TS-Optics 8" f/12 Cassegrain telescope 203/2436 mm OTA

[josefk]

It is a bit irritating @magnahrl but I think it’s more irritating in theory than in practise if you know what I mean. I have the CO calculated at 38% after measurements in the flashlight test but in any event I get nice dark skies and good contrast for eg something like M97 or M57 or M27.  I mean really nice so I don’t think it’s impacting the view really. Around the new moon mine “competes” with a nice 5” refractor and I never feel disappointed in the aesthetic comparison between them (apart from diffraction on planets - sorry to mention that again).
 

Ergonomically it is lovely. You’ve used it so you know. Though I occasionally add a DIY dew shield (belt and braces) I don’t think I’ve ever had a real dew “event” with the CC8 with or without it (and frequently the outside of the OTA would be dripping wet on nights with high RH). Even though I will buy more aperture I would keep the CC8 for this quality alone.

I’ve never looked through a Mewlon. I guess (purely from reading the experiences of others) the Mewlon will be better than the CC8 on axis but the DK prescription of the Mewlon would be worse than the classical cassegrain prescription of the CC8 off axis. Off axis is important to me. I use the field stop quite a bit so I like things tidy fully across the FOV. 
 

all the best Magnus.
 

Cheers Joe. 

[magnahrl]

Hello Joe,

Once again, thanks for your valuable feedback..🙂

Hmm 38%, after all not all that bad....

The scope seems and feels very well built, almost like my MK66 really. My belief is this scope is actually made in Taiwan and not in China.

I am quite sure I will buy this instrument. Like it and the price is so good and the seller has been so serious and sympathic. He prefers his 120 SW Esprit for imagening. The CC8 was a mistakepurchase.  I fully understand that if you are imagening. f/7.5 vs f/12 are two different things.

I just hope for 1 last night of decent seeing so I can really value this scope. So far the "testingstars" have never really settled. At high mag the images are slowly moving from tight points to points of all sorts of figures. I have been out several hrs it gets better but never stops. I have never seen this effect in my other scopes, not even in the open tube Newtonian. Instead stars tend to quickly flicker before the scope is in terminal balance. If seeing is bad stars look like small flickering cottonballs. In the CC8 it`s something else, something slowly moving all the time. No flickering. As the image is moving it must be the air in the tube or the atmosphere. Not the optics it self. Hmm very strange. Any CC effect?

Thanks for reading👍

Cheers Magnus

 

[magnahrl]

Had a clear and steady night  Sat - Sun. Startest looked good. Not perfect not bad just simply good. Stars at focus?  - well not much to talk about and that means good. (As Ed Ting, usually puts it🙂) Hard round Airy disc and almost uniform rings at 400X (not quite 100% collimated yet?). Lambda Cyg almost fully sep and M13 was so full of pinpointstars. I was actually impressed by the view. So I bought the CC8.

Maybe the best thing of all was the seller and I will start observing together now and than. I live in a small town on an island in the Baltic Sea  -Gotland. We did not know of each other and thought no one else was intressted in active amateuar astronomy here on Gotland. So I did not just get a new scope, also a friend to enjoy the nightsky with. 2 persons, time to start an astronomyclub.😁

Magnus A.

[Ags]

On 27/04/2024 at 07:38, josefk said:

I’ve never looked through a Mewlon. I guess (purely from reading the experiences of others) the Mewlon will be better than the CC8 on axis but the DK prescription of the Mewlon would be worse than the classical cassegrain prescription of the CC8 off axis. Off axis is important to me. I use the field stop quite a bit so I like things tidy fully across the FOV. 

I saw a spot diagram for the Mewlon 180 once - off axis performance is unbelievably poor according to Takahashi’s own diagram.

[josefk]

8 hours ago, magnahrl said:

Had a clear and steady night  Sat - Sun. Startest looked good. Not perfect not bad just simply good. Stars at focus?  - well not much to talk about and that means good. (As Ed Ting, usually puts it🙂) Hard round Airy disc and almost uniform rings at 400X (not quite 100% collimated yet?). Lambda Cyg almost fully sep and M13 was so full of pinpointstars. I was actually impressed by the view. So I bought the CC8.

Maybe the best thing of all was the seller and I will start observing together now and than. I live in a small town on an island in the Baltic Sea  -Gotland. We did not know of each other and thought no one else was intressted in active amateuar astronomy here on Gotland. So I did not just get a new scope, also a friend to enjoy the nightsky with. 2 persons, time to start an astronomyclub.😁

Magnus A.

Well that sounds excellent Magnus on both fronts. Really a win win. Enjoy!

[josefk]

On 27/04/2024 at 15:26, magnahrl said:

At high mag the images are slowly moving from tight points to points of all sorts of figures.

This sounds to me like heating effects in the OTA. I haven’t seen it too often but occasionally on a star bright enough to cause diffraction spikes and early in a session there has been been other “wispy” moving artefacts in the diffraction X. I never gave it it too much thought because I don’t recall seeing it later in an evening ever and being a transitory thing I classified it as either cooling or seeing related with my bet on cooling.