TS 90mm f5.5 APO

[hickeydp]

Hi All,

I was just wondering if any of you are familiar with this scope...

http://www.teleskop-express.de/shop/product_info.php/info/p1838_TS-ED-APO-90-500mm-f-5-5---fast-optics---2-5--focuser.html

I enquired from TS about what kind of glass was in the optics and they came back saying they didn't know???!!!

Can any of you guys enlighten me?

Also has anyone bought/used one that could give a quick appraisal?

I'm in the market for a decent APO for imaging at the 500mm fl range, preferably with an 80mm or 90mm aperture and this one seems to fit the bill.

Cheers

Damien

[johninderby]

Same as the Revelation 90.Maybe TH can enlighten you as to the glass used.

http://www.telescopehouse.com/acatalog/Revelation_90mm_Apochromatic_Refractor.html

I had the 100mm version and it was very good. Has FPL-51 glass I believe.

John

[ollypenrice]

That's very cheap for F5.5 so I'd be wanting to know about blue bloat. That F ratio in that size is Takahashi country. I wouldn't take a punt without seeing some images. I also think, from the picture, that the Crayford drives the alloy drawtube directly, which means it probably won't work properly.

Olly

[hickeydp]

@Olly: Hadn't noticed that with the focuser. Very like the setup on my old 110 Megrez. It worked ok once it was tensioned properly.

@John: I think it is the same as the Revelation 90. With a FPL-51 doublet I'd be worried about CA for imaging. What was your experience with the 100 like in that regard. I found a review of a 90mm f5.5, no brand mentioned, on CN and the guy there was not very complimentary on the colour correction.

[alan potts]

I don't know what glass it is either but I have a mate with one here in Bulgaria, he is pleased with it and I am happy with it too but I have only used it a few times .

Alan.

[Earl]

@Olly: Hadn't noticed that with the focuser. Very like the setup on my old 110 Megrez. It worked ok once it was tensioned properly.

@John: I think it is the same as the Revelation 90. With a FPL-51 doublet I'd be worried about CA for imaging. What was your experience with the 100 like in that regard. I found a review of a 90mm f5.5, no brand mentioned, on CN and the guy there was not very complimentary on the colour correction.

The Revelation 100 is a very good scope combined with the Sky Watcher flattener its a nice F6 Imaging scope I was very happy with it, one of my biggest gear regrets was selling it to upgrade, none of the scopes I have had since is as good including the Evostar 80 Pro;s.

[ollypenrice]

In discussing the correction it's vital to be clear that what is fine in visual is not necessarily fine at the camera. I'm not saying it won't be fine, I'm just doubtful about fast f ratios at low budgets in doublets.

You won't convince me that driving a smooth anodized surface with a Crayford roller is the way to do it, though. I have a WO with that system and with CCD gear it's very marginal. I've seen lots of other problem focusers here as well and driving the anodized surface is one common factor. A mat surfaced steel strip is much more convincing.

Olly

[Earl]

Agreed Olly, the Feathertouch low end are also crayfords, with steel strip and the bearings running internally (inside the drawtube) on steel rails. You get what you pay for in this department !!!

The Revelation 100 iirc also had the Metal Strip and flanged bearings internally, it was not Feathertouch by a long way but much better than direct onto the drawtube.

[hickeydp]

I'd tend to agree on both counts Olly.

I have my doubts about fast doublets and I'd hate to drop a lot of cash on one when a few hundred more would buy a triplet with little or no CA.

As regards the focuser, I'll take your lead on that. I never hung more than a DSLR from my old WO110. I'd agree that a heavier imaging train would make this design marginal.

[MRAPO]

damiem how much are you willing to spend.

[mchiv80159]

Asked them the question and got the answer its fl51 glass.

[laser_jock99]

I'd tend to agree on both counts Olly.

I have my doubts about fast doublets and I'd hate to drop a lot of cash on one when a few hundred more would buy a triplet with little or no CA.

As regards the focuser, I'll take your lead on that. I never hung more than a DSLR from my old WO110. I'd agree that a heavier imaging train would make this design marginal.

At that kind of price level you're not that far off triplet money. Depends on wether you preffer minmal CA or slightly shorter exposure length!

[Coco]

The Revelation 100 is a very good scope combined with the Sky Watcher flattener its a nice F6 Imaging scope I was very happy with it, one of my biggest gear regrets was selling it to upgrade, none of the scopes I have had since is as good including the Evostar 80 Pro;s.

Mine too