Which Cassegrain?

[vk5cp (Chris)]

I have a 12" DOB but would like to buy another scope with goto athat I could use with a camer and use mobile. I was thinking of a Meade LX90 8inch or a LX200 8inch. Any advice from the brains trust out there.

Chris

[cometcatcher (Kevin)]

G'day Chris. The LX90 and LX200 series are fork mount. For long exposure astrophotography you need a GEM or wedge mount. LX80 series, LX600 or LX800 series. Kind of expensive though.

A cheaper option might be a HEQ5 goto or NEQ6 and pick a scope to mate with it. Depends what you want to shoot. Planets, wide field deep sky or narrow field deep sky. They all require slightly different setups.

A bit OT but have we spoken on 6m in the past? The call sounds familiar.

Kevin / VK4BKP

[vk5cp (Chris)]

Thanks Kevin,

I have decided to go with the LX90ACF (just ordered it will arrive next week) Hopefully this will allow me to go portable and start playing with AstroPhotography. If the photo bug bits I guess it will mean another (bigger) scope and a dome.

The last time I worked 6m was a couple of years ago from Lord Howe Island. There was an opening and I got most of VK on a 40M dipole! running about 10W.

73 de Chris VK5CP

[Poita (Peter)]

Damn, I have a C8 Edge HD with Hyperstar that is looking for a home.

The ACF is a nice scope, a bit heavy for its size. I had the 10" version and it gave really great views.

[Saturn%5 (Graeme)]

Originally Posted by vk5cp

Thanks Kevin,

I have decided to go with the LX90ACF (just ordered it will arrive next week) Hopefully this will allow me to go portable and start playing with AstroPhotography. If the photo bug bits I guess it will mean another (bigger) scope and a dome.

The last time I worked 6m was a couple of years ago from Lord Howe Island. There was an opening and I got most of VK on a 40M dipole! running about 10W.

73 de Chris VK5CP

Seems this turned into ham meeting place good luck with the new scope lets see some pics soon.

73 Graeme vk7dz

[alanwilko (Alan)]

lX200 is damn heavy with the field tripod !

[OICURMT]

Originally Posted by cometcatcher

The LX90 and LX200 series are fork mount. For long exposure astrophotography you need a GEM or wedge mount.

This statement is is a bit vague...

There is a lot of AP performed on fork mounted telescopes and the fork design is one of the most tried and true. Depending on the use, longer wide field exposures can be achieved without a wedge, depending on the exposure time. The Fastar system only requires a stack of 30 second exposures, thus limiting rotational effects.

Long exposures are easily achieved either via using a wedge or a field de-rotator. If you are imaging the sun, moon or planets, then the standard alt-az configuration is fine.

I'm sorta tired of listening to the standard "internet myths" of the disadvantages of fork mounted scopes... if they are so bad, then why are most large scale scopes (i.e. metres in diameter) mounted that way?

I have both types and honestly, I don't give a flying... which one I use.

As for the comment about weight. I will admit that the LX200 with a field tripod is heavy. But honestly, the NEQ6 is not made of cheese... damn heavy as well. That's why I have my U2K, light as a feather compared to others.

OIC!

[Poita (Peter)]

Originally Posted by OICURMT

This statement is is a bit vague...

There is a lot of AP performed on fork mounted telescopes and the fork design is one of the most tried and true. Depending on the use, longer wide field exposures can be achieved without a wedge, depending on the exposure time. The Fastar system only requires a stack of 30 second exposures, thus limiting rotational effects.


OIC!

Fastar is not available for the LX90ACF though which the OP is buying I think. It also reduces your focal length on an 8mm scope to under 600mm, and only works with certain cameras and scopes so there are considerations there.

I never managed to get long guided exposures happening with the fork on a wedge at full focal length, I found it was just too unstable whatever I mounted it on.
I never tried a derotator, what are they worth?

[barx1963 (Malcolm)]

Originally Posted by OICURMT

I'm sorta tired of listening to the standard "internet myths" of the disadvantages of fork mounted scopes... if they are so bad, then why are most large scale scopes (i.e. metres in diameter) mounted that way?


OIC!

Most large scope are mounted this way because EQ mounts are impractical at that size. The 200" Hale at Palomar is mounted on a horseshoe mount which is a variant of an EQ, as is the AAT at Siding Springs. Modern big scopes (Keck, Gemini etc) are mounted alt az and as I understand it use something similar to a field rotator to compensate.

Malcolm