Why has my scope stayed collimated for so long?

[bendiddley]

Hi all. I've had my telescope since June last year and I have only collimated it twice. I use it at least 3 times a month, usually in my back garden, I carry it from the garage where it is stored each time to the garden which is about 5-6 metres and probably move it once or twice more during a session to different parts of the garden, probably another 5-6 metres each time, to get better views etc. I've also taken it on 5 car journeys (10 if you count there and back). Even when I collimated it the 2nd time I don't think it needed doing as I was practicing to remind myself how to do it. I have done star tests and the rings of circles are all as they should be and everything is crisp and sharp and has been the whole time. When I collimated it I was careful not to apply too much pressure to the locking screws when turning the alan key so I'm fairly sure it's not over tight and preventing the mirror from moving at all, but I have heard of mirror pinching, so not actually sure what to look out for if it was too tight. I've read people saying they collimate their scopes every time they use it, but this is just not the case for me. So does anyone know why this might be? Thanks in advance.

[LeeB]

some scopes do, the 200 p is well made and its quite tolerant at f6. the screws are just tight enough and you handle with care. well done.

[RikM]

It tends to be bigger and faster OTA's that need more attention. I certainly 'check' my 250px every time I use it, but don't have to adjust anything very often and when I do, it is just a case of very slight tweak of the primary. My 150p very rarely needs anything doing to it but again I check it every time.

Collimation is not the ordeal people assume it to be. Although it does get more important the bigger and faster your scope.

[bendiddley]

Ok thanks that's good to know. I agree with you RikM, I was like that too thinking collimation was going to be a bit arduous but it has come as a pleasant surprise not to have to do it very often. I do still do star checks and on the look out for any changes, but quite often I don't even think about it and many sessions may go by before I do another check. Cheers

[ronl]

That's good to hear, as the skyliner 200p dob is the scope I have been

thinking of getting, collimation seems to dissuade some people from getting

a newt, but like everything it's part of the learning process of this hobby.

Clear Sky's

[Hzadbhat]

I've read here and elsewhere that the bigger the mirror, the more often you need to collimate. It's got a lot to do with weight, and how it's stored. Transport is also an issue.

I've got an 8 and a 10 and the bigger one needs adjusting more often, but certainly not every viewing session. As I take my scope out a fair bit, the vibrations from the road are also a factor.

If you don't need to collimate very often, congrats. Now that it's becoming a semi - regular routine for me, it's quite easy to do. But I appreciate that for those who have not done this, or maybe once or twice, it is a nervous time. Lots of us have had to learn the exact same way. By doing it.

[umadog]

Don't forget that lot of the larger scopes are trusses not solid tubes and that can contribute to an increased need to collimate. Also, whether you need to collimate does to some degree depend on how picky you are. If it's a little out, some people might leave it and others might fix it. The tools make a difference too: an accurate Cheshire or an auto-collimator will show up a smaller degree of misalignment than a "collimation cap"

[nephilim]

I've had my f5 200p (Skywatcher) for a few months now, I take it in the car often & its always getting shifted around the house (carefully) & its still pin sharp.

Steve

[bingevader]

Also, whether you need to collimate does to some degree depend on how picky you are.

Nope, not necessarily, he may just have a good 'scope and obviously looks after it well.

If it's a little out, some people might leave it and others might fix it.

Or, it might not be a little out, he might not have OCD, and might just be happy to leave a perfectly collimated 'scope well alone!

But, back to the OP!

Well done on a well collimated and cared for 'scope!

Cheers

[Carbon Brush]

Reaching for hard hat for being controversial.

Some people make too much fuss of collimation.

My experience of some half dozen newts from 4.5" to 10" goes along with bigger/faster = more attention.

But having said that, the amount of attention is minimal.

By way of example, about 2 years back I bought a 200P F5 2nd hand. The previous owner had it as his first scope and knew nothing of collimation. It was basically OK when I got it home (90 miles drive). Minor tweaks only to keep the Cheshire happy. The views were OK.

Since then it has not really needed any attention.

If a scope needs frequent attention, then something is wrong mechanically and should be rectified, or it is being badly treated.

Dives for cover....

[NGC 1502]

Well it's +1 for the 200p Dob then best value going.

The OP asked how to spot if the mirror is held too tightly.

That's not down to how tight the collimation screws are, but can be caused if the clips holding the mirror to the cell are too tight. The clips on the 200p are made of hard rubber, with a screw that goes through a small metal plate. You certainly don't want to clamp the mirror in place, but you don't want it flopping around either.

Some say a credit card gap between the clips and mirror surface, but I really do think that's way too much. Just a 'smidge' is fine.

You can recognise if the mirror is clamped too tight by watching for a triangular out of focus star. This can be very subtle, not a triangle with sharp corners, but not quite round. But as with all this stuff, better not to over obsess. Just take a careful look, and then don't spoil the night by checking again & again.

There's a lot more to look at than out of focus stars

Regards, Ed.

[bendiddley]

Thanks everyone for your comments. It's great to hear that it's not abnormal for mine to not need collimating very much and how easy it is maintaining collimation when it needs doing. Really glad I chose the scope I've got, it is such a great all rounder and so easy to use and look after. Clear skies to all!

[twotter]

My experience with my 200P dob 'mirrors' yours (ahem ) It holds collimation very well and I've only done it a couple of times in over 3 years of ownership.

[bendiddley]

My experience with my 200P dob 'mirrors' yours (ahem ) It holds collimation very well and I've only done it a couple of times in over 3 years of ownership.

Blimey! That's good to know.

[ollypenrice]

Our 20 inch truss, F4.1, is remarkably stable. It's visual only, and really is no trouble at all. I usually collimate each (serious) session but it needs the merest tweak and I only use a laser. If I didn't bother hardly anyone would notice, quite honestly. Very fuss free indeed despite the size, the truss construction and the F ratio. I'm not sure, by the way, that a truss is more fussy than a tube. I suspect it's the reverse if the truss is well made. It's certainly better for cool down as well. The high end imaging reflectors are almost all truss because they tend to be stiffer and hold the focuser more firmly.

Olly

[LukeSkywatcher]

I really think it boils down to how much "abuse" the scope goes through. Certainly there are people who collimate scopes each and every time they take them into the garden from where they are stored. That could be overkill and really not needed (certainly not for visual use). For people who transport their scopes by car for observing/imaging sessions.........its probably a good thing to check it each time.

Its a personal thing really. My Heritage 130P has not needed collimating since i bought it about 3.5 yrs ago. I did it once to see how the process works and it has not needed it since. It never traveled more than 30-40ft from house to garden and never met a bump and its only a 5" mirror which according to the destructions only needs collimating probably once a year if treat well.

My 8" SCT, i'd probably have to chuck that out the top window of the house to make it lose collimation. Ive had it 16 months now and its been perfect from day one.

[umadog]

Our 20 inch truss, F4.1, is remarkably stable. It's visual only, and really is no trouble at all. I usually collimate each (serious) session but it needs the merest tweak and I only use a laser. If I didn't bother hardly anyone would notice, quite honestly. Very fuss free indeed despite the size, the truss construction and the F ratio. I'm not sure, by the way, that a truss is more fussy than a tube. I suspect it's the reverse if the truss is well made. It's certainly better for cool down as well. The high end imaging reflectors are almost all truss because they tend to be stiffer and hold the focuser more firmly.

Olly

I see what you're saying. I've often seen people on SGL saying that they hardly ever need to collimate their solid tube Newts, so I assumed it was the solid tube that made the difference. Perhaps it's just that there are more solid tubes out there or that many people with trusses tend to break them down between sessions and so that necessitates at least a quick tweak. I have to say, though, that there are plenty of times when I've re-built my truss and the collimation is very near.

[Moonshane]

checking collimation is very easy and adjusting it is very easy too. The secondary I check every few months and the primary I check every time and adjust a tiny bit if needed every time. Takes maybe 30 seconds-1 minute tops. It's really a non issue

[stem1989]

I have never needed to adjust my 150p its just never needed it, I check it before every session, but the f/4 Quattro is another story, taking it outside makes means it needs a tweak...literally

[LeeB]

I check collimation weekly for all the scopes, but,,, its only cause the weathers bad and I need to fiddle with the scopes or i get twitchy, (has anyone seen my camel)........

Seriously most of the time its a quick tweak if that....

longer f's are easier and have more error tolerance and seem to hold better...

stripped and resprayed the 8.5 inch dob last week, down to the last bolt , total rebuild and collimate in 30 minutes flat. newts are great because they are so easy to work with.