| Peter in Reno |
| (sage) |
| 07/02/09 06:05 PM |
Fork mounts vs GEMs
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I know that there are many advantages of GEM over fork mounts. Good GEMs like CGEM or Atlas EQ-G are generally more stable and have less vibration than fork mounts. Also, it can be easier to transport GEM especially for large OTA because it's easy to transport in separate parts where fork mounts require to carry both the mount and OTA and they can be heavy. In my opinion, one big disadvantage for GEMs is meridian flip. Forks don't require meridian flips. I used to own both forks and GEM both performed just about equally well. I would like to be able to image the same object from east to west without meridian flip.
My real question is how does Meade LX200-ACF series perform? How accuarte is the GoTo feature? If I use Mitty wedge, is it as stable as GEM? The electronics and firmware seems to be a little out of date as compared to Celestron. The main reason for picking Meade is that their OTAs have mirror locks and Celestron do not have them. I prefer guiding with guide scope than Off Axis Guider. Celestron requires OAG for longer than 10 minutes exposure thanks to mirror flop. With mirror locks and guide scopes, over 10 minutes subs can be done.
Peter
| snowdragonusa |
| (Pooh-Bah) |
| 07/02/09 07:58 PM |
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Re: Fork mounts vs GEMs
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The ACF on a Mitty is very stable. I really like my system. The setup will be a little longer than a GEM but not anything too great.
You may (I stress MAY) see a little mirror flop at the meridian still but it will be very minimal. The mirror lock still has to keep that big heavy glass in one place and gravity is not its friend.
| JAT Observatory |
| (Got Cookies?) |
| 07/02/09 08:07 PM |
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Re: Fork mounts vs GEMs
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Peter,
I also like the fork mounts for being able to follow an object from one side of the sky to the other.
My LX200GPS did a great job of traoking. I like to show people this 8 hour animation of the asteroid Vesta. It was taken using a 4" refractor on top of the wedge mounted LX200GPS. The LX200GPS was guided by a DSI Pro and a F6.2 reducer. The images were not post aligned, registered or processed. The scope moved from the eastern sky across the meridian to the western horizon. So good tracking can be had from a fork mount.
Now one last thing. If you decide to go with a GEM, some GEM mounts will let you image past the meridian. For ones that don't programs like CCD Autopilot will handle the meridian flip for you as well as the plate solve so the scope get repointed were it is suppose to be, once on the other side. It can also automatically reacquire the guide star and continue autotracking. It does however require either MaxIm DL or CCDSoft, but it's the next best thing to being able to image past the meridian if you have a GEM that doesn't.
| Joe Lalumia |
| (Post Laureate) |
| 07/02/09 10:57 PM |
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Re: Fork mounts vs GEMs
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JAT--- very neat video. !