means postponing until Tuesday, then I can be there
for then.

 

One of our members was looking for help learning how to use a CPC1100
computerized telescope. So I have put together some helpful hints that I
learned having owned a CPC1100 for 5 years. At the end of this "article" I
will offer some tips specific to a CPC100, but most of these tips apply to
many different computerized telescopes. After AstroCATS is put to bed I will
have some time to post this as an article (with photos) on our website.

 

For the benefit of beginners, I should warn you that amateur astronomers,
just like religion, come in many flavours. To many, having electronics of
any kind on a telescope is "Blasphemy". This article doesn't not attempt to
promote one deity over another, but rather will help those who own, or are
considering purchasing a computerize mount.

 

Termanology: Telescope and Mount are used interchangeably. Even if you have
a "Fork-Mount" where the telescope is permanently attached, it still has a
mount. Those types of telescope are typically referred to as "ALT/AZM" vs. a
"GEM" (German Equatorial Mount). Some "Dobsonian" telescopes also have
go-to/push-to computers. COMPUTER generally means the Hand Controller.

 

No Substitute For Experience: Beginners that own computerized telescopes
often conclude they have done something wrong because they are looking
through the telescope but are not seeing what they expected to see. More
often than not, they have done the set-up and alignment procedure perfectly
and their telescope is pointing at exactly the right place. The real problem
is inexperience in selecting an object to look at. Their computerized
telescope will offer to take a tour of the sky for objects that are
currently in view. Some of those objects are in fact, quite challenging and
require a trained eye to detect and interpret what they are seeing. Knowing
which objects make for enjoyable viewing comes with experience.

 

Observing List: Before heading out, make a list of objects that you would
like to see. The easiest way to do that is to consult a Planetarium program
that will show you what will be in view. It will also provide details of how
bright those objects are by displaying the "magnitude". Magnitude is a
measurement of brightness but like many things in astronomy, it is a
"backwards scale" where a low magnitude number is actually brighter than a
high magnitude number. For example, our Sun is -26.74, Jupiter is -2.3, M31
(Andromeda Galaxy) +3.5, M43 (Orion Nebula) +4.2, M51 (Whirlpool Galaxy)
+8.4. Magnitude is an "exponential scale" (just like the Richter Scale). For
example, a magnitude 1 star is approx 6 times brighter than a magnitude 2
star. A magnitude 1 star is 10,000 times brighter than a magnitude 10 star.
My math might not be correct, but you get the idea.

 

In a really dark sky (far away from cities) beginners should stick to
magnitude 9-10 or brighter. At the club observatory, stick to magnitude 6 or
brighter.

 

There are several FREE planetarium programs that you can download and
install on your PC. Stellarium is one of the most popular. You will tell it
your location and it will know time from the PC clock. You can advance the
time so that you can see what will be in view at 10:00 PM. Common objects
even display a colour image of the object. You can also set-up
"Field-of-View" indicators that use the specs on your scope/eyepieces/camera
to show you how big the object is relative to your scopes field of view. 

 

Completely Automated Mounts

Some of the computerized telescopes are now completely automated. If you
have one of these, you can stop reading now. These mounts have a built-in
GPS (time and location), electronic level and compass. They also have a
small camera used to fine-tune pointing accuracy. Meade and Celestron both
now offer this technology. When you turn the mount on, time and location is
taken from GPS. From the electronic level and compass it also knows where it
is currently pointed. It then begins an automatic alignment process where it
will slew to several stars. When the mount stops turning, it takes a image
with the built-in camera. A computer looks at the stars in the image and
compares them to a database. If the stars in the image are not quite in the
right place it then calculates the difference. It does this again for 2 or
more stars. 

 

I have only seen this done with the Meade brand. What I did NOT like is that
it also talks.... and talks, and talks, all night long, and you can't shut
it off! When you ask it to find an object, it starts yakking and entire
description. At first, it is a fun novelty, but quickly becomes annoying.

 

For owners of most Celestron Computerized mounts, there is now an accessory
called StarSense AutoAlign that can be attached and it makes your mount
completely automated. Using its small camera it will take care of
automatically aligning the mount in approx. 3 minutes!

 

My first tip: Telrad Finder "Scope". This is the best $ 60.00 you will ever
spend on the hobby. Forget "red-dot" and laser "finders", get a Telrad. It
is a "zero magnification" finder "scope". For owners of computerized
telescopes, it is only used during the initial alignment process and it
guarantees that once you put your eye to the eyepiece, the star you are
trying to centre on will be in view. It is a simple piece of glass that has
a red target projected by a light inside the unit. It allows you to see the
entire sky. A traditional "finder scope" has a limited field of view and it
is often difficult to see the star you are looking for.  That star might be
ever-so-close, but if it is outside the FOV you now have to guess which
direction, and how far, to move the scope. Beginners will find this
especially frustrating, so heed the advice and get a Telrad. Don't bother
with the other accessories, just the plain Telrad and mounting base is all
you need.

 

2nd TIP: Dew Control. To guarantee that you will have an uninterrupted
evening of viewing, you are going to need a dew heater and a way to power
it. Nothing attracts dew (or frost) faster than glass. Your favorite
astronomy dealer can equip you with the heater strip and controller. Do NOT
buy those "power tanks". For their size, the battery inside is quite small
and for the same amount of $'s buy a big honkin car battery to power it. A
heating element will drain those power tanks in less than 30 minutes. Buy a
car battery! Better yet, a Deep-Cycle Marine battery.

 

Typical Issues with Computerized Telescopes:

"Go-To" vs. "Push-To"

Both have a computer and "encoders" that keep track of how far, and in which
direction, the scope moves. A "Go-To" scope has motors but a "Push-To" is
human powered and the computer will tell you which direction to "push" and
when to stop.

 

New owners of computerized telescopes often share the same confusion about
the alignment process. Different Brands use slightly different techniques,
but in general, they all start out "very dumb" when you first power on. They
have no idea where they are currently pointed which is why you need to
perform "an alignment". The start of that process is telling the mount
exactly where you are (LAT/LON) and what time it is. 

 

As a beginner, one of the things that really confused me is the TIME issue.
All computerized mounts work in UCT time (formerly GMT). The computer will
ask you for the local time and then it will attempt to calculate UTC based
on where (on the Earth) you are located.  It will also ask you if you are on
"DST" (Daylight Savings Time). So, what is it asking? Does it want to know
if I am in a region that observes DST OR.... does it want to know if the
season is DST or not? If you get this wrong, your computer will be off by
1-hour and you won't get very far. THE ANSWER IS: What season is it?
Spring/Sumer, DST = YES  but Fall/Winter, DST = NO.

 

GPS Option:

Many brands offer an optional GPS device and some have them built-in. A GPS
will tell your mount the exact time and location (LAT/LON). If GSP is an
option, it will save you a lot of time and go-to accuracy will be much
better. Generally, it is worth the extra (typically $ 100 or so).

 

Some mounts also have a feature called RTC (Real-Time-Clock). It uses a
small battery to keep track of time. When you turn the mount back on, it
knows what time it is and it will also ASSUME that you are in exactly the
same location. But if you have a GPS unit, most mounts should have the "RTC"
feature turned OFF. Generally, use GPS or RTC, but NOT both! On Celestron
mounts, use the "Utilities Menu" to turn RTC OFF when using a GPS.

 

With  GPS, you need to wait for the GPS to finish syncing with the
satellites. BE PATIENT. It can be as quick as 1 minute or as long as 10
minutes. If you have moved the scope to another location it can take longer
because the mount looks for the same satellites it used the last time and if
it got moved, it takes a few minutes to find new satellites.

 

The Alignment Process: 

Most computerized mounts will ask you to centre 3 stars, 1-at-a-time, in the
eyepiece. Once that task is complete, the mount now knows where it is
pointed and from there can find any object in its database (typically 40,000
objects).

 

*         All mounts assume that the tripod is level, and in some cases, you
are pointed North. 

*         Some mounts only allow a specific list of stars that can be used
as alignment stars. They will typically display their preferred star and
once you select it, the mount will slew the telescope to where it thinks
that star is located. In the case of non-motorized "push-to" mounts, you
become "the motor".

*         Your job is to figure out which star is it trying to point to and
then slew the telescope until that star is centred in the eyepiece. A Telrad
will help you slew close enough to the target that you will see it in the
eyepiece. Typically, the star you are aiming for is fairly bright and will
be the brightest star in that area of the sky.

*         Slew Speed. Once the star is near the centre of the eyepiece it
slowing down the slew speed is helpful. RATE 5 is usually a good speed.

*         After centering the 1st star the same process is repeated using 2
more different stars. On some mounts the computer will suggest the next star
to use. There are times when the star is low on the horizon and blocked by a
tree or other obstacle. To skip that star and use another, the most common
method is to "UNDO" and then scroll through a list of alternate stars.

*         Fine Tuning Go-To accuracy: After alignment, you may find that the
objects are not perfectly centered. Most mounts will allow you to fine-tune
using a built-in "Align/Sync" utility. This involves slewing to the object
and then "syncing" that object. The computer will calculate the correction
that was made and use that intelligence to update alignment data. The end
result is that the next objects should be perfectly centered.

 

Celestron "NexStar" Mounts:

Almost all of the "fork-mount" computerized telescopes use a feature called
"SkyAlign". The advantage is that you can use any 3 bright stars to complete
the alignment process and you do NOT even need to know which stars they are.
Simply look in the sky and find 3 bright stars. 

*         Slew to the 1st star using the hand controller and centre it in
the eyepiece (a Telrad will make this easy).

*         Then pick another bright star and do the same. And then a 3rd
star.

*         Once you have aligned on 3 stars, the computer will calculate the
distance and direction that those 3 stars are apart from each other in the
sky, compare that to a database and deduce the names of the 3 stars you
chose.

*         For this to work, it will assume that you chose only the brightest
stars in view. In all, there are approx 40 stars that qualify as "the
brightest stars". In not-so-dark skies it will be easy because any star you
can see will be one of those 40 stars. BUT, in REALLY dark skies, all stars
tend to look bright and you will occasionally suffer "alignment failure" if
you happened to pick a star that is not on that list of 40 stars. Simply try
again using 3 different stars.

TIPS: My personal experience is:

*         If you have GPS, wait for the GPS to finish syncing satellites. Be
patient and wait until the hand controller says "CPC Ready"

*         Avoid stars close to the horizon

*         Avoid stars at the polls.

*         Avoid stars that are directly overhead (zenith).

*         Sometimes that star is really a planet. Most of the time it works
just fine, but it would be best to avoid choosing a planet as an alignment
star.

*         Pick stars that are in the same 1/3 of the sky. I found that go-to
accuracy did NOT improve by choosing stars on opposite sides of the sky. 

*         Speed counts. Don't dilly-dally with perfect star centering. A
Telrad will speed up the process immensely. The sky is spinning while you
are doing this task so the sooner you finish, the better.

 

Alignment Complete:

So now you're ready to start observing. What would you like to see? Doing
some homework (observing list) ahead of time will improve your enjoyment
immensely! The mount has a "Tour" feature but often times it will point to
things that are just way too dim unless you are under really dark skies. It
is best that you decide ahead of time what you would like to observe. 

 

Don't be discouraged by unimpressive objects. A little experience is all it
takes to find objects that are beautiful, and well suited to your optics and
sky conditions.

 

Enjoy!

 

 

 

Gary Bennett

 

http://bendun.net/

http://photos.bendun.net/

 

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