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C thread tap and die?


Ant
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I'm looking for a C thread tap and die set?

I have a OAG and anyone with an OAG will know that it is a pic to get the guide cam and main cam focused at the same time.

This is especially a nightmare for me when I change from one filter to another that are not parfocal.

The focus adjustment on the guide cam is a very coarse affair - so what I was thinking of doing was making a locking washer. So that I cam use the C Thread as a kind of Helical focuser, using the locking washer to ensure that the guide camera doesn't turn in because it isn't tight.

So two questions really...

1. Where can I get a tap and die set for the C thread. Or what is the technical specification for this thread so that I can go on a search..?

2. How thin could the locking washer be 1/2mm, 1mm?

Cheers

Ant

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Nice one Ken.

T2 Konterring zur exakten Abstandsbestimmung - nur 1mm dünn

One of these for the T thread part of the system - might actually work as it's the main camera that I have adjusted at the moment...

I only thought about adjusting using the guide cam as the male C thread is longer than the male T thread.

Maybe I could do with both :D

Cheers

Ant

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To get the camera to focus on the spectroscope I'm finding that the TS adaptor TST2Vvar and a TST2We - which effectively give you a combined helical focuser with a 360 degree rotator, to be very good.

A T thread is 0.75mm pitch, so a 1/4 of a turn gives you 0.18 mm movement - we can get the camera position within 0.1mm which for spectroscopy is ideal.

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C thread spec is 1" x 32 TPI...

http://www.schneideroptics.com/info/faq/industrial.htm#qu4

C-Mount is a camera / lens standard that is commonly found on CCD/CMOS Digital Cameras as well as 16mm film cameras. The C-mount specification has several dimensions associated with it:

Mounting Thread = 1 inch x 32 tpi UN 2A

Length of Lens Thread = 3.8mm

Lens Flange Focal Distance = 17.52mm

Camera Depth (C-Mount Face to Image) = 17.52mm

The above dimensions are employed by all C-Mount lens manufacturers as well as all C-Mount camera manufacturers in order for any lens and camera combination to image properly.

http://cgi.ebay.ie/1-X-32TPI-TAP-UNS-HSS-/160208823258

Edited by Psychobilly
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Ant

Don't understand mate, why do you need to refocus the guide-cam (DMK?) when you change filters?

The focus of the main camera needs to be changed between filters (or no filter) - albeit very slightly. This means that the guide cam is then not focused...

A bloke I spoke to at Kelling wondered the same - he surmised that it might be because it's a refractor?!?

Thanks for the link Peter!

Ant

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The focus of the main camera needs to be changed between filters (or no filter) - albeit very slightly. This means that the guide cam is then not focused...

Ant

AH OK.

I don't refocus the guide cam between filter changes and I have the same OAG and main cam as you...

Maxim doesn't (usually!!!) have a problem with guiding on a slightly de-focussed star - does PHD?

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For guiding you don't need to be perfectly focussed - in fact Terry at SX recommended the guide star being out of focus as it's easier for the software to get the centroid and is less affected by seeing.

Helen

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AH OK.

I don't refocus the guide cam between filter changes and I have the same OAG and main cam as you...

Maxim doesn't (usually!!!) have a problem with guiding on a slightly de-focussed star - does PHD?

Do you both have the same filters though?

I believe some are parfocal for different wavelengths, others require refocusing....not sure which do what though.

but yes I've found better success with a softly focused guide star.

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Hi

I used to run a Security Co and we fitted CCTV camera and I still have a few C/CS mount adaptors laying around if you want any to try and have them machined down to make the thin locking nuts you have talked about then by all means i will send you a couple, But at the thickness you mentioned it would only make it about 1.3 Threads Per mm

Andy

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