Why no premium Hyperstar?

[sharkmelley]

I'm very interested to see how well the Riccardi Honders works out in the long term.  On paper, at least, it ought to give Tak Epsilon performance but without the diffraction spikes. It's slower than a hyperstar but its main advantage over the "premium hyperstar" idea is that the camera isn't hanging out in front.  I watch with interest ...

Mark

[ollypenrice]

Yup, but that's on paper. Out under the stars give me an FSQ refractor any day. Fast enough and infallible.

Olly

[Chris]

Fascinating thread, I don't think I will be Hyperstaring (if thats the phrase) my C8 in the future but might try f/6.3 if my mount can cope with a 1.3m focal length which I have doubts about. The coment about the old school Meade 3.3 reducer is an interesting one as I do wonder if modern computer aided design would allow for a better corrected design (no spikes then!). I might still buy a 3.3 reducer if one pops up, wont make a difference imaging with an Atik titan!

There is another design I've seen which is interesting and would at least reduce spike artifacts, I can't find the link but it was similar in design to a Newtonian but the primary focused the light to the front edge of the tube where there was a secondary bang opposite the focuser. The result was just a small bite of obstruction on the edge of the circle. I think I saw it on the Telescop Service site, not sure how fast it is though or how fast it could be made?

[Chris]

Found it:

http://starizona.com/acb/basics/equip_telescopes_other.aspx

The primary looks a bit crazy so I have a feeling that making a really fast one would be expensive and weird to collimate?

[ollypenrice]

More paper!!

Olly

[Merlin66]

Olly,

What happened to those fast (f3.5) Cometrackers/ Comet Seekers?

I had the Meade 6" f3.5 newt for a while and it seemed to work well.....

Then you have the Schmidt cameras circa 1970....it may be easier to design a field flattener for them than for some of the others??????

[ollypenrice]

Olly,

What happened to those fast (f3.5) Cometrackers/ Comet Seekers?

I had the Meade 6" f3.5 newt for a while and it seemed to work well.....

Then you have the Schmidt cameras circa 1970....it may be easier to design a field flattener for them than for some of the others??????

I don't know. There are lots of rum designs out there but making them work is the thing.

Olly

[FraserClarke]

What do you think would be your ideal parameters then Olly?  What is the useful range of pixel size and field of view? (OK, can accept the 'as big as possible' argument for that, but there is a size which would do 'most' objects of interest).  F/ratio isn't everything (otherwise we'd all be using 50mm f/1.2 lenses).

Putting things at prime focus on a small telescope is always going to be tough, just because there isn't much space for the necessary mechanics. Some narrowband filters are going to have issues working in a very fast beam, which might be a limit.

One thing I've never seen on small telescopes is an equivilent of the instruments that are used on big telescopes. Large telescopes have native speeds of F/8 to F/15, but the instruments on the back end take this beam and reimage it down to F/2 or so (like a focal reducer, but with a few more features).  That means the 'fast' optics are relatively small, making them easier to handle. They also include a collimated beam with a  'pupil plane', which is the ideal place to put filters as it's the smallest point in the optical beam (so the size of your filters don't really increase with the size of your detector).

I wonder if there would be mileage in building something like that for a small telescope. It'd have all the speed advantages of the hyperstar, but probably less field. It would though be much easier to fit in a big set of filters, and could work with many more cameras on the back end.

[ollypenrice]

What do you think would be your ideal parameters then Olly?  What is the useful range of pixel size and field of view? (OK, can accept the 'as big as possible' argument for that, but there is a size which would do 'most' objects of interest).  F/ratio isn't everything (otherwise we'd all be using 50mm f/1.2 lenses).

Putting things at prime focus on a small telescope is always going to be tough, just because there isn't much space for the necessary mechanics. Some narrowband filters are going to have issues working in a very fast beam, which might be a limit.

One thing I've never seen on small telescopes is an equivilent of the instruments that are used on big telescopes. Large telescopes have native speeds of F/8 to F/15, but the instruments on the back end take this beam and reimage it down to F/2 or so (like a focal reducer, but with a few more features).  That means the 'fast' optics are relatively small, making them easier to handle. They also include a collimated beam with a  'pupil plane', which is the ideal place to put filters as it's the smallest point in the optical beam (so the size of your filters don't really increase with the size of your detector).

I wonder if there would be mileage in building something like that for a small telescope. It'd have all the speed advantages of the hyperstar, but probably less field. It would though be much easier to fit in a big set of filters, and could work with many more cameras on the back end.

Interesting. I'm sure there are ideas out there that haven't filtered through. I guess I'd be happy at around F3 but I'd want to cover a 46mm diagonal. Probably 1.8 arcsecs per pixel would be my ideal. The nearest would be an optical window version of the Epsilon, I guess. However, I like things to work so I'm very happy at F5 with the FSQ.

Olly