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Economical refractor

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#26 ppfilbert

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Posted 10 January 2013 - 05:34 PM

aye i have been using http://www.12dstring.me.uk/fov.php to check my camera and the scope together. think it will do fine, and i see almost NO fdifference in the view form that andn the Es80triplet. therefore WE HAVE A WINNER. now to get the money, heck at that price i might be able to get my SSAG!!!!

#27 ppfilbert

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Posted 10 January 2013 - 05:40 PM

out of Morbid curiosity, whay is this scope 599, and the es80triplet 799?

#28 Jon Isaacs

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Posted 10 January 2013 - 06:08 PM

out of Morbid curiosity, whay is this scope 599, and the es80triplet 799?


- The ES 80 triplet is larger but the objective is based on FCD1 rather than the more desirable FPL-53 that the 65 quad uses. The 80mm also lacks the ED based field flattener that makes the 65 what it is... and too, the 65 has a two speed rack and pinion focuser instead of a Crayford, a quality rack and pinion is a better choice for heavy eyepieces and diagonals... the TeleVue and Takahashi's mentioned below all have rack and pinion focusers.

- There are 5 other apo's I know of that are Petzvals or at least have built in field flatteners, the Takahashi 85FSQ, the Takahashi 106 FSQ, the TeleVue NP-101, the TeleVue NP-127 and the new William Optics GT-81.

The two Takahashi's are $3650 and $5150, the TeleVues are $3800 and $7000 and the William Optics is $1200. The Takahashi's and TeleVues are legendary...

The AT-65 Quad offers an entry into this elite field at a price that is a tad bit more affordable, it's small but widefield imaging is all about short focal lengths and flat fields.

Jon

#29 jrbarnett

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Posted 11 January 2013 - 10:51 AM

"...and the new William Optics GT-81."

Uh, no. The GT-81 is a conventional air spaced triplet with a doublet field flattener mounted aft. 5 elements and more akin to adding a separate FF to any other triplet.

I used to have a Pentax 105mm doublet that had a permanently mounted singlet flattener in the OTA, so the integration of a flattener with a conventional OG up front isn't novel, and in fact may have some limitations compared to using a conventional OG with a removable FF.

Regards,

Jim

#30 Jon Isaacs

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Posted 11 January 2013 - 10:56 AM

"...and the new William Optics GT-81."

Uh, no. The GT-81 is a conventional air spaced triplet with a doublet field flattener mounted aft. 5 elements and more akin to adding a separate FF to any other triplet.

I used to have a Pentax 105mm doublet that had a permanently mounted singlet flattener in the OTA, so the integration of a flattener with a conventional OG up front isn't novel, and in fact may have some limitations compared to using a conventional OG with a removable FF.

Regards,

Jim


Probably has some limitations as well when compared to the FSQ and NP series.

I have been looking into using a field flattener/focal reducer with my 80mm F/7 apo. The problem with using a focal reducer is that focal reducers eat of back-focus, that is they require inward focuser travel. With a camera, this is not a problem because normally one does not use a diagonal but visually, it's a real problem.

For visual, scopes with dedicated flatters/focal reducers are desireable.

Jon

Jon

#31 SteveG

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Posted 11 January 2013 - 12:48 PM


- There are 5 other apo's I know of that are Petzvals or at least have built in field flatteners, ......... the new William Optics GT-81.


Yes - has a built in flattener as John stated. William Optics has a soon to be released 102mm, 5-element as well.

#32 Mike W

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Posted 11 January 2013 - 06:21 PM

Take a close look at the Astro Telescopes 102 f11. It's a great performer and quality built! With tube rings and rotating focuser for $599. from Hands on Optics! :refractor:

#33 rflinn68

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Posted 11 January 2013 - 07:21 PM

Take a close look at the Astro Telescopes 102 f11. It's a great performer and quality built! With tube rings and rotating focuser for $599. from Hands on Optics! :refractor:


I dont think he'd want to image at f/11

#34 WarmWeatherGuy

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Posted 12 January 2013 - 02:46 AM

I would consider the Astro-Tech AT72ED and field flattener. This if f/6 and will allow fairly long exposures unguided due to the short focal length. You didn't say what camera you have. There will always be bits and pieces that you find you want or need, like a 2" diagonal or extender so there's no need to spend the full $1000 all at once. This combo will be around $500 (you get a discount for being a Cloudy Nights member). The other $500 can go to accessories or in your pocket.

There are lots of great pictures taken with this scope:
http://www.astrobin....ro-tech-at72ed/

#35 Mike W

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Posted 12 January 2013 - 08:34 AM

I missed the imaging part! :shrug:

#36 cloud_cover

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Posted 12 January 2013 - 12:19 PM

Hello!
Let me say for starters even though we are in the refractors forum that you don't NEED a refractor.
Can I ask how experienced you are in imaging? No offense meant but when imaging with an f/10 scope or for that matter a C8 on a CG-5 many factors come into play other than just the scope itself. Are the images bad because of the optics or are things like mount wobble, poor alignment, periodic error, wind, dew etc playing a part as well?
If the C8 truly needs replacing, have you also considered an imaging newt or RC? Some of the models from Astronomics will fit your budget.
The "problem" with a refractor is the curved field (as I'm sure you've experienced when setting up your C8 for imaging) and chromatic abberation, which is expensively fixed. Furthermore, if you are getting a 300mm lens for piggybacking, you already have, essentially, an achromatic to ED grade refractor at 300mm. Most of the 80mm scopes function at a fairly close focal length as well, hence they may not be a useful addition to your imaging equipment. An AT8IN by contrast, functions at 800mm at a fast f/4, although I'm not sure if the CG-5 will comfortably mount that for imaging use.
Another alternative is instead of replacing the C8, use your 300mm to capture wider objects and use the C8 to autoguide. Guiding is fairly tolerant of bad optics.
Hope it helps!

#37 ppfilbert

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Posted 25 January 2013 - 08:32 PM

So after all that happened, i took my C8 with camera piggyback on it, and when i came back in my corrector was cracked. so now i dont even have a fallback large scope. SO instead of the AT65EDQ i went and bought today a ES AR127. that way ill have a lil better deep field, and then in 2 months or so i can buy the at65edq. so all in all tday is a Good Day.
sadly in 7 days when it arrives it wont be good for about 2 weeks :(






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