Scope compare

Junming-jm · Post by **Junming-jm** » Mon Jan 03, 2011 7:18 pm

celestron c5 vs celestron nexstar 5 vs Sky-Watcher Black Diamond Maksutov 127mm which is better

tungkian · Post by **tungkian** » Mon Jan 03, 2011 8:52 pm

1. nexstar 5 is out of production.

2. c5 is expensive when bought as an OTA; better off buying the nexstar 5SE.

3. the mak is heavier than the c5 OTA.

4. most importantly, OTAs 2 and 3 are useless without a good mount because they have long f-ratios.

cloud_cover · Post by **cloud_cover** » Mon Jan 03, 2011 10:13 pm

I thought you're thinking of the Orion 100mm f/9 refractor?

Post by **weixing** » Tue Jan 04, 2011 9:18 pm

Hi,
Basically:
1) C5 require collimation (not difficult if you had a tracking mount), but the Sky-Watcher Black Diamond Maksutov 127mm usually don't,
2) C5 is lighter, and
3) if buy locally, the Sky-Watcher Black Diamond Maksutov 127mm is cheaper by quite a lot.
4) Image quality is around the same.

Happy shopping and have a nice day.

Junming-jm · Post by **Junming-jm** » Tue Jan 04, 2011 11:56 pm

Ya if Buy the orion refractor I will be pull my whole hair off because of storage problem and transport . Btw for the sky watcher BK MAK 125 is it suitable deep space object?

rlow · Post by **rlow** » Wed Jan 05, 2011 1:13 am

C5 and Nexstar-5 are basically the same Schidmt Cassegrain (SCT) optical tube assembly (OTA). Older versions do not have XLT coatings, but I don't find it significant.

Essentially you are comparing SCTs with Maksutovs (MCTs). All scopes can be used for observing deep sky objects (DSOs). Although both ota have the same aperture, the focal length differ, and this has an effect on framing wider DSOs. If you want to get the widest true field-of-view, use a 2" 40mm eyepiece with 70 deg. AFOV. Then the C5 will give you about 2.2 degrees while the Mak only give about 1.8 degrees. Hence the C5 will have an advantage over the Mak for viewing the wider DSOs.

The Mak optical design is generally slightly superior to the SCT design in terms of contrast and sharpness. These are mass-produced scopes, and there are product variations, so sometimes you get a lemon and if you are very lucky, you get an optical gem. I have only seen two excellent SCT gems out of a few dozens in three decades, but this are exceptions, not the norm. Of the same aperture, Maks have an advantage over SCTs if your primary interest is planets, Moon, planetary nebulae and/or double stars. However Maks also tend to be heavier, longer length, longer cool-down time, and need a sturdier mount & tripod.

SCTs have the most compact ota, but once you consider bigger apertures >8", the overall size and weight including mount and tripod can get quite daunting. SCTs tend to be the 'jack of all trade but master of none' kind of scope. SCTs and Maks also attract dew forming on the optical plate on the front of the ota. This becomes an issue when you observe overnight or on certain nights which tend to dew easily. Then you need to add on dew heaters.

If this is going to be your first scope, you should also consider the other two main category of scopes, namely, the refractor and Newtonians.

The 100mm f/9 achromat can be a good start for beginners. Storage may not be an issue if you have an air-con room, or you can unscrew off a portion to fit into a dry cabinet. Apochromats and long-focal-ratio achromats give excellent optical performance, and are the best among all the different types of scopes. The downside to this is the cost. Short focal-ratio achromats suffer from chromatic aberration (CA) which limits its performance at higher magnification, though they are fine for low-power view of DSOs. Dew can be a potential issue though it doesn't attract dew as easily as SCTs and Maks.

Newtonians are the best value-for-money scopes among these four categories of scopes, if you compare them of the same aperture. And well-made high-quality newtonian is a close second to apos in optical performance. And because these good newts are now of short focal ratios ( f/4 to f/5), they have wide true field-of-view for DSOs and yet their excellent mirrors allow high magnification for exellent planetary observation. No CA, and coma can be taken care of with a coma-corrector. Not much of an issue with dew, compared with the other types. The downside? Need to collimate (easy once you learn it, takes less than 5 mins), and it needs better wide-field eyepieces. Some may think newts are bulky, but the 4.25" f/4 and 6" f/5 newts are very portable! And I can tell you as a matter of fact that my 11" f/5 truss dob is more compact, easier to transport and faster to set-up than my 6" f/8 refractor with EQ6 mount.

As usual, your mileage may vary. But I hope this info helps you in selecting your scope (:

Junming-jm · Post by **Junming-jm** » Wed Jan 05, 2011 2:44 pm

Ill follow richard advise . So I decided on the vixen r130sf newtonian but still I wanna know how good is the optics , diffs of dso through orion 100ed and this scope and lastly how good it is at holding collimation

orly_andico · Post by **orly_andico** » Wed Jan 05, 2011 2:51 pm

This may or may not be relevant, but all the Vixen scopes with "f" in their model name are made in China, probably by Synta.

e.g. the Vixen 100mm f/9 ED Sf is actually exactly the same optics as the Orion 100ED and Sky-Watcher 100mm f/9 ED. To get a Japan Vixen it must have "SS" in the model name.

Celestron used to sell some Vixen Japan Newtonians on the Vixen Polaris mount long, long ago, well before they started pushing Chinese stuff. I'd take one of those over an R130Sf any day..

Junming-jm · Post by **Junming-jm** » Wed Jan 05, 2011 4:20 pm

Is it a good scope for beginner?