C9.25 and hyperstar

[paraletic mirror]

Hi star gazers

A standard C9.25 is a f10 making it a nice big scope for visual astronomy, but my question after doing a tiny bit of research, and just wadding into this pool of astrophotography im wondering if fitting a fastar compatible C9.25 with a hyperstar 3 lens adapter will make it a good imaging scope? Turning the f10 into a f2.3 is a massive difference making the scope so much faster that im not even sure how that works.

para

[kirkster501]

At F2.3 you will find focus incredibly difficult and the tiniest mirror shift that the SCT's are prone to will throw out the focus considerably.  You'd be better doing what most of us with C9.25 do; use the SCT for "close up" work at F10 or reduced and using another scope to get you the shorter FR, such as an ED80.  You then get best of both worlds without the complexities of Hyperstar.  Don't get me wrong the C9.25 is great, I have one  But Hyperstar is expensive and prone to cracking the corrector if the mount should be loose at any point in RA.  

[lensman57]

Hi star gazers

A standard C9.25 is a f10 making it a nice big scope for visual astronomy, but my question after doing a tiny bit of research, and just wadding into this pool of astrophotography im wondering if fitting a fastar compatible C9.25 with a hyperstar 3 lens adapter will make it a good imaging scope? Turning the f10 into a f2.3 is a massive difference making the scope so much faster that im not even sure how that works.

para

HyperStar works by removing the secondary and replacing it with HyperStar lens and a CCD, usually OSC. The F2.3 is the native F Number  of the primary and provided that your set up is robust and the centering accurate you will have a fast imaging scope , but as everything else in imaging there is no free lunch  here either. The problems with the stress on the corrector plate, the orthogonality of the set up and an almost none existant depth of focus @ F2.3 will cuase you a lot of headache. The price of the Hyperstar lens is almost as much as none Primium Apo triplet and I would rather use the APO any day, I do have an F4 imaging Newt and I find this a handful @ F4 let alone F2.3.

A.G

[ollypenrice]

Good replies above. What they don't tell you in the adverts is that the Hyperstar is hypersensitive - to everything - and, while you occasioanlly see stunning results you often see very bad ones. It can be made to work by people who are very good at making things work, but personally I steer away from utra fast F ratios and certainly from utra fast f ratios contrived out of budget mass produced instruments. The earlier phrase, 'No free lunch' hits it on the head.

Olly

[kirkster501]

Good luck with your decision but I think the Hyperstar is just  a means of "sweating the asset" of a SCT.  I had the good fortune of being able to borrow a HS (which convinced me to buy my ED80) and I can tell you right now that for me, at any rate, the whole HS thing is pig with lipstick.  Much better to get a proper short FL refractor if you want wide field.

Just my 2c.  Your mileage may vary.

Steve

[GuillermoBarrancos]

Above says it all.

You need the EdgeHD version of these SCT's as they at least are produced from ground up to be used with HS/FS due to having mirror lock.

[laser_jock99]

How about F2.2

http://www.optcorp.com/celestron-11-rasa-rowe-ackermann-schmidt-astrograph-ota.html

[Baffa]

How about F2.2

http://www.optcorp.com/celestron-11-rasa-rowe-ackermann-schmidt-astrograph-ota.html

This looks quite interesting, think a proper "hyperstar" telescope might work. 11" and 620mm focal length, nice! This could work quite well with all those new cameras with smaller pixel sizes.

[ollypenrice]

It does look interesting but I can't do with mumbo-jumbo like, 'better apparent tracking.'

A thouroughly sorted, sealed tube, spikeless fast astrograph is always going to be temptng but never going to be easy and very, very unlikely to be cheap.

Size of image circle? Not mentioning this in the specification is hardly 'serious,' though, now is it? So two major 'Tut tuts' from me for the web pages.

Olly

[paraletic mirror]

thanks all, some good info to mull over

atb para

[lensman57]

It does look interesting but I can't do with mumbo-jumbo like, 'better apparent tracking.'

A thouroughly sorted, sealed tube, spikeless fast astrograph is always going to be temptng but never going to be easy and very, very unlikely to be cheap.

Size of image circle? Not mentioning this in the specification is hardly 'serious,' though, now is it? So two major 'Tut tuts' from me for the web pages.

Olly

Imagine putting a 6" filterwheel infront of those lovely optics.

A.G

[GuillermoBarrancos]

There is actually already a Whole discussion about this New Celestron Scope here:

http://stargazerslounge.com/topic/213716-new-celestron-rowe-ackermann-f22-astrograph/