multi mirrored optics.

[bmitchell82 (Brendan)]

Okay, pie in the sky...

I know they have massive mirrors utilizing a multi mirrored setup. how do they do it, and is it useable to astronomy guys like us?

Are the mirrors figured differently or are they just a set of hyperbolic mirrors coming together at a common focal point?

I was thinking this while i was trying to fall asleep last night, as a test you could utilize something like 8" GSO mirrors giving you a total light capacity of 192 cm^2, to get something of that mag you would require a close on a 14" monolithic mirror.

I do understand that it wouldn't be easy to set up, and collmination might be "tricky" but if it ment you could have bigger mirrors made up of multiple small ones that could be a bit of a "journey"

3 x 10" mirrors gives 300cm^2 eqiv to a 17.3" mirror. how hard are 10" mirrors to obtain.?

Ide like to get your opinions as i could start off with small mirrors at low cost and if the project works. then i could basically ramp it upto something a bit better.

[GrahamL]

I don't think it works quite like that .. I'm pretty sure this has been discussed in a thread round here which I can't seem to find for now

Due to the difficulties in aligning, much less phasing, an array of mirrors, the only real application for a telescope like this would be as a light bucket.
The image quality from an array of mirrors will be less than that of a single mirror due to interference between the separate wavefronts. Mirror arrays like the Keck telescope that do succeed in behaving like a single mirror only work because the mirrors are in phase. This means that they are held in very very very careful spatial alignment in such a way that their optical surfaces can act as one continuous surface. For example, if one of the segments of a Keck mirror drops down by half a micron relative to its neighbors, you have a mirror that acts like a single mirror with a big fat 1 wave depression in it. Another problem is that an array of mirrors has more “edge” per unit surface area than a single mirror. This will increase diffraction, though if you managed to even have to worry about this, bravo!
If all you want is a light bucket, say for spectrography, the idea isn’t all that bad. But then you could probably find someone with a big crappy mirror they would be willing to sell cheap, and forget the whole problem of making the elaborate mirror cell.

[koputai (Jason)]

Yep, not long ago, here:
http://www.iceinspace.com.au/forum/s...ad.php?t=31364

Cheers,
Jason.

[bmitchell82 (Brendan)]

so its a case of specially figured mirrors. though the sums still stand with the square of size for mirrors. Now if only we could figure the mirrors. my idea would be you would either need 3 mirrors with a cassigrain setup or run it like a newt and shoot it out at the side.

I belive that if you configure 3 mirrors in a paraboidal shape and get them shaped following that curve you will essentially have 1 mirror, but split into smaller parts. Collmination would be a little tricky like i originally said but not impossible, understanding the light path will give you the needed techniques as all collmination is doing is making sure the lightpath focus's in the middle of your eye piece/ccd/camera what ever.

I can see after drawing down a mirror that putting 3 paraboidal mirrors would send the light paths in different directions.

Like it was said why should the professionals have all the fun? i think i might start playing! compulsive tinkerererererrrrrrr.

[Satchmo]

What you need essentially are off -axis parabaloids which are very expensive and difficult to make unfortunately, which would defeat the purpose.

A binocular telescope, using a mirror for each eye is still the easiest form of multi-mirror telescope giving much more light for a given field of view and 40% higher visual contrast over one eye, but not much use for astrophotographers

[bmitchell82 (Brendan)]

OH HE WHIPS THE HORSE HARD AS IT PLOUGHS INTO THE GROUND.... getup you useless beast

[Paddy (Patrick)]

Originally Posted by bmitchell82

OH HE WHIPS THE HORSE HARD AS IT PLOUGHS INTO THE GROUND.... getup you useless beast

That was how I felt after posting my thread on the subject. Then I thought about a more conventional binewt and the need for duplicating eyepieces, peering backwards from the front end when observing on ladders for the zenith and squatting for any low objects. Came to the conclusion that a scope with one big primary was the way to go.

I also wondered how 2 primaries affect resolution, given that a bigger primary resolves better. Then saw an article on the Large Binocular Telescope which indicated that the resolution was increased by the separation of the two mirrors, but only in the direction of the separation. they said that the Giant Magellan Telescope would have equal resolution as it has a radially symmetric array of mirrors. I thought this was interesting as well as being another advantage for a single large primary. I'm happy to be corrected if I'm talking through my hat.

[GrahamL]

OH HE WHIPS THE HORSE HARD AS IT PLOUGHS INTO THE GROUND.... getup you useless beast

Dont be to hard on yeselves its not an unreasonable idea .. a lot of us
over the years by Mr googles reckoning think this I'm sure .,

The real problem lies in that when the economic reality and its practical application are finished butting heads they are both lying dead on the ground with the horse

[bmitchell82 (Brendan)]

ahh well happy days, im sure with the advent of the industrius little buggers in our oceana area theyll figure it out sooner rather than later