Is poor collimation hard to see for newbs?

[HiveIndustries]

I have a 10+ year old 100mm Orion Skyscanner and a 20+ year old Celestron C8. The latter I just picked up and I met the guy before me and he wasn't collimating anything having maybe taken it out a few times in his back yard pointing it at the moon with a solo 40mm eyepiece and had it for 5 years.

How is it I've never had to collimate? Everything looks balanced but it seems like the best newb advice is, "collimate, damn it."

Just don't know how long I can go never having to touch anything before I conclude that maybe things are screwed up and I'm just not discerning.

Out of focus stars are always perfectly balanced on all sides. Am I just really good about not banging my scopes around or something?

[PeterCPC]

Collimating a C8 is very straightforward. Centre a star then move it in and out of focus with a fairly high power EP and see if you get the Airey rings ok.  There are guides on line. It does help if you have Bob's Knobs.

[philj]

If you have concentric circkes when looking at out of focus stars then all sounds Ok, I woukdnt worry too much. A case of Don,t fix it if it aint broke.

However sct collimation is straightforward as per Peters post above.

[vlaiv]

It is fairly easy to see, but you need to be careful of what is it that you are seeing.

First of all - you need to go very high power until you can see the star as being disk rather than just point. You need to start resolving Airy disk and airy pattern (often 200-300 power or more for larger apertures).

Second - all sorts of things can look like collimation issue. Thermals, seeing, you name it.

Put star in dead center of the FOV, and it should look like this at high power:

Left is good collimation - right is poor one.

That is under perfect conditions. In reality, in very good seeing, it will look like this:

And it will be slowly changing, maybe like this:

(Taken from here: http://www.damianpeach.com/pickering.htm)

If you move star of axis - towards the field stop of eyepiece - it should start slowly to look like right star in top most image - with that thicker ring always pointing towards near field stop (so first image / right star should show what star would look like when moved toward right field stop edge in the eyepiece).

Telescopes can hold collimation very well. I haven't collimated my dob mounted 8" newtonian in maybe 2-3 years. I sometimes check collimation to make sure it is good and that is it.

Make sure your scope is thermally stable and had plenty of time to cool and pick star that is high in the sky as stars towards horizon tend to be affected by seeing more. If you have manual mount - pick Polaris (or any star with high DEC as it will drift more slowly over FOV) as it is stationary and you won't need to nudge the scope.

[tripleped]

I went many months without collimating my Skywatcher 10” Dob and during that time had several excellent views of Jupiter and Saturn. Star testing was always pretty darn close to perfect.  Wanted to fine tune so bought a HoTech laser collimator with crosshairs (which I love!) and got it aligned perfectly, confirmed by star testing. In retrospect I was a bit off for all those months but not by much and I don’t think it compromised my views at all.  I’m not in any way negating the importance of good collimating but it may be that some scopes hold it better than others. Perhaps more knowledgeable folks can comment further. What I have learned is that, at least for me,  “pretty darn close” works “pretty darn well”  and doesn’t seem to affect my viewing experience. 

[Richard N]

1 hour ago, vlaiv said:

It is fairly easy to see, but you need to be careful of what is it that you are seeing.

First of all - you need to go very high power until you can see the star as being disk rather than just point. You need to start resolving Airy disk and airy pattern (often 200-300 power or more for larger apertures).

Second - all sorts of things can look like collimation issue. Thermals, seeing, you name it.

Put star in dead center of the FOV, and it should look like this at high power:

Left is good collimation - right is poor one.

That is under perfect conditions. In reality, in very good seeing, it will look like this:

And it will be slowly changing, maybe like this:

(Taken from here: http://www.damianpeach.com/pickering.htm)

If you move star of axis - towards the field stop of eyepiece - it should start slowly to look like right star in top most image - with that thicker ring always pointing towards near field stop (so first image / right star should show what star would look like when moved toward right field stop edge in the eyepiece).

Telescopes can hold collimation very well. I haven't collimated my dob mounted 8" newtonian in maybe 2-3 years. I sometimes check collimation to make sure it is good and that is it.

Make sure your scope is thermally stable and had plenty of time to cool and pick star that is high in the sky as stars towards horizon tend to be affected by seeing more. If you have manual mount - pick Polaris (or any star with high DEC as it will drift more slowly over FOV) as it is stationary and you won't need to nudge the scope.

I often wonder that if it’s so hard to see if a scope is collimated, what difference minor discrepancies make to seeing in real life observing?

[skyhog]

I think getting that perfect collimation only becomes an issue with planetary or lunar imaging. Vlaiv has a link to damian peach who wants all the boxes ticked and his results speak for themselves. 

[vlaiv]

4 minutes ago, Richard N said:

I often wonder that if it’s so hard to see if a scope is collimated, what difference minor discrepancies make to seeing in real life observing?

If you have faster newtonian - that is easy to check. Take wide field (lower power) planetary eyepiece and observe planet at the center of the FOV and somewhere near the edge. Granted, some of aberrations will be due to eyepiece and not scope itself, but if you have well corrected eyepiece - you'll see blurring caused by miscollimation.

Another way to  visualize is to do simulation.

Check out this page for different effects (like central obstruction, spherical aberration and seeing):

http://www.damianpeach.com/simulation.htm

Coma will produce similar blurring effect on the image.

 

[John]

The signs that you might need to pay attention to collimation are if you often read reports on forums from folks who have the same equipment as you do but seem to be able to regularly see more detail / tighter resolution on the moon / double stars / planets or if you look through a similar scope to yours at a star party or similar and the views seem noticeably better than your scope is delivering.

I've looked through 8 inch SCT's that have been struggling to split the "double double" epsilon lyrae, for example. Some collimation adjustment and this showpiece binary pair becomes a clear and easy split.

 

 

[skyhog]

31 minutes ago, John said:

The signs that you might need to pay attention to collimation are if you often read reports on forums from folks who have the same equipment as you do but seem to be able to regularly see more detail / tighter resolution on the moon / double stars / planets or if you look through a similar scope to yours at a star party or similar and the views seem noticeably better than your scope is delivering.

I've looked through 8 inch SCT's that have been struggling to split the "double double" epsilon lyrae, for example. Some collimation adjustment and this showpiece binary pair becomes a clear and easy split.

 

 

That's a very good point John. I have never been to a star party as I like to go off to my obsy and do this hobby on my own. I'm a sociable guy but I really enjoy the me time when I'm observing, it's how it's been for years. That said it would be interesting to observe through a variety of scopes under the same conditions, as you say, the definitive way of assessing the performance of your own scope. I may have to check out future get togethers😉

[Stu]

3 hours ago, skyhog said:

I think getting that perfect collimation only becomes an issue with planetary or lunar imaging. Vlaiv has a link to damian peach who wants all the boxes ticked and his results speak for themselves. 

 

4 hours ago, Richard N said:

I often wonder that if it’s so hard to see if a scope is collimated, what difference minor discrepancies make to seeing in real life observing?

SCTs and Maks in particular soften in terms of planetary and lunar contrast and detail when out of collimation, something that is visible when observing as well as imaging. As John says, it’s important for doubles too. It is less obvious for low and mid power observing but it must still have an impact on contrast.

[HiveIndustries]

We'll never know since I just swapped the C8 for a used Lightbridge 12"

I finally pulled the trigger on a Farpoint laser, I fully expect to now have to do it all the time based on everything I've read about big dobs. I just sat ready waiting to purchase something to do it and every session I'd check the stars out of focus and they'd be perfectly balanced.

Thanks for the info all.

[skyhog]

15 hours ago, Stu said:

 

SCTs and Maks in particular soften in terms of planetary and lunar contrast and detail when out of collimation, something that is visible when observing as well as imaging. As John says, it’s important for doubles too. It is less obvious for low and mid power observing but it must still have an impact on contrast.

Totally agree and I hope I didn't give the impression its not worth taking the time to do as well as you can. It's always nice to know you have that base covered when those nights of exceptional seeing come along, however infrequent they are. I also think it's worth getting over the fear factor. It can be quite daunting at first but today's webcams, where you can see the results on the screen as you tweek the little screws, make the process very simple. 

[HiveIndustries]

You did not! In fact I think this thread was kind of looking for an excuse to collimate. The lightbridge is at the shop getting the focuser fixed (because of course I wouldn't get second-hand first light, first night)

Today I'll be taking apart the 100mm just so I have an excuse to play with the new toy sitting in its plastic, in fact so no fear instilled at all

[AstroMuni]

On 12/10/2021 at 12:26, HiveIndustries said:

How is it I've never had to collimate? Everything looks balanced but it seems like the best newb advice is, "collimate, damn it."

There are several needs to be done activities that are seen on forums (collimate, guiding, parabolic mirror etc). I have had my scope since 2012 and although I had done some preliminary checks after reading up about the need for collimation, I stayed put as the quality of my images whilst viewing was good enough for me. Even when I got into imaging this year, it seemed fine. But now with a few months of imaging under my belt, I started noticing that my stars were not as sharp as I would like it to be. So I guess at the end of the day its what you are happy about