0.00
#...
·
·
1
like
|
|---|
|
Hi all, I was wondering if the GEM28 mount having 13 kilos of payload capacity handle the Celestron C8 for deep sky astrophotography? I do know that the thumb rule is to have gear that weight half of the mount's payload capacity! The total weight of Celestron C8 attached with the guide scope and the camera will weigh around 6.5 kilos. And GEM28 includes a 4.5 kilos counter weight, so I thought of purchasing an extra 2 kilos weight for the gear to balance with it. I intend to capture the Pillars of Creation (Eagle Nebula) using the C8 in its native focal length i.e 2032mm with an ASI294MM unlocked bin1 mode. The CCD suitability does over sample by 0.23"/second and its slightly over sampled when using a 0.63x reducer. If not GEM28, can I buy the CEM40 for this purpose? |
1.20
#...
·
·
2
likes
|
|---|
|
I'use GEM45 for a RC8 setup of about 11 kg and in my honest opinion is not fully usable. It is enough for a mosquito to pass within a meter of the telescope that the guide makes it worse. |
0.00
#...
·
·
1
like
|
|---|
|
Hi mate, I have the CEM26 which can carry a similar payload. I purchased it with the intention of using it with my EdgeHD8 inch and in my experience the CEM26 is not suited for carrying the EdgeHD8 and astrophotography. Though mine weighs a little more than yours. I have a Celestron 0.7 reducer and a Celestron Focus Motor so mine weights closer to 8 kilos. My mount really struggles with the payload. I also purchased an extra counterweight and I can get a fantastic balance and polar alignment on it, but it really struggles to track accurately. Even the slightest vibrations transfer through to the OTA. When I use my Askar FRA400 with the CEM26 it is rock solid and preforms fantastically just not with the EdgeHD8. If you are trying to decide on a GEM28 or CEM40, go for the CEM40. I made the mistake of buying a mount that is a little overwhelmed by a larger OTA. I should have purchased the CEM40 or even the 70, it does not cost much more than the 40. I hope that helps |
7.75
#...
·
|
|---|
|
Just a comment in case there is a misconception on your side: The counterweight doesn't have to match the weight of your equipment. The product of mass times distance of the centre of mass from the rotation axis has to be equal in oder to be able to balance your setup. Let's assume centre of mass of the C8 + camera with a weight of 6.5 kg is 5 inches away from axis of rotation you can balance the setup with a 4.5 kg counterweight at a distance of 5 x 6.5 / 4.5 = 7.22 inches. You'll need very good seeing to image around 1 arcsec ... Clear skies Wolfgang |
3.10
#...
·
|
|---|
|
Realistically, the C8, with all the kit attached, will probably weigh in at around 9-10kg (that is, camera, filterwheel, some kind of guding solution, dew shield, etc). So that would be a big no regarding the GEM28. If you do not want to stretch your budget any further, consider the Skywatcher EQ6-R. It's not that much more expensive and will serve you just fine for years to come. Otherwise, the CEM45 is a viable option of course. |
|
7.31
#...
·
·
2
likes
|
|---|
Kanak RT: There is nowhere on Earth where you can get that sort of actual resolution with a 8" scope ( I mean at native FL) for deep sky targets, so give up on it and use a more sensible bin2 mode. It will still be a stretch but with more chances to bear fruits. As for the GEM28 (which I own) let's not kid ourselves. To hope to guide with a residual error of the same order of your pixel scale you'd need far better mount than that! |
3.31
#...
·
|
|---|
|
I have used a GEM 28 with an Edge HD 8 both at f10 and at f7. I used an ZWO OAG L and a 1s guiding interval I managed to get good guiding with an RMS below 1" over several nights. There are a couple of other posts on Cloudy Nights that give the same results. Note my seeing is average I suspect with excellent seeing the mounts frailties might show. It wouldn't be my main mount for such a long focal length scope without a doubt the GEM 45 or CEM 70 will work far better (or any other equivalent capacity mount). I was just using it as a travel set up because I had a heavier refractor on my main mount. So yes the GEM 28 can handle the an 8" SCT but it's not a perfect solution so I wouldn't use that as my primary rig. If however I had a 500 mm refractor that I was going to use most of the time and a C8 sitting around to use during Galaxy season I wouldn't go out and buy a new mount. That said what I liked about the iOptron mounts was the weight the GEM 28 is so light it's ridiculous but the GEM 45 isn't much heavier so still super portable. If I had my time again I'd probably buy the GEM 45 as my travel mount. I hope that's useful. John |
2.11
#...
·
|
|---|
|
This combination is pretty painfully under-mounted. At least if you're trying to push anything close to the level of detail which a C8 is capable of resolving. I have a CEM-40 (one which runs extremely well) which handles it, and my RASA-8, reasonably well. And I'm happy with that because portability is a big priority, for me. All of my imaging is on the road. But I have to make sure everything is set up meticulously and it does not tolerate even a little wind without signifiant degradation. I'd really want something like this to be on a CEM-60/70 for a more ideal pairing. (This isn't strictly about weight capacity. Imaging with such a narrow field of view, and with a telescope that has that sort of surface area for air circulation to catch—especially with dew shield—becomes correspondingly much more demanding of the mount relative to capacity.) I think I may be a fair bit pickier than the average about sub quality, and I do my imaging under skies which tend to have good seeing conditions, so that may all be weighed into my opinion. But I *would not* deliberately pair this telescope with the GEM-28/CEM-26. |
|
0.00
#...
·
·
1
like
|
|---|
| Thank you gentlemen, I was in same dilemma as is the thread starter. I got my answer. |
3.53
#...
·
·
1
like
|
|---|
|
I have both a GEM28 and a GEM45, I also have an EDGE HD8 with Mono Camera, OAG and EFW… I use the GEM28 with a Redcat 51 and need a counterweight under the dovetail at the front to balance the rig far enough back for cables and EFW to clear the mount… In this configuration (see photo) it guides at around 0.5 to 0.6 and works beautifully; however, it doesn’t cope well at all with the Celestron SCT on it, whereas the GEM45 handles the EDGE HD with ease…   |
|
0.00
#...
·
|
|---|
Olly Barrett: Is there any major difference between GEM 45 and CEM 40? |
|
3.53
#...
·
·
1
like
|
|---|
| Just the payload capability as far as I know |
3.81
#...
·
·
2
likes
|
|---|
|
I’ve had a couple GEMs and CEMs. They operate almost identically with the only real difference I can tell is how they center weight on the tripod. (Indicative of the name) If you want to keep it fairly portable, the Ioptron carbon fiber tripod is solid and I think it’ll hold the cem40 |
|
0.00
#...
·
|
|---|
Marc: Hello Marc! Thank you so much for giving your input. After conducting extensive research and planning, I have finalized my setup. Portability of the mount is my top priority. I have decided to pair my DSLR with Canon Lens for now (later RC51) with the iOptron SkyHunter mount initially, and later upgrade to the Celestron C8 Edge HD with the iOptron HEM27 or ZWO AM5 mount, which has a maximum payload capacity of 20 Kilos with counterweights. I have not considered the Skywatcher EQ6-R due to the unavailability of trusted dealers in Bengaluru, India. Other brands like Celestron, Meade, iOptron, ZWO, Bresser, Explore Scientifics have a good reputation here in terms of quality and service. Another factor influencing my decision to not consider the EQ6-R is the significant increase in cost due to added taxes, which makes it less affordable compared to other options. For example, if I were to purchase the ZWO AM5 mount, which costs $1,999.00 (mount only) in the US, I would have to pay $3047 in India. Hence, I am leaning towards iOptron as it offers a more budget-friendly option for mounts considering the price difference in India for other brands. |
1.43
#...
·
|
|---|
| I have an EdgeHD 8 and SkyWatcher EQ6-R Pro. The EQ6-R handles the Edge 8 with all the accessories you can fit into its back focus no problem, but is a Very Heavy mount. I went with an Askar 130PHQ and wore out the EQ6-R and upgraded to a CEM70G. If you can afford the CEM70 it handles much more payload, has more options/functionality (GPS, WiFi, USB 3, etc), weighs a lot less, easier to use (easier to level and balance) and higher quality. Once you buy a very nice mount everything else gets easier/better. It would future-proof any option you might go to unless you got your sights on an EdgeHD 14 or a Planewave. Clear Skies & God Bless. Kip |
