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Skywatcher 190mm Maksutov-Newtonian Astrograph
Posted 04 November 2008 - 08:57 PM
Sorry to be a pain, but does anyone know what the back focus on this beastie would be? Hunted on the 'net but cant find any details, though my gogle skills might be lacking!
Posted 04 November 2008 - 09:07 PM
The OTA is designed to work as an imaging scope primarily, and the native focus point is designed to provide focus for CCD/DSLR/webcam/etc as it is. If you want to use it for visual, you have to use the extension tube supplied to get to focus for eyepieces.
Posted 04 November 2008 - 09:22 PM
Sorry, I'll try and make myself a bit clearer, just not using the right terminology.... :oops: I currently image with an SXV-AO and associated OAG, filter wheel and Atk16hr, so the imaging train is quite lengthy. This is fine on an ED80 but not sure that I will be able to come to focus with such a long train with the 190MN. Eg say arbitrarily the image train is 100mm from the focuser and the 190MN comes to focus 80mm from focuser then with best will in the world I will never be able focus as the ccd will always be beyond the focus point? Is that any clearer?
Posted 05 November 2008 - 09:44 AM
Posted 08 November 2008 - 09:10 PM
The telescope certainly delivered on flat-field performance and even illumination:
CCD Inspector shows a VERY flat field from a raw full size FITs file.
Edited by FLO, 11 April 2009 - 06:06 PM.
Posted 08 November 2008 - 10:25 PM
Posted 08 November 2008 - 10:46 PM
Posted 08 November 2008 - 11:18 PM
In other words, what is it measuring in order to arrive at a graphical representation.?
Posted 08 November 2008 - 11:27 PM
I regularly use this to collimate my Hyperstar, as it also shows "lopsidedness" in the star sizes, but also shows just how well its coping with keeping the image flat across the chip. It also displays where it thinks the centre of the collimation point is, using the 2D/3D map it has generated, so you can adjust the collimation accoringly with the CCD in place.
Posted 08 November 2008 - 11:37 PM
Posted 08 November 2008 - 11:52 PM
I'm beginning to understand it.
Could a Newt 8" f5, perfectly figured, be capable of a similar result, without the aid of a coma corrector, or even with it.? It isn't 20 questions, honest.
Posted 09 November 2008 - 01:28 PM
Wowser...thats flatter than a flat thing thats been flattened by a flat thing flattener !!!
hahahaha, liked that one Billy, :-)
Posted 10 November 2008 - 01:02 AM
Could a Newt 8" f5, perfectly figured, be capable of a similar result, without the aid of a coma corrector
No, not without a coma corrector. If used with a coma corrector then it could deliver similar results, particularly if it has been designed with imaging in mind (has a larger than usual secondary for a wider field of illumination).
It isn't only the incredibly flat, wide, even field of illumination and 'built-in' coma correction that separates the Mak-Newt from regular Newtonians. The 190mm Mak Newt is a sealed tube so is less prone to tube currents. The tube is also made from 1.5mm steel so is less likely to flex and knife-edge internal baffles reduce internal reflections for increased contrast.
Posted 10 November 2008 - 10:14 AM
I have not seen the weight of the OTA in print, at least I don't remember seeing it. SteveL had the unit side by side with his ED80 at Kielder, and stated indirectly, that the load was lighter than when his C11/ED80 Combo occupied the mount. He had three counterweights fitted to balance the SW & ED80. That means I would need another weight, unless two would cope with the SW OTA and a ZS66 scope. What say you sir.?
Posted 10 November 2008 - 10:39 AM
Posted 11 April 2009 - 02:35 PM
Posted 11 April 2009 - 06:28 PM
Yes I really want one of these, and no I can't afford it (at the moment)
WO ZS80 FD
Atik 314L+ / EFW2
Posted 11 April 2009 - 07:45 PM
Are you going to Salisbury and if so will you be bringing one along for us to drool over?
WO ZS80 FD
Atik 314L+ / EFW2
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