Paracorr and laser

[Scooot]

I've been tweaking my collimation with my laser in the type 2 Paracorr for a while now and it's seemed mostly very accurate. However I recently decided to change the setting on the tuneable top with the laser in place to see how stable it is. So with the tuneable top set at the lowest (A) the laser beam shines straight at the secondary to the middle of the primary. As I wind the tuneable top out I can see the beam waver, and if I lock it in place at a different setting the beam is now off centre.

I tend to think my Hotech laser is accurate which means the Paracorr isn't, which being Televue surprises me. Has anyone else noticed this? Is it just a fault in the manufacture of my Paracorr?

[crashtestdummy]

Well for a srt your are meant to move a paracorr when collimating.have you done comparisons with and without it at the same focus travel to see if your focuser is off centre?

[Scooot]

Well for a srt your are meant to move a paracorr when collimating.have you done comparisons with and without it at the same focus travel to see if your focuser is off centre?

Thanks for the reply.

Focuser is bang on, no movement all the way in and out with just the laser in the focuser. I prefer to collimate with the paracorr in the focuser because the beam moves to a lesser or greater extent when I replace the Paracorr in the focuser, depending on how it sits in the focuser. It collimates well, but just moves as the tunable top is adjusted. Have you tried it with yours? Be interested to know if its just mine.

[crashtestdummy]

No I never tried the laser with my paracorr before I got rid if it.wonder if it's just the curved nature of the lenses in the paracorr that once you extend the tunable top it bends the light a bit.you could contact televue directly for feedback.on my SIPS system it states to remove the paracorr lens section when collimating so assuming it will be for the same reason

[Scooot]

I've read on here http://www.obsessiontelescopes.com/learning_center/collimation/#anchor_Barlowed_Laser_Technique

that a Paracorr is a good substitute for a 2" barlow when using the barlowed laser technique so I doubt the lens bends the beam and I've read a few posts on CN about people collimating with the Paracorr in place.

Anyway I think I've sussed it. I don't think my focuser is straight. If I rotate the Paracorr itsel in the focuser with the laser inserted the beam forms a circle. It also does it if I just put the laser in the 1.25 to 2" adapter and then rotate the adapter. So I think my focuser is tilted slightly. This doesn't matter once I've collimated if I only move vthe focuser in and out as the beam stays put but the act of adjusting the tunable top performs the same function as rotating the Paracorr or adapter. 

So my thinking at the moment is that my focuser is slightly tilted. Thanks again for your input.

[RAC]

Are you sure the laser is collimated. Turn only the laser to see if it still forms a circle.

[Scooot]

Are you sure the laser is collimated. Turn only the laser to see if it still forms a circle.

Thinking about it I think you might be right. even if my focuser wasn't straight it shouldn't make a circle. I'll try to test the laser when I get home. Reading Hotech's site its best to test it in the focuser anyway as the usual V block doesn't work with these apparently.

[Scooot]

Are you sure the laser is collimated. Turn only the laser to see if it still forms a circle.

Yes its the laser that's out thank you very much. Now I just need to work out how to collimate it.

If anyone can help Its this one http://www.firstlightoptics.com/hotech-collimation-tools/hotech-sca-laser-collimator.html

but I cant see any obvious collimation adjusters.

[RAC]

Having the laser collimated only matters for setting up the secondary. I just adjust mine so its close and always turn the laser and see where the middle or the circle is to make sure the secondary is good. Then just use the barlow effect with the paracorr for the primary and it does not matter to a point how straight the laser is for that.

[Scooot]

Steve at FLO very kindly sent me another laser to test, although pointed out that premium lasers are thoroughly tested and very rarely faulty.

I received it today and he's correct, the new laser does exactly the same as my original. Even if I put it directly in the 1.25" adapter without the Paracorr and rotate it, it forms a small circle on the primary after bouncing off the secondary. It's easier to see if I carefully rotate the adapter. I must confess I'm baffled as to where the error is, if the laser wasn't sitting in the focuser correctly the beam would miss the ring in the middle by more but would stay in the same place if I rotated it, wouldn't it?

Any pearls of wisdom gratefully received.

[Mike73]

Wish I could help Richard but I'd be guessing TBH.

Strange how the Hotech beam is a circle though, and thats without the Paracorr? The secondary looks ok I take it?

[Scooot]

Wish I could help Richard but I'd be guessing TBH.

Strange how the Hotech beam is a circle though, and thats without the Paracorr? The secondary looks ok I take it?

What I mean is as I rotate it, the moving beam (dot) traces a small circle, the beam itself isn't a circle. I can only think I'm introducing a bit of a wobble whilst rotating it but how I'm stumped.

[faulksy]

What I mean is as I rotate it, the moving beam (dot) traces a small circle, the beam itself isn't a circle. I can only think I'm introducing a bit of a wobble whilst rotating it but how I'm stumped.

hi richard, sounds like the colimator needs colimating, have you tried it in a v block ?

[Mike73]

Mike may be on to something but Hotechs are usually very good and for it to happen with two Hotechs!?

Does the same happen when you put the Hotech straight into the focuser draw tube without the extension?

[Scooot]

Apparently testing it on a V Block doesn't work. http://www.hotechusa.com/category-s/58.htm

I can't imagine both lasers are out. No I haven't tested it without the extension tube in but its a good idea.

[Scooot]

hi richard, sounds like the colimator needs colimating, have you tried it in a v block ?

Mike may be on to something but Hotechs are usually very good and for it to happen with two Hotechs!?

Does the same happen when you put the Hotech straight into the focuser draw tube without the extension?

I've just unthreaded the eyepiece holder with the 3 thumb screws to leave just the extension tubes in place in the focuser. I then retested both the lasers again by just tightening the laser into my 2" to 1.25" adapter and holding the two in the extension tubes. When I rotate the old laser I get the trace of an obvious small circle. With the new laser hardly any movement.So all those that said it was the laser's collimation were right. Not sure why I couldn't establish that yesterday when I received the new one to test but today the difference is very noticeable. I think doing it without the threaded eyepiece holder made it easier to rotate it without movement. Anyway looks like the problem is now solved thank you all very much pity it's not possible to collimate the old laser to fix it.

[faulksy]

I've just unthreaded the eyepiece holder with the 3 thumb screws to leave just the extension tubes in place in the focuser. I then retested both the lasers again by just tightening the laser into my 2" to 1.25" adapter and holding the two in the extension tubes. When I rotate the old laser I get the trace of an obvious small circle. With the new laser hardly any movement.So all those that said it was the laser's collimation were right. Not sure why I couldn't establish that yesterday when I received the new one to test but today the difference is very noticeable. I think doing it without the threaded eyepiece holder made it easier to rotate it without movement. Anyway looks like the problem is now solved thank you all very much pity it's not possible to collimate the old laser to fix it.

you would of thought you could colimate the laser, you can with the cheaper ones

[Scooot]

you would of thought you could colimate the laser, you can with the cheaper ones

I did read somewhere there's a way but it invalidates the warranty, so might as well swap it for the new one if that's an option.

[faulksy]

im sure flo will honour that richard

[Mike73]

I really like my Hotech, infact I sold my Catseye kit as I liked it so much!

How long have you had yours Richard? Do you think its had a knock to make the collimation go out? 

I should check mine again really as I haven't for a couple months.

[Scooot]

I really like my Hotech, infact I sold my Catseye kit as I liked it so much!

How long have you had yours Richard? Do you think its had a knock to make the collimation go out?

I should check mine again really as I haven't for a couple months.

Bought last November. Not aware it's had a knock, I suspect it's always been like it but difficult to spot if you don't rotate it.

I spotted it because of the Paracorr settings , changing from say setting A to F had the affect of rotating it. So if I collimated on setting A, and the next time I checked collimation I was on setting F I'd think the secondary needed tweaking.