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First proper night observing.

Ben Cole

By Ben Cole
in The Astro Lounge

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Ben Cole

Ben Cole

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Finally a clear night. So I got out back on the patio and tried to get set up. Not ideal as I have a long garden with trees all down either side. But it did allow access to the usual suspects Saturn and M42.

Little bit fiddly for my first polar alignment but after about 20mins of unpacking and adjusting the mount was set up. ON goes the telescope and there's Saturn. Even with 10mm eyepiece and 2x Barlow there was no appreciable drift even after going inside for a cup of tea for 30mins. Very pleased and impressed.

Also after a manual pointing the scope the hand controller is great for moving around. Even though I expected it to make the session much more enjoyable I was blown away by it. Being able to look at Saturn for as long as I want at my highest available magnification was an awesome experience.

Enjoyed looking so much that by the time I started trying to get some pictures it came to rain and I had to quit.

Saturn looks tiny when trying to photograph through the scope with the barlow(camera adapter) so I'll have to try something else. Looked great with the Barlow and 10mm though!!!!!!

Regarding collimation. If I'm looking art a bright object well out of focus and it looks like a perfectly circular doughnut then it means collimation is pretty good? If it's oval then I have problems correct?

I think astrophotography is a classic example of the more you get into it the more you realise how little you know. I knew I knew almost nothing but wow what a massive subject.

Did just have time to get this.

firstattempt.jpg

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John

John

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Regarding collimation. If I'm looking art a bright object well out of focus and it looks like a perfectly circular doughnut then it means collimation is pretty good? If it's oval then I have problems correct?

I think, if the doughnut is circular with the "hole" smack in the middle then you are collimated. If the hole is off centre then the collimation needs adjustment (a little off centre does not seem to do any harm but well off centre is not good). If the doughnut is oval shaped then you have other problems like pinched optics.

John

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FLO

FLO

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I think, if the doughnut is circular with the "hole" smack in the middle then you are collimated. If the hole is off centre then the collimation needs adjustment (a little off centre does not seem to do any harm but well off centre is not good). If the doughnut is oval shaped then you have other problems like pinched optics.

That is my understanding too.

I have limited success collimating a Newtonian on a star; it works better with refractors... Perhaps its just me?

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The Warthog

The Warthog

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Regarding collimation. If I'm looking art a bright object well out of focus and it looks like a perfectly circular doughnut then it means collimation is pretty good? If it's oval then I have problems correct?

Yeah, pretty much.

Good night out! Glad you enjoyed it.

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Astroman

Astroman

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Regarding collimation. If I'm looking art a bright object well out of focus and it looks like a perfectly circular doughnut then it means collimation is pretty good? If it's oval then I have problems correct?

I think, if the doughnut is circular with the "hole" smack in the middle then you are collimated. If the hole is off centre then the collimation needs adjustment (a little off centre does not seem to do any harm but well off centre is not good). If the doughnut is oval shaped then you have other problems like pinched optics.

John

John is right on the money with the first two but only close with the other one with one exception. It's very very important to make sure the donut hole is perfectly centered, especially for planetary viewing and even more so for photography. If the donut hole isn't round, the simple answer is pinched optics. This usually shows up more of a pincusion shape-a rough square pulled in along the sides if you have 4 mirror clips or triangular with 3 clips. If it's oval or elliptical, it could be astigmatism in the figure of the mirror itself. This is more serious. Check the donut hole inside focus and note which way the oval is aligned-L-R or U-D. Move to the other side of focus and if the alignment changes, your mirror has astigmatism. If it's severe, it will show up in astrophotos and you'll notice visually that something "isn't quite right." The only ways to fix it is to send it in for refiguring, or build a mirror cell that will "pull" the glass one way on one side and "push" the glass the other way on the other side. I know of only one such mirror cell, made by a pal of mine here in The States, but it's possible.

Don't Panic!

It may not be that at all, so you'll need to consult an optics guy locally for an evaluation.

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Ben Cole

Ben Cole

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Well thanks for the info astroman. TBH I wouldn't know whether my scope was collimated well or not.

I'd read about the shape of objects out of focus being doughnuts and thats what I've observed.

All stars look like the ring nebula :D

The question about collimation was just a small aside in a topic about me being chuffed with my new scope. It may need some tweaking but what I can see so far looks great so I'm very happy.

This thread has been taken off topic by peoples willingness to help.

Thanks for the sentiment but I'm happy with my scope....I'm sure I'll be back at some time asking for advice with collimation though :?

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