New Telescopes, First Light Reports

[Roy Challen]

First Light Report – Tal 100R and Prinz 660

I bought a Tal 100RS a few months ago and a new universe was revealed to me. Previously I had only ever used or looked through short tube 70mm aperture scopes. I found that I could live with the very small amount of chromatic aberration, and found the scope very enjoyable to use on my SkyTee mount. As I learned more about Tal and long focal length refractors in general, I decided that I wanted to compare my Tal RS to other, similar telescopes. So, on a whim, I bought a Tal R and shortly after that, a Prinz 660.

The Tal came complete in its large, heavy ‘coffin’ which included its equatorial mount and tripod. It needed a bit of a clean so I removed the lens cell and focuser and gave the inside a wipe. I noted a few tiny scratches on the lens but these seem to be on the air spaced surfaces so leading me to think that a previous owner has disassembled it at some point. The tube is fairly thick aluminium and rings like a bell when tapped. It is about 50mm longer than my Tal RS. The focuser needed some attention in order to be usable, the holes that attach the rack to the draw tube had the threads stripped, so I re-drilled, tapped and re-fitted the rack so that the focuser could operate as intended, albeit with its very short travel. The tripod and mount are in excellent condition, I just fitted new screws to the fittings on the tripod and thee mount needed nothing doing to it at all, the whole assembly with telescope attached feels solid – about the same as an EQ3 on a decent tripod.

It was a few weeks before first light but eventually it happened, and was a kind of shootout between the two Tals as they were both on the SkyTee. Here are extracts from my observing notes of that evening.

   

  “I went through the Max Visions, first trying them in the R, then the RS. I found there to be very little difference between the two scopes. There was a bit of chromatic aberration in both, perhaps a tiny bit more in the R. The R is harder to achieve sharp focus due to its inferior focuser, however, when in focus there is no discernible difference. All three Max Visions displayed a bit of distortion near the edge of field of view. This begins at around 85-90% out from the centre. It was noticeable if looked for but in practice it is unobtrusive.

Both Tele Vue Plossls were equally sharp, although the 10.5 mm showed some very slight dimming as the object passed out of the field of view.
All eyepieces performed well on the Moon and there is little to choose between any of them other than magnification and AFOV.

This was the first proper session with Saturn in a reasonable position to view. All eyepieces performed admirably, but the 10.5 mm TV really came into its own here. There was distinct banding of the planet’s disc and a very strong hint of the Cassini Division using averted vision, then with direct vision. During moments of clear seeing, the gap almost resolved sharply. Titan was easy to make out and another moon, Rhea, much closer in was visible, needing averted vision occasionally and sometimes visible directly. This moon was visible in all eyepieces once I had spotted it in the TV 10.5mm, although it seemed to be easier to see in the RS.

This is the first observing session that I’ve ever had that the Cassini Division became possible to see, even if it was just a hint, and when a moon other than Titan revealed itself.
This was a very rewarding and informative session. It would seem that the RS has a slight edge over the R. The SkyTee benefits immensely from the wooden tripod legs, it is much lighter and the vibrations from focusing or moving the slow motion controls die down very quickly. The slow motion controls themselves add greatly to the viewing experience.”

The tripod legs and slow motion controls mentioned came from the Prinz setup which I bought after the Tal R. They make a huge difference to the viewing pleasure (and aesthetics) to be had from the SkyTee – anyone who has this mount should consider doing the same. Anyway, I did the same cleaning routine with the Prinz although this was in much better condition from the start. I just needed some tube rings and when they arrived the scope was installed on the SkyTee (I love this mount!). Again, it was some time until first light, but last night coincided with clear skies and no work the next morning so here are my extracted notes from the session.

“All three telescopes were allowed to cool. The Tal RS and Prinz 660 were on the SkyTee, the Tal R on its own mount. The eyepieces used were the Tele Vue Plossls ( I did use all but the 8mm and the 13 and 10.5 are the most used), Meade RGO and the Tal Plossl. As I don’t have three diagonals, I used the Prinz in the straight – through viewing position. I did the roughest of polar alignments with the R, and actually just pushed the scope around to the targets, much like a Dobsonian mount. Seeing was pretty poor for the whole session.

First up - Venus. In the Tal 100 RS, It could be seen to be at half phase. There was quite a bit of chromatic aberration and I quickly moved on to the Prinz. The CA was much better controlled, although still present. No details could be seen on the disc of Venus. There didn’t appear to be much, if any, difference in sharpness.

Then Jupiter was located and viewed with the RS. The seeing was poor with the disc of Jupiter shimmering quite a lot. However, the equatorial and northern and southern belts could be seen. All four Galilean moons were visible and one was eclipsed during the session. There was a bit of CA with the RS, but not a large amount and not distracting. It didn’t seem a constant amount. In the Prinz, the CA was almost completely absent. You had to really look for it for it to be visible. Even with the poor seeing, a good amount of detail was visible, and the image brightness doesn’t suffer from a smaller aperture compared to the Tal RS.

I didn’t view Venus with the Tal R, so the first object for the R was Jupiter. This scope showed the most CA for this object, and I was a little bit surprised at this as I have read a lot about the lens being slightly better than the RS’s. It wasn’t a huge amount more, but it was noticeable. The level of detail was about the same as the other two scopes. The next object viewed with the R was the Mizar system. Mizar and Alcor were easily split as expected, and Mizar itself was also split with clear space between the components. The R performs much better on star systems, there was no CA visible on the Mizar system, and the stars were tight pinpoints of light against a nice, dark background.

All three scopes were then swung over to the southeast for Saturn. First up- the Prinz. Although the poor seeing was never going to allow the greatest view, there were hints of the Cassini division. Titan was visible but no other moon could be seen in any of the scopes. This is in contrast to the previous session when Rhea was quite easily visible in both Tals. I put it down to the seeing. There was some banding visible in both the Tal RS and the Prinz, but it was harder to see in the R.

This evening’s session was interrupted by a large spider the likes of which I haven’t seen before. I don’t know how I managed to spot it 10 feet away in the dark, but that tells you somewhat of its size. I took some pictures of it, so I’ll process them soon. (see my post in the photography forum)

Overall, I am very impressed with the Prinz. It is a very elegant looking telescope with excellent optics, the only thing that lets it down it the focuser. I don’t really like rack and pinions, this one isn’t the worst I’ve used, but it’s still a little difficult to adjust fine focus. My second impression of the Tal R echoes my first – it’s a little disappointing. Perhaps the interior of the tube needs flocking/painting and the focuser needs sorting/replacing and the diagonal needs collimating but, as it stands, it performs less well than the RS.”

The finders on all three scopes are very good. The Tal R has thicker crosshairs than the RS, but the two together would make a nice set of binoculars!
So there you have it. The Prinz is a very capable scope despite its age, both Tals CA suffers in comparison to the Prinz although in practice it’s not an issue except maybe on Venus and I found that I don’t like rack and pinion focusers!

Thanks for reading

[xtreemchaos]

great report mate,i may get hold of a tal myself,thay sound like a very good scope.thanks for sharing.charl.

[NGC 1502]

Great report, thanks !

Some of those older Prinz refractors were very good, unlike the much later offerings from Dixons......

Interesting the differences you noted between the R and the RS.

Venus is about the toughest test for a refractor.....

The R&P focuser on my elderly TV Pronto is silky smooth, zero backlash or wobble, but I do know that many R&Ps can be dreadful, as can some Crayfords. It's not about the design, it's how well made it is......!!

Regards, Ed.

[happy-kat]

interesting read

the Prinz can't be anything like my 135mm lens flavour that has shocking CA