The Great Orion Nebula

[Ian]

well, if the sky is dark enough, you dun really need big scopes for imaging. A modest 3-4 inch scope will do. But need the tracking mount though....

I disagree, aperture rules for serious astrophotography and of course a decent mount is as you rightly state paramount. It's a shame that Meade/Celestron etc cut corners in their mounts as the optics are quite good for a mass produced scope.

 

[Wai]

I disagree, aperture rules for serious astrophotography and of course a decent mount is as you rightly state paramount. It's a shame that Meade/Celestron etc cut corners in their mounts as the optics are quite good for a mass produced scope.

quite true....the mount got some problem already, need to modify something inside to fine tune it...

 

[Ian]

quite true....the mount got some problem already, need to modify something inside to fine tune it...

All the common mounts by the following manufacturers have IMHO major design flaws:

Celestron
Losmandy (except their biggest mount)
Meade
Vixen

In most cases no amount of fine tuning will fix what are major design flaws and cost cutting exercises eg:

Insufficient shaft diameters to produce the necessary rigidity to ensure flexure is under 5-10 arc seconds.

Bearing centers insufficiently spaced which leads to high radial loading of the bearing journals as well as flexure in the bearing assemblies. (particularly bad on fork mounts)

Incorrect bearing selection and or material choices.

Low quality drive components - eg: Byers wheel/worm sets used in the Meade/Celestron telescopes have terrible natural periodic errors and no amount of electronic compensation will really sort the mechanical problems out.

Equatorial wedges (Meade/Celestron) - God awful heaps of crud, they suffer from massive amounts of flexure, poor design and even lower grade castings.

The other major problem (this one is fixable) with Meade/Celestron Fork mounts as found on the LX series Meades is that the manufacturers cut a massive corner by not helicoiling the base mounting holes on the drive base. Threads in Aluminum are extremely soft and over time the threads strip. In professional engineering/manufacturing it is standard practice to fit helicoils or their equivalent in all threaded holes over 4mm diameter that are subjected to either high loading or constant use. 3 bucks worth of helicoils at the time of manufacture per unit would solve this problem permanently.

As for the OTA's they suffer even worse technical design and manufacturing flaws :devil:

 

[Starman]

All the common mounts by the following manufacturers have IMHO major design flaws:

Celestron
Losmandy (except their biggest mount)
Meade
Vixen

In most cases no amount of fine tuning will fix what are major design flaws and cost cutting exercises eg:

Insufficient shaft diameters to produce the necessary rigidity to ensure flexure is under 5-10 arc seconds.

Bearing centers insufficiently spaced which leads to high radial loading of the bearing journals as well as flexure in the bearing assemblies. (particularly bad on fork mounts)

Incorrect bearing selection and or material choices.

Low quality drive components - eg: Byers wheel/worm sets used in the Meade/Celestron telescopes have terrible natural periodic errors and no amount of electronic compensation will really sort the mechanical problems out.

Equatorial wedges (Meade/Celestron) - God awful heaps of crud, they suffer from massive amounts of flexure, poor design and even lower grade castings.

The other major problem (this one is fixable) with Meade/Celestron Fork mounts as found on the LX series Meades is that the manufacturers cut a massive corner by not helicoiling the base mounting holes on the drive base. Threads in Aluminum are extremely soft and over time the threads strip. In professional engineering/manufacturing it is standard practice to fit helicoils or their equivalent in all threaded holes over 4mm diameter that are subjected to either high loading or constant use. 3 bucks worth of helicoils at the time of manufacture per unit would solve this problem permanently.

As for the OTA's they suffer even worse technical design and manufacturing flaws :devil:

I agree that most of these mounts has some problems expect for maybe the losmandy G-11. Or William Optics GT-1. Or of course the AP series....

But for short guiding, most of these mounts are ok. If they are well polar aligned, 3-10 minutes should be ok...if not, we can always do a manual guide.

Nowadays because we can use digicams and stack, we don't really need long exposures anymore. Mike Unsold of the ImagePlus software took a lot of very nice photos with just couple of minutes of guiding with the 10D. Quite awesome.

 

[Ian]

I agree that most of these mounts has some problems expect for maybe the losmandy G-11. Or William Optics GT-1. Or of course the AP series....

But for short guiding, most of these mounts are ok. If they are well polar aligned, 3-10 minutes should be ok...if not, we can always do a manual guide.

Nowadays because we can use digicams and stack, we don't really need long exposures anymore. Mike Unsold of the ImagePlus software took a lot of very nice photos with just couple of minutes of guiding with the 10D. Quite awesome.

The Losmandy G-11 has heaps of problems, it's drive gear is just accpetable and it suffers from the normal bearing problems and undersized shafts

If you can get any of the mounts (with exception of th G-1 and williams) to do 3 minutes with-out a guide correction and retain a star image of under 5 arc seconds then I'd be frankly amazed. I've never seen it done as the periodic error is so bad on most drives.

DSLR's aren't capable of the longer exposures required to do real deep sky work on the faint fuzzies .. and no amount of stacking will change that That's why proper cooled ccd cameras are the way to go for deep sky. With planetary work nothing beats a good webcam eg: Toucam, Vesta etc.