premium 8" mirror

[Brian W]

Hi all, I currently own and enjoy a Meade 8" LightBridge which will take me years to outgrow. However when I do develop the skills to warrant a finer instrument rather than succumb to aperture fever we will probably install a superior primary and secondary.

Living in the Philippines means shipping is less expensive from Australia.

Any recommendations about who the better mirror makers are down under would certainly be appreciated.
Brian

[Garyh]

Try Mark........... Satchmo (http://www.iceinspace.com.au/forum/member.php?u=633)
Can`t think of his website at the moment but he shall make you a premium mirror!
cheers Gary

[Brian W]

Thanks for the heads up, I just e-mailed him.
Brian

[koputai]

http://deepsky.cia.com.au/optics/

Though I think Mark has said here before that he doesn't do 8 inch mirrors.

Is there really that much difference between a decent GSO/whoever mirror and a custom mirror at this apperture and f-ratio (8inch f6) ?

Cheers,
Jason.

[Garyh]

Maybe you would be better off getting your 8" mirror refigured?
May save you a few dollars?
I think you will need really good seeing conditions to see the difference but.

[Brian W]

I don't know if there is a great difference between my present mirror and a premium one but that is one of the unknowns that I hope this thread will answer.

I do know however, to answer another question, that we have very dark skies where I live in the Philippines and on occasion our sky is exquisite. Some refer to it as the Flame nebula, some as the Tank Tread Nebula and Orion software refers to it as Orion B, but by whatever name you use last year I caught it in my 4.5" short tube Orion reflector, on 2 separate nights.

[toyos]

In that case, there's no better option than getting a quality 4"-6" Apo refractor :D You will see a much bigger improvement in image QUALITY under various seeing conditions (quantity/extra aperture aside) than replacing the mirror of the same dob.


Anyway, good mirrors are cheaper in USA and there's a greater selection of companies to choose from, you'll still save more getting it from there even though the postage cost is slightly higher.

[Starkler]

Royce in the US does quality mirrors in a range of sizes down to 6".

http://www.rfroyce.com/stand_mirrors.htm

[Satchmo]

Succumbing to aperture fever generally means getting a 16" to 20" scope. A good 10" Newtonian will generally leave any 4" to 6" Apo for dust on any kind of celestial target.

[Brian W]

And if you would be so kind as to deposit the needed funds in my bank i will order the Takahashi :thumbsup:
Brian

[Brian W]

Thats what I have always been told Satchmo. And thanks for the advice about moving up to a 10. However I have always been a bit of a minimalist, mini cooper, 650 single motorcycle, and the venerable fleet canuck was one of my favourite planes to pilot so the 8 is great.
Brian

[rmcpb]

If you want to "improve" your 8" run the stats on the secondary size and see if you can replace it with a smaller one. I did that by installing a low profile focuser and the contrast is better on my 8".

Even without the low profocle focuser you will probably find the standard secondary is oversize.

[Satchmo]

That at least narrows down your choices but you can concentrate on optimisation. I agree with Rob a smaller secondary would be a start. Perhaps a curved vane spider + Quartz secondary from Protostar would be a good option.

[Brian W]

All of the above I will look into, thanks for the advice.
Brian

[tnott]

I would star test the setup you have first, before replacing everything with optics that may only give better images on 1% of nights. Then maybe replace the secondary first, if you think it is needed.

[Satchmo]

Thats some kind of generalisation. I find that really good optics perform noticeably better for longer moments in poor seeing conditions. Mirrors that have a _geometric_ blur spot of half the airy disc diameter, with the wavefront deflections of some kinds of poor seeing, seem to show tighter star images for longer periods. This is not theory its on the basis of 30 years of practical observing. In short, I find better mirrors can give superior performance all year round under more varying conditions.

In the case of some of the scopes I see at star parties, with collimation problems and no maneagement of thermal issues, there'd be no benefit from better optics. Many of the large cheap Dobs I see in the field are let down on that score as the owners are too busy being `blown away ' by the brightness of the images.:)

[tnott]

Sure, but at least check the optics you have first before spending big bucks.

I would also second the comment about cooling and collimation.