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Travel scope: 70/500 vs 80/400 achromat?

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Travel scope: 70/500 vs 80/400 achromat?

Postby zolantal » Tue Jul 03, 2018 1:12 am

I'm looking for a lightweight telescope under $300, capable of being transported in a backpack for hikes (along with its mount). For general purpose: I'll use it for both astronomy and terrestrial. I live in a white zone, so from home it'll be planets and the Moon, but from out of town I can hit some brighter DSOs too. I'd also like to take photos of birds and such, by attaching a DSLR. I realise that no scope exists in this price range to equally satisfy all these, but I'm willing to compromise.
Also, I'm not a complete newbie, I have a 8" Dob, but I won't have access to that in the coming years. I'm new to spotting scopes and terrestrial viewing though.

The scopes in question are these:
SW StarTravel 70/500: astroshop.eu/telescopes/skywatcher-telescope-ac-70-500-mercury-az-3/p,3073
SW StarTravel 80/400: astroshop.eu/telescopes/skywatcher-ac-80-400-startravel-az-3-telescope/p,33049

I was more or less convinced on the 80/400, based on online research, but in the shop they told me that it's basically rubbish above 60x power, so for planets and the Moon and high-power terrestrial, becuse "the chromatic aberration is so bad that the scope can't even be focused". Is there such a thing? I thought that if you get used to CA, it's not a deal-breaking problem. Also, can't CA be reduced by stopping down the aperture? I've read people using this scope up to 120x on forums, so I couldn't really believe what they were telling me in the shop.

They offered me the cheaper, smaller aperture 70/500 instead, saying that can truly go up to 120x for viewing planets, with little CA. I wanted to turn it down straight away, as it's 10cm longer (portability is a huge factor for me), and 10mm smaller aperture, but after doing some research, it seems like a decent scope too, with still relative large FOV at lower powers. The only downside is that it has a cheaper plastic focuser (the 80/400 has a metal one).

So, which one do you recommend? If you have any experience with either, a short summary would be much appreciated.

Also, on which mount should I get it, AZ-3 or EQ-1? I'm leaning towards the AZ-3, as I read that the EQ-1 is a bit rubbish (too wobbly), and the AZ-3 is more compact. However, for terrestrial, I'm planning to use it on a simple light photo tripod, so maybe the EQ-1 would be better for astronomy?
zolantal
 
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Re: Travel scope: 70/500 vs 80/400 achromat?

Postby The Man with the Corrugated Iron Roof » Sat Jul 28, 2018 10:30 pm

I have the 80/400 and bright objects, like the Moon, show CA. However, on deep sky objects it is much less noticeable. In theory, the CA on the 70/500 is less but it would not be THAT much less.

My 80/400 has been around the world.
How can I be one with the universe when we don't know what 96% of it is.

My website: http://www.philippughastronomer.com/

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Location: Wiltshire but can be just about anywhere up to 41 000 feet


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