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My eyes are blown away by...nothing special


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On 11/01/2022 at 21:36, clafann1 said:

By zooming on a bright star and going out of focus, I cant see any circular pattern, all I see is the shadow of the secondary.

The oddest thing is that shadow looks concentric at the center of the eyepiece field of view, but when I move it to the edge of the field of view, it's no longer concentric.

If you are seeing the shadow of the secondary - you are too far out-of-focus for a star-test. You can use this view to do a rough check that things are aligned, but a proper star test involves only adjusting things slightly off-focus to either side of focus. The 'rings' you see are pretty small and their diameter is not big. You will need high magnification.

As for the test being different away from the centre - that's correct. You want to check for concentricity at the centre of the view. It changes as you move away, which is why it's important to do the test on Polaris (which will move very little) or with a driven scope. In fact - that's how you collimate with a star test: you find the location in the view where the rings are concentric - and if that is off-centre, you adjust the primary mirror to move the 'concentric' star back to the centre of the view.

https://www.astroasheville.org/wp-content/uploads/2013/09/No-Tools-Collimation.pdf

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Got it decently collimated (secondary concentric and primary center matching the collimation cap hole).

The views didnt improve anything, so, guess this is what it gives for real. Maybe collimation improves photography, but for seeing directly on the eyepiece, good enough and perfect are pretty much the same. Lesson learned.

There are so many factors that allow for a great view that if you mange to meet them all at the same time, it's a celestial miracle, Amen...

Edited by clafann1
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It's difficult when you first start out know what to expect from your kit and being able to optimise what you have before you spend any more money.

It's good that you have checked the collimation but first I would have a go at low power with the moon and if you get the focus right for a sharp image there then next try Jupiter.  It's not going to be huge but it will give you an idea of where the focus point is for the scope. Do that a few times with the eyepieces you have and you will realise which one seems to give the best balance of magnification versus sharp focus. Let the telescope steady itself first though and look into the eyepiece without touching it.

For me the biggest improvement with a small scope is to get to a dark site at sunset, set things up with the caps on to stop dew , and let it cool for an hour. That way there is less heat shimmer (which would be magnified) and at a dark site the sky is blacker, the stars show more contrast against that black sky, and those objects that struggle in town against a lighter background can stand out more. In addition to this your eyes can truly adapt to the darkness rather than have that ruined by street lights or next doors security light.

These things don't cost any money , apart from some fuel for the car, and will help you understand what the scope can do. The eyepiece you think works best might be the one to upgrade first as you know that seems to give the best balance of magnification and field of view.

Cheers

 

Edited by astronymonkey
typos
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F/4.4 is a very fast focal ratio for a beginner’s visual scope. Because it’s so short, it means the light has to bend more, and that exposes weaknesses with the optics - particularly with cheap eyepieces. Am sure it’s still capable of good views (maybe up to 100x) with the right eyepieces, but it’s more of a low power telescope, so good for sweeping star clusters etc, not so great for planets. 

Edited by Highburymark
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1 hour ago, clafann1 said:

Instead of wasting more money on this one, I'm gonna try a long focal ratio refractor next, any recommendations?

I’m sure more experienced people will give their recommendations and obviously it depends on your budget, but the Altair Starwave or Starfield from FLO 4 inch refractors have very good reviews and I think are good all-rounders. Similar scopes are sold by several suppliers but here are two examples:

https://www.altairastro.com/starwave-102ed-r-fpl53-refractor-459-p.asp

https://www.firstlightoptics.com/starfield-telescopes/starfield-102mm-f7-ed-doublet-refractor.html
 

The Altair version also comes with FPL-51, rather than FPL-53, glass which is less expensive.

I bought the Altair Starwave 102 ED-R just over a year ago, based on good reviews here and on other sites, and I’m delighted with it as an all round portable refractor.

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