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One for TAL 100RS fans


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I know you TAL 100RS owners love ‘em to bits but how do you get on with the chromatic aberration? I only ask because I am again considering getting another scope but looked through a TAL 100R several years back and the CA on Venus was atrocious. (I realise Venus is the worst possible thing to view for showing CA)

Unfortunately, I don’t remember seeing anything else through it – maybe the clouds rolled in.

I found a table which showed that a 100mm f10 achromat would show “filterable levels” of CA. Do you use filters with your TALs?

Has anyone any experience of comparing the view with a Skymax 127?

I’m wondering if the Skymax would show equal lunar and planetary detail but without the CA. Also a bit more manageable with its lighter, shorter tube.

Look forward to hearing your thoughts.

Dave

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I have owned the Tal Dave & enjoyed it. CA is very well controlled at f10, but it is there all the same. Venus is the worst possible target to test on though, I have read that even ED100's will show some colour on this target. The Skymax 127 should slightly outperform the Tal with its increased aperture and will of course be colour free.

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...I’m wondering if the Skymax would show equal lunar and planetary detail but without the CA. Also a bit more manageable with its lighter, shorter tube.....

I think thats a fair assessment. The Skymax will take longer to cool if it's stored in the house (about twice as long), will need a dew shield / dew band and is limited to 1.25" eyepieces. The TAL's have 2" focuser's now so you have that option if you want it.

My ED120 does show some CA on Venus by the way. Not loads but its there. I've had some lovely views of Venus with it though, especially when there is still some light in the sky, ie: twilight or just pre-dawn.

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Thanks for the replies, John and Damo636. I'm a bit biased towards the mak because I'm used to Newtonians having no CA.

It's just that I keep hearing such good reports of the TAL.

I suppose the only way to be sure is to look through both.

Thanks again.

Dave

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Every observer has his or her bete noire. Some people can tolerate CA better than others in just the same way some people can accept coma at the edge while others need a perfect edge to edge view. Its the same for pin cushioning, field curvature, eye relief, exit pupils and every other optical aberration which a telescope and eyepiece are heir to.

Its impossible given that to state with any certainty what another observer will find acceptable. I cant comment on the Skymax 127 except to say its effective aperture is only around 117mm and it has to give up some aperture because of its central obstruction.

Whether its better CA characteristics are worth the trade off in eyepieces and field of view is worth it is a judgement only you could make. I find the TAL to exhibit very low CA and well within what I can live with. It can be muted further by using a light yellow filter which removes the worst of it on bright targets. Cant say what Venus is like with it as ai have never used it on Venus.

My bet would be the 127 would be superior contrast and obviously CA free but with its more restricted field of view might be less of an all rounder. Depends on your needs and interests a lot. For me the TAL is a grab and go but over last year its been left as a hanger queen a bit as I have been working with the Skymax 180 mostly while ai test out things.

If your anywhere near Surrey your welcome to come take a look through my own TAL if the weather ever clears down here.

Edited by Astro_Baby
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To be honest its a tough call between the 127 and the tal 100, like astro baby, i have the 180 mak and a tal, i find the tal gets used a lot more, interestingly i had a 102 mak for a short time, it was very good but not up to the tal 100, the 4" refractor is just a darn good multipurpose scope the small amount of ca does not bother me

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Thanks both for very interesting replies. Doesn’t sound like there’s much between them performance wise. I hadn’t given much thought to the difference in FOV thought I’m not put off by the mak’s local length of 1500mm. Might even come down to ease of storage in the house!

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Being an achromatic the Tal 100rs will 'suffer' from CA. Nevertheless, its relatively small aperture and long focal length pretty much dampens it on all but a couple of objects in the Solar System. I haven't seen through a Mak 127, so I cannot comment but it would be interesting to see how it improves on the sharp and superb contrast offered by the Tal 100rs and how it compares with other Maks of similar aperture two or three times its asking price - as does the Tal 100rs when being compared to ED glass, for example.

I've never seen CA when observing the Moon or Saturn, there's slight CA or halo around Jupiter but the quality of view and sharpness of image overrides any concern of false colour and I've found that on bad nights of transparency a cheap light blue or yellow filter works wonders. Needless to say, open clusters, star fields, are mesmorising.

Like all things telescope wise, I imagine both designs have there pros and cons. Would it be nice to own a Tal 100rs? Sure. It's relatively light, has superb Russian optics, needs no coolling down and is a fantastic all-rounder. Do I think it out performs the Mak 127? No, I imagine not.

If you're on holiday in Spain, you can always nip across and try mine :smiley:

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