Tal100RS Main objective glass

[jonzo]

Good morning, Just wanted to ask if anyone knows which glass is used in the Tal100RS 100mm F10 1000mm focal length refractor?

The coating reflects an orange tint with hits of purple and green.

 

 

 

[mikeDnight]

I'd suspect its just a standard crown and flint Fraunhofer objective lens, but looking at the noticeable lack of chromatic aberration around the limb of the moon in your video, its a very good Fraunhofer lens. I'm not certain about Tal's choice of coatings, but they are doing their job! It's a very nice scope!

Mike

[jonzo]

3 minutes ago, mikeDnight said:

I'd suspect its just a standard crown and flint Fraunhofer objective lens, but looking at the noticeable lack of chromatic aberration around the limb of the moon in your video, its a very good Fraunhofer lens. I'm not certain about Tal's choice of coatings, but they are doing their job! It's a very nice scope!

Mike

Yes it seems to be the standard Fraunhofer design, yes even when observing the moon or planets or even stars there is minimal CA, a scope to keep for a lifetime I reckon.

[John]

TAL changed the coatings that they used on the TAL 100. The early ones had a purple sheen to them and the later ones were more greenish. It does depend on the angle you view the lens from. The are very good achromat refractors but don't use an ED / low dispersion glass element. Just well figured lenses

I found that the one I had (one of the older ones) was fully as good optically as the Vixen SP102M that I'd had before it. Thats quite a compliment to the TAL because the Vixen's are super scopes !

 

[jonzo]

1 minute ago, John said:

TAL changed the coatings that they used on the TAL 100. The early ones had a purple sheen to them and the later ones were more greenish. It does depend on the angle you view the lens from. The are very good achromat refractors but don't use an ED / low dispersion glass element. Just well figured lenses

 

Ah I see, yes I noticed that from a different angle there was the green tint/purple tint but from the angle I took the iamge from it was rather orange! I must have the the later version.

[John]

Optically they maintained the quality so the change of coatings had no adverse affect. The focusers on the later ones (like yours) were much better than the earlier ones.

[jonzo]

1 minute ago, John said:

Optically they maintained the quality so the change of coatings had no adverse affect. The focusers on the later ones (like yours) were much better than the earlier ones.

I see, do you have any web articles on the history of these scopes? I'm curious to read up on them. 

[John]

1 hour ago, jonzo said:

I see, do you have any web articles on the history of these scopes? I'm curious to read up on them. 

There are lots of posts on the TAL 100's on this forum and across the web - they are popular scopes !

Neil English wrote a good piece on the scope a while back:

http://www.cloudynights.com/page/articles/cat/user-reviews/telescopes/100mm-110mm-refractors/a-little-piece-of-russian-magic-r1960

I bought one of the early ones to come into the UK - back in December 1999. They have been around quite a while !

[nightfisher]

There is  a VERY strong rumor that TAL 100 lens is made by LZOS in Russia, this would be backed up by the general good quality of the optics, original coating was purple, then it changed to the green that you have, then in the last run it went to a kind of aqua blue