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A Celestron GOTO Mount - The Missing User's Notes with
Astrotime Not Quite Redux

By Duane Dunkerson

Fess Up

It had become too annoying to not have GOTO: 1. There is the time factor, not much time now to observe what with increased familial duties. 2. Then, too, more time is lost by means of the need to plan star hops. Not enough can be seen as executing the hops. 3. There is too little opportunity to observe here as it rains or is preparing to rain for eight months per year. 4. There can be much difficulty in finding guide stars for hops. My eyes are deteriorating. In addition, sky glow and ground level neighbor-lights blanch the eyes. Municipal security lights contribute to a backyard that is without darkness. 5. With my refractor, the bending, squatting, kneeling, and flat-on-the-back contortions had become more than enough of a workout that I paid for in muscle and joint pain all day next day.

The GOTO was seen as a way to increase astro-time and decrease the frustration of the immediately attendant and prerequisite non-astrotime. The non-astrotime, such as the preparation for the star hops, could take away significant amounts of astrotime. For me, astrotime had come to mean the observation, not the prep or whatever got you there observing during an observing session.

Also, dissatisfaction with the Orion shaky EQ3 mount for the Orion 120mm refractor at f8.3 helped to prompt a change. I did add an Orion 9X50 finder and an Orion RA clock drive but it was not enough. I had ordered the 9X50 three times from Orion. They insisted on sending me a solar filter for an 8-inch scope. The cost of the filter was four times the cost of the finder. If I had been a modern man, I would have kept the filter, sold it, purchased a finder elsewhere and pocketed the difference. I am not modern. Modern or not, I was peeved at having ordered replacement Orion tripod legs four times. The legs are to be tightened on extension to "firm" or "snug" not "tight", as I wanted for equipment safety sake. My GOTO would not be from Orion.

Shopping Around

I researched via the Internet for what options there were for GOTO. Realistically for me there were two options - the Meade LXD75 or the Celestron CG5 Advanced Series GT. The Meade cost less but comparison reviews pointed out that the C (Celestron) was better for me than the Meade.

That the C has a 40,000-object database is hardly a selling point with me. As an Internet observer noted, most of the database will remain unobserved by the usual apertures employed under the usually far less than dark skies that are available to most observers. Then the C's tripod legs had to be an improvement over the easily flexed EQ3's shakers. Furthermore, the reviews made the mount into a precise locator.


After ten days of ownership, counting from the date of placement on my doorstep, I could not yet say a field test had been done. Cloudy nights (of course) and days spent getting the 120 mm refractor to fit the C had consumed the time. The C arrived in an undamaged box. I thought I did not have the counterweight bar and something else at first. They were not obviously placed in the boxes within the box. There was no parts list. There was a lightweight manual and it contained the addendum for the hand control operation that I had seen in pdfs that C provided on the Internet. The addendum was not separated as such in the manual but incorporated into the text. I thought they had had a two year warranty, another selling point vs. Meade's one year warranty, but Internet sources put the warranty at one year. No, it was for two years after all.

I set it up from instructions in the manual, and all seemed well. I had thought it could only move in RA and Dec with motor power. No, it can be moved about, but no manual slow motion controls are provided. The tripod legs can be extended. How far can they be extended? C does not say and an Internet source had an 18-inch extension. I eventually settled on a 16-inch extension. One of the legs must be pulled and twisted with effort to get it to extend.


I had ordered the C from Anacortes. The guy there seemed to know what he was talking about except the C does not have a battery pack which I specifically wanted to be sure was present since the Anacortes guy said there was to be a one month delay on getting C's AC converter to power the mount. Once I found out there was no battery pack, I cancelled that AC converter item of the order. I then tried to order the AC converter from Oceanside in Calif. They also said a wait of one month would have to be undergone. Then, via email, a woman at Oceanside said they could supply me with a Vector AC converter putting out 6 amps. C says it needs and their converter supplies 2.1 amps. The Vector is Rubbermaid by Black and Decker. C provides you only with a car battery (cigarette lighter) plug in. I plug in the C's car battery cord male end to the Vector receptacle. The Vector plugs into the wall.

I contacted the Oceanside email woman by phone. She said she would run the converter to the outgoing truck. I believe she did. The tracking report from the shipping company leads me to believe this. Anacortes did not ship the third item I had ordered on the same or following day as the mount. The third item was the dovetail adapter plate. I called to inquire as to its whereabouts. They shipped it the next day. I had decided to order the C from Anacortes since they are less than a shipping day away. I expected there would be less wait and less chance of damage en route.

I had seen photographs in reviews of the mount showing my OTA (optical tube assembly) on the mount. However, the reviews never said how such an arrangement was accomplished. The Anacortes guy said I could mount my Orion refractor directly onto the C mount. I checked. I called back. No, that won't work I said. So he said try the adapter plate. I got it. No holes on it lined up at the proper distance for the location of the tube rings as I had on the EQ3. I emailed Astronomics about using such an adapter plate. The man who replied said it could be unstable, use a Meade saddle plate. Another email, this time from John Crilly, my main source for reviews of the C and comparison reviews of the C and Meade mounts of interest, had responded with the comment that the C plate or Meade plate would work.

My Orion threaded screws would not fit any holes in the C plate. Also, the tube rings sit up on top of two rails of the plate, it does not fit down flush in the trough - so it is in theory unstable. Theory would not be allowed to dominate this time. I got longer screws of the same type as Orion. I went to a machine shop to have two holes drilled and tapped to take the longer screws. Then I placed a lock washer and a wing nut on the screws on the underside of the plate. To date, so far, so good. I had heard that the top of the mount has an adjustable slot to accommodate various plates, and thus, various scopes. It is one screw that angles in. There is a tiny "security screw" also. I would much prefer another large screw or, better, clamps.

Dry Run

A dry run in the home office seemed to work OK. It was daytime outside so I was in the darkened room. The two line red display of the hand control scrolls horizontally if need be. I did not like an oddity in start up after the first time it was turned on. This oddity is the necessity of entering location (for a present latitude and longitude) for every time a power loss or shut off is done. If you shut off during a session, startup again requires the same information from you. OK, it showed my city, I pushed Enter and on we go. Then, as the scope did not slew as it should, I recalled that I had not entered the time. It turns out you must deny that is my city, by pushing Undo, then confirm it is my city, and then it allows you to go on to time entry. Location and time and else are necessary to get going on alignment to put the scope into use.

For the dry run, I selected objects from Muirden's constellation lists in his old The Amateur Astronomer Handbook. Other sources that I have can be brought in later. Not all of Muirden's objects are readily to be found in C's lists and menus. Some of Muirden's objects are in C's constellations tours or in its double star lists. If not in these places, then one can try C's SAO (Smithsonian Astrophysical Observatory) list. C would not accept SAOs of less than six digits. Or so I believed at first. I had to look up the star(s) RA and Dec via SkyMap Pro. You can enter RA and Dec and C will get your scope there. It also reads out the current RA and Dec if requested.

Before you get to any object and after location and time are entered, you do the alignment. I do two-star alignment and two stars for calibration. I discovered knowing constellations and their stars mostly as alpha, beta; etc. is not enough. C lists the alignment and calibrations stars only by proper name. Most appear to be from Arabic sources. I used SkyMap Pro to find out where these named stars are located. I had to be careful to get alignment or calibration stars in the high south and mostly due east or due west, since trees intervene to the north and the roof of the house looms to the south. Also, I found on the Internet (not C) an Alignment Star short program to give the best alignment stars for a session.

Real Running

I must watch the mount constantly as it slews since the Dec cord can be pulled out (longer cord!) and the mount can close in on the tripod for the high in the sky objects. Internet sources (not C) said the mount can sense if about to hit the tripod. I'm not letting a failed test case end in a smash. The Internet (not C) sources say hit any of the arrow buttons to stop a slew. The Internet (not C) sources say for alignment you need the RA axis aligned (pointed at) to Polaris. You can sight Polaris through the RA axis tube (remove the front cover) and the rear hole in the RA scale (remove rear cover). Then level the tripod. I agree with an Internet source that it is enough to make the tripod visibly level and not to go chasing the bubble in the tripod's little dome. If you make a two-star alignment and use two calibration stars as I do, it is expected that leveling is not critical. Of course, location, time, and date must be accurate for alignment. I use my city's latitude and longitude from C's list. I suppose one could go all the way with topographic maps or GPS. The index marks for RA and Dec on the mount must be correctly aligned - in the Home position for alignment. Internet sources (not C) have noted those marks are notoriously ill-placed by C. They say a special level can be purchased to help in adjustment. My marks seem to be OK. Lastly, get the best alignment stars, taking into account the separation and altitude of the alignment and calibration stars.

The first field test was done between the house and the trees. The alignment and calibration stars were the main worry. I must do a dry run prior to that field test to ascertain what named stars are where. Also, if any viewing of other than alignment and calibration stars is to be done, then I have to know what is where. I was ready for the first alignment star. C was showing Arcturus on the display as an alignment star in the west. It will get two stars west of the meridian as alignment stars and then two stars east of the meridian as calibration stars or vice versa. It went and stopped not close to Arcturus. I was in distress. I did not yet know Internet sources (not C) said it could be off by ten degrees on first alignment if initial setup with point to north as I do and with not chasing the level bubble as I also do.

So then push the buttons, the four motion arrowed buttons are labeled up, down and left, right. With this equatorial mount, which button corresponds to what direction in either RA or Dec depends on where you are in what cardinal zone of the sky. Center the star in the finder. Push Enter. Center in the eyepiece. Push Align. The C has different speeds in response to motion button pressing for the finder view and for the eyepiece view. The C will automatically track in both axes once an object is centered.

It was twilight. I assumed, without prior Internet knowledge that Arcturus would be in the finder view. I centered on the brightest in the FOV (field of view) of the finder. After twilight ended and on another alignment run, I found out it had not been Arcturus in the finder. The second alignment was in Leo, a star not well known to me. Again, I assumed the brightest star in the finder was it. Wrong.

A few days later, I was at it again with more alignment-calibration exercises. Yes, Arcturus is off by at least ten degrees. Center it. Go into Leo, which star is which? Gave up on starting with west of meridian. Press Menu button before selecting the first alignment star. Now have displayed alignment stars east of the meridian. Ah, Altair. Naturally, scope ended up not close to Altair. Centered. Next alignment star? Try Vega. Centered. First calibration star? I tried my old buddy Arcturus. Centered. The scope did not point close to any of these three stars after C slewed to them. Second calibration star? No thanks, enough with the inaccuracy.

Oh well, how far off would C be if I told it to go back to Altair? It put Altair in the FOV of the 25mm (40X) EP. Huh? Ok, so Altair had been one of the alignment stars. No fair. Let's try Mizar. C slewed and Mizar ended up in the FOV of the 25mm. Is this going to be SOP? Three or four slews off by a considerable amount, so where is the accuracy? If they are going to be so far off, then one needs to sweep them up like in the good old pre-GOTO days. Time for bed. Stay tuned.

Another session of alignment and calibration. Altair was not close. Then Deneb and the scope was closer to Deneb than it had been to Altair. Now to west of the meridian and Arcturus was in the finder FOV. The last calibration star was Cor Caroli. It was nearly centered in the finder. What happened? I have a steadier tripod. I can focus at high power without scope or tripod movement. Such can not account for the improvement. I continued to operate in ignorance for another session with the same four stars - Altair, Deneb, Arcturus, and Cor Caroli. Now they all are in the finder FOV. If it ain't broken…

This last session required me (so I thought) to use RA and Dec entry to find a star. The C accepts RA and Dec entries and it went right to the star. I thought I could not make SAO entries of less than six digits. But then an Internet source (not C) told me to add left most zeros, one zero for a 5 digit SAO and two if a four digit SAO. The SAOs mostly pertain to doubles. I check for doubles, NGCs, ICs, Caldwells, and Messiers in separate lists or set SkyMap Pro to a certain magnitude level and check out the NGCs or ICs that result. C has a complete listing of NGC and IC. I still check these lists occasionally but I mostly now depend on RTGUI+S version 8.1.

RTGUI is a free of charge software product for Windows. It has text information though one can get a sky chart by hookup to the freeware Cartes du Ciel. The RTGUI has settings for the size of your scope and the amount of light pollution at your site. It can generate a printable list of Best of Sky for a time or you can get info via Simple Search or the Search Wizard. The latter generates lists based on altitude and magnitude limits. The lists can be for the entire sky or a constellation. The reports list doubles, NGC, IC, Messiers, and Caldwells. The program gives sidereal time and GMT. All SAO and all Washington doubles can be added to its catalogs for lookup. A large number are already in the program's database. Planets, quasars, and variable stars can be found. If it is fed the correct name for comets and asteroids, it will go out to the Internet and get RA and Dec for 60 days worth of positions. The program is 650K. It can be used to control most GOTO scopes. It has altitude, rise, set, and transit times for objects of interest.

What C Wants, You Get

The hand control has buttons to be pressed for Align, Enter, and Undo. These are at the top of the button section. The button section is below the display. Below the three aforementioned buttons are the four direction buttons that you press to do the moving of the scope when it is not slewing. Below these four arrowed buttons are buttons for :

Messier objects (all of them)
Caldwell objects (all of them - a mix of the reputed 109 of the best of the NGC and IC)
NGC (all of them can be listed or rather scrolled through)
Planets (includes Pluto and the Moon)
Stars (a large number of the brightest from the SAO catalog)
Info (coordinates and other info about the objects you select)
Up and Down buttons for scrolling lists of objects
Tour (the what for all the sky for your particular when and where)
Rate (to quickly alter slew rate)
List (this button gives access to other lists such as Named Stars (some bright ones), Named Objects (50 that C thinks are most popular), Double Stars (the most stunning according to C), Variable Stars (some of the brightest short period variables), CCD Objects (galaxies only), IC Objects (all of them), Abell Objects (custom list of the Abell catalog of deep sky galaxies), and Constellation (you can tour each of the 88, should you be so located).
Menu (lets you set up "user-defined objects", has tracking mode and rate, get and go to RA and Dec of an object, identify what is in the eyepiece FOV, polar alignment, and axis position in altitude and azimuth)

I have yet to push all the buttons.

















Copyright © 2007
by Duane Dunkerson

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