Takahashi 1.6X 2" Extender TOA130EX

[Tandum]

Has anyone used one of these? I was thinking of using one on my FS-102 to push it up to 1280mm. Do they introduce any aborations in the image at all? A new one will be almost AU$500 and I'm not sure it's worth it considering it will also push the scope to F12 odd. F12 would be a bit tough on any camera.

[AlexN]

I know Marcus uses one on his TOA152... the images he gets with it are fantastic... Although yes, slowing to F12 could be a bit of a struggle..

My question is, why spend $500Au to stretch your refractor to 1280mm FL when you could use your VC200L + 6.4 reducer to get 1260mm FL at a much faster F/ ratio? Seems like false economy to me..

[Tandum]

There's a huge difference between the images from each scope. I don't think there's any need to say which one produces the sharpest images with the most contrast ;)

[JohnG]

Hi Robin

I have one of these extenders and use it with both my FS-128 and TSA-102, I use it visually so I can't help you with how it performs photographically although I see no reason why it would not perform OK given the quality. Visually, I see no aberations or ghost reflections and have pinpoint stars right to the edge of the FOV.

I have had no reason to use it with either scope as the FS-128 with the ST4000XCM is running at a focal length of 1040mm anyway and give a nice closeup view, the TSA-102 is mainly used as a wide field instrument with the Tak reducer.

Cheers

[Hagar]

Hi Robin, I did a test image some time back with my FS102 and a 2 X powermate which took the FL out to about F16. Yes the exposures needed to be quite a bit longer and the seeing needs to be very good but it did work quite well.

[Tandum]

Cheers guys, I'll have to think about this one, they're pretty expensive.

[gregbradley]

Hi Robin,

I got one of these 2nd hand on Astromart for about US$200 or so.
I got an adapter so I can use it on a Tak BRC 250 or TEC180mm APO.

That gives me F8 on the Tak and F11 on the TEC. I don't think exposure times will blow out too badly in those instances but haven't had the chance to tell with poor weather the last few times I went to my rural observatory.

I think it will work well as in the case of the Tak, the new Tak BRC250 has a special 1.6X extender and a reducer to make it more versatile so Tak are using it.

Greg.

[Tandum]

Thanks Greg,

Sorry for the late reply, I just revisited this topic.

I have 'paid' and joined Astromart and am watching for an extender.

This tak is really the first quality refracter I've ever owned and it's so good, I have already bought a WO70ED to guide it, which is also looking to be an excellent scope.

If the extender is of similar quality to the tak, and that looks to be true, then I won't need my vc200l any more.

And I used to think refractors where just guide scopes :)

[gregbradley]

[QUOTE=Tandum;477333]Thanks Greg,



If the extender is of similar quality to the tak, and that looks to be true, then I won't need my vc200l any more.


You may find it is better to use the FS102 for widefield imaging and get the F6 reducer for it. And use the VMC200L for longer focal length shots like galaxies where the FS102 will struggle no matter what you use as aperture ultimately rules.

The extender on the native F8 will give you F12.8 which is pretty slow for 102mm of aperture and will require a lot longer exposure times than your 200mm Vixen.

Greg.

[Omaroo]

Robin - I was looking at an extender for my 102 (and another for the 90), but bought a photographic teleconverter - a good one. I bought a Nikon TC-300 from Zane Hammond a while back, and it gives me better results than any barlow I've tried. It ain't a Tak extender matched to the scope, but it's a lot better than anything else I've tried.

http://www.mir.com.my/rb/photography/companies/nikon/nikkoresources/teleconverter/index2.htm

[Tandum]

With a 40% obstruction the vc should be similar to a 5" scope so not as miuch difference as you might think.


That's definately another option Chris, thanks.

[Exfso]

I have one of these on order from Peter Tan in Hong Kong, apparently they flatten the image as well which is all good. It will take my TOA130 from F7.7 to F12.3 going to be interesting to see what it is like on DSO stuff.

[AlexN]

Robin, A central obstruction reduces resolution, however it does not reduce your aperture.. it might have roughly a similar aperture clear diameter as a 5" refractor, but the primary mirror is still 8" in diameter... Overall clear aperture of an 8" reflector with a 40% obstruction is still higher than a 5" with no obstruction...

Exfso : how will it go on DSO's? A lot slower at F/12.8 than it does at F/7.7 :)

[Tandum]

Alex, There is an equation that calculates light gathering capacity from aperture. From this you subtract obstruction. However the obstruction calculation is a log curve not a linear one. I revisited the calculation and I under estimated by an inch. So it's 6" instead of 5". However, I don't think there's an equation that measures contrast :)