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New CGEM, OTA, and 450D Short Report

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#1 Dave H.

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Posted 04 February 2009 - 01:30 PM

I thought I would post a short “first light” report on some new astro gear including the CGEM I have just acquired as perhaps some novice observers like myself may find some of these items of interest.

First, I picked up a new Skywatcher Pro ED120 F7.5 OTA package just a little over a month ago, and until a few days ago I had only been able to use this scope on a mount built for an 80mm scope. To my eye the views were always very sharp, but the undersized mount would shake if I so much as breathed on it. Now that I have used this OTA on the new CGEM IMHO this OTA performs excellent views with virtually no hints of color on bright objects such as Rigel and Castor, and these can both be easily split with a moderate eyepiece.

In my opinion this beautifully painted metal flake OTA scope package (which is very similar to the Orion 120ED) provides not only excellent views with the FPL53 lens cell as has already been widely reported in other forums, but is also an amazing value at $1495 with an 8x50 finder, 2” dielectric diagonal, hard case, and 2 above average eyepieces. My personal experience has been that Joe Gordon (who runs Skywatcher USA) and all the folks at Skywatcher are simply great to deal with, and they provide the type of customer service experience most in this hobby expect and which has been sorely lacking at most of the competitive astro companies I have dealt with over the last few years. For more information on the Skywatcher Pro 120ED OTA package check out the link below. At this point I can only say that I have owned 6 other 80mm-102mm Chinese or Taiwanese FPL53 ED/APO equivalent refractors which I have already sold, but I have found the Skywatcher 120ED a definite “keeper”.

http://www.skywatche...apo-s11130.html

Right after receiving my new Skywatcher 120ED, Santa visited and left a pretty new Canon 450D DSLR under the Christmas tree. Having never even used a DSLR and considering myself at the very best a total DSLR “Novice” I have been reading and “fumbling” around with the new DSLR as time permits. I guess since at this point I am still pointing the camera with one hand, and reading from the user’s manual with the other, one would suggest I have probably still not quite past the initial learning curve. As a point of reference like many others I have used an old analog SLR in the past, so I did have some very basic concepts of aperture and the former ASA, now ISO. I have also used an Orion SSDSI CCD a few times for some preliminary crude attempts at astro imaging. While I have bought and sold a few different GEM mounts, I have never had an EQ mount I considered to be capable of proper tracking for astro imaging so my astro imaging experience is just about non-existent.

I have previously owned 2 Celestron CG5 GOTO mounts and an Orion Atlas, but while I recognize these mounts have worked well for others, for various reasons none of these mounts really worked well for my needs. Since the announcement of Celestron’s new CGEM mount and the “All Star Polar Alignment” routine, I have thought that perhaps this mount might really work well in my environment. You see one of my constraints is that on my back deck where most of my observing is done I have a very restricted field of view, and I never have a view of Polaris. So when the UPS truck pulled up a few days ago with my new Celestron CGEM mount, I was anxious to see if the CGEM polar alignment would perform as well as I had hoped.

I’m a bit of “Bottom Line” sort of person and suspect many other CN members might be as well, so I’ll skip to what I consider the most important attributes of the Celestron CGEM mount.

1. This is a reasonably heavy mount at 58 pounds with the tripod and EQ head, and has a real world payload of an honest 40 pounds.
2. The All Star Polar Alignment Routine worked perfectly, just like advertised.
3. GOTOs were right on, and preliminary tracking observations were excellent.

Please review the link below for more detailed information about this mount.

http://www.celestron....php?ProdID=548

At the time of the announcement of the Celestron CGEM I had just sort of overcome the learning curve of my still relatively new Orion Atlas EQG mount, but my first thought was that the All Star Polar Alignment feature of the new CGEM mount made my Atlas EQG mount immediately antiquated for my needs. The good news to me was that my Atlas mount sold on another Astro forum the very same day I decided to sell it, but the bad news was that the new CGEM mounts were back ordered…

Like I stated above, the All Star Polar Alignment routine worked perfectly just as advertised, now let me explain the primary reason for my writing this brief report, as to me this feature alone is an amazing benefit. If unlike myself you have an unobstructed view of Polaris this feature might not seem to be very beneficial, but in actuality the accuracy of the polar alignment might really be more beneficial than realized.

In essence the All Star Polar Alignment consists of a basic alignment, and an additional Polar Alignment Routine and works like this:

Time/date/location data is entered as is typical of the alignment of virtually any mount, and then a simple 2 star alignment is performed as is customary, with the user provided many choices of various alignment stars. Both alignment stars must be on the same side of the Meridian and it seems default is to the West, and I chose Rigel and Aldederan which were both clearly visible from my location on the Western side of the meridian. The user can also opt to add multiple calibration stars on the opposite side of the meridian if so desired to increase pointing/GOTO accuracy, and I chose to use Pollox and Procyon for calibration stars which were on the Eastern side of the meridian. Each star was in turn centered in the finder and then aligned in the center of the OTA eyepiece. Following completion of the alignment, the mount calculates position data, and then displays alignment success.

The next step is to add the optional All Star Polar Alignment:

The user selects any star of their choice from the huge Nexstar database, and the GOTO feature of the mount slews to that star. I selected Rigel again, and the mount slewed to Rigel. The user then centers the selected star (Rigel in this example) in the eyepiece, and enters “Align” on the keypad, and then selects “Align Mount Position” from the few drop down options provided. The mount then calculates the correct position of the true North (or South if you are "Down Under") polar axis, and prompts the user to hit enter to continue to Polar Align. The mount then slews to WHERE THE STAR (RIGEL IN THIS EXAMPLE) SHOULD BE IF THE MOUNT WERE PROPERLY POLAR ALIGNED.

The user then adjusts the CGEM mount’s altitude and azimuth settings mechanically to center the Polar Alignment Star, and upon completion the mount is properly polar aligned. Please view the link below for more information and FAQ:

http://www.celestron....php?PageID=370

So I’m sure if you have plodded through all this rambling thus far you are probably wondering something like “Well does it all actually work?”

In My Humble Opinion, the All Star Polar Alignment is one of the best astro features I have encountered to date. As I mentioned above, I do not have a clear view of Polaris from my back deck, and so have no ability to use a polar finder scope. I do not have an observatory, and just can’t justify the time of a tedious drift alignment. My “first pass” of the All Star Polar Alignment took me about 10-15 minutes to both figure out and complete, and I suspect subsequent alignments should all take easily less than 5 minutes to complete. For what it is worth I pre-aligned the CGEM mount with accurate marks on my deck indicating the alignment path of the true North celestial pole, and set the elevation to 38 degrees for my latitude in Virginia consistent with the mount’s user manual, as well as every other GEM user manual I have encountered. What was surprising is that while I suspected my alignment marks for the true North celestial pole were pretty accurate and in fact they were as the mount needed very little azimuth adjustment, the altitude needed a substantial adjustment of well more than 1 full degrees! Following the Polar Alignment, the mount now shows the latitude at closer to 36 degrees, and I have found that to be quite surprising. In case one is wondering, the bubble level on the mount was well centered, and GOTOs in all directions were really quite accurate consistently placing the selected object in the field of view. Time will tell as to the accuracy of the mounts elevation gauge and the bubble level, but certainly the initial results were what I would consider a very good polar alignment.

Now back to the results…

First, please no flaming attacks about my lack of imaging skills as they are not neccesary, my lack of skill in this area is readily acknowledged. I was interested in the results of the unguided tracking, and attached is a link to an image I posted on our local club site of what I think is the very first moderately acceptable image I took with the new Canon 450D DSLR, Skywatcher 120, and Celestron CGEM last Thursday evening, 1-29-09. Please note this image was posted just for what it is intended to be, a single unguided 45 second exposure.

http://www.novac.com...=2616&ImageID=1

If you can, please allow your mind’s eye to picture a guy with a DSLR user’s manual in one hand, a Celestron CGEM user’s manual in the other, using a red flashlight to skim through the most appropriate reference materials trying to determine how to photograph a deep sky object he can barely see with his finder scope… This would have probably made for a hilarious YOUTUBE video, and that is pretty much what I was thinking as I was laughing at myself. Well I can tell you the Canon “Live View” feature that displays your image on the LCD display is certainly much better than trying to peer through a view finder in the dark, but I will really have to work on my focusing technique as the first results were certainly less than impressive.

But the image in the link above is a single 45 second exposure of the familiar M42 Orion Nebula taken in the “RAW” mode, and just cleaned up slightly with the 450D included utilities. This single image was taken with no guiding, and a simple prime focus attachment using the ED120 as a telephoto lens for the Canon 450D. I did try a few longer exposures of 90 seconds and it seemed the CGEM mount tracked perfectly and I suspect even longer unguided imaging can be expected, but my lack of focus skills and experience with the live view function on the 450D were much more evident, and I recognize focusing will require much more work in the future.

While this brief review is not intended to be an in depth technical analysis that many of the advanced astronomers here might appreciate, I thought other novice observers like myself might benefit from some of the results from my recent experience. In my novice opinion the initial performance results of the new Celestron CGEM mount are really quite promising, and I hope other amateur astronomers can benefit from understanding the functionality and benefits of the All Star Polar Alignment routine.

Please feel free to comment or ask any questions, I’ll do my best to help any way I can.

Keep looking up!

Attached Files



#2 Lane

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Posted 04 February 2009 - 04:36 PM

So when does the C11 arrive?

#3 Dave H.

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Posted 04 February 2009 - 05:00 PM

Lane, Funny you should ask about a C11...

Actually I have already experimented with a C11 and C9.25 as well when I had an Atlas mount that I felt would be a great "dual purpose" mount, but decided for me one dual purpose visual and imaging platform was really not optimum.

Personally, I decided to save and invest in seperate platforms for visual and astro imaging attempts, and the new CGEM Skywatcher 120ED is what I elected for venturing into astro imaging. I'll also add a guide scope but I suspect your point is that the CGEM can probably handle much more payload, and that is obviously true, but it certainly seems to track nicely with the ED120.

Now for visual use I just use a CPC1100 which is very easy to set up and align, and captures enough light to provide nice views of most Messier objects when conditions permit.

#4 Obs30

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Posted 04 February 2009 - 05:03 PM

Hi Lane,

Very good. I just bought the CGEM myself through Orion Telescopes last week. It was actually on stock. I want to mount my 102mm F/7 ED Orion Refractor on it that I have since one year on a versago mount. The visual images are superb. Last October I bought a Canon 1000D (Rebel Xs) and I tried out the Liveview at several terrestrial objects. When buying the mount I also got the Orion autoguider that I want to mount to my old 114mm F/9 Newtonian reflector next to the 102ED onto the CGEM. Let's see whether this will work.

So basically now I could put everything together... but I do not have the right dovetail plates. The will take about two weeks, since I have them made at AOKSwiss (I live in Switzerland). Fortunately, the weather is not the greatest these days... so waiting is less stressful.

Since we have almost the same equipment, I am looking forward to comparing our results here at this forum.

#5 Tim C

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Posted 04 February 2009 - 05:03 PM

Nice report

#6 Obs30

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Posted 04 February 2009 - 05:11 PM

sorry... I meant "RideSober". Thanks for the nice report.

By the way should one use an illuminated reticule eyepiece for all the mount alignments? Or is it sufficient to center the alignment star by "eye-balling"?

I have another questions:
Somebody on this forum recommended NOT to use an AC/DC converter as a power supply because it might burn the electronics. Anyone else with the same experience?

#7 Skylook123

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Posted 04 February 2009 - 05:34 PM

Nicely presented. Love the idea of the Polar Alignment routine; I set my Atlas up three or four times a month, always at a different site, and I could use a capability like that!

Hope your success with the CGEM continues.

#8 Dave H.

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Posted 04 February 2009 - 06:27 PM

By the way, I also added a ScopeStuff Losmandy to Vixen adapter that seems very well made, and very sturdy. I had my 6" Celestron achro on the mount and it handled that weight with absolutely no problem at all. Here are some photos of the ScopeStuff adapter.

Attached Files



#9 Dave H.

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Posted 04 February 2009 - 06:31 PM

Another shot of the ScopeStuff adpater.

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#10 PMS

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Posted 04 February 2009 - 11:49 PM

Ridesober,
How much weight do you have on the CGEM mount?
Do you think the CPC1100 could do as well with an EQ wedge? AND can it handle extras? (IE: what is its' payload)
Thanks
PMS

#11 Dave H.

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Posted 05 February 2009 - 08:28 AM

PMS,
In terms of current weight/payload on the CGEM, with the 120ED, finder, 2" diagonal, and 2" eyepiece I have only about 16 pounds, a little less with a prime focus adapter and the Canon 450D, but my guide scope and autoguider will probably add about 5 more pounds. To be sure, the CGEM can handle much more payload, and is rated for 40 pounds which seems very reasonable for a beefy mount like this.

There are plenty of folks that image with a CPC1100 on an equatorial wedge, and if one chooses to go in that direction it certainly can be done. But by all accounts a very substantial wedge like a Milburn wedge is required for this application as the concensus seems to be the Celestron wedge is really not up to carrying the 65 pound weight of the CPC1100 OTA/fork mount plus the added weight of the required counter balance, guide scope, cameras, etc. Further, I have read many opinions about loading up the CPC1100 and this is known to require a set of counter balances, and many seem to indicate all the combined added weight will usually cause the provided nylon bearings to wear prematurely. The Yahoo CPC group has many threads about the bearings in these scopes developing flat spots from added weight requiring replacement with ceramic bearings, so one just needs to recognize that there could be a few obstacles to getting a CPC1100 set up properly for imaging.

As I indicated earlier, while I love my CPC1100, I choose to use it for visual use only and my CGEM will be used for astro imaging.

Hope this helps and thanks for your interest, Dave

#12 Chris Rowland

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Posted 06 February 2009 - 02:55 PM

By the way should one use an illuminated reticule eyepiece for all the mount alignments? Or is it sufficient to center the alignment star by "eye-balling"?

I believe that a reticle EP will help enormously in getting good alignment and so good polar alignments. It doesn't have to be illuminated. What works well, especially with a SCT, is to have the scope slightly out of focus, then you can see the cross hairs against the unfocused doughnut - and with an obstructed scope there's a tiny bright dot in the centre of the obstruction for precise alignment. Don't change the focus.

Chris

#13 CounterWeight

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Posted 06 February 2009 - 11:53 PM

Dave, great report, glad all your recent aquired equipment is working out for you! That is all nice stuff you have there - and the all-star polar align sounds very bankable. Interesting how a tech feature can greatly increase usefulness and useability. That 45 sec unguided exposure says a lot. I want to get one of those mounts myself sometime soon! Are you using battery power or 115?

Obs30 - illumited reticle is great, but anything with crosshairs or target circle will do the job, eliminates most common sighting errors. But if your not going to do astrophoto work, just a good careful eyeball center works well.

#14 Dave H.

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Posted 07 February 2009 - 08:38 AM

Thanks for the feedback.

While I have a pretty decent quality 110 to 12 volt converter, for fear of possible damage to an expensive board due to an electric spike, I don't like to run the 110 to 12 volt coverter right to my scopes. While many others have made many different choices for powereing their astro gadgets, personally I use an all purpose 12 volt power supply for my scopes. On a recent frigid public night the 12 volt power supply easily powered both my CPC1100 and a small Nexstar mount with my 120ED until exposure to the elements brought the evening to a close.

http://www.harborfre...temnumber=96157

Here is a link to the 12 volt power supply I have been using, and while certainly not designed for this purpose, it has been convenient and served me well.

#15 Obs30

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Posted 09 February 2009 - 04:29 PM

It doesn't have to be illuminated. What works well, especially with a SCT, is to have the scope slightly out of focus, then you can see the cross hairs against the unfocused doughnut - and with an obstructed scope there's a tiny bright dot in the centre of the obstruction for precise alignment. Don't change the focus.


Very good idea. Thank you for hint with the defocusing trick. I still have an extra EP with a crosshair.
Once I have my mounting/dovetail plates, I can try out the accuracy.

#16 PhilCo126

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Posted 04 March 2009 - 02:48 PM

Great report indeed, I'mtill hesitating to get the CGEM or to save a bit and get the CGE larger mount






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