Talk about sucker for punishment! The CAS Committee has asked me (well I offered as well ) to remount one of the CAS scopes.
This scope is a Takahashi MT-16 Newtonian OTA only. Apparently the scope was mounted on a very wobbly GEM and this is what saved it from the fires as it was in a workshop off the mountain for repair. No sign of the mount now, just the OTA.
Thisis the first time I have seen a Tak close up. Very solidly built with the most amazing focuser and a very nice finder scope. I understand the optics are outstanding. I will just mount it in a simple dob mount for the moment to get the scope operational, but I am very tempted to suggest I turn the optics into an ultralite "suitcase" telescope for members to use when travelling. Not the sort of thing you can just go out and buy!
I have started fabricating a dob mount for the OTA, pictures attached. I need to get this finished ASAP and out of the workshop before the 16" mirror arrives .
<P>Hi Ian</P><P> Nice project</P><P> Should find the views to be as good as a 5" refractor.</P><P> Louie ( Atalas ) used to have a MT130 and found it to be better than his Tak 4" APO.</P><P> I think the reason the old mount was not working so well is someone at the club decided that if you have a very long counter wieght shaft you only need a small counter wieght , quite true but makes for a poor mount.</P><P> Did the mount survive to fires.</P><P> </P><P>Zane</P>
Yes, I am looking forward to having a look through it to see what it is like.
WRT the mount, Peter B was uncertain as to the location/status of the mount. On the basis it aparently was NBG, I haven't followed up on this matter.
I am in two minds about this scope. In its current configuration it has a heavy closed mirror cell in a very heavy 200mm steel tube, a magnificent (and very heavy) Tak R&P focuser with a clear apature of about 2.7" and a focal plane positioned about 150mm outside the tube with a resultant large secondary mirror. It also has a lovely Tak 6X30 finderscope (sharp right to the edge!!). I suspect it has the thermal mass of a typical 12" scope!
This scope is clearly designed as an excellent astro photography platform and is beautifuly balanced in the centre of the tube for GEM mounting.
I am putting it in a dob mount for the moment just to get it operational and star test it. CAS can at least then use it as a hire scope. I suspect it will suffer from tube currents due to the closed mirror cell. I also suspect that an "all nighter" during a Canberra winter may well result in primary mirror fogging due to the steel tube "super cooling" and the resultant cold air pooling around the primary mirror.
Where to from here? The options I see are:
1. Leave it as is for general visual use on a dob mount.
2. Acquire a suitable GEM and CCD. It could them be a hire scope for members wishing to investigate astro imaging. (It's F6.25 BTW).
3. Assuming the mirror is as good as you are likely to get, keep the primary mirror only, around which build a custom dob mount, tube and well ventilated cell for high quality visual only work. The rest of the scope could go into storage for parts.
Looks like a nice project. Would like to see some details of your 16" string dob as well. BTW where did you get the 16" mirror? Would like to build something like this myself.
Refurbished focuser and trialed the JMI Motofocus unit (removed for the moment).
Fitted stering handle to tube.
Washed primary mirror and adjusted mirror cell.
Fitted Ebony Star on Teflon bearings.
Completed most of timber work. Couple of holes to fill, final sanding then finishing.
The complete scope weighs 17kg thanks to the very heavy tube (11kg).
1 hr observing session last night. Seeing was just average but Jupiter was quite sharp (very sharp indeed in moments of good seeing @222X) and the scope had a very nice "snap" to focus so I think the mirror should be quite good . The scope is outside cooling down for a second session tonight.
I have attached a couple of photos of progress:
Note the mirror cell, the mirror just rests on a sheet of rubber like material which rests in turn on a ring which is the inner part of the mirror cell.
The 16" .......... mmmmmmm ...... yes, well I have the mirror which I acquired from Lester through the IIS Buy/Sell forum and an AstroSystems Crayford focuser and filter slide. I also have a stack of hoop pine plywood which has yet to meet saw or router WRT parts for the 16". No further progress at this stage.
Spent a couple of hours observing with the 160mm Tak and comparing it to my 200mm string truss dob. Jupiter is over the roof of the house now and thermals off the house are affecting the seeing in that part of the sky, so I have given up for the night.
Seeing was much better tonight, 5/10 most of the time, with 7-8/10 on occasions.
Both scopes showed a lot of detail on Jupiter during moments of good seeing @ 222X to 285X. I felt the 200mm showed slightly more detail, but there wasn't a lot in it. Interestingly the Tak, during moments of good seeing, showed beautiful complete diffraction rings around Jupiter’s moons. The 200mm did show the diffraction rings but they tended to be broken and less steady.
Antares was a surprise. The Tak showed a wonderful clean wide split @222X. Once the 200mm mirror had cooled down, it too easily split Antares, however, I must say it did look a little cleaner in the Tak .
Hi
I think the scope is one of the ones that the Japanese guy donated to the Downer club which may include Strongman Mikes 6" Apo .
I may be wrong though I'm sure one of the guys in the club would know , I may be thinking of another scope and it may have been cooked in the fires .
Zane
Quote:
Originally Posted by stringscope
Hi Zane,
Yes, I am looking forward to having a look through it to see what it is like.
WRT the mount, Peter B was uncertain as to the location/status of the mount. On the basis it aparently was NBG, I haven't followed up on this matter.
I am in two minds about this scope. In its current configuration it has a heavy closed mirror cell in a very heavy 200mm steel tube, a magnificent (and very heavy) Tak R&P focuser with a clear apature of about 2.7" and a focal plane positioned about 150mm outside the tube with a resultant large secondary mirror. It also has a lovely Tak 6X30 finderscope (sharp right to the edge!!). I suspect it has the thermal mass of a typical 12" scope!
This scope is clearly designed as an excellent astro photography platform and is beautifuly balanced in the centre of the tube for GEM mounting.
I am putting it in a dob mount for the moment just to get it operational and star test it. CAS can at least then use it as a hire scope. I suspect it will suffer from tube currents due to the closed mirror cell. I also suspect that an "all nighter" during a Canberra winter may well result in primary mirror fogging due to the steel tube "super cooling" and the resultant cold air pooling around the primary mirror.
Where to from here? The options I see are:
1. Leave it as is for general visual use on a dob mount.
2. Acquire a suitable GEM and CCD. It could them be a hire scope for members wishing to investigate astro imaging. (It's F6.25 BTW).
3. Assuming the mirror is as good as you are likely to get, keep the primary mirror only, around which build a custom dob mount, tube and well ventilated cell for high quality visual only work. The rest of the scope could go into storage for parts.
Many thanks for the info Zane. I will ask a few more questions and see what I can find out.
Decision has been made, cloth covered tube (gloss finish) and Jarrah stained mount (satin finish.......I think ). I am planning to completely disassemble the OTA tonight and prepare the tube for cloth covering later in the week.
The cloth we have picked will be complimented by the grey colour of the end rings and focuser base so they will not need repainting.
Disaster with the first attempt to glue the cloth onto the tube . The glue I was using, the baked enamel finish and the first coat of Estapol did not agree (bubbled terribly) so I had to strip the cloth off and do what I should have done in the first place. Strip the tube back to bare metal and start again . Fortunately I had purchased spare cloth so I had enough for a second attempt. I have used "Weldbond" glue this time which seems to have worked OK.
I have at last made some more progress on the CAS Tak:
OTA finished.
Damage to tube repaired as best I could.
Covered in star patterned cloth with 6 coats of Estapol on top. (Estapol coats have taken all week and lots of heating in the garage). 14 of the brightest stars from Crux applied to the opposite end of the tube from focuser unit.
Interior is fully lined in flock paper.
Refitted end rings, focuser, steering handle and secondary spider (optics are safe in storage).
) to remount one of the CAS scopes.
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. The glue I was using, the baked enamel finish and the first coat of Estapol did not agree (bubbled terribly) so I had to strip the cloth off and do what I should have done in the first place. Strip the tube back to bare metal and start again 
