Yet another finder scope question...

[mdstuart]

I find a 50mm finder best as the mag range matches the TAKI atlas I use..

If the finder picks up too many stars it might be harder to use it as a finder?

Just a thought..

Mark

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[swamp thing]

1373008198[/url'>' post='1980907']

If the finder picks up too many stars it might be harder to use it as a finder?

Just a thought..

Mark

I'd been thinking exactly this Mark. I was going to fit a super finder (4.5" newt) to my Dob, but as you say, too many stars may make things harder.

[emadmoussa]

Gonna need a bigger mount

I'm not sure any of the regular amateur astronomers can afford anything larger than the NEQ6 or AZ...

That's fine though, I use the C11 combination only for visual and lunar...

[michael.h.f.wilkinson]

I'd been thinking exactly this Mark. I was going to fit a super finder (4.5" newt) to my Dob, but as you say, too many stars may make things harder.

The 70mm I have is fine, especially when combined with charts drawn up with the ocular tool of Stellarium. I added the 70 mm as a scope, and the 25mm Antares with its 27.3mm field stop (measured) and you get a very good map of what you should see when the object is centred in the finder scope. In theory, the 70mm reaches mag 10.2 for average observers and 10.8 for experts under mag 5.0 skies, but the fainter ones do not confuse me. My atlas goes to mag 8.5, and these stars do stand out sufficiently to see the patterns. Even under mag 6.0 skies, I find that the mag 11.8 limit does not throw up so many stars that I get confused. It might take some getting used to, but I find the extra information I get from the big finder very, very useful. More often than not the target is dead centre in the FOV of the scope after the star hop.

[Pingster]

I the TS 80mm finder scope pictured in authors post. IMO its terrible. Stars have CA around them even the ones in the centre area of the FOV.

The eyepiece that comes with it had terrible stars from 60% of the FOV, turning into long streaks! With a 24mm tele vue pantopic the fov is actually far better with stars "good" to 90% of the fov. Now i say "good" because even tho they are far better than the default eyepiece, theres far too much CA on them and they are just not "satisfactory to view". Also please note the 24pans vignette a lot in this finder.

I am considering getting an Alstair astro 10x60, if if its the same finder rebadged... Then i would not buy it unless the 60mm version gives "nicer" star fields.

Has anyone found their perfect optical superfinder? Im so tempted to get a tele vue 60mm apo to achieve perfection if it can exist.

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[emadmoussa]

I the TS 80mm finder scope pictured in authors post. IMO its terrible. Stars have CA around them even the ones in the centre area of the FOV.

The eyepiece that comes with it had terrible stars from 60% of the FOV, turning into long streaks! With a 24mm tele vue pantopic the fov is actually far better with stars "good" to 90% of the fov. Now i say "good" because even tho they are far better than the default eyepiece, theres far too much CA on them and they are just not "satisfactory to view". Also please note the 24pans vignette a lot in this finder.

I am considering getting an Alstair astro 10x60, if if its the same finder rebadged... Then i would not buy it unless the 60mm version gives "nicer" star fields.

Has anyone found their perfect optical superfinder? Im so tempted to get a tele vue 60mm apo to achieve perfection if it can exist.

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I used the Altair Astro for few months, absolutely loved it. You still get a degree of coma, but all in all is brilliant. Now I'm using a Skywatcher right angled finder and quite happy with it...not as good as the AA, but is good enough for my needs, especially it's not as heavy as the AA finder.

[russ.will]

I had the AA 10x60 and to be honest, I was slightly underwhelmed with the mess of stars toward the outer FOV. Initially I thought it was the EP, but even using my MV SWA 20 & 24mm didn't help much. i just didn't get on with it and as one of my scopes was a Dob, it was a bit hefty too.

I swapped it out for the Williams Optics 50mm F4 which I believe is a Stellarview F50M clone. I partnered it with the TS 20mm illuminated reticle EP . Now the finder inc taxes from Agena was £106, the EP £70 and the ES tall finder rings (also from Agena and hard to get over here, hence shopping in the US) stood me in at another £35.

That's £211 all in which lets be honest, isn't cheap and was a bit of a punt sight unseen, but blimey, what a cracking finder. The EP is actually surprisingly good when used as, believe it or not, as an EP! But I haven't looked back. It's smaller, lighter, remarkably free of colour and much tidier around the edges. Sometimes, I just grab it and go outside with it for a quick squint at the night sky when lack of time precludes everything else.

I justify it to myself in the terms that it is useful on all three of my scopes and unlike the scopes, it's unlikely to be subject to the whims of upgraditis, so worth spending the money on. In terms of the AA 10x60, it's worth pointing out that the AA is a LOT cheaper, but I personally feel this is one of the few times where a significant price hike directly correlates with the improvement in view.

Russell

[michael.h.f.wilkinson]

First of all, these big finders sport very fast optics, so CA is going to be a problem whatever you do (MUCH more so at larger apertures). The TS 80mm has a 330 mm focal length, I gather meaning it is F/4.125. This is seriously fast, and should result in CA similar to that of cheap 80mm binoculars. Besides, F/4.125 is seriously pushing the (Erfle? Kellner?) design of the EPs. Astigmatism is bound to be awful. Most of these special purpose finder scopes come with a 90 deg Amici prism intended to illuminate a 22mm image circle (the largest diameter reticle I have found in illuminated reticle EPs). They will vignette in a Panoptic 24mm, no doubt. By contrast my 70mm is F/5, which is a big difference in terms of CA and  astigmatism in the EP. Even with my fairly straightforward Antares 25mm 70 deg EP (with crosshairs put in by yours truly) the astigmatism is quite bearable (noticeable beyond 80% out but still tolerable). Inserting an MV 24mm improves matters, but I am not putting crosshairs in one of those. I had a 20mm illuminated reticle EP before (still lying around somewhere) and although the quality was good, the FOV was a bit disappointing (22mm field stop mentioned before). I got a separate Amici prism (90 deg) which does not have (severe, there's bound to be some) vignetting over the 27mm field stop of the 5mm Antares.

Regarding image quality: I do not expect or need to have a finder scope performing at APM/LZOS level. It is there to help me find things. Astigmatism can be such a distraction that it renders the edges of the FOV unusable, and I would certainly draw the line there. I would say the views through my 14x70 finder scope are close to those in my Helios Apollo 15x70 bins. That is certainly good enough.

[Pingster]

Hi Russel.

You seem to have chased the same problem as me and its good to know i am not alone or insane in this endeavor.

I have a 16in dob and a 12in dob, because the dobs show me so much and do high mags so well, i want a above standard quality finder that can give me a complimentary low power wide field view. To appreciate the high power view i enjoy in the dob. Being able to switch between the two views instantly, put a greater sense & appreciation to what i am looking at. The correct view of the finder inspires me to search around the target to investigate its surrounding, then i can check it out further in the dobs power view.

Anyone who owns a dob can relate to how the inverted view can make you lazy to explore the area around your "target" as its just not satisfying and you dont really appreciate what you are seeing as its "too easy" at high mag. However in the finder it looks like a tiny speck. I love looking at the tiny speck in the finder and going wow its 4 stars in the dobs view.

Also i find if you go stargazing with casual friends. If you show them andromeda in a dob or any other galaxy.... They say "you spent this much to see just that?". But if you show them in the finder first they appreciate what they see in the dob.

I think because if the red dot finder and telrads. People may have forgotten the beauty of a great optical finder, and in many ways i am using the wrong term... All telescopes need a "low power telescope" to compliment their main scopes high power potential.

The finders have have tried so far:

Skywatcher 50mm RACI finder: pretty good, but the stars just dont quite focus well even in the centre stars start to flare a tiny bit from 80% fov. I would rate it 7/10.

TS 80mm : With default eyepiece its a 3/10. Terrible. Stars are long streaks from 60% out of the fov. With a 24 panoptic the stars are actually sharpe up to 90% of the fov, massive difference. However when i say sharpe, the stars are not perfect. They are ever so slightly flared to one side or the other depending on focus, and theres far too much CA.

So thats why im still chasing that perfect finder. I dont expect it to resolve M13, but i want apo quality starfields. Thats why im looking at the Tele Vue 60mm APO. Its 1.25kg which should be just about ok to mount on my 12in Dob. But @ £1000 including diagonal.... Its insane.

For that price i could buy the WO 50mm Russ recommended... And a quark..... And thats so tempting xP

Russ can you give me an in depth opinion of the WO finder? The stars... Are they pleasing to look at. Thats what im looking for. At this price i dont expect perfection, but it needs to be far better than the skywatcher RACI 50mm i have in terms of crispness for stars.

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