Hi guys,
just want to check with those guys that have fork mounts, how do you observe objects towards the north? the way the scope is postioned is impossible. does the EQ mount have any limitations such as that of the fork mount?
Thanks,
Colin
Fork Mount
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weixing
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Hi,
Have a nice day.
You mean fork mount in EQ mode, right?? I think the EQ mount may also have some difficulty to see the direct North or direct South position since the scope is parallel to the polar shaft. Anyway, that direction has nothing much to see in Singapore, so I seldom point my scope at it.just want to check with those guys that have fork mounts, how do you observe objects towards the north? the way the scope is postioned is impossible. does the EQ mount have any limitations such as that of the fork mount?
Have a nice day.
Yang Weixing
"The universe is composed mainly of hydrogen and ignorance."
"The universe is composed mainly of hydrogen and ignorance." -
weixing
- Super Moderator
- Posts: 4708
- Joined: Wed Oct 01, 2003 12:22 am
- Favourite scope: Vixen R200SS & Celestron 6" F5 Achro Refractor
- Location: (Tampines) Earth of Solar System in Orion Arm of Milky Way Galaxy in Local Group Galaxies Cluster
Hi,
Anyway, EQ mount don't have such a serious problem... may be only have difficulty when point to area that are very very near to the pole.
Have a nice day.
Oh... That is really bad..ya the fork in eq position. actually the southern side is not too bad.... can see up to about40 deg above horizon. but for the north, its bad. lots of problem in seeing hercules, cygnus, etc.
Howabout the german equatorial mount? does it give any such limitations ?
Anyway, EQ mount don't have such a serious problem... may be only have difficulty when point to area that are very very near to the pole.Have a nice day.
Yang Weixing
"The universe is composed mainly of hydrogen and ignorance."
"The universe is composed mainly of hydrogen and ignorance." 
For fork mount on altazimuth mode, not much problem pointing at any part of the sky or tracking except maybe tracking at zenith.ya the fork in eq position. actually the southern side is not too bad.... can see up to about40 deg above horizon. but for the north, its bad. lots of problem in seeing hercules, cygnus, etc.
Howabout the german equatorial mount? does it give any such limitations ?
For fork mount on equatorial mode, usually have restriction pointing south as the optical tube hits the fork base. Pointing north is possible for polar alignment and observation at higher lattitudes but no practical use on the equator.
For german equatorial mount, usually no issue pointing at any part of the sky, while there will be change in tracking at the local meridien.
hi oxyqn,
the GEM does not have any problem with directional pointing on any part of the sky. As rlow has pointed out, when the GEM is placed on tracking mode and it traverses across the meridien (the hemispherical line cutting from north to south across the zenith), there might be a slight shift in moment due to the counterweight and optical tube. However, this problem is very slight when proper balacing is achieved. An additional note on AZ mode of the fork mount, from experiences with the celestar 8 in AZ mode, it is difficult to see circumpolar constellations and objects due to the physical limitation of the fork traversal. Nevertheless, it is highly recommend to get a GEM instead if you are thinking of getting a mount, as it allows for greater expansibility into the imaging arena.
The benefits are as follows:
1) Almost any OTA can be used within the limits of the mount capacity.
2) Pointing limitation is nullified.
3) Greater moment stability (as compared to EQ mode of fork mount where the SCT OTA is tilted precariously to one side and the tripod at the other end) This is ok if you have the bare OTA, but if you put more accessories, balancing is more critical)
4) No limitations to the use of off-axis guiders, photo adpaters, etc. For a fork mount, if you put a prime focus camera at the SCT visual back end for example, and you are shooting a zenith object at AZ mode, it is not possible due to hindrance of the base plate of the fork mount. In EQ mode, you might have problems shooting circumpolar southern objects due to this similar hindrance problem.
One disadvantage would be the GEM is normally heavier per se given a specific OTA application, and comes in more parts that will take a longer time of assembly for the beginner. However, personally, the advantages listed above outweighs the cons.
good luck!
the GEM does not have any problem with directional pointing on any part of the sky. As rlow has pointed out, when the GEM is placed on tracking mode and it traverses across the meridien (the hemispherical line cutting from north to south across the zenith), there might be a slight shift in moment due to the counterweight and optical tube. However, this problem is very slight when proper balacing is achieved. An additional note on AZ mode of the fork mount, from experiences with the celestar 8 in AZ mode, it is difficult to see circumpolar constellations and objects due to the physical limitation of the fork traversal. Nevertheless, it is highly recommend to get a GEM instead if you are thinking of getting a mount, as it allows for greater expansibility into the imaging arena.
The benefits are as follows:
1) Almost any OTA can be used within the limits of the mount capacity.
2) Pointing limitation is nullified.
3) Greater moment stability (as compared to EQ mode of fork mount where the SCT OTA is tilted precariously to one side and the tripod at the other end) This is ok if you have the bare OTA, but if you put more accessories, balancing is more critical)
4) No limitations to the use of off-axis guiders, photo adpaters, etc. For a fork mount, if you put a prime focus camera at the SCT visual back end for example, and you are shooting a zenith object at AZ mode, it is not possible due to hindrance of the base plate of the fork mount. In EQ mode, you might have problems shooting circumpolar southern objects due to this similar hindrance problem.
One disadvantage would be the GEM is normally heavier per se given a specific OTA application, and comes in more parts that will take a longer time of assembly for the beginner. However, personally, the advantages listed above outweighs the cons.
good luck!
In addition, fork mount are limited usually for short tubes such as schmidt cassegrain and maksutov cassegrain scopes, harder to balance, and have limited versatility for adapting different ota. As Remus has pointed out, it is however lighter, easier to setup and more portable than GEMs, and maybe more useful for those who are grab-and-go visual observers, while GEMs are heavier, more balanced, versatile for adapting different scopes, and favored by astrophotographers.