GSO v Meade v Planewave

[acarleton]

So i am playing the game "what setup would i get if i had the money" and it brought me to a question that i have not been able to find the answer to. for any given aperture, what is the real difference between GSO, Meade and Planewave optics. With each being twice as expensive as the last, is there much of a difference with the clarity of images obtained in each of these?

example of 3 dream scopes;

GSO
http://www.andrewscom.com.au/site-section-10.htm

Meade
http://www.bintel.com.au/Telescopes/Cassegrain/Meade-14--f/8-ACF-Optical-Tube-Assembly/1550/productview.aspx

Planewave
http://www.bintel.com.au/Telescopes/Cassegrain/PlaneWave-CDK-14-/1769/productview.aspx

[gregbradley]

For visual of for imaging?

I have Planewave for imaging and have had a Meade scope. Not had a GSO.

From what I can tell - GSO have good optics but poor focusers etc. So if you spend the time upgrading them you can have a nice imaging machine. RCs are not great for visual.

Meade are mostly SCTs which are good for visual and planetary imaging. Not so great for imaging due to mirror flop. Also they tend to have largish stars in the image and a small corrected circle for the camera so only smallish cameras work with them.

Planewave is more high end optimised for imaging and they are very good. The promo says they are good for visual. I have a 17 inch and only looked through it a few times and it was not a good view. They show up the seeing more and perhaps the seeing was bad at the time.

Greg.

[acarleton]

Thanks for that Greg, i would also intend on imaging. The GSO focusser could be upgraded and you would still have a bucket load of cash left over from a Planewave ... Has anyone had a go at one of the new truss RC GSO's ? any good?

i have a 10" newtonian GSO and i have been really disappointed in its planetary imaging capabilities. it might be something that i am doing but for the life of me i am unable to resolve any detail of note.

[gregbradley]

Planetary imaging requires excellent seeing primarily. Also a power barlow from Televue and F40 or so. I have only done a bit using an 11 inch Celstron SCT and it was fun and I got OK results. Nothing spectacular.

I would go for the GSO myself. As you point out the savings are enormous and the optics seem to be quite good. As you say a nice new Feathertouch or Moonlite focuser and you have something quite nice.

Depending on your budget the 10 inch truss or the 12 inch truss would be the way to go if your mount can handle it. Solid tube might be ok up to 10 inches but really a truss leaves a tube for dead. Thermal currents in a tube are going to cause some difficulties.

2.5 metre focal length on an inaccurate mount could be a challenge though.

Greg.

[raymo]

Your 10" GSO Newt, assuming that all is well with it, is quite capable of
giving you good images of planets. You don't say what camera or method
you used. Video is really the only way to go, and it takes perseverance
and good seeing. If the seeing is not good enough, you will get rubbish.
raymo

[acarleton]

Hi Raymo,

i brought this up a while ago and still haven't been able to resolve the issue.

i am using my 10" newt
QHY5L-ii mono camera
5X televue powermate (1.25")
stacking in registax

and i have attached my efforts, i tried Saturn for months and that is the best i could come up with. i have similar issues when i shoot the moon at high magnification, it always seems to be out of focus.

[SkyWatch]

Hi Aidan,
Three questions:
Have you done a star test on your mirror to assess the figure?
Do you use a Bahtinov mask to focus?
How's your collimation?

All the best,

Dean

[acarleton]

Hi Dean

1) i am not sure what you mean by a star test ... can you please explain
2) no i dont have a Bahtinov mask but i have been thinking about getting one. i dont think it is a focus issue because even when i change the focus slowly it never becomes clear.
3) Collimation is good, i use a laser collimator, i thought this was the issue so spent a long time on it.

[gregbradley]

Newts can be good for planetary as that is what Wesley uses and his images are at the top.

His though has the mirror cooled. That gets rid of the thermal boundary layer on the surface of the mirror when there is a temp difference between the mirror and ambient temp (there almost always is a lag for the mirror to catch up).

So the scope needs fans and better still a cooler to get the mirror cool.

But at that mag you also need good seeing and clear skies.

Greg.

[raymo]

From looking at your images I would say that there is nothing much
wrong with your scope. Your focus is probably a bit off, and possibly
the seeing was just not good enough. It has to be really good in
order to get nice images. The Saturn image is almost there; it took
me a while to get one better than that. Are you full bottle with the
Registax procedure?
raymo

[SkyWatch]

Hi Aidan,

A star test is when you move a star in and out of focus and look at the image to see if there are any aberrations. Lots of material out there, but a good place to start for a basic explanation is: http://starizona.com/acb/basics/using_startesting.aspx
A Bahtinov mask isn't expensive, and you can even make your own (just google it to get templates etc): but it really helps when you are trying to get best focus.
I am always a bit wary of laser collimators as they can easily be off-collimation themselves in your focuser. Have you twisted it around in the focuser to make sure the laser doesn't move?

Good luck!

Dean