#21  
Old 22-02-2013, 05:15 PM
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Originally Posted by Bassnut View Post
Ultra wide field is evil, the work of the devil. Those that fiddle in ultra WW territory will suffer, and rightly so, astronomy is all about zooming in .
Fred I just cannot stop sinning.

Bert
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  #22  
Old 22-02-2013, 05:53 PM
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This is part of the solution for differential flexure between the camera and optic.

Bert
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  #23  
Old 22-02-2013, 10:18 PM
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Originally Posted by Bassnut View Post
Ultra wide field is evil, the work of the devil. Those that fiddle in ultra WW territory will suffer, and rightly so, astronomy is all about zooming in .
Forgive me Fred, I know I have sinned, and strayed from the righteous and narrow field path.

But at F3.8 I have had no flexure, diffraction or attenuation.

Images have remained pure and self guided ahead of deep H-alpha filter-darkness.

And there have been twilight apparitions...stars with the hair of the Angels!

But I was not swayed by those red Honders demonds!

With Christen purity, I was guided by Saint Barbara.

I feel I will one day return to (the) flocking, within the straight and narrow fields.

Last edited by Peter Ward; 22-02-2013 at 10:58 PM. Reason: hamming it up
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  #24  
Old 22-02-2013, 11:20 PM
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marc4darkskies (Marcus)
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Quote:
Originally Posted by Bassnut View Post
Ultra wide field is evil, the work of the devil. Those that fiddle in ultra WW territory will suffer, and rightly so, astronomy is all about zooming in .
Quote:
Originally Posted by Peter Ward View Post
Forgive me Fred, I know I have sinned, and strayed from the righteous and narrow field path.

But at F3.8 I have had no flexure, diffraction or attenuation.

Images have remained pure and self guided ahead of deep H-alpha filter-darkness.

And there have been twilight apparitions...stars with the hair of the Angels!

But I was not swayed by those red demonds!

With Christen purity and being guided by Saint Barbara.

I feel I will one day return to (the) flocking, within the straight and narrow fields.
Peter is a little lost lamb - let us pray for his return to the flock. Forget about Bert - too far gone - his scope even looks like the spawn of the devil

Oh Fred, who art in Sydney somewhere
Hallowed be thy focal length
Thy zooming be done
In Peter's observatory as it is in yours.
Give us this night our evening closeup
And forgive Peter his tresspasses
As we forgive those who do widefields and then scale them down
Lead us not into widefield, but deliver us from tiny galaxies
For thine is the focal length, the planetaries and the bok globules
Up closer & closer
Amen

PS: Sorry Martin!
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  #25  
Old 23-02-2013, 07:40 AM
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Here are a few notes from my own experience with the RH200.

First of all, OS ships this unit with no tube rings. A single arm, off-axis mechanical support is wrong if you expect to have any mechanical stability.

A myth: Having tube rings on this telescope does not distort the wave front, or mechanical orthogonal of the system.

The STI guider and lens assembly works like most autoguiders - it measures the centroid of the star image. I use mine on the RH200 without any guiding problems.

Tested: 3nm filters are a no recommend for f/3. Been there, done that. The transmission impact is serious. So much so that my 6nm bandpass shows more nebulae in 600 sec exposures than 1800 sec the exposure through a 3nm filter.

And finally, it's not about wide field, its about very short FL that mandates close attention to the image train, optical collimation, and focus control. It takes a real master to tame the beast.

jg
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  #26  
Old 23-02-2013, 11:07 AM
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Quote:
Originally Posted by marc4darkskies View Post
Peter is a little lost lamb - let us pray for his return to the flock. Forget about Bert - too far gone - his scope even looks like the spawn of the devil

Oh Fred, who art in Sydney somewhere
Hallowed be thy focal length
Thy zooming be done
In Peter's observatory as it is in yours.
Give us this night our evening closeup
And forgive Peter his tresspasses
As we forgive those who do widefields and then scale them down
Lead us not into widefield, but deliver us from tiny galaxies
For thine is the focal length, the planetaries and the bok globules
Up closer & closer
Amen

PS: Sorry Martin!


Someones preeetty happy these days..? I wooonndddeerrr whyyyyy?

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  #27  
Old 23-02-2013, 12:50 PM
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A myth: Having tube rings on this telescope does not distort the wave front, or mechanical orthogonal of the system.


Not sure what you meant here - the tube rings do not distort the wave front and its a myth that they do?

So I take it from your brief review here you would not recommend this scope over a good fast refractor despite the fast speed of the RH200?

Greg.
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  #28  
Old 23-02-2013, 02:47 PM
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Quote:
Originally Posted by gregbradley View Post
A myth: Having tube rings on this telescope does not distort the wave front, or mechanical orthogonal of the system.



So I take it from your brief review here you would not recommend this scope over a good fast refractor despite the fast speed of the RH200?

Greg.
Hi Greg, No, I did not say that. I make no such recommendation. F/3 requires a mastery of the beast. You are dealing in collimation and tip tilt adjustments of just a few microns, and systems with this tight tollerance need the mechanical + thermal stability, and fine adjustments to enable success. It could be an f/3 refractor, f/3 compound telescope, or f/3 Newtonian. You also need to make sure that your narrowband filters are optimized for f/3 as well. And as you have read, the steepness of the light cone negatively impacts the use of an OAG.

I solved a few things with the RH200 which is typical of any telescope shakedown for imaging:

- precise and measured adjustments of the tip-tilt backplate
- proper spacing of the CCD camera from the rear optical element
- motorized focuser
- optimized bandpass for narrowband
- Classic tube riings with dovetail support for stability
- Separate guidescope with high sensitivity
- Dew heater tape on the front element
- Solid, precision mount (in my tests, an AP 1200 goto)

There are some clear advantages to the FSQ:

- Larger image circle
- Ability to motorize the rotation of the camera angle
- f/5, better performance with 3nm narrowband filters
- No dependency on critical distance from optics to the CCD array
- No central obstruction


jg
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  #29  
Old 23-02-2013, 04:17 PM
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Thanks John.

Greg.
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  #30  
Old 23-02-2013, 05:09 PM
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Originally Posted by strongmanmike View Post


Someones preeetty happy these days..? I wooonndddeerrr whyyyyy?

Mile, I'll soon be running a FLI atlas focuser with the Honders. They look to be the bizzo for low profile plus zero tilt.

Last edited by Peter Ward; 23-02-2013 at 09:18 PM. Reason: insane spell checker
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  #31  
Old 24-02-2013, 07:57 AM
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Mile, I'll soon be running a FLI atlas focuser with the Honders. They look to be the bizzo for low profile plus zero tilt.
I'll be putting the Atlas on my 305 when it arrives. Have one on the FSQ in Coona and it rocks. I've even made focus corrections during exposures without any shift. Highly recommended for its extreme precision and load carrying ability.

j
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