Author Topic: First impression  (Read 4688 times)

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spendrey

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First impression
« on: Mar 17, 2004, 18:40:00 »
At last I got the chance last night to try out the new scope.
Obviously after using an old 4.5" Tasco all these years anything was going to be an improvement but it was very impressive. It was a funny night last night, although it was clear from cloud it seemed very light, the sky seemed very red round my way as if there was more than the usual light pollution. Even so the first thing that really impressed me was that I could see Jupiter's moons and Saturn's ring even through the finderscope which I really was not expecting. It took me some time to work out how to move the scope about and to align the finderscope but once I did the images were very clear. Having a motor and handheld controller is superb too. Now I need to read up on polar aligning so I can track objects. Is it as complicated as the instructions seem?
I can't wait to get my new adapter for the toucam now (my old scope had a .965mm eyepiece) so I can start making some images. One thing I did notice though was that Juipiter had some very big diffraction spikes which I'm worried may be a problem when I start imaging. Do you think I could get rid of these by collimating?
One last newsworthy item, as I was looking through the scope last night I heard a bang on the fence behind me and when I spun round an object came hurtling towards me in the darkness. It turned out to be nextdoor's cat but I it took quite sometime for my heart to calm down again after that!

Rick

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First impression
« Reply #1 on: Mar 17, 2004, 19:25:00 »
Jupiter shouldn't show diffraction spikes. Sounds more like stray internal reflection or scattering. Check for shiny objects in or close to the optical path.

Whitters

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First impression
« Reply #2 on: Mar 18, 2004, 05:04:00 »
Polar Alignment.
To start with just make a best guess at pointing the axis of the acope north, you can get a protractor and tilt it up by arround 50-52 degrees. That should be good enough to enable you to take an aiv with enough frames of the planets before it drifts off.
Cats and Hedgehogs can be rather alarming.
Surprisingly though, the least alarming was when I heard someone trying to break into my neighbours house, telling them to B***er off. It was only later while phoneing the police and the adrenaline wore off that I got the shakes. But I did carry on taking images for another hour.

[ This Message was edited by: Whitters on 2004-03-17 21:06 ]

spendrey

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First impression
« Reply #3 on: Mar 18, 2004, 16:09:00 »
Thanks guys. I have checked the optical path for objects that might be causing the stray reflection resulting in the diffraction spikes on Jupiter but can't see anything that looks out of place.
Do you think colimation would do the trick?


Ian

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« Reply #4 on: Mar 18, 2004, 17:07:00 »
Collimating your scope is always a very good idea. It is well worth the effort learning how to do it.

However, if what you are seeing are diffraction spikes, collimation will not help.

Although you are calling them diffraction spikes, are you sure that that is what they are? I have a 200mm newtonian and I've never seen spikes in the eyepiece, they're much dimmer that the object, and your eyes adjust to the bright object making the spikes very hard to perceive.

Could you describe what you're actually seeing? How does the appearance change as you move through focus?

spendrey

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« Reply #5 on: Mar 18, 2004, 17:58:00 »
Thanks Ian. So diffraction spikes are not usually visible in the eyepiece? That's interesting, I wonder what my problem is then?
What I see when I look at Jupiter is a long band of light extending north and south of the disc. I assumed therefore that it was a diffraction spike but maybe it's not. It doesn't disappear when focusing but just gets either sharper or blurrier along with the disc itself. I hope I don't have something seriously wrong with it?
Any ideas?

Delphine

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« Reply #6 on: Mar 18, 2004, 18:32:00 »
I know this sounds weird but I have been seeing the above mentioned spikes when looking at Jupiter with the naked eye!  I originally thought I was looking at Saturn but I wasn't. Very puzzling!  

PS - I haven't been drinking!

Rick

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« Reply #7 on: Mar 18, 2004, 19:24:00 »
When you're looking at a bright object any scattered light will be much more obvious. All sorts of things can cause scattering. Dust and greasy marks on lenses (eyepieces, spectacles, objectives) seem likely.

Mike

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« Reply #8 on: Mar 19, 2004, 01:38:00 »
Do you wear contact lenses? I do and when they are getting near the end of their life lookin at objects does this - especially street lights at night when rainbow haloes appear around them !
We live in a society exquisitely dependent on science and technology, in which hardly anyone knows anything about science and technology. Carl Sagan

spendrey

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« Reply #9 on: Mar 22, 2004, 17:11:00 »
Thanks for the help everyone.
Chris came round yesterday afternoon with his Cheshire and kindly collimated it for me. The secondary mirror was quite off-centre and now looks spot on. I haven't had a chance to test it out again yet but will do as soon as the clouds permit.
My new webcam adapter turned up on Friday too so I'll post a pic as soon as I can.
Thanks Chris!!!

Rocket Pooch

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« Reply #10 on: Mar 22, 2004, 18:36:00 »
Hi again,

Sorry about rushing last night I had to get back quick.  

Anyway, there are two sets of instructions for collimating this telescope, I've attached both links below.  

It seems the cross heads hold in the mirror cell and there are some hidden Allen keys which adjust the collimation, or a combo of both.

http://www.skywatchertelescope.net/Downloads/AdjustableLens.pdf

The instructions below look like the set you had last night and are exactly the opposite.

http://www.skywatchertelescope.net/Downloads/Collimation.pdf

I'd suggest you give the shop a quick call to check which one you have.

Chris

spendrey

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« Reply #11 on: Mar 22, 2004, 19:56:00 »
Thanks again Chris. Do you have a link to that place you got your Cheshire from?

This is that site I was telling you about where the guy has given detailed instructions on building a roll-off observatory.
http://www.linnhe2.free-online.co.uk/observatory/
I reckon he must have had a lot of free time on his hands!

Rocket Pooch

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« Reply #12 on: Mar 24, 2004, 02:24:00 »
Its calles http://www.jimsastro.com but I also like Sherwoods Matt is very helpfull as well.

I think mine was about £25?

Also an IR blocker helps as well.

If you need to borrow the cheshire I'm only 10 minutes away.

spendrey

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« Reply #13 on: Mar 24, 2004, 16:42:00 »
Thanks Chris, I'll get one (and an IR blocker) as soon as the dust settles with my wife over my recent spending on this hobby!


Mike

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« Reply #14 on: Mar 24, 2004, 20:09:00 »
Just get a divorce it's cheaper !
We live in a society exquisitely dependent on science and technology, in which hardly anyone knows anything about science and technology. Carl Sagan