NetNews Usenet Archive 1992 #31/NN_1992_31.iso/spool/sci/astro/13390

Text File | 1992-12-23 | 7.9 KB | 160 lines

Newsgroups: sci.astro
Path: sparky!uunet!zaphod.mps.ohio-state.edu!darwin.sura.net!gatech!usenet.ins.cwru.edu!agate!linus!linus.mitre.org!mandolin!chaloux
From: [e-mail] (Dave Chaloux)
Subject: NGC MAX Setting Circles
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Sender: [e-mail] (News Service)
Nntp-Posting-Host: mandolin.mitre.org
Reply-To: [e-mail] (Dave Chaloux)
Organization: The MITRE Corporation, McLean, Va
Date: Wed, 23 Dec 1992 18:44:34 GMT
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Someone on the net recently asked about NGC MAX and other comparable setting
circles. I have recently bought the NGC MAX for my Obsession 20" and
thought I might give my first impressions.

Installation:

They advertise that most of their installations involve no drilling etc.
This was not the case on the Obsession. In particular I had to drill two
holes into the cast aluminum bearing for some self threading metal screws.
They specified using a #35 drill for this. I took a look at the screws and
at the specified bit and decided that this couldn't be right. I am fairly
sure that if I had followed the instructions, the screws would have been too
loose. I can't prove it since I used a 41 drill bit instead which worked
fine. My guess is that they substituted a slightly smaller screw and forgot
to change the instructions.

I also had to use a total of 7 woodscrews for my installation. I pre-drilled
the holes although this was not strictly necessary.

Other than the question about the #35 drill bit, the instructions were
brief (1 two sided page; 1st side illustrations, 2nd side instructions) but
were easy to follow. I did take the time to look at the instructions and
the parts and understand the instructions before I started.

Installation took about 1 hour but I could have done it quicker. I think
I could do it over again in 15 to 20 minutes. I took the time to make sure
I did it right. I didn't want to end up relocating items having
done it wrong and ending up with a bunch of lousy looking holes in the
telescope rocker.

Overall, the installation went very smoothly and looks to have been well
thought out. I can't think of a way that the installation would have been
less intrusive. I think they did a good job of doing the minimum harm.

I talked to the guy at JMI about the #35 drill bit and he thinks it is
right but he is going to check.

Instructions for using the unit:

In general I think the instructions for using the unit are very clear. There
are a few minor mistakes. There is also one thing they should have made
clear but did not in the instructions. They advertise that you only need
two stars to align. In general this is correct. However, Polaris should not
be the first star and if you use it, then you need a third star (which can be
Polaris). This is not in the instructions and I ran into the problem very
quickly. This will probably happen to other users as well.

This fact was verified talking to JMI.

Out under the stars:

These things can be addictive. I got mine and installed it the same day. I then
went out that evening despite the variably cloudy whether. Variably cloudy in
this case usually meant partially to completely cloudy. I did my alignment
using Polaris and Navi. (Yup, I made the aforementioned mistake). It didn't take
so I aligned on Polaris again. This time it took. I pointed the scope at the
double cluster in Perseus, hit identify and NGC 869 popped up. Moving to 884
it now showed up on the display. No more confusion which is which 8-}. I then
entered Catalog Mode and called up M52. I popped into guide more and met my
biggest surprise. Despite the fact I was already close it wanted me to swing the
scope around almost 180 degrees and then move up over the top which on the
Obsession is impossible. This turns out to be user and installation error
but more about that later. I switched into RA DEC mode instead, moved to the
proper position, looked in the eyepiece, and saw clouds. I waited for the
clouds to move on and there it was. Arguments can be made all day about the
merits of starhopping vs setting circles but one thing is for sure. Starhopping
to M52 under these conditions was pretty much out!

I then got bolder and decided to go for some galaxies in Cetus. Again, I was
able to move to the position using RA and DEC mode and then when the clouds
cleared I discovered I was 1/2 degree away. One of the nice things is that in
Catalog mode it will give you either the Sky Atlas chart or Uranometria chart
that the object is located on (depending on how you set the computer up).
Because I had looked on the chart, the error was immediately obvious. I moved
to the galaxy and then went into align mode so that things were properly
initialized for that part of the sky. You might think that 1/2 degree is
pretty poor performance but I was impressed. You got to remember that I had
used two stars that were very close together for my initial alignment which is
definitely NOT recommended. Cetus is well away in the sky from either. The way
the system works it keeps two alignments at a time. If you do a third alignment
like I just did, it throws out one of the previous alignments to optimize its
accuracy. From this point on, the system was pretty much dead on.
I had set to NGC 908 and I noticed on the Uranometria chart that there were two
nearby galaxies. I moved the telescope to where I thought they would be and
quickly spotted one. I put the NGC MAX in identify mode and it told me it was
NGC 899 and not NGC 909 which was the other possibility. I moved around some
more and found another one. Sure enough, NGC 909 was on the display.

I then set over to NGC 936 and 941 and did much the same thing. Observing was
a pleasure on a night where normally, I wouldn't have even attempted it
because of the cloud cover.

My only beef was the guide mode. More on that follows.

Guide mode follies:

I called up JMI and asked what was going on with guide mode. The person I
talked to (Brian) was very helpful but did not know what was going on. He
took my number and told me he was going to talk to the guy who does the
software and that he would then call me back. About 15 minutes later I got
my call. He mentioned that there are 4 ways to install the encoders and that
two of the four ways will give correct RA DEC readings but one of those two
will give bad guidiUnread news in sci.astro                                   3 articles +   799 oldng. It turns out that one way to end up with this problem
is to install the altitude encoder on the wrong altitude bearing. They always
set the thing up on the right altitude bearing and naturally, I had used the
left for my installation. This had not been mentioned in the installation
instructions.

However, I am not without fault. There were instructions for checking out the
encoders which I had followed loosely but not exactly. If I had followed the
instructions exactly, I would have found the problem and the solution. All
I need to do is change the Polarity of the Altitude encoder and guide mode
should work fine. I say should because I have not tried this yet.

I am very happy with the customer service I received tracking this down.

What is in the Database?

7840 NGC objects.
2852  IC objects.
 110   M objects.
 369 Double stars.
  44 Multiple stars.
 333 Variable stars.
  77 Red stars.
   8 Planets.
  25 User definable objects.
 367 other objects (from about 40 different misc. catalogs)

This is 12025 objects although most of the Messier objects are double counted
appearing in both the M catalog and the NGC catalog.

There are also 30 Alignment stars some of which are also among the doubles and
variables (such as Polaris).

What is a Typical Description in Catalog Mode?

NGC 7331 gives "Mag = 9.5 Size = 10 Pegasus Very Elongated Galaxy Dusty with
Bright Core UA = 123"

If I had set it for Sky Atlas #s it would have given the Sky Atlas chart instead
of the Uranometria chart.

Would I Buy it Again?

One night is a bit premature to give an opinion but at first look, I think
this one was worthwhile. I like it.