My SkyWatcher... SCT just arrived

[riklaunim]

It's just a Celestron SCT 11" under SW brand. It comes with a big finder, 32 mm Plossl, diagonal and 1,25" holder. No first light yet, but no problems spotted.

I got it from teleskop-spezialisten but they are also on astroversand.com. Spezialisten gives all sold OTAs a full checkup (colimation, tuning, optics test). Those two German shops have it and it's some sort of direct import from Synta = much cheaper (they aren't normally available in Europe due to brand collision. AFAIK SW SCT are for Asia markets).

[JCJC]

Looks very nice, congrats!

Can't wait for results from it.

Jordan

[riklaunim]

Got few night to use the scope and equipement. What's noticable - it need more than 2 hours to cool in winter (~30 degrees to cool). That can be reduced by a cat cooler.

Second thing - when focusing the mirror moves more in the focuser spot and the object will move in some direction. Compared to C8 this is very annoying as turning the focuser knob focus much slower than in C8 while the shift is noticable. Sometimes I turn the knob a bit and wait for the object to drift back a bit, but still corrections are needed. I have a JMI motocryford but thats only for fine focusing (like while imaging).

Planetary imaging - that needs good seeing for the C11 to show its resolving powers. Didn't had that good seeing yet, but Saturn at f/20 has a nice size

ToDo is to check the counterweight extension bar/shaft how it will perform. I have HEQ5 with around 16kg of counterweights but due to "short" counterweight bar they barely do their job

Second mount change are the Celestron vibration pads - they noticably limit vibrations when imaging. Wind blows doesn't cause the setup to bounce back and forth and building wibrations doesn't show up too (like someone slams the doors below). And thats 12kg C11 on HEQ5 SynScan

I'm also thinking about adding a flip mirror to the setup. Either (2") Vixen flip mirror attached to the motocryford (so +/- barlow/reducer/oag goes after it causing focus problems for the flip) or T-threaded Orion/BS Astro flip mirro which could go on the end (but still not usable with Reducer + OAG, usable in other configs). It would be nice if a flip mirror could also have a mathing guide head

C11 in a Geoptik bag (very handy):

And some collimation star test

Overall it's a good scope, although I would expect better construction. Celestron isn't backporting improvements from HD to standard OTAs (like ventilation holes). All SCTs have problems with moving primary mirrors. If you have big drawtube in 11-14" OTAs then why not making a fixed primary mirror and dedicated cryford with large focusing range using drawtube in drawtube to handle this? Reducers/correctors and telecentric barlows could be designed to fit insite the drawtube to save space/backfocus and make it easier to use the OAG/wheel, camera or other accessories.

I've choosen the 11" SW SCT as it popped out in Germany much cheaper than Celestron SCTs. Now the prices are starting to rise up again after bashing all those SW SCT sellers If I wouldn't buy that SCT I would probably try to get TAL 250K in resonable price. £ 1899 in opticalvision isn't that bad (cheaper than 11" SCT at my local astro shop O_o) and I still don't know if much cheaper SCT was a better choice than fixed-mirror open cat like the TAL (or VMC Vixen).

One other thing - 11-14" SCTs have also 3,3" big SCT thread - I wonder how a f/3.3 reducer of that size would perform. Should illuminate bigger circle.

[Live_Steam_Mad]

Interesting to see that test certificate that they supplied you with. I can see quite a bit of Spherical Aberration in that Star Test, about 1/2 wave overcorrected (see Suiter's book on Star Testing). I am not convinced that your C11 is even Diffraction Limited (the standard that SkyWatcher officially certify their optics to), judging by the look of that Roncigram and the in focus star image (as well as the actual Star Test images). I would be asking for another OTA or a refund. I would be interested to hear what magnification it tops out at on double stars and is still sharp?

My own Celestron C11 (year 2000, bought second hand in 2006, Starbright non-XLT, non-Edge, non-Fastar, ex-CG11)  has very good / excellent optics (accuracy) (8.5 / 10) but with noticable scattered light compared to my 7" Mak. Still outperforms the Mak on Jupiter, 1/3 more detail visible at 350x. Cools down completely in about 90 minutes with 14 degrees C difference in temperature with ice pack on rear cell. Better on double stars such as Epsilon Lyrae than the 7" Mak due to smaller Airy discs and much more real color (e.g. Xi Bootis) instead of 7" Mak washing out color-wise as the power is increased due to dimming. Very practical to use on CG-5 mount for visual at high magnification with 6" counterweight bar extension (been using it that way for over a year). Mounting made much easier with head torch (Energiser, 3 LED, 8.50 GBP from Tesco). Mine has the Losmandy style dovetail and radius blocks but a Vixen style short dovetail is bolted onto the bottom of the wide dovetail.

Mine has "colored coma" even at centre of FOV at very high magnification that changes with diagonal orientation, obviously visible in one diagonal position but not visible at another, due to misaligned primary that was RTV glued in at the wrong angle by the factory, can't be dialed out with doing collimation in focus at 700x. I use the inherent coma of the C11 to remove it by moving the star to another part of the FOV, then the image becomes diffraction limited. Very crisp sharp high contast views of Airy discs in focus at 700x, very low Astigmatism.

Mine has almost no difference in the size of the central breakout on the Star Test on either side of focus, but a difference in the intra and extra focal image that resembles Suiter's test images for 1/5 wave of High Order Spherical Aberration.

Mine had mirror flop (changes in collimation due to elevation) caused by my primary mirror retaining ring being loose. I tightened it and now it's much better.

Regards,

Alistair G.

[riklaunim]

Interesting to see that test certificate that they supplied you with. I can see quite a bit of Spherical Aberration in that Star Test, about 1/2 wave overcorrected (see Suiter's book on Star Testing). I am not convinced that your C11 is even Diffraction Limited (the standard that SkyWatcher officially certify their optics to), judging by the look of that Roncigram and the in focus star image (as well as the actual Star Test images). I would be asking for another OTA or a refund. I would be interested to hear what magnification it tops out at on double stars and is still sharp?

It was a artificial star, quite likely to close to this OTA (as they do mostly do small refractors). As for image quality it rocked.