Hyperstar

[vincentnm]

Hi All,

I am thinking of going the hyperstar route. I plan to buy a used C14 and fit it with a hyperstar lens. Since this venture will literally blow my pocket, I'd like to be really sure what I am getting into.

I've read many of the FAQs and tech specs. But I cant find too many field reports.

What are the caveats ? Anything potential problems I should be aware of before I bust my hump on this?

Thanks,

Vincent.

[SteveL]

As an (Ex)Hyperstar owner, I think I can chime in here with some experience

Focus is uber-critical! I mean really silly critical. The CFZ is somewhere in the region of 6 micrometers. Manual focusing just isnt going to cut it with the standard SCT focuser. And because the camera is stuck out the front, you cant use a crayford style focuser on the raer... because the light never gets that far!

Collimation is also critical, for exactly the same reason as above. Expect to purchase something like CCD Inspector to enable collimation to be a much less stressful job.... you cant collimate a hyperstar by using your eyeballs!

The distance form the Hyperstar to the CCD itself also needs to be exact. Even a few mm will cause some coma round the edges. This is why Starizona do two adapters to focus distance. One for the QHY8 and one for the SXV cameras. Talk to them directly if you are not using one of these two cameras,

One issue that I did have, and never managed to "sort" was that @ f/2, the angle of the light cone at the egdes of a large format CCD comes in at such an angle, I ended up with what looked like vignetting and radial gradients. No amount of flat taking helped, and with the One Shot Colour QHY8, the radial gradient was actually a colour shift at the outer egdes. (I know my flat taking routine was OK because I use the the same routine on my other OTAs and they work fine). On the other hand, I know that Greg Parker doesnt see these issue on his C11, so you might want to talk to him about it.

Do I miss my Hyperstar? Yes!

[vincentnm]

Thanks Steve. Looks like these are rather serious considerations.

When super critical focus and perfect collimation become an absolute necessity than an improvement, I need to re-think the whole thing.

How does a 3.3 focal reducer on my C 9.25 compare to a hyperstar on a comparable scope, say a C8 ? Would I get nearly the same benefits as a hyperstar and get rid of some of the constraints?

Thanks,

Vincent.

[SteveL]

Which camera would you be using (for either the Hyperstar or the 3.3FR)?

[Merlin66]

You do need to define the camera you'll use....

The x0.33 gives a very small chip coverage, will handle a webcam chip but not much more before vignetting becomes a MAJOR issue.

I ended up going to the Optec NextGen x0.5 reducer (now up for sale) to get "reasonable coverage" on the Canon 350.

[CELESCOPE]

Getting the SCT down is not so easy , having had all the SCT Celestron other than the 14 inch lol , i found the 3,3 pretty useless , with coma problems , the 6.3 however does a very good job as one would expect .

the other option is a better reducer which would bring the SCT down to around F5, for the life of me i cant remember its name , but SteveL has it as i sold it to him.

This takes alittle time to get right ,distance wise ,but once done it does give a magnificant flat field no coma.and of course would bring your exposure times down, also it still gives a presentable image scale.

Rog:)

[SteveL]

the other option is a better reducer which would bring the SCT down to around F5, for the life of me i cant remember its name , but SteveL has it as i sold it to him.

An Alan Gee telecompressor

[CELESCOPE]

Thats the one Cheers Steve , old age ya know .

[vincentnm]

Thanks guys. I've tried to use the 3.3 reducer with a canon 350d and the vignetting is horrible as you've mentioned. I am gonna get rid of the 3.3 reducer.

I want to go down the hyperstar route. However, I've changed my mind on the C14 and instead getting a C8. I dont have an obsy setup and poratbility is important.

I got an offer for a C8 + hyperstar3 + micro touch auto focussing kit for £1400. I've almost decided to take that up. Any problems you guys can forsee, which I might have missed?

Thanks,

Vincent.

PS. I know I need to shell out on an SVX or a QHY to fit on my hyperstar

[SteveL]

Blimey, thats sounds remarkably like my old rig. Is it a NS8GPS, or a C8 with dovetail for a EQ mount?