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#1 Rait

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Posted 13 November 2012 - 02:06 PM

Hello!
First of all, English is my second language and sorry for my bad writing advance.
I am new on this forum. Reading your post have been developed me. Thanks.
I am planning to buy refractor Triple APO 130 mm or 150 mm. As my experience is only with 85 mm I need some advice. 150 mm accumulate 30% more light than 130 mm but it is 100 % higher price. Here is my question, do anybody in this forum have experience with both sizes APO refractors. Would it be big difference for deep sky photography and for solar system viewing. Thanks advance. :)
Rait

#2 Jon Isaacs

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Posted 13 November 2012 - 05:09 PM

Rait:

Hello and Welcome to Cloudy Nights :waytogo:

I have never owned a 130mm or 150mm apo, I am sure some who have will chime in...

And don't worry about your English, it is plenty good...

Best wishes

Jon Isaacs

#3 M13 Observer

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Posted 13 November 2012 - 05:19 PM

For solar system viewing, larger is better if the optics are of reasonable quality. The 150mm will be better than the 130mm. The image will be brighter allowing higher magnification and the resolution will be higher.

For imaging, the focal ratio and focal length are somewhat more important. The lower the focal ratio, the more light is getting to the detector which reduces the length of exposures. The longer the focal length the larger the magnification. It all depends on what you are imaging so it is hard to determine which would be better.

#4 Eddgie

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Posted 13 November 2012 - 05:22 PM

I have not owned a 130mm, but a 127mm.

Also 80mm, 102mm, and 152mm APOs or ED scopes.

The step up from 80 for me to 102 did not seem to make much difference in performance, but this is becase both of these apertures to me seem to be a bit small for much observing unless skies are very dark.

The bump from 102 to 127 is a decent bump because you are not getting enough aperture to see into some catalog items off of the couple of hundred "Showcase" objects that are usually the limit for 4" apertures under many sky conditions.

152mm is though to me a threashold size, not just in APO, but in just about any scope. This is the size that starts to allow for much more deep sky observing in many typical suburban loccations. 8" would be better of course, but for me, a 6" refractor is about as small as I personally care to use becuase I found that it was the only size that could get me away from the showcase objects and into more deep space.

The question you want answered though is impossible for us to answer for you.

This question comes up time and time again, and you will get as many options saying that 5" is enough as you get saying "Dude, get the 6" if you can afford it!"

Only you can answer this question.

I don't even use my 6" APO much anymore because I just can't get enough light gathering from it to make me happy so I may be the wrong person to ask, but I could never be happy with a 5" refractor again in my life. It was just too small. The 6" is right at the bottom of my aperture limit for most observing.

#5 chboss

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Posted 13 November 2012 - 05:22 PM

Hello Rait

Welcome to Cloudy Nights. :cool:

Both a 130mm or 150mm triplet Apo would work great for AP and solar system viewing. There is of course a light gathering difference between the two but I would personally look more at restrictions in size and weight in case you want to use the telescope mobile.
The mounting needs increase exponentially with the scope size especially if you have AP in mind.

best regards
Chris

#6 Paul G

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Posted 13 November 2012 - 05:31 PM

I'm a lunar and planetary observer and have both 130 and 155 mm apo refractors. There is a significant difference in planetary detail between them. The only reason to choose a 130 over a 150-155 would be portability.

I don't image so I can't address that side of it.

#7 snommisbor

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Posted 13 November 2012 - 05:53 PM

Depending on budget you have, also depends on scope to recommend. But the TEC 140 would be a great alternative.

#8 Rait

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Posted 13 November 2012 - 05:53 PM

Eddgie,
You are correct. As we have learned from our life, we always want bigger and better. I am thinking that large than 150 mm prices will make so big jump and this will be never logical (never say never). And if I buy 130, when I can afford 150 I afraid that I will think as you pointed. I need to think more. Thanks.

#9 Rait

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Posted 13 November 2012 - 06:03 PM

Chboss,
Thanks for replay. Your advert to weight have point. Mobility is important but I think that extra 5 kg is not big problem. Do you thing iOptron ieq45 will be good for 150 mm apo. By specifications this mount is ok for 20 kg and 150 mm apo is 13 kg. Thanks.

#10 Ziggy943

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Posted 13 November 2012 - 07:08 PM

Chboss,
Thanks for replay. Your advert to weight have point. Mobility is important but I think that extra 5 kg is not big problem. Do you thing iOptron ieq45 will be good for 150 mm apo. By specifications this mount is ok for 20 kg and 150 mm apo is 13 kg. Thanks.


I have a TEC 160 F/8 that I use on an AP900 mount. It is a very good combination. I dont recall if the iOptron ieq45 breaks into pieces like the AP900. Even with my bad back I have no problems setting it up.

#11 SteveG

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Posted 13 November 2012 - 07:19 PM

Rait - which scopes are you looking at?

#12 Rait

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Posted 13 November 2012 - 07:55 PM

SteveG,

In 130 mm is on my attention TS Photoline 130mm and William Optics AP 132/925 but in 150 mm is in my price range only TS Optics AP 150 at the moment.
Rait

#13 chboss

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Posted 14 November 2012 - 03:34 AM

Chboss,
Thanks for replay. Your advert to weight have point. Mobility is important but I think that extra 5 kg is not big problem. Do you thing iOptron ieq45 will be good for 150 mm apo. By specifications this mount is ok for 20 kg and 150 mm apo is 13 kg. Thanks.


I use a 155mm telescope on the iEQ45 which works for visual observation but my feeling is that is the absolute maximum, this also because it is a long focus (f/9) telescope. I am using the mount on a permanent pier, which helps the stability. With the original tripod I do not think the iEQ45 is enough for a 6" class telescope.
A shorter focus 130-140mm telescope would be no problem.

Below an image of my setup with the smaller 4" Apo.

best regards
Chris

Attached Files



#14 Emanuel

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Posted 14 November 2012 - 06:03 AM

Hi Rait, hows going?
I have a WO 132mm FLT, wich i love. I got it at a very good price, second hand, and for deep AF its awesome, not sure about planetary, didnt made a real test with it, but i saw very nice photos on the net made with it on planets. I use it on a Celestron Cgem mount, so, i dont know nothing about the iEQ45.....
I assume that you from Europe, by speaking on the TS telescopes, but, i think that you should think better; i explain:
I was going to buy the TS 130mm triplet, and i only didnt buy it, because of the very good deal that i had with the WO; anyway, i think that is a very good option on this price range; but, if you are thinking of a 150mm Apo, i say, dont go for the TS 150 triplet, go for a better one; in Europe, at TS website, this scope costs 5190 euros, and for this price, for me, it would be better to go for a APM 130mm or even better, a TEC 140mm. They maybe be more expensive, but, im sure that the quality is worthy. And why not a doublet? Did you saw the new scope from APM? Its a 150mm, doublet, and it will be delivered from this December. Check it out on APM website: http://www.apm-teles...s-OTA/Apochr...
Cheers :)

#15 Rait

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Posted 14 November 2012 - 06:45 AM

chboss,

Thanks, you made point. 150mm can be too much for ieq45. Tube plus accessories can be near maximum. And mount is same important as tube. :)
Rait

#16 chboss

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Posted 14 November 2012 - 07:02 AM

In this price range you need to be sure that not only the optical quality but also the lens cell and the rest of the mechanics are first rate.
APM LZOS, TEC, AP or Takahashi are the long term proven scopes but come with a high price tag.

The scope from APM that Emanuel mentions is an interesting option, but brand new and manufactured in China. There is no long term experience with this scope yet. This ED Doublet was designed for visual observers. Here I would personally wait for first reports from users before buying. There should be an optical bench test from Germany in the coming months. ;)

best regards
Chris

#17 Emanuel

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Posted 14 November 2012 - 07:23 AM

Yeah, Chris, you got a very strong point on that, something that i tend to forget. The APM doublet is a new scope, and yes, manufactured on China. With no reports yet, about the scope, the best thing is to go for a brand that as all kind of good states about them. Any of the brands that you mentioned is excellent, and if i had that kind of investment......it would be one of those. :)

#18 Patrick

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Posted 14 November 2012 - 08:00 AM

Would it be big difference for deep sky photography and for solar system viewing.



For deep sky photography, the aperture difference is not as important as the focal length. The focal length determines the size of the field of view and therefore the size of the object in that view, and then the imaging time can be varied to compensate for the aperture difference. Resolution between the two sizes is not that significant either. If it were my decision I'd have a hard time justifying paying 2x the price for 20mm aperture gain.

For solar system viewing, aperture is more important because you can increase magnification as the seeing conditions permit. Again, I don't think the resolution difference between a 130mm and 150mm aperture is that significant, however. For myself, I've found that larger instruments like 8-10" Newtonian's or SCT's will perform better on planets than smaller refractors (at far less cost). The added advantage of those larger instruments is that they perform better visually on deepsky objects as well. The down side is that they are not as easy to use for astrophotography.

So, the bottom line for me would be to determine what focal length instrument you want for astrophotography based on what objects you want to capture. If you're going after small faint galaxies you'll want an instrument with a large aperture and longer focal length. If you want to image wide field objects, your current 85mm scope could possible serve you well.

You might want to take a look at the SEDS Catalog to get an idea of the sizes of various objects and download a copy of the CCD Calculator available at The New CCD Astronomy website. I've also used The Sky 6 software program to help me understand the FOV of various size instruments with various camera's for image framing.

In the end imaging is not just about the OTA...a lot of other factors are important as well.

Regards,

Patrick

#19 Rait

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Posted 14 November 2012 - 08:07 AM

Emanuel,

Thanks, I will check. Your replay put new questions in my mind. Have you compared your WO 132 with TS or AMP? Are they in different in image quality level? How you would compared triplet and doublet, is it better image quality? Yes, I am from europe country where unfortunately weather conditions are very unpleasant for sky lover. :bawling:
Rait

#20 Rait

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Posted 14 November 2012 - 08:44 AM

Patrick,
As I understand you would prefer 8-10" SCT or newtonian additionally to 85 mm APO than new 130 or 150 mm. I thought in beginning same but I do not like to have two mounts (double work to set up) so I think easy way will be upgrade my refractor. You need heavy mount to use both on one. I see that you are experienced and here is my question, what would you purchased if you have to spend 5000 eur ( 6500 use) for new tube and you have ieq45 (max 20 kg) and 85 mm apo (ed) refractor (10 kg with dslr and other accessories). Thanks.
Rait

#21 Patrick

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Posted 14 November 2012 - 09:22 AM

It depends on what you want to image. Think of the scope like a camera lens. Obviously you wouldn't want to use a wide angle lens to capture an image of a bird at a fair distance away. It's the same thing with imaging deepsky objects. Some are quite large and bright and some are very small and faint. The small faint ones require a scope with more aperture and a longer focal length to make the image scale larger and the f/ratio lower.

What I'm suggesting is that you consider what it is that you want to capture before making your purchase. It can be disappointing to find out after buying your gear that the image you took of a galaxy is so small you can barely see it...or that the image you want to take of a large object won't fit in the frame.

I'm not saying I prefer 8-10" Newts or SCT's or anything. I'm saying you need to choose the right tool for the application. It's not uncommon for imagers to have multiple scopes for different objects. It could be a 130mm to 150mm APO is exactly what you want. I'm only suggesting you do some research to make sure you can get the kind of framing you want with the camera you'll be using on the objects you'll be imaging.

I can't afford expensive APO's so I have limited experience in that regard. ;) I can tell you that the longer the focal length the more challenging it becomes to get good images. :smirk:

Patrick

#22 Emanuel

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Posted 14 November 2012 - 12:34 PM

Rait, i didnt have the chance to compare my WO with the Ts or Apm scope.
Anyway, you have to think this way: Ts 130mm triplet is made in China, wich is the place where more telescopes are made. This means that is mass producted, and as so, the same telescope is sold under several diferent brands; if you want a example, the new Meade 6000 series 130mm triplet is exactly the same as the Ts 130 mm triplet; Williams optics sometimes use the same manufacturer and sometimes uses the very best on their objective, like the Russian Lzos. On the top of all this ,manufacturers like TEC, AstroPhysics, Takahashi, or APM, manufacture their own lenses or use Lzos/Lomo optics at the very best standars on the market; as so, the price of the scopes is also very high. It is expensive, but, if you can afford it, its worth every dimme.
When it came to comparison, between a doublet and a triplet, you have to think this way: three lenses will correct better the chromatic aberration of an image than two, right?
By the way, from wich country are you? Im from Portugal, and luckly the weather is not that bad, for this time of the year.
:)

#23 Ron Luxemburg

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Posted 14 November 2012 - 06:33 PM

Rait,
Just a quick FYI, I just got a 132 and I really like it, however be aware that more then likely if you decide to go with the WO 132 F7 FLT you will very likely need to add a 2 inch extension for your eyepieces to reach focus in the diagonal as well as prime focus with a DSLR. I put together a spreadsheet noting the distance indicated by the Digital Guide focuser in millimeters and added that number to the 2 inch extension that I was using which in my case was an additionall 55mm. I'm running all TeleVue eyepieces, mostly Panoptics and Naglers and one Ethos. The current focuser will give you 100mm maximum extension however when I averaged out all my eyepieces on average they come to focus in the 110-115mm range on the 132. My 11mm T1 Nagler needs to go to nearly 130mm to reach focus in a diagonal. *Note I'm not counting the diagonal in the sum total here just the extension and the focuser read out.

#24 chboss

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Posted 14 November 2012 - 09:26 PM

Emanuel,

Thanks, I will check. Your replay put new questions in my mind. Have you compared your WO 132 with TS or AMP? Are they in different in image quality level? How you would compared triplet and doublet, is it better image quality? Yes, I am from europe country where unfortunately weather conditions are very unpleasant for sky lover. :bawling:
Rait


Especially with the WO FLT-132 you need to be careful, some lemons have been floating around on the used market. There are optical tests available on a German site that proof this. It seems there was a problem with the lens cell design at some point. So buying used is a risk!

TS in Germany seems to do some in house checks of their optics before shipping which would eliminate serious problems not discovered during production...

regards
Chris

#25 Rait

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Posted 15 November 2012 - 10:20 AM

Emanuel,
Thanks, I am from Estonia. We have long nights in winter time, at the moment sunset is 15:53 and sunrise 07:59, but in wintertime we do not have many clear nights. Summer time we have more clear nights but then in July example sunset 21:00 and sunrise 03:30 - no night at all. So it is terrible and I always envy who's live in better area.
Rait






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