3" Wynne Corrector Placement

[Benny L (Ben)]

Hi All,

In the coming months I will be building my very own Newtonian Astrograph. I have decided on a 12.5in f3.8 mirror giving me a focal length of 1208mm

I also have my sights on the 3" Wynne Corrector by ASA. The thing is that there is no information on where to place it in the optical path. I know that it goes in front of the camera but that is about it.

Does anyone know if you need to alter your focal point seeing as it is a big beast, 5.5in long , from what info I have gathered.

I'm assuming that you cant just have 50+mm of corrector poking into the tube

So i'm asking anyone who has ever seen one of these or knows of someone who owns/owned one to help a fella out so I can start drawing up my tube/focuser combo.

Cheers in advance,

Ben

[bmitchell82 (Brendan)]

they sit infront of the camera, and virtually form the nose piece coming out. they are damn expensive but well worth the size of fully corrected circle! there will be a specific distance from the chip to the corrector. If you need any help with building the newt let me know

[Benny L (Ben)]

Thanks for your quick reply Brendan

So basically I will need to make the focal point far enough outside the tube for the Wynne corrector to not interfere with the light path?

I just had a look at the ASA website and they say they can make up adaptors to suit the required camera position but for 150 Euro it might be worth hitting up Precise Parts in the US and seeing if they can knock up something cheaper

Ben

[Doomsayer]

You specify what f-ratio, filters and chip cover slip thickness (used for optical back focus calc) are in the system and ASA calculates the depth for the custom spacer/adapter which goes between the Wynne and the specific camera/CFW. ASA hava a spreadsheet for this purpose on their website. These systems require a very large secondary if you wish to fully illuminate a full frame chip.

150 euro for an essential adapter like this is quite reasonable when compared to the price of the corrector itself.

If you are planning to hang a large and heavy CCD camera and filter wheel off this Wynne you will need to have a very strong base connection for the focuser to avoid flexure.

guy

[Benny L (Ben)]

Thanks for your reply, Guy

Perhaps you are right in regards to the adapter.

I had a look at the ASA systems before and noticed that they have a huge secondary, on the order of a 40% obstruction. I had already decided to go with a 5in secondary in order to fully illuminate my STL with room to spare should I ever have the cash for something like a STX-16803.

For the focuser I am looking at the Clement Bellerophon III and the tube is all up in the air at the moment. I'd love to have a 6.5mm thick carbon fiber tube, but that would probably cost more than the mirror Maybe I could use some sonotube and wrap it in carbon fiber to increase stiffness or something..

The only thing i need to figure out is how far in the tube I can have the corrector itself protruding. If I can just shove it all the way in and there is no problems then I will be a happy camper but i have a feeling that it will create and obstruction of the light path so I mght have to have the focal point far enough outside the tube for that not to be a problem. I think i'll send ASA an email and see what they come back with.

Cheers

Ben

Ben

[Doomsayer]

Hi
Yes I am also about to order one to use for an 11k chip. I have found that the ParacorrSTL does not apparently correct fully into the corners of the 11k chip. The Baader MPCC is worse - I could have sworn the Baader covered 35mm film OK (must be the slight film emulsion curvature in the corners?). I had to shorten the paracorrSTL to get to the "correct" spacing with the Proline.

You would need the 4" wynne corrector to fully illuminate a 16803 based on the ASA specs. I have already built the telescope but still need to sort out the corrector. Carrying the massive load of a FLI Proline, CFW and PDF focuser off the side of the tube has been a challenge.

guy

[Satchmo]

Ben

A simple way around the problem would be to build a mock up tube with say for example 14" cardboard tube, which they sell for concrete column forming. That way you can put your whole assembly together , placing the camera and corrector with exactly the right position to leave you some in travel , then just move the primary in its cell up and down the tube to get focus. That will give you the spacings without any guess work before you drill holes in an expensive tube.

I would have thought a computer controlled focusser add on like Robofocuss would obviate the need for an expensive CF tube. There is a very good source for custom made aluminium telescope tubes in Sydney.

[Ian Robinson]

Why not just contact the manufacturer and ask them up front ?

You might also get some responses from ATMers in the USA and internationally who have been there done that and can tell you what they did with their 3" or other size Wynne Corrector installations in their fast newtonian astrographs by creating a tread at CloudyNights. There is a much larger pool of people there than here.

[Moon (James)]

What about this document?
http://www.astrosysteme.at/images/Corr_3Zoll_Wynne.pdf

Refer to to the table to get the value for "A"

James