Atair Astro 6" f9 RC

[steviebee]

Right silly question I know. I saw the Altair Astro 6" F9 RC on display at my club on Friday night and rather liked the look of it. I didnt ask any question's, but when I got home and had a look I found they can be got for a resonable price second hand ( about 50% of new price ). I have read they have a 77mm central obstuction. Now comes the silly question. Do you see this obstrruction when you look through? It will be mainly used for visual in my Graden to go along side my Startravel 102mm.

Steve.

[mikeyj1]

Steve

No you don't see the central obstruction, although it does reduce the amount of light entering.  You should be aware that RC scopes are primarily used for astrophotography, although they can be used visually as well, but i am sure you looked at the altair astro webpage.

Visually you are probably better with an SCT or MAK of 5-6 inches Dia, you will get the longer focal length with those also, and still retain the compact body.  Having said that, try one out first, you wont get much light difference to the 102mm, just more magnification on planets

HTH,

Mike

PS: see you already got a 200P, so honestly spoken, not sure why you would want the extra scope at all...and that's from someone that can justify almost any astronomical purchase ;-)

[steviebee]

Hi Mike, thanks for the quick response. I do have the Altair Astro webcam and My Cannon 1000D, so it would not be waisted on visual alone. Perhaps this scope would be an excuse to do more astrophotography stuff. Just enjoying the visual at the mo. I should have asked some questions at my club, but I think I was too made up with having just won the raffle lol! I was using my 102 last night. I have a lot of light pollution in my garden, but I managed the Pleiads and they looked amazing ( had to drag the mrs out to look at them as well ). That was my biggest worry when I read about the 77mm obstruction that you actually saw it. Again thanks for your quick reply, gives me a bit more to think about now before I take the plunge.

Regards.

Steve.

[Louis D]

That 77mm obstruction will lead to decreased contrast photographically and visually.  In photography, you can do a contrast adjustment in post-production to counteract it somewhat.  Visually, it throws light energy into the outer diffraction rings decreasing contrast and thus perceived sharpness.  This is most obvious on low contrast, extended objects like Jupiter.  That's the main reason APO refractors are "magical" on planets visually.  They achieve the maximum contrast possible for a given aperture.  Planets just seem so "sharp" because of it.

It's my understanding that collimating RCs has a steep learning curve.  It would be best to read up on them before committing to one.  They also have a curved focal plane, so a matched field flattener would be a must for either photographic or visual usage.

[Dave In Vermont]

I wouldn't suggest an RC-telescope for visual purposes. I've read many reports of 'soft' and 'fuzzy' views being obtained. Sometims even for astro-photo uses, too.

To each their own,

Dave

[Stu]

As per the other comments, I think there are easier ways of starting AP. For deep sky, a small fastish frac would be simpler, and as has been said, an SCT would likely be easier for lunar/planetary.

The large obstruction doesnt get seen, but impacts contrast for visual use. It also impacts in AP but can be processed for so it less of an issue. The larger aperture does give improved resolution but you have the 200p for visual already.