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lamplight
Carpal Tunnel
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Re: Hypothetical 4" budget APO choices.. WWJD? new [Re: lamplight]
      #5642921 - 01/25/13 04:26 PM

Well I bought a nice JMI focuser ona whim and then started thinking I should put this ona better scope.. So the comments on focuser upgrades are good news. I didn't realize there were such big differences even in APOs so ill get reading. I am just now understanding that the color correction needed varies from design to focal length and I d just assumed that all APOs had corrected color. Jerry would go for the purest view for sure. I'm wondering if its even worth it where I live as I've been using my achro a lot with the cold (easy to bring out) and I can't find a lot of the objects I have found with my SCT, so I just don't know. Now I see an sv102 for 700, and a vixen ed103s for 1500. See these used ones are going for about 75% of new, so while not a steal they're not breaking the bank. I did not intend this to be a teach me everything about APOs , this must get so boring for you guys.. Ill do my own research, but I do thank you for making me aware of some of the differences so I can go from there. I'm thinking at a used price it might be nice to just see side by side how one of these doublets compares to my achro.


So can I ask: in a more affordable doublet design, what kind of focal ratio should I be looking at in a 100mm 4" scope with the -least- chromatic aberration ? Nothing faster than say F/7 or is that pushing it? Is the question too oversimplified?

All the years combine.. They melt into a dream... - stellarvue, I mean Stella blue.


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lamplight
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Re: Hypothetical 4" budget APO choices.. WWJD? new [Re: newtoskies]
      #5642928 - 01/25/13 04:29 PM

Quote:

lol Matt you gonna buy another scope..lol




Still have to pay the balance on my DOB when it is ready to ship so I have to, gasp, take it slow on this..


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Jon Isaacs
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Re: Hypothetical 4" budget APO choices.. WWJD? new [Re: lamplight]
      #5642941 - 01/25/13 04:36 PM

Matt:

I suggest reading this review of the Astro-Tech 102ED, it's essentially the same scope as the StellarVue 102ED, the Orion 102ED Premium and the Lunt 102ED.

Astro-Tech 102ED

You might notice my able assistant, Monkulus who was pictured earlier this week viewing through a 125mm Cometron Jr.

Jon


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lamplight
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Re: Hypothetical 4" budget APO choices.. WWJD? new [Re: lamplight]
      #5642942 - 01/25/13 04:36 PM

Maybe I need to rethink this . I have reflector and SCT for added light grasp. Only reasoni wanted to stay at 4" as that seemed the largest size that I wanted to deal with to get the most aperture. I just got a new book in to , the Messier objects, and was reading about M79 which I've been unable to detect other than as a faint star in the reflector. I'm sure part of that is the seeing as I haven't had anything good since the fall even on "clear " nights, but even so I'm sure I didn't have perfect conditions then and did not have trouble finding and viewing M79 with the SCT .

Maybe just an 80mm triplet for grab n go and occasional AP (NOT first priority!). But then extra aperture is always good right? Argh.


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Paco_Grande
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Re: Hypothetical 4" budget APO choices.. WWJD? new [Re: Jon Isaacs]
      #5643342 - 01/25/13 08:53 PM

Quote:



I think it is fair to compare a TeleVue 102 to the Skywatcher ED-100 They are both very similar scopes,




Well, yeah. Compare up to a point. I've owned both Mini Coopers and Porsches and can safely say the Mini is just as fun to drive, plus you don't have the worry of parking dings, nor the cost of repairs. That said, when it comes down to it, the lap times between a Mini and a Porsche don't provide any useful information to a prospective buyer. You also need to drive both to understand.

Edited by Paco_Grande (01/26/13 12:02 PM)


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Fogboundturtle
professor emeritus


Reged: 05/20/09

Loc: Burnaby, BC
Re: Hypothetical 4" budget APO choices.. WWJD? new [Re: bierbelly]
      #5643413 - 01/25/13 09:35 PM

Note to self : don't read the Beginner CN forum. Now I feel like I have to replace the focuser on my SW 80ED...grrrrr

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CJK
professor emeritus


Reged: 12/05/12

Loc: Northeast TN
Re: Hypothetical 4" budget APO choices.. WWJD? new [Re: Fogboundturtle]
      #5643800 - 01/26/13 04:51 AM Attachment (15 downloads)

Quote:

Note to self : don't read the Beginner CN forum. Now I feel like I have to replace the focuser on my SW 80ED...grrrrr






-- Chris


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0luke1
newbie


Reged: 12/15/12

Re: Hypothetical 4" budget APO choices.. WWJD? new [Re: CJK]
      #5643980 - 01/26/13 08:54 AM

I like to buy used gear and let someone else take the depreciation. I've never seen a hotter marketplace than this one. Good gear sells in hours. You may want to track the scopes you're interested in and see what sells the most quickly. May not mean it's the best equipment, but it will mean that, when you want to trade up, you can.

Btw, this is my first post after lurking for some time. This is a great forum and I've learned a great deal. Thank you.


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lamplight
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Re: Hypothetical 4" budget APO choices.. WWJD? new [Re: Jon Isaacs]
      #5644044 - 01/26/13 09:46 AM

Good review monkey, thanks.. More is revealed. I was afraid i was seeing some CA on some stars.. Chris you meanie. Lol
Welcome lurker. Tonight should be clear so there will be more doubles to be split. I signed up on astromart so, yea.. Keeping eyes peeled . That review was perfect Jon


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dr.who
scholastic sledgehammer
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Reged: 01/05/12

Re: Hypothetical 4" budget APO choices.. WWJD? new [Re: lamplight]
      #5644866 - 01/26/13 06:29 PM

Afraid I have to beat my favorite drum here. While just shy of half again the price at $1,400 the new carbon fiber explore scientific is worth a look for what it comes with.

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Jon Isaacs
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Re: Hypothetical 4" budget APO choices.. WWJD? new [Re: Paco_Grande]
      #5644963 - 01/26/13 07:26 PM

Quote:

Quote:



I think it is fair to compare a TeleVue 102 to the Skywatcher ED-100 They are both very similar scopes,




Well, yeah. Compare up to a point. I've owned both Mini Coopers and Porsches and can safely say the Mini is just as fun to drive, plus you don't have the worry of parking dings, nor the cost of repairs. That said, when it comes down to it, the lap times between a Mini and a Porsche don't provide any useful information to a prospective buyer. You also need to drive both to understand.




The mini-Cooper and the Porsche are not all a like, different displacement engines, different engine designs, different tires, different wheel bases, different weight distributions, different suspension systems.

By comparison, the Synta ED-100 and the TeleVue 102 are basically twins, they have the same aperture, the same focal length, both are doublets and both use the best quality ED glass available.

There is not going to be much difference at the eyepiece...

Jon


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lamplight
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Re: Hypothetical 4" budget APO choices.. WWJD? new [Re: Jon Isaacs]
      #5645660 - 01/27/13 09:22 AM

At106LE ooh.

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Paco_Grande
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Re: Hypothetical 4" budget APO choices.. WWJD? new [Re: Jon Isaacs]
      #5646006 - 01/27/13 12:50 PM

Quote:


The mini-Cooper and the Porsche are not all a like, different displacement engines, different engine designs, different tires, different wheel bases, different weight distributions, different suspension systems.





Sure. But they both have 2 doors, a windshield, an engine, 4 wheels and disc brakes. They both have glove boxes, and steering wheels. They're both meant to be driven. And they both have [ad nauseam...]

We could go on forever debating this point.


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Jon Isaacs
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Re: Hypothetical 4" budget APO choices.. WWJD? new [Re: Paco_Grande]
      #5646237 - 01/27/13 03:11 PM

Quote:

Quote:


The mini-Cooper and the Porsche are not all a like, different displacement engines, different engine designs, different tires, different wheel bases, different weight distributions, different suspension systems.





Sure. But they both have 2 doors, a windshield, an engine, 4 wheels and disc brakes. They both have glove boxes, and steering wheels. They're both meant to be driven. And they both have [ad nauseam...]

We could go on forever debating this point.




There is something worth understanding here. Comparing the Mini Cooper to the Porsche is like comparing a 3 inch apo to an 8 inch apo, they are just very different animals and there is no reason to expect that they would perform at all alike.

The Skywatcher 100ED and the TeleVue 102 are in all optical aspects essentially identical, the same aperture, the same focal length, the same materials. One would expect them to be very similar in performance and in fact, they are very similar in performance, whether it's splitting double stars or hunting down faint deep space objects, both perform as one might expect a very good 4 inch telescope to perform.

One difference between cars and telescopes: There are theoretical limits the govern the resolution and contrast of a telescope of a given aperture. High quality telescopes perform very close to those levels, within a few percent of less and even moderate quality telescopes perform at similar levels. These limits are determine by the very nature of light passing through an aperture.

Jon Isaacs


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JoeR
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Re: Hypothetical 4" budget APO choices.. WWJD? new [Re: Jon Isaacs]
      #5646721 - 01/27/13 07:06 PM

My Sky-Watcher 120ED consistently gives fantastic views. Very impressed at how deep it can go at dark sites with only 120mm aperture. Not a light bucket by any means but the views are still pleasing.

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Tony Flanders
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Re: Hypothetical 4" budget APO choices.. WWJD? new [Re: lamplight]
      #5646949 - 01/27/13 09:08 PM

Quote:

I was reading about M79 which I've been unable to detect other than as a faint star in the reflector.




That doesn't sound right at all! Are you sure you're looking in the right place? M79 is not a particularly difficult object, even in light-polluted skies.


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Paco_Grande
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Re: Hypothetical 4" budget APO choices.. WWJD? new [Re: Jon Isaacs]
      #5647006 - 01/27/13 09:45 PM

Quote:



There is something worth understanding here. Comparing the Mini Cooper to the Porsche is like comparing a 3 inch apo to an 8 inch apo, they are just very different animals and there is no reason to expect that they would perform at all alike.






I have to disagree. The two cars (Mini Cooper S and any 2 door Porsche) are surprisingly similar. The average person will decide which one feels best and that's that, with no idea how each will behave when you push them closer to the limit. For most, they don't care.

But, performance-wise, they're very close except for the horsepower. Where the difference is how the car behaves near and at the limit, and where that limit is. Horsepower is an advantage on certain tracks, on some tracks it's a hindrance. Even at the limit they're not much different.

I guess my main point is, mechanically, the TV would be expected to be superior else it's not meeting up to its brand image - it had better be! Would you expect a Chinese focuser on a TV? I didn't think so. The SW ED's simply offer a lot of value for the money. Televue? Well, who sells the most telescopes?

Bottom line is, quality is in the eye of the beholder. Each person weighs what's important, considers the cost, and then makes a value judgment. We all do it, every single time we spend our money. And ultimately, contrary to what people typically think, every single buying decision is emotion, not rational.





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Jon Isaacs
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Re: Hypothetical 4" budget APO choices.. WWJD? new [Re: Paco_Grande]
      #5647145 - 01/27/13 11:02 PM

Quote:


I have to disagree. The two cars (Mini Cooper S and any 2 door Porsche) are surprisingly similar.




Let's get back to the comparison between the TeleVue 102 and the Skywatcher 100. The Porsche is a rear engine, rear wheel drive car, the Mini C is a front engine, front wheel drive car. Major differences...

The goal here is to provide some understanding of the differences between various 4 inch apochromatic refractors. It is worth noting that the TeleVue 102 has been discontinued and certainly one of the reasons was that the arrival of the affordable ED-100s that were very similar in capability.

These are the specifications for the Synta ED-100:

Aperture: 100mm
Focal length: 900mm
Optical design: FPL-53 doublet
Dawes limit: 1.16 arc-seconds

These are the specifications for the TeleVue 102:

Aperture; 102mm
Focal length: 880mm
Optical design: Doublet Unspecified glass, most likely: FPL-53.
Dawes Limit: 1.14 arc-seconds.

Mechanically, the Televue is superior with it's rack and pinion focuser and overall robustness but the Synta mechanicals are sufficient that they are not a hindrance in getting the best quality views. In a comparison, the views will be very similar, probably depending on the optics in the particular scope.

The TeleVue NP-101 is a very different scope than either of these, a more sophisticated design with a 540mm focal length, perfect color correction and a flat field of view.

Jon Isaacs


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Paco_Grande
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Re: Hypothetical 4" budget APO choices.. WWJD? new [Re: Jon Isaacs]
      #5648026 - 01/28/13 12:29 PM

So Jon, based on your comments, there is no reason to purchase (even if you could) a new TV102 at four times the cost of the Sky-Watcher.

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Fogboundturtle
professor emeritus


Reged: 05/20/09

Loc: Burnaby, BC
Re: Hypothetical 4" budget APO choices.. WWJD? new [Re: Paco_Grande]
      #5648111 - 01/28/13 01:00 PM

Quote:

So Jon, based on your comments, there is no reason to purchase (even if you could) a new TV102 at four times the cost of the Sky-Watcher.




That's not what he was saying. He was saying. You will be a lot more money for that 1-2%. Sky-watcher series is 98% there.


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