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Maximum real world loading for EQ6-GT?


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I'm presently working out my options for upgrading the set up in my observatory.  My plan is (or possibly was depending upon the answers I get here) to mount a Celestron 9.25 SCT OTA along with my existing SW 80ED and Revelation 66mm Apo on a Skywatcher EQ6-GT on a pier in my observatory.

Adding up the weight of the scopes + mounting accessories and cameras, filter wheel etc.  This all comes to between 20 and 22 kg depending upon how I mount everything.  FLO state the maximum recommended loading for the EQ6-GT as 25kg with a recommended maximum loading for imaging of 18kg.  Assuming I get my weight distribution good and the system well balanced, am I likely to be pushing this mount too hard for long exposure astrophotography with the Celestron with an f6.3 reducer?

Thanks

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My answer would be 'yes, you're being a bit too optimistic.' It will partly depend on the pixel scale of your imaging setup, though. While weight has to respected, so does accuracy. There's no camera in your signature but a typical DSLR in the 9.25 would be imaging at about 0.6 to 0.7 arcsecs per pixel. Ouch, that is premium mount territory in terms of accuracy. An EQ6 is going to need all the help it can get to deliver that kind of guiding accuracy. Minimum payload, OAG, great care. If you don't keep your guide error down to about half your imaging scale then there is no point in imaging at that focal length. If you were using, say, an Atik 383 then in Bin1 you'd be at an optimistic 0.71"PP but if you binned you'd be at 1.42"PP which would be far more likely to be reachable in reality.

Another small point, but the 'round stars' test is only half a test. If they are not round you clearly have a problem. If they are round you might still have a problem because random and roughly equal errors on both axes will give round stars while not indicating that you are resolving to the theoretical limit of your rig.

Olly

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Thanks Olly.  

I'm looking at getting a CCD camera (possibly the Starlight Xpress Truis SX694) as part of this upgrade, so the DSLR would probably end up being used primarily for widefield shots on my Astrotrac.  Looking at FLO's CCD calculator, this will give me 0.6"/pixel.  If I bin it at 2 x 2 then this gives me 1.2"pixel.

The problem I have is that I need a single CCD camera that will be suitable for a wide range of focal lengths and apertures and I know that compromises are going to have to be made.

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The C9.25 is going to have a very small FOV with the Sony chips. The 8300 would give you more FOV and 1.4"PP binned. However, the Sony chips are nice to work with. You can make a case for both, but I'd feel very cramped by the Sony/Celestron.

Olly

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