Bought my first Tal (100R)

[rikroe666]

When this came up for sale i couldn't resist to see what all the fuss was about, I've heard lots of good things about them and this was going very cheap.

I took a bit of a chance as it was in N Ireland so could only go from photos, the seller told me he could get it to within an hours drive from where i live free of charge on his works transport so how could i say no.

It came with a broken tube ring and unfortunately it was missing a couple of parts including finder scope, end cap and diagonal but everything else was present.

It all came in the massive coffin box, the tube paint was a bit tatty but the objective lens is immaculate with the deep purple coatings, the EQ mount although seems quite good will be staying in the box i think but the nice wooden tripod is now carrying my Vixen GP and looks good It also had the excellent 25mm purple coated eyepiece and a 10mm plossl with what looks like a yellow-ish coating.

The only part i don't like is the 1.25 R&P focuser, it only has around 25-30mm of travel and doesn't come to focus in any eyepiece's bellow 10mm.

The 1.25 focuser also needs the missing diagonal as it has a strange flange fitting, this means you can't just put any old 1.25 diagonal in without some modification,  it has to be a Tal.

I was going to put up a wanted add for a replacement diagonal but when a used 2" Tal focuser came up for sale i bought that instead but to fit this means shortening the tube as its a lot longer than the 1.25 (see pics) but wont be hard to fit.

I don't know if this is right but if i rack the 1.25 focuser about half way out and measure then rack the 2" focuser out half way and measure and cut the difference off the tube will that work? this should mean when the 2" is racked half way out the eyepiece should be in the same position as the 1.25" racked half way out i will also have to remove the the rear baffle will this create any problems?

 

Rick

 

 

 

 

[Fozzie]

Got to love that.. gorgeous purple hue on that lens too.. 

Very nice, worth the gamble... 

 

[AndyH]

Hi !

 

The 'flanged' Tal 1.25" diagonal, which was originally included with this scope, has(from memory) a light throughput of 72mm(ie: uses up 72mm of available focus). For example if you wanted to use the original focuser 'straight through', an extension tube of 72mm length would be needed for the focuser to be in the same racked position. Tal also produced the same diagonal, but with a std 1.25" nose. The flanged models were produced for the 100R and the 150K/200K 6"/8" Kevtsov's. The flange is actually a rather clever idea if you think about it as when you tighten the focuser thumbscrews, in effect you are pulling the diagonal up tight against the focuser, keeping it centred and true, with no off centre slop.

A way to simulate the flange is to get someone with a lathe to machine you up a flange that can slide onto a straight nosepiece and should have 2 or three small grub screws to tighten it down on the nose. I can remember someone on SGL doing this very thing.

Most widely available 1.25" diagonals are in the 80-85mm light throughput range. This is obviously going to cause issues on the 100R.

A good replacement for the original diag would be a Takahashi 1.25" prism. This has a very good quality prism inside that in no way lessens the images, especially in a F10 scope. This one has about 63mm light throughput, which is great news for folk whose scopes have limited 'in-focus' availability. I have one and can confirm it's optical quality. For Tak, it's surprisingly not that expensive.

If you fit the bigger focuser, the amount you cut off the tube not only depends on the difference in focuser body lengths, but if you are going to use a 2" diagonal. Be aware that most of these units have a light throughput of about 110mm, not including the 2"-1.25" ep adapter, which can add another 10mm.

 

So.

1/ Measure the length of the 1.25" focuser fully racked in, then the length of the 2" focuser, also fully racked in.

2/ Difference is what you need to cut off the tube, if using a 1.25" diag. I'd add another 10-15mm to that amount, just to be safe.

3/ If you reckon you're going to use a 2" diagonal, I'd say add another 50mm to the above figures.

 

The focuser drawtube, in your pic,  is very long. Chop too little off and there is the danger of the drawtube entering into the lightcone/lightpath, when your ep is in focus, thereby making the scope operate at way less than it's 100mm objective. I think the difference in tube lengths, 'tween the R & the RS(newest version with 2" crayford focuser) models is around 4".

ps: The early 100RS I used to have had that Tal 2" R&P as in your pic. Basic but solid

pps: I'd be filling up the holes around the edges of the interior tube baffles and check that they haven't moved off centre. This was a common problem with these early R models. Either that, or remove them and fully flock the interior. Whaterever you do, be it flock or paint, try & cut out as much interior stay light/reflections as poss.

 

I've waffled on long enough and probably not answered all your questiions. Blame it on me reminiscing about my old 100RS scope . Was a cracker.

 

Cheers,

Andy.

[Moonshane]

Great answers above. Hope you enjoy the scope when you eventually look through it!

The focuser was nice and smooth on my pstal which also has the purple coatings.

 

 

[AndyH]

If you have the broken part of the ring, a repair is possible. I had a pair of 100RS tube rings, one of which had snapped. I wanted to use them on my Tal 'M', which by luck used the same aluminium tube as the older refractors. So with a piece of alu square bar and some hand tools I worked the following repair.

Anything is possible, said Mr Impossible.

 

[rikroe666]

Thanks Shane, the focuser is very solid and seems much better built than the Synta equivalents that i have and luckily should be quite easy to fit on the tube.

 

AndyH - Thanks for all your help with this so far i decided to go with the 2" focuser as this was a much easier option as Shane was selling one just as i was deciding and it gives me more options for eyepieces to use and even binoviewers maybe. I am going to cut the tube tomorrow and fit the focuser, is there any way of knowing if and how much i will need the cut off the draw-tube? 

Unfortunately the top part of the tube ring is missing so a fix is not possible, i have put a wanted add on ABS to not very hopeful to be honest, i think TS sell some nice 105mm cnc rings so theres always that option. 

I pointed a torch down the tube and saw how bad the light gets past the baffles so flocking and sealing around the edge of the baffles are on my to do list, it looks like Shane has already flocked the draw-tube so saves me a job

 

Rick

[AndyH]

Hi.

Here's how I go about checking my scopes & homemade finders etc.....

 

Measuring for clear aperture in an optical system:

 Insert low power eyepiece, focus on infinity(** this is tres important! In daylight, fluffy clouds are good!), position scope approx 12"/300mm from wall, same for laser/single LED torch, maneuver torch 'til circle appears on wall, measure circle diameter. If it's not the same or close in size as your scopes aperture, then there's some clipping of the lightpath/viginetting going on.

 

 

Andy.

[brantuk]

I had 10mm cut off my tube and a flange made up to fit a S/W standard frac focuser. It works fine with eyepieces and a 2" diagonal but can't focus with bv's. The baffles needed straightening and I fitted new rings - I think tube pinch in the past was responsible for bending them. But out of that all I now have a very nice sharp contrasty achro which is a joy to use.

[nightfisher]

Rik, i have a pair of skywatcher tube rings that i had machined out to fit the tal, they are very thin in places but i can let you have one to get out of trouble, 

[rikroe666]

Thanks Jules I might take you up on that, I will be in touch.

Andy I will try that method tonight thanks.

So this morning I went to work on shortening the tube, I only have a wood workshop at my disposal so that had to do, I put an old blade on the table saw to start with and chopped 80mm off, the size difference in focusers racked in was 60mm so I took a bit more off to allow for the 2" to 1.25" eyepiece adapter and longer light path of modern diagonals.

Then I set the blade around 0.5mm up to reduce the tube so the new focuser could slip over the top as the old one did.

Next job will be to remove the rear baffle and check the others are square then check I haven't gone into the light cone with the draw tube.

[Jim Steele]

Welcome to the Tal owners club, I personally love mine (Tal100rs) super crisp on doubles and planets, don't get me wrong there times I wish I had more light grasp but for the money they are excellent and a bargain is to be had second hand. I am tempted to get a 100rt just for the tripod and dew shield (modern rs models use a plastic 'plant pot' which take the shine off an otherwise classy instrument).

I think you have done a good job in shortening  the tube, I wouldn't have attempted it eeek.

As others have mentioned sort out the baffles, check the focuser isn't impinging on the light cone, and get some flocking material. Orthoscopic eyepieces give a lovely crisp view, and the 25mm stock plossl is excellent.

I hope she brings you much enjoyment.

 

Ben

 

[Moonshane]

Given the baffle aperture is less than the diameter of the focuser I doubt there will be a problem given the cone is presumably smaller than the draw tube before if gets there.

[rikroe666]

16 hours ago, Jim Steele said:

Welcome to the Tal owners club, I personally love mine (Tal100rs) super crisp on doubles and planets, don't get me wrong there times I wish I had more light grasp but for the money they are excellent and a bargain is to be had second hand. I am tempted to get a 100rt just for the tripod and dew shield (modern rs models use a plastic 'plant pot' which take the shine off an otherwise classy instrument).

I think you have done a good job in shortening  the tube, I wouldn't have attempted it eeek.

As others have mentioned sort out the baffles, check the focuser isn't impinging on the light cone, and get some flocking material. Orthoscopic eyepieces give a lovely crisp view, and the 25mm stock plossl is excellent.

I hope she brings you much enjoyment.

 

Ben

 

Thanks Ben

To be honest I didnt really want to chop the tube, I would of liked to keep it original but I think I will use it more now it has been updated a little.

I have done the flocking etc, I was about to post with some pics but for some reason I can't get on SGL using the laptop at the moment, hopefully it will let me on later and I will update what has been done so for.

 

Rick

[rikroe666]

So with the tube cut down and rear baffle removed it was time to check if the draw tube entered the light cone using Andy's method above i also racked the focuser all the way in.

As Shane said there was no problem at all, it measured as it should at 4" 

 

Next job was to check the remaining two baffles for been square, to my surprise they to the mm spot on, maybe the previous owner already did this.

 

Then on to the flocking and filling the holes around the baffles, i was surprised at how bad the light bounced around in there, it had shiny black paint and the holes around the baffles didn't help.

 

I think the filler i used to fill the holes around the baffles was an Araldite product, it was a bit like putty that you had to squeeze and had an activator within it and set in around 30 mins, apparently you can drill it etc it goes that hard.

Next was the flocking, for this i used the Wilko stuff, you can click and collect online and it only cost £5 and seems to work pretty good.

This is the first time i have ever flocked a scope and the first time i think one of my scopes would benefit from having it done. I think the results are pretty good and should improve things, unfortunately i didn't get the chance to try the scope out properly before it was flocked so cant compare the views through the eyepiece.

Here are the results ( i hadn't flocked the center part of tube when i took the photo that's why its shiny, its done now though!)

 

 

The end cap is from Tool Station, cost around £5, its a rubber end cap for plumbing etc.

It had some small ridges on the inside, once these were chopped off with a stanley blade it fits over the dew shield very well.

and a couple of pics with the focuser attached

That's it for now, next thing to sort out will be the tube rings and maybe the paint work.

Rick