Saddle/Dovetail replacement for captive tube ring setup on Tal 1

[Alfian]

Hi all, I'm considering a "project" in the coming months to do a bit of a overhaul of my Tal 1. This will include the removal of the captive tube rings which are attached to the mounts top plate, and fit a saddle to which I can fit dovetails. This will enable me to fit other OTAs to the sturdy Tal pillar/pedestal mount.

Hunting around I came across this:

http://www.teleskop-express.de/shop/product_info.php/info/p388_Starway-Quick-release---dovetail-adapter-for-diverse-mounts.html

Am I somewhere on the right track or could some one give a better solution.

Additionally I think I've read somewhere that the Tal1 mount has a maximum weight capacity of 7Kg. I would not want to overstretch things, but figure it should take an OTA up to about a 150/750 f5 reflector OTA  (about 6Kg)  or is that too ambitious?

[nightfisher]

Dont quote me on this but the Tal mount has a sturdy reputation, so it may well be okay, i have a 150 f5 you can try on it before buying an ota

[Alfian]

Hi Jules, that's extremely kind and I may just take you up on that at some point. I had kinda thought of this as a summer project but there is no real reason why I could not bring the mount bit forward a tad. The big BUT is that I do not want to set too hacking tube rings off until I'm sure I know that I can replace them with a base plate to attach to the existing top plate, and a dovetail saddle that will not compromise the rigidity of the mount.

I had looked at the 130/900 but have more  or less decided that if I were to fit a scope that would be a good upgrade to the Tal it would have to be something like the 150 f5 or f6. Alternatively the smaller 130P DS looks  a good quality scope albeit another f5! 

[nightfisher]

Can you post up a close up pic of the mount and rings assembley, Andy H is the person to comment....he is our russian informer 

[Alfian]

Thanks Jules, will do.

[Alfian]

Hi I have attached a couple of photos of Tal1 top plate. It measures 20cm x6cm. Although the top plate edges are flat, and a suitably sized plate would sit flat upon it, below it is dished and ribbed for strength. (I assume). At either end there are "hole marks" which I assume (again) are drilled through on maybe another model. These could be the means of attachment. to a prospective new plate to which a dovetail clamp would be attached.

The good news is that a fellow forum member has offered me a clamp at a very useful price. Its the best means of completing the top plate conversion that I need to be sure about.

[nightfisher]

So the rings are an integral part of the dovetail bar, could you remove the entire assembly and retro fit a clamp 

[Alfian]

Hi Jules, the dovetail is the "top plate" of the Dec  axis to which it is firmly attached and is also integral to the dec slomo control.

I have looked at other possibilities in terms of mounting other OTAs,  though not the convenient one of having a dovetail clamp. 

Assuming the removal of the existing tube rings, the mentioned holes could be drilled out (or ones close by)  and tube rings of the required size could be directly allen bolted in place. I have also played around with a long dovetail bar that with relatively minor alteration could be made to fit fairly snugly into and attached to the top plate. Tube rings etc could be then fitted to this making changes just a little more convenient. If it would work it would also be a cheapish option.

The second hand dovetail clamp I had lined up wasn't to be. but not to worry.  

I have PM AndyH to hopefully gain his informed opinion. 

[AndyH]

Got here a bit late Thanks for the pm headsup, Afian

Similar modifications have been done to the Tal 2 mount. See here..... http://stargazerslounge.com/topic/102744-got-a-tal-mount-but-want-to-use-a-non-tal-scope-on-it/

Whilst the above didn't require the removal of any cast on tube rings, the idea is similar. 2 1/2" wide alu flat bar is available from alu/non ferrous stockists, for a decent fit on top of the Tal 1 top plate. This plate can then either be drilled for rings and/or a saddle plate. Chinese rings of 140mm I/D can be bought for the Tal 1 ota. I did this many moons ago, to let my ota be used on other mounts. I found the chinese rings were rather over sized, but some velcro(the wooly part, rather than the hooks) stuck onto the existing ring felt, packed it up for a good fit round the ota.

[Alfian]

That's brilliant Andy. Looks like I was on the right track but it is so good to see how someone has actually done it, plus all the links. Thanks Andy (and Jules)