Virtuoso 90mm Mak - Advice Sought

[AdeKing]

I have recently acquired one of these nice little scopes, but have noticed that the Dovetail has been getting a bit loose. 

Last night I managed to knock the scope over, fortunately it fell into a covered pile of grass cuttings sp it had a soft landing, but this was enough to really loosen the dovetail.

I tried to tighten the screws attaching the dovetail last night, but they are now too loose, and the nuts inside the OTA just spin, so the tension doesn't increase.

It looks as though I can remove the corrector plate by unscrewing three philips had screws at the front of the OTA, but I'm rather nervous about doing this. 

I assume that if I do this, I will need to re-collimate the scope, but I can't find any adjustment screws anywhere at the focusser end, just the smooth plastic cover. 

I know that the Skymax range have collimation screws at the focusser end, but the Virtuoso 90mm Mak does not.

Is there anyone out there that has either replaced the dovetail or the finder scope on a Virtuoso 90mm Mak that can give some guidance please.  On the face of it, it looks simple, but I've been caught out like that before and as I like this little scope, I'm concerned about messing it up.

Thanks for looking.

Ade

[cuivenion]

I wouldn't open the scope up personally. Have you tried pulling the dovetail towards you so the nuts are tight against the side of the tube when trying to tighten it. That should increase tension. Just make sure make sure you turn the right way so the nuts don't fall off inside the tube! If you're not sure send it back to the supplier to be looked at.

[AdeKing]

Hi cuivenion,

Thanks for your suggestion about pulling the dovetail outwards to increase the tension on the nuts.  This was the first thing I tried last night, it worked to a degree, but not enough to enable the bolts to be properly tightened unfortunately, and after a while all it succeeded in doing was to scrape off the black paint around the bolt.

I don't particularly want to open the scope up, but as it was purchased secondhand I didn't think that OVL would want anything to do with it.

I know that there is a thread on here detailing how to strip down a Skymax 90 Mak, but the images don't show up for me, so I'm reluctant to try.

Thanks again,

Ade

cuivenion

[cuivenion]

Best of luck with it mate. Afraid I can't help as far as stripping the ota down is concerned.

[AdeKing]

Currently thinking I might just leave well alone and fit some tube rings and a new dovetail, but now struggling to find the right sized tube rings and dovetail to fit it.

Sure I'll get there eventually.

Ade

[John]

With the Skywatcher maks the secondary mirror is an alluminised spot on the inside surface of the corrector / meniscus so there is no adjustment you can make to it. The collimation adjustments are to the primary mirror only. If you mark the orientation of the meniscus carefully you should be able to remove it, tighten the internal nuts on the dovetail bar screws and then replace the meniscus in exactly the same orientation so re-collimation should not be needed.

Obviously tube rings and a dovetail bar would work, when you can find the right size tube rings, if you don't fancy removing the corrector plate.

[RT65CB-SWL]

Currently thinking I might just leave well alone and fit some tube rings and a new dovetail, but now struggling to find the right sized tube rings and dovetail to fit it.

Sure I'll get there eventually.

Ade

I attached a dovetail bar to my ETX105 with two Jubilee rings/clips - posted under the title/name "My 'modded' Meade ETX105 OTA" (with photos) in the DIY Astronomer sub-section.

[Alien 13]

To be honest it would drive me nuts and I would be tempted with disassembly making sure everything is marked as to its position and add some blackboard paint to any exposed metal near the offending screw.

Alan

[Stu]

To be honest it would drive me nuts and I would be tempted with disassembly making sure everything is marked as to its position and add some blackboard paint to any exposed metal near the offending screw.

Alan

Drive me nuts? I see what you did there

I agree, if they are loose there is always the possibility of something coming free and rattling around the tube causing damage. If you proceed carefully and mark everything, removing the corrector plate should not be that tricky.

[AdeKing]

Thanks for all the suggestions to resolve this.

I have spent this evening trying to remove the corrector plate, but it doesn't seem to pull off or unscrew, so it could well be epoxied in place in addition to the three retaining screws.

Anyway, although I really would like to tighten and re-use the existing dovetail, I think that something may well break.  This also suggests that it is not the same OTA as the Skymax 90 as was previously suggested, although the specs may be the same.

I attached a dovetail bar to my ETX105 with two Jubilee rings/clips - posted under the title/name "My 'modded' Meade ETX105 OTA" (with photos) in the DIY Astronomer sub-section.

Thanks very much for this suggestion, I have just ordered a short (15cm) Skywatcher dovetail from FLO and will pick up some appropriately sized jubilee clips later this week. 

Drive me nuts? I see what you did there

I agree, if they are loose there is always the possibility of something coming free and rattling around the tube causing damage. If you proceed carefully and mark everything, removing the corrector plate should not be that tricky.

I am slightly concerned that the nuts may come loose, but given that the jubilee clips will be holding a new dovetail, I'm hoping that there will be minimal movement of the old nuts and bolts and that the nuts will be retained, at least until I pluck up the guts to be a bit more forceful with the correcter plate.

Thanks again for the help with this, I have emailed WEX to see whether tightening the dovetail will be covered by warranty (its less than 8 months old), as the previous owner is a member of our astronomy group and has provided me with the original receipt, but I guess we'll just have to wait and see.

[beamer3.6m]

You can remove the mirror cell very easily on the scopes.

Just undo the screws around the bottom of the scope (opposite end to corrector plate) and the whole mirroe cell comes out.

I found that it did not have the option to collimate the mirror so it went back in just fine. I just marked which screw went in which hole.