The following pages are my very first attempt to review a piece of astro kit. Astronomy has been a hobby of mine for, on and off, 20 years. The last 3 years I have been well and truly hooked on ‘Astrophotography’ , with equipment prices falling (cameras especially) it has opened this fascinating field of photography for many of us, you only have to join a few forums to see how its popularity is growing.
Before I go any further, convention dictates that I assure you that I am in no way affiliated with any equipment manufacturers, wholesalers or vendors of any kind but simply want to contribute my thoughts for open discussion. This entire document is purely a personal point of view of my own making and is not intended or designed to influence the thought processes of anyone else.
Now, let’s get on with the more interesting stuff. I purchased my CGEM very slightly second hand, I say very slightly because the previous owner had owned it for about 4 weeks before deciding he didn’t like it. Luckily for me I got it for a reasonable bargain price and it came with all the ‘knobs and whistles’ upgrades, lovely big bronze coloured knobs which I am lead to believe do not come cheap if purchased separately. I will refrain from telling you the price I paid, as I said before I am not here to upset people....... Well delivery day arrived and not unlike an excited child at Christmas I welcomed my new prize with open arms and a grin like a Cheshire cat, straight into the front room where the cardboard packing cases didn’t stand a hope in hell of withstanding the full on assault of my eager hands. Straight out of the box’s and into my obs it went and within minutes it was set up and looking more gorgeous than a bag of cabbages to hungry hippo.
My immediate impression was that of the feel of the mount, solid doesn’t quite cover it, very solid is more to the point. Quite heavy as you lift it out of its box, surprisingly so, so be warned if you have a fragile spine disorder this will catch you out. Its surface is tactile, pleasing to the touch and its granite grey finish is very pleasing to the eye.
Ok so it’s out of the box and I’m setting it up so here is my first gripe, the hand set has a ‘pig tail’ lead which connects it the mount. This is short, sorry not just short but too short! Honestly I have strung longer sentences together than this lead is. WHY?? (A rhetorical question for Celestron, just in case anyone from there should grace this review with their presence).
Now, I use two set ups, both include my 70mm ‘Astro Engineering’ guide scope and I simply swap between my 8” LX200 OTA used primarily for planetary imaging and my 8” GSO F4 Newtonian for deep sky work.
Balance was next on the agenda and as I use the GSO far more frequently than the LX so I balanced to that first. This was extremely easy although as you can see in the second picture I had to purchase a second 5kg weight to achieve perfect balance. The CGEM comes with just the one 10kg weight. Once this balance was found I then swapped to the LX ota and found the balance by simply sliding the side by side bar a little to the left, it couldn’t be any easier.
When that was completed I switched the mount on and settled down to read the instructions, now normally , if I am honest, I wouldn’t bother with the instructions until after I had got hopelessly stuck but this time the instruction manual had caught my eye earlier and seemed to be quite informative. Well I wasn’t disappointed, the instruction manual is written very clearly and in sequence with plenty of diagrams and simple step by step instructions....well done Celestron !
I uploaded my local data, lat and long, time and date etc. I find this to be easier than hunting through endless lists of worldwide cities. Then had a play with the buttons slewing back and forth, changing the slew speed etc etc. The hand set is slightly different to what I am used to but very nicely laid out and very easy to use with a little practice. The buttons are soft but have a positive feel to them when pushed, not a bad thing if you have prying little fingers around the house (I mean the wife as the kids are far too sensible) The duel line screen is very clear even in daylight, having the brightness adjustable is always useful in differing light conditions.
Well it took a few nights to come and go before i could put my new beast through its paces but eventually the weather here in England did behave itself enough for me to get an hour or two of clear sky’s. First on the list was a two star alignment. I set the slew speed to maximum, aligned the index marks on both axis and pressed enter. The hand set will select the first star for you (you can change this if you want but i let it be) Vega was the first target, press enter and off it marches. The slew was very smooth, no hunting or juddering was noticeable and it came to rest really quite close to its target. I must emphasise that the accuracy of the initial slew is directly relevant to accuracy of the home position information you have entered into the hand set and the accuracy to which you have positioned the ‘Index Markers’. All mounts need a start point so the better this is then the more accurate the slew will be. You are then instructed to centre the target and press ‘enter’, then to fine adjust the centre and press ‘Align’. At this point a second star will be selected for you (again you can opt for your own if you like and again I left it be) Altair this time so pressed ‘enter’ and off we marched again. This time the target was well in my eye piece with very little adjustment needed to centre it. That done the hand set will prompt you for ‘Calibration stars’ it is worth mentioning that the calibration stars will always be on the opposite side of the meridian to that of the alignment stars so if your alignment stars were to the west, as mine were then the calibration stars will be to the east. I always do three calibration stars, using the rule that the more you do the more accurate the result, i have found that three is ample for almost perfect accuracy.
Once completed I have found any and every object I select from the extensive data base is always and without exception in the central area of my eye piece and when using the ‘Precision’ slew option, the object is within 30 arc seconds of centre EVERY TIME.
So having confirmed the mounts accuracy my attention turned to drives, or to be more specific the PEC. A quick read of the instructions again and we are off. I should probably explain that as i am an inherently lazy person I use PHD to guide while recording the PEC, I really couldn’t sit there for 8 minutes, my eyes won’t work for that long. I selected PEC from the menu and then PEC RECORD, I had already centred a reasonably bright star and had calibrated my PHD guiding. When you press ‘enter’ at PEC RECORD the mount will move the star by turning the worm gear, this is so the mount can find a start point on the worm itself. You re-centre the star, start PHD guiding (give it a minute just to settle down) and then start the record sequence. A full PEC RECORD sequence takes exactly 8 minutes and when completed the hand set will tell you. All that is needed now is for you to select ‘Replay’ in the PEC menu and PEC correction is up and running. Please remember that if you, for any reason undo the clutches then the PEC will have to be re-recorded.
To give you some idea of just how good this PEC recording can be just take a look at the picture below. This is a 15 minute un-guided sub of NGC 7380, it was a very misty night so no nebulosity can be seen but you can certainly see the stars. This sub is untouched by human hands except to reduce (not crop) the file and convert to a Jpeg.
I will post a copy of the full frame image so it can be inspected properly but just by looking at this one you can see how impressive this mount can be.
