Catseye collimation tools

[Astronut]

What with all these cloudy nights, I've become rather [removed word] about collimation almost to the point of obsession and after doing a few tube mods (new focuser, tube handles, etc), I've been fine tuning my methods with a standard cheshire/sight tube and a baader laser but I'm never completely satisfied with the results. It looks bang on but I'm never quite sure and a star test is impossible at the moment.

Anyway I was just browsing through some old threads and I found this link posted by James (Maccers)

http://www.catseyecollimation.com/index.html

Anybody got a set of these seemingly top quality collimation tools? I've had a quick read of some reviews (highly favourable) and a quick read of the site but I'm a little confused at the moment on what pack to get. I'll read some more later and gen up on it all when I get more time but for now I'm really intrigued and tempted.

[philsail1]

Hello "Astronut"

Just read your piece about the "Cats Eye" Collimation set.

There's quite a good site which has an interesting section on collimating Newtonians here:-

http://www.maidenhead-astro.net/links.htm

Regards,

philsail1

[Astronut]

I have most of those collimation links listed there but the "Collimation, A Treatise" link is one I didn't have and is especially interesting. http://www.catseyecollimation.com/mccluney.html

Thanks for that

[Astronut]

Just spent the last 3 hours reading the whole of this thread.

I'm now suffering a bit from information overload but I'm thinking a set of Catseye tools will probably be my next purchase.

[James]

I'm very happy with mine and the knowledge that once the autocollimator says I'm collimated I am as collimated as is possible to be (I think we're talking about being collimated to one thousandth of an inch :shock:), certainly collimated enough to satisfy even the most [removed word]/fussy person (cough )

James

[philsail1]

Dear All,

I've noticed when I collimate my Skywatcher 200mm Newtonian, using a cheshire collimator, that after I have got the collimation as near to "spot on" as I can get, if I slowly turn the cheshire round 360 degrees whilst still in the eyepiece, I can see the collimataion drifting off centre? When I correct the collimation at a new set point, and slowly turn the collimator, it shows collimation slightly off at another point? It seems to be impossible to achieve accurate collimation through 360 degrees rotation of the Cheshire.

Could this be due minor imperfections in the eyepiec tube, or on the surface of the collimator, or in the configuration of the telescope tube itself?

Also, I wonder if it matters that much in an f5 reflector?

I'd be interested in your thoughts.

Regards,

philsail1

[Xunil]

Dear All,

I've noticed when I collimate my Skywatcher 200mm Newtonian, using a cheshire collimator, that after I have got the collimation as near to "spot on" as I can get, if I slowly turn the cheshire round 360 degrees whilst still in the eyepiece, I can see the collimataion drifting off centre? When I correct the collimation at a new set point, and slowly turn the collimator, it shows collimation slightly off at another point? It seems to be impossible to achieve accurate collimation through 360 degrees rotation of the Cheshire.

Could this be due minor imperfections in the eyepiec tube, or on the surface of the collimator, or in the configuration of the telescope tube itself?

Also, I wonder if it matters that much in an f5 reflector?

I'd be interested in your thoughts.

Regards,

philsail1

This gets me with my laser. I've collimated the collimater as best I can, after having to dig out the filling and invalidate the warranty on my skywatcher unit to access the allen key holes (took me a while to work out that was what they were, it's impossible to see on such a small hole). I can rotate the laser and see the spot isn't moving via the little window. But when it goes in the scope, it'll make little circles on the primary if i rotate it. I think im collimated. I hope im collimated. I don't know if im collimated...

[Whippy]

Phil, Xunil. A lot of people (including me) find this is a bit of a problem! AFAIK what happens is that the cheshire/laser unit slightly moves when it's rotated and hence shows that you're slightly out. But you're always going to get a small about of movement, especially with focusers that don't use compression rings so you could drive yourself mad going back and forth between alignments not getting anywhere fast!

IMO, use your collimation tool (whatever you use) to get yourself close as possible, then do a star test to get it spot on because after all, it's an eyepiece you look though, not a cheshire!

Tony..

[philsail1]

Ah! thanks for that Tony.

It's reassuring to know I'm not too far out with my collimation attmepts.

However, I've never, ever done a star test with my Newt!

I will do one when we get into the warm summer nights (well, one has to remain optimistic!!).

Regards,

philsail1

[Astronut]

I'm very happy with mine and the knowledge that once the autocollimator says I'm collimated I am as collimated as is possible to be (I think we're talking about being collimated to one thousandth of an inch :shock:), certainly collimated enough to satisfy even the most [removed word]/fussy person (cough )

James

Thanks James. I didn't realise you'd actually got the kit. Well if you're happy with it then that's good enough recommendation for me. I'm definately ordering this weekend just as soon as I get home. I think I'll opt for the Triplepack Pro XL package which includes Telecat XL, Blackcat XL and Infinity XL units and I'll get the reflective white triangle instead of the red one.

I like the idea that these collimators are 2" versions and are adjustable for different focal ratios which allows you to fine tune the view through the pinhole and get more precise alignment. I've always found it tricky to see the whole of the secondary inside the circle of a standard 1.25" cheshire sight tube (pulling the cheshire part way out of the focuser) and I don't like the idea of using the 1.25" eyepiece adaptor to fit a standard cheshire - if there's any play between the adaptor and the focuser tube and the adaptor isn't quite square or machined to fine tolerances then that's just going to introduce errors especially when using a 'is it collimated or not?' laser collimator.

p.s. I've given up hope of doing a star test so I just hope that the optical centre of my mirror is the actual geometrical centre as it should be. AFAIK the only way to know for sure is collimating with a star test and then seeing how far the marked centre of the mirror is off centre from the collimation using the cheshire, etc. I've not seen any reports of an optically off centre mirror anywhere so maybe I needn't worry about it.

[James]

That’s the exact package I went for although I got the red triangles. I’ll be asking Jim Fly to send through some white ones soon I think. Once you’re using the Catseye system you’ll become all to aware of the oddest sources of miscollimation and you’ll need to draw a line somewhere. For instance using the autocollimator when I take my scope out the house sorts the collimation then but an hour or so later when the scope has cooled the collimation looks way out. In fact its only out a little bit but the minute you see one of the triangles not stacked with the others you’ll have to learn to not worry too much or you’ll forever be tweaking. Even slewing from one part of the sky to another will sometimes dislodge one of the triangle reflections. I find though that I can control the urge to fiddle with the collimation fairly easily while observing as it throws off the goto’s…

Regarding the adaptor in your focuser you should find that the adaptor on your MoonLite is good enough that there is only a very minimal amount of ‘play’ in it. Once I knew I was definitely as collimated as was possible I put my Baader Laser Collimator in and it was spot on. That way I can collimate in just a few seconds throughout the night if I need to and I just make sure I put the laser in the same way every time with the open section facing the rear of the scope to give consistency.

I found that the doughnut on my mirror was off centre by about 4-5mm. This made a difference to my collimations straight away but I’ve long since decided not to worry exactly where the optical centre of the mirror is! The views are good…!

James

[Astronut]

I'm not at all worried about machining tolerances of the adaptor in the Moonlite - it just oozes quality, it really is a thing of beauty and perfection

I'm actually hoping now that my current doughnut centre spot IS slightly off-centre - it might go along way to explaining some of the less than perfect slightly blurry views I've been getting eg. Cassini division not at all visible and no 'spirality' seen so far in M51 although this could have just been a case of bad seeing conditions or just my ageing eyes. We shall see.

As for my fear that the geometrical and optical centres of the mirror might be different, I'm a little less worried about it now after reading a few bits of info from various sites that's it's virtually unheard of in modern mirrors but only a star test or a professional optical lab can confirm any suspicions that the centres don't match up.

James - do you find it difficult to see the 3rd and 4th inverted reflections of the red triangle? I've read that some people have had to use stronger lighting to see them.

Is this why you're getting the white ones?

When you're stacking the triangles with the autocollimator, do you adjust the secondary tilt or the focuser tilt? I've read that it's better to adjust the focuser tilt if possible. I find adjusting the secondary is a frustrating and fiddly thing to do even with bob's knobs fitted. I wish secondary's were as easy and as precise to adjust as the primary. Bad design IMHO.

Also, which size centre hole did you opt for in the triangle - 1/4", 3/16" or 5/32". I'm thinking the 1/4" hole might make for a bit of a flimsy triangle until it's on the mirror and more suited for a barlowed laser but for a standard laser one of the smaller sizes would do.

[James]

I've yet to see the 4th reflection - or at least I've been too nervous to shine the required level of light into the tube (i.e into my eye!). I'm going to try the white reflective triangles to see if that makes it better. That said, getting three of the triangles lined up is pretty good!

With the autocollimator I've never touched the focuser tilt. Firstly because I'm confident its OK and secondly unless its well off getting the primary and secondary right should be all you need. It is fiddly to adjust the secondary, perhaps someone will come up with a better design one day (or even a motorised secondary adjuster.. ). To be honest I think the vast majority of any collimation changes I get are probably from the secondary. I usually use the Blackcat Cheshire to adjust the primary and then use the autocollimator to adjust the secondary knobs.

Regarding the Cassini division - I've been having problems with seeing it recently but was able to see it (just) on Monday evening at 300x. The seeing was pretty good but even so the division would appear for a few seconds then disappear again... Spiral features in M51 were clearly visible on Tuesday night, viewing from one of my out of town sites. With your 12" scope you should be able to see spiral features on M51 - are you in a light polluted area? I doubt its your vision as 0.5 diopters astigmatism isn't a huge amount but you could try with glasses?

James

[James]

Forgot about the triangle size. I think I got the 1/4" ones.

James

[Astronut]

Yes unfortunately I am in a LP area although once the neighbours have gone to bed and turned their lights off, there's no direct light, just the usual orangey glow from the town lights although that's mainly towards the SW. By this time though, it's usually clouded over It's a frustrating hobby isn't it.

M51 is very high up though at this time of year and I can see the core and it's companion's core no problem. I know the spirals should be easily visible but I've yet to see them

I need to get to a dark site asap.

In the meantime, I'm going to have another read of that long cloudy nights thread and see if there's any other opinions on triangle hole size choice that I may have missed. I don't suppose it matters really but I'll have another read anyway and then I'll place an order.

There's a good write-up here which explains the reflections and includes the "carefully de-collimated primary" procedure which I remember seeing mentioned while reading that long thread last week. I think it's supposed to make things simpler but it does require all 4 reflections to be visible.

[James]

I need to get to a dark site asap.

If you can I'd recommend it. Objects like M51 really benefit from getting away from the city lights. I seem to recall from Salisbury last year that you were able to squeeze the scope into your car and still drive it...??

One thing about the carefully decollimated primary concept to note: to do it you have to get pretty much properly collimated! Once there I'm not prepared to move anything else!

James

[Astronut]

I had to pay £33 to customs :shock: before I could collect it from the depot but my Catseye Triple XL Pro kit has arrived

The last time I ordered stuff from the States I got away with it but this kit came very well packed in a rock hard cardboard tube - maybe customs thought it was a telescope

I haven't had chance to play with it yet (only just unpacked it) but all the bits are there complete with a set of very comprehensive instructions.

Had a quick look at the various tubes and it looks like a top quality well made kit.

Here's some piccies of the unpacked kit (packing tube is at bottom of first pic) spread out on my kitchen floor:

(click to enlarge)

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(click to enlarge)

Looks like some seriously good collimation is on the cards but I have a laptop to nurse back to health this weekend so it'll have to wait

[James]

Glad to hear its got to you. Mine got lost by Parcelforce and was only rescued by a bloke who worked for a waste disposal firm and who thought I was another James Mackay and decided to try and extort a few quid out of me to repay some debts this other James had incurred.

The problem was resolved very quickly when he realised that I wasn't that James and that I was a close colleague and friend of his manager

Enjoy the collimating Ian, when its done you will know you have it absolutely perfect! And it will be a lot easier second time round.

James

[Astronut]

...Mine got lost by Parcelforce and was only rescued by a bloke who worked for a waste disposal firm and who thought I was another James Mackay and decided to try and extort a few quid out of me to repay some debts this other James had incurred.

The problem was resolved very quickly when he realised that I wasn't that James and that I was a close colleague and friend of his manager

....

Sounds like the short version of a long story - what a set of coincidences :shock: Talk about luck