95 replies to this topic

[dp297]

Any opinions on the tair 33 with kiev88 mount. How can I find an adaptor for canon?

[Falcon-]

Very good question... I was wondering exactly the same thing a couple days ago. I saw some note about converting to Kiev88 to <something> and then to EOS, but can not recall what that intermediate something was any more.

[dp297]

It was...KIEV 88 to KIEV 60 and then to Canon EOS.
But one could purchase the TAIR 33 KIEV 60 version ...
I was wondering about the optical quality of these lenses. They are heavy and well built I guess.

[Falcon-]

They are heavy and well built I guess.

That applies to the Tair-3 as well of course. I have the impression that they are optically very similar to the Tair-3 - but naturally I have never seen one in person so that is hardly an authoritative answer....

[Dan Watt]

I want to add to this that the Tair-3 performs perfectly @ f4.5 with a 12nm h-alpha clip in filter. I also did more testing on my two Tair-3cs and can confirm that f8 is the absolute sweet spot on these lenses when used for rgb.

[Falcon-]

I want to add to this that the Tair-3 performs perfectly @ f4.5 with a 12nm h-alpha clip in filter.

Really? Do the stars not still get distorted at f/4.5 when using h-alpha? My assumption would have been that Ha should be shot at f/8 purely for star shape based on my RGB tests.

I would be happy to be wrong on that, narrowband does like long exposure times....

[Dan Watt]

It looked good to me on a small laptop screen at 2 in the morning, I'll try to remember to post my results tonight when I get home.

[avarakin]

Narrow band images are less critical an quality of optics. I saw some nice narrow band images taken with acromats. So no surprise that even 4.5 gives decent images in Ha. I also tried Ha with my Tair at 4.5, but I saw slightly elongated stars.
BTW, if anyone is interested, I figured out how to modify the lens to focus beyond infinity mark, which might be useful in case if your setup does not focus stars nicely because of lack of travel of focusing mechanism.

Alex

[Dan Watt]

I am interested! I don't have any reason for it now but it would be good to know about.

[avarakin]

I like shooting Ha + OIII, gives nice looking result and works great with mediocre optics like Tair:



Alex

[Falcon-]

Narrow band images are less critical an quality of optics. I saw some nice narrow band images taken with acromats.

See this statement makes sense to me when speaking of chromatic aberration since narrow band is.... too narrow.... for colour focusing at different points to matter. So ya, an acromat would be perfectly fine in that regard...

But why would be be less sensitive to other optical aberrations like coma and astigmatism?

BTW, if anyone is interested, I figured out how to modify the lens to focus beyond infinity mark

Yes I *am* interested! Please do post it to the forums!

[dp297]

Also interested....

[terry59]

Narrow band images are less critical an quality of optics. I saw some nice narrow band images taken with acromats.

See this statement makes sense to me when speaking of chromatic aberration since narrow band is.... too narrow.... for colour focusing at different points to matter. So ya, an acromat would be perfectly fine in that regard...

But why would be be less sensitive to other optical aberrations like coma and astigmatism?

So....an achromat for Ha and an APO for RGB. Is that what I'm reading here?

[Dan Watt]

Finally got around to this. Here is the Tair-3c with a 12nm HA filter on my 350Da. Wide open.

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[Dan Watt]

Sorry there isn't much detail, this was just taken from some 20 minute exposures of the area around That is actually Antares on the bottom right.

And the RGB @ F8. 20 Minute exposure with full spectrum T3 and CLS-CCD filter.

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[Falcon-]

Dan: Thanks for posting those. My read on it is that the stars wide open in h-alpha do show a bit of distortion, but much less then I expected. I might stop down some when I try it myself but not as far as I would for RGB.

Speaking of "when I try it myself".... Alas I have the first clear night in something like 8 months and I find myself stuck on the mainland with the only part of the sky visible from my backyard devoid of H-alpha targets!

[Samir Kharusi]

We are all over-obsessed with star shapes My stance on this is as follows. Check chromatic aberrrations dead center and find the f-stop where the colour fringing is "acceptable". Note that pursuing perfection using a moddded camera may be futile even dead center because of the excessive sensitivity to Red. Any slight over-exposure may give red donuts, especially after sharpening. Your lens seems to be fine for on-axis even wide open, and the star shapes along the edges do not seem over-distended to justify closing down even one-f-stop to f6.3; and committing to doubling both the length of subs and the integration time, IMHO. ImagesPlus "Star Halo Reduction" works wonders both on-axis and off-axis. Still unhappy with the zapped stars shapes? Just add a couple of subs at f8, same length of subs (and hence darks) and use the stars from those f8 frames to overlay your processed/stretched stack for the nebula/ galaxy. It takes remarkably little exposure to record stars, even at f8. Integration time is where we are always short, and closing down from wide open is rarely worthwhile for tele primes. By the way, ImagesPlus also enables zapping the stars with different strength in each of RGB, so even red donuts can be super-zapped in R. Best tool I ever came across to deal with our quest for tiny, sharp stars from consumer optics, and that includes premium APOs. Just one viewpoint.

[Falcon-]

I tend to think of star shape as a proxy for other effects... that distortion seen in a star may not be so noticeable in a nebula but surely the same optical aberration is happening to the light from the nebula itself, resulting in a less sharp image or the target then could be obtained stopped down further.

[dp297]

Real heavy monster though that lens....just got mine

[Falcon-]

That it is!

But is it much heavier then a 67mm f/4.5 triplet refractor would be?

[Falcon-]

Ok, here is my own go at H-alpha an the Tair-3

Oh, and this is also FIRST LIGHT for my new Astronomik 6nm EOS-clip filter! I have been either waiting for that filter to arrive or waiting for clear skies for 5 months now - SO glad to see results like this with my first session.

I am going to capture more data tomorrow but to start with attached is a quick stack of the full frame. This is 11x 600s exposures at f/5.6, ISO1600 on the Canon 350Da. No darks, no flats - just an align, stack, and histogram stretch of the Red channel only.

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[Falcon-]

Here are the corners - there is a bunch of hot-pixel streaking (short vertical lines) and strong amp glow here due to the total lack of calibration frames, so ignore that. Also there is a reflection artifact just above Sadr - I *think* that came fromt he UV filter in front of the lens that I forgot to remove before beginning my imaging session.

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[Falcon-]

Lastly, just because BackyardEOS saves framing snaps... here is the focus I had. I focused on Vega with the 6nm HA filter in place - even with Vega's brightness getting that tiny bahtinov pattern required a 30s exposure wide open.

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[ghataa]

Really nice Ha work with the Tair. I hope I hope I can do nearly as good Yours! I just got mine yesterday and need to get it mounted as it is heavy and I am worried about just using the camera screw.

I have a Baedder 6 nm Ha filter and it too really takes a bright star to adjust focus. Glad to see good success with the clip-in.

Best,

George

[Falcon-]

I just got mine yesterday and need to get it mounted as it is heavy and I am worried about just using the camera screw.

Well for whatever it is worth I just used the tripod mount myself. It is far too easy to kock things out of alignment but I do not *think* I had any flex issues.... I used the side-by-side tripod ball head mount shown here to capture the image, in the configuration shown in the second image in the thread.