Moving the SkyWatcher 130M primary mirror up

[pjac]

Hi all. I have a SkyWatcher 130M (aka SK1309EQ2), and in order to take prime focus images with a DSLR camera I wanted to move the primary mirror about 2cm up the tube. I was hoping to follow the method on this thread for the SkyWatcher 130P, but the mirror mounting is different.

Here's the original SkyWatcher 130M primary mirror mounting:

And here's my first attempt at moving the mirror - described in more detail on my blog post:

I'm now waiting for some clear nights to try this out... fingers crossed.

[Peter Drew]

Looks like a neat way to address this issue. I'm not 100% confident that the adjustment via the 5mm nuts will work as well as you hope unless they are somehow captive, but as you say, a trial will prove one way or the other. If it isn't satisfactory, you could tap the mounting ring M6 and use larger diameter screws. Shortening the tube might ultimately be the easier option. Good luck.

[pak1234]

Hi Pjac

Just had the same problem modding my 130M. ended up cutting 25mm off the tube, now getting great focus on the camera and with the help of an old barlow minus the lens all EPs now in focus. I have also shorted the focus draw tube so that its not in the light path, still gives me around 40mm of travel which seems to be plenty either side of focus.

[pjac]

Its still cloudy here so I've not been able to try it, but the potential for the nuts to come loose in the current prototype setup bothers me. I've come up with a couple of alternatives to tryout if the weather doesn't improve.

The simplest route does now seem to be cutting the tube down. I'm pondering getting a hacksaw with a rotatable blade and doing it by hand, then filing down the surface for a smooth finish. pal1234 how did you cut yours?

P.S. Looks like I messed up the link to the SkyWatcher 130P modification thread, which is here:

[pak1234]

Hi pjac

Just used a hacksaw very carefully....

[pjac]

The initial modification worked well enough for some moon and Jupiter shots with direct DLSR attachment, but it was too windy to really test stars and collimation.

I'm trying a spring based modification now, based on the ideas in the SkyWatcher 130P mirror thread - it seemed a shame to waste all the springs I'd bought

This seems more secure, but has moved the mirror a few mm higher still. Maybe I can leave out some of the washers - but if anyone else wants to try on their own SkyWatcher 130M, shorter springs might be better.

[bogdog]

also have same problem with camera not focussing,just wonder if its possible just to unscrew focuser and widen the hole kinda elongated that when replaced focusser

it moves from side to side ,could cover the gap with tape as temp measure? or would this throw it out altogether?

[pjac]

You can easily cut about 1cm off the plastic collar of the focuser, so that you can get the camera 1cm close to the mirror. However that on its own will not be enough.

There's a photo of this option and other good information about reaching focus on the SkyWatcher 130M on this blog post:

http://www.alananna.co.uk/blog/2012/using-an-slr-with-a-skywatcher-explorer-130m-telescope/

[RichCliff]

Hi, my first post here, I have recently (a week ago) purchased the same telescope and finding the afocal side of aligning my 350D lens with the EP quite difficult.

I just saw the new Optical Tube Assembly from SkyWatcher that has the modification already done, it is going for £164 and from what i can gather, its pretty much what pak1234 has done. They state the Primary mirror has been moved up the OTA and the overall length is shorter. Now, i am unsure if they mean the length is shorter due to the fact they have cut off 3cm or they have a shorter length and also moved the mirror as well.

Although i am a mechanical engineer (used to huge plant machinery) i still don't feel confident in modifying my tube as of yet. Just incase i mess it up and cannot undo it.

[booth_robert]

So how much should be cut of the end as mines still in bits from flocking and cleaning and center spotting the primira mirror so mite as well get the hack saw out now lol