Scope advice sought

[knobby]

Sounds like cooling... My 4 se takes up to 2 hours and its smaller than yours!

[greglloyd]

Hmm. One thing I've noticed when looking into the OTA from the front this evening is that there are actually a few dust particles inside (which must have been there from manufacturing I'm thinking as the scope was sealed up when it arrived. One or two specks on the primary mirror and a few individual dust particles on the inside of the corrector. Anyone else seen this before with a brand new SCT? I didn't expect that with a closed tube.

[nightfisher]

The dust flecks wont do any harm to the views and best leave them there

[greglloyd]

Yes, I'm aware that they will not affect the views so no probs there.

This is Celestron's take on the matter :-

http://www.celestron.com/c3/support3/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=2186&nav=0,266

[greglloyd]

Mostly clear skies here this evening and the scope has been cooling down now for around 90 mins ahead of a collimation test. Already did a quick test 10 mins ago and the patterns look much better than the other night. Will continue to let it cool down more and test the optics around 10:30pm. Juptier still didn't look as sharp as I would like at 125x and 214x. When defocusing I noticed that it started to ghost from the bottom side of the planet first. Hoping for nice symmetrical airey disk patterns later as the dot in the very centre of the pattern still appeared slightly shifted above centre when looking at the patterns just a while ago. Don't know if that correlates with the Juptier effect I mentioned earlier and indicates a slight correct is needed to the collimation?

[John]

If you de-focus the star a little more you should get a small disk of light with the black shadow of the secondary in the centre of it, or thereabouts. A central shadow is what you are looking for from a collimated scope.

Star testing using airey rings needs a fully cooled scope. Currents of warmer air still in the tube can skew the symmetry of the rings.

[greglloyd]

Ok, cheers John. Did a second test there and it's getting better looking. Will do proper test later at 10.30 onwards.

[Graham Darke]

I have C6SE and love it. Views are like an 8 inch but more like a 5 inch to store and move around. Eyepiece wise, I find that I use my Televue 18mm Radian the most. In fact some nights I only use that one eyepiece. It gives 83x magnification which seems to be good for most applications. The optics are bit odd on my scope. Intra and extra focal patterns are not symmetrical but the in-focus views are good. I use mine for double star observing and have been really pleased with it. Would recommend bobs knobs for collimating. You'll find it holds collimating very well once done.

[greglloyd]

Thanks Graham. Very much agree that it gives views similar to an 8 inch scope but with portability that is better than a regular 6" Newtonian (have previously owned 8" and 10" dobs). Can't wait to get a few more sessions with it under the dark winter skies.

[Dunkster]

Not sure if this helps, but might be worth a read: http://www.robincasady.com/Astro/myimages/collim.html

I've been lucky with my SCTs as they've always star tested OK with first use and I occasionally double check, but find they tend to hold collimating remarkably well...I've not yet been tempted to tweak (yet).