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Something for nothing: Celestron C90

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#51 michalh

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Posted 06 February 2012 - 08:22 PM

Looking at the photo, the 1.25" nosepiece will slide directly into the C90 visual back, no adapter needed (assuming this is one of the new C90's). You might have noticed further up in the thread, however, that some folks have issues with the visual back's rather coarse texture & set screws that might scratch accessories. Check Jim's post from 1/25 for his thoughts.

#52 Starlon

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Posted 07 February 2012 - 12:02 AM

Nope, no adapter needed. Standard 1.25" accessories.

This is a fun little scope. I actually was toying with the notion of a used (or new..!) Questar. This scope has allayed all that for me. This is a newer C90 design. They did well. Even the 3 ep's they include - not half bad.

#53 darth panda

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Posted 08 February 2012 - 06:44 PM

It's here!!!!!!!

#54 jrbarnett

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Posted 08 February 2012 - 10:38 PM

Excellent!

I have mine out (C90 version) cooling now.

For short after-work, before-bed sessions, I use it or one of my 60mm achromats. It's quite a nifty little scope. Unbelievable, really, for the low price.

You're going to enjoy it, I suspect.

Regards,

Jim

#55 tnakazon

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Posted 15 February 2012 - 06:44 PM

The prices for the Celestron C90's are rapidly going back up. At Optics Planet and Amazon, they are now $209 (scope, no tripod) and $219 (scope and tripod). No longer a bargain. Fortunately, I was able to order mine a few days ago at Amazon (scope, no tripod) for $169.95 (free shipping and no sales tax).

#56 jrbarnett

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Posted 15 February 2012 - 07:04 PM

All good things must come to an end. :grin:

You can still get the Skywatcher version for a decent price, though ($179).

http://www.amazon.co...0/dp/B001QS0B40

Regards,

Jim

#57 stargazer83

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Posted 16 February 2012 - 03:22 AM

I was on the Amazon web site tonight and the price for the Celestron C90 is back to $169.95 :cool:

#58 tnakazon

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Posted 17 February 2012 - 08:39 PM

The Amazon price for the C90 is now back up to $189.95.

#59 darth panda

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Posted 22 February 2012 - 08:15 AM

I finally checked out the optics and everything seems fine. I am going to order the Astro Tech diagonal today. Does anyone have any recomendations on a replacement finder or the Celestron 8-24mm zoom?

#60 RichD

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Posted 22 February 2012 - 08:50 AM

What a deal, should be the standard first scope for youngsters really - would remove all the disappointments of department store refractors touting 700x magnification.

I have been really pleased with my synta 127mm MCT, I originally only bought it to look at the moon and planets when I couldn't be bothered to drag the dob out but the thing is so sharp and pleasing to use on a variety of deepsky objects that it's become my most used scope.

Like the C90, it too shows loop shaped glares when a 1st mag star is positioned just outside the field. I have heard that it's due to an inadequately baffled or flocked central baffle rather than the tube interior itself. I don't know if this is true as the glares don't bother me too much so I haven't dismantled to correct it.

#61 tnakazon

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Posted 22 February 2012 - 02:43 PM

I just got my C90 over the weekend and checked out the optics - mine seemed good as well (e.g. concentric airy disks on bright stars). My other two small scopes are fast ones (F/5 Orion ST80A and F/4 Orion Skyscanner), so it's nice to have one that I can really up the magnification on, especially on the planets.

I just got an Orion dielectric mirror diagonal (99% reflectivity) for this scope. I'm satisfied with the supplied finder.

BTW, this scope is back down to $171.78 (no shipping or sales tax) on Amazon.com.

#62 jrbarnett

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Posted 22 February 2012 - 04:21 PM

Rich:

I think you've nailed it.

One of the 90mm MCTs (even on a photo tripod available for an extra $30 or so) is going to produce better results than the typical 60mm to 70mm achromat on a really inadequate alt-az mount. I did the math and roughly the C90 (when factoring in obstruction, surfaces, caoting losses for corrector and mirrors, etc.) had light grasp equivalent to an unobstructed 85mm scope, no false color, minor system aberrations (a little field curvature), and is rugged and robust, easy to transport, etc., etc.

It would make for a very attractive first scope.

Regards,

Jim

#63 mwedel

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Posted 22 February 2012 - 05:15 PM

GREAT thread. I've owned several 90mm Maks, including the Orion Apex/StarMax model, an old orange-tube C90 with the rotating-barrel focuser, and the f/5 MC90.

The Starmax was my favorite, but I dropped it one night and managed to slightly hork up the optics. I sold it cheap to a fellow CNer who thought the problem was fixable (for him, not for me, I'm all thumbs). I also sold the orange-tube C90; rotating the barrel to focus got to be a pain, especially at high powers. The MC90 is on semi-permanent loan to my brother as his grab-n-go scope.

I still have a very big soft spot in my heart for little Maks. I currently have an Apex 127 and I'm loving it. But I'm thinking hard about getting one of these cheap bundles. That SkyWatcher version on the tracking mount is VERY attractive.

One very odd thing is the tendency for astro vendors to have the OTAs priced higher than the bundles. For example, Orion's tabletop StarMax 90 comes with a 90-degree mirror diagonal, red dot finder, two eyepieces, and an alt-az mount that can be used on a tabletop or mounted on a tripod, and that bundle costs about $20 less than the Apex version with the 45-degree prism diagonal, tiny optical finder, one eyepiece, and carry bag (but no mount). How Orion is selling any of the Apex versions when the (IMHO) better StarMax bundle is cheaper I'll never know.

Okay, gotta go off to Amazon and lose some money... :jump:

#64 mwedel

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Posted 22 February 2012 - 11:09 PM

Well, I done did the dirty deed. A SkyWatcher 90 Backpacker is on its way to me. I'll report back when it comes in.

...seems like lots of folks on this thread are buying scopes. What are the implications for the weather? :question:

#65 stargazer83

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Posted 22 February 2012 - 11:40 PM

I finally checked out the optics and everything seems fine. I am going to order the Astro Tech diagonal today. Does anyone have any recomendations on a replacement finder or the Celestron 8-24mm zoom?



I bought a Orion 50mm right angle finder for mine. It was way too big so I returned it. So now I'm looking at getting a 6x30 right angle but I'm balking at the price. It seems Orion has the only 6x30 right angle finderscope in the United States. I'm thinking of getting the Baader Sky Surfer III red dot finder instead.

#66 jrbarnett

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Posted 23 February 2012 - 12:03 AM

Depending on the mount you use, the stock 8x20 that comes with the scope may be sufficient. On the other hand, if you're hopping with the little guy (without GOTO), the Orion 6x30 RACI is really nice. It puts up a full 7-degree TFOV which nicely complements the C90s lowest power true field (~1.3 degree). The 9x50 RACI only has a 5-degree TFOV and, you're right, it's large relative to the scope.

Regards,

Jim

#67 _Z_

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Posted 23 February 2012 - 08:23 AM

How would you guys compare the 90mm Maks to something like the Celestron's powerseeker 80eq?

At f/11 and 900mm it's close to the Mak, comes on a smaller eq mount but Optics Planet has a package on sale that includes a RA tracking motor at no extra cost. No cool down times really makes it tempting...

$145 for a tracking 80mm?

http://www.opticspla...-with-moto.html

#68 Binojunky

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Posted 23 February 2012 - 09:08 AM

I think the mak is more multi purpose, mine is used more in daylight than in the dark,you can grap the back pack in one hand and a small tripod in the other, take it to the local park and generally be nosey, not very realistic with a longer refractor,Dave.

#69 stargazer83

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Posted 23 February 2012 - 09:09 PM

On the other hand, if you're hopping with the little guy (without GOTO), the Orion 6x30 RACI is really nice. It puts up a full 7-degree TFOV which nicely complements the C90s lowest power true field (~1.3 degree).



The Orion RACI sounds like the way to go then, I will be using the C90 on my Televue Panoramic mount and a regular camera tripod so I want to keep it as light as possible. No goto for this guy. I already know where all the planets and brighter DSO are.

#70 stargazer83

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Posted 23 February 2012 - 09:15 PM

How would you guys compare the 90mm Maks to something like the Celestron's powerseeker 80eq?

At f/11 and 900mm it's close to the Mak, comes on a smaller eq mount but Optics Planet has a package on sale that includes a RA tracking motor at no extra cost. No cool down times really makes it tempting...



Portability was the main factor for me with The C90. It's so small you can tuck it anywhere. Especially when traveling.

#71 esldude

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Posted 24 February 2012 - 03:29 PM

Don't have the Celestron 80 EQ on hand. I have a similar Orion 90 Deluxe EQ. Your basic Asian source achro. I thought it was pretty good for what it was. I have run across two scopes that generally lick it pretty well all things considered.

One is this C90. It will take a few minutes to throw up its best images though not too long a wait. The refractor doesn't. Otherwise, it seems to outperform the Orion 90 in most every way. Consider it is much smaller, and handier well you wonder why bother with the longer achro. The basic optical quality is better on the C90.

The other is the very affordable Orion Skywatcher 4.5 Dob. Not the tabletop model, but the one with a short tube and conventional dob mount. It has surprisingly good optical quality. It too takes a few minutes to cool down though again not very long. It has a bit more light gathering. It too would make a good first scope for someone. It also seems to simply be better than the achro. I would say mechanically the C90 is much better than the little Dob. Optically they are in generally pretty close. The brighter image of the dob is offset by diffraction spikes. I actually was never bothered by them until getting the C90. Sure is nice for them not to be there.

The C90 is in some ways more portable than the dob in others it is not. You can literally grab the dob by the handle and need nothing else other than eyepieces. The C90 is smaller for putting in a vehicle to take somewhere though add in the tripod and it isn't. For at home use I very much prefer EQ mounting to the Dob. One could get alt/az mount for the C90.

Bottom line to me is a cheap achro simply looses out to newts and maks. Then again that is sort of how it goes with bigger scopes too. A comparable sized refractor is much more expensive or a smaller one of high quality is more expensive too. So maks and news give you more for your money.

#72 mwedel

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Posted 01 March 2012 - 02:49 AM

Well, I done did the dirty deed. A SkyWatcher 90 Backpacker is on its way to me. ... What are the implications for the weather? :question:


I just had to go and say it, didn't I? The scope came in today. I would be posting a first-light report, but--despite Weather Underground predicting clear skies tonight for the entire previous week--my skies are totally clouded over.

Oh, and my resident hummingbird is still a psychic camera-phobe, so no digiscoping today either. Lots of attempted digiscoping, no actual pictures of birds. :nonono:

In lieu of a first-light report, here are some unboxing photos.

#73 jrbarnett

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Posted 01 March 2012 - 04:18 PM

A most excellent unboxing blog entry. The scope looks great, too. I like the Skywatcher OTA better than the Celestron one, actually, as the Celestron OTA has superfluous extra metal on its front and rear castings (for "style" presumably).

Re: the weather curse, as Sheldon Cooper would say: "Bazinga!"

:grin:

This thread and some of the comments on it has me thinking. Earlier someone put forward the premise that a 90mm MCT would be a better first scope than the traditional long focus achromat. Though a dyed-in-the-woll refractor blueblood, for general use (i.e., no particular specialization; wanting a taste of all the hobby has to offer) I agree with the suggestion.

However, that lead me down another path. Many years ago the "copy scope" was all the rage in DIYer circles. It involved recycling the 80mm optics from a defunct photo copier and building a fast-ish achromat around the optical group. That humble format involved into what became a small refractor revival, where the small refractor - 80mm this time around - became the fashionable recommendation for a first telescope.

Stellarvue, in particular, founded its business on this development (a very savvy move, IMO). The original Stellarvue offerings were 80mm achromats. Typically f/6 but I actually owned an early 80/9D which was an 80mm f/9.4 achromat.

Back in those days Stellarvue's founder, Vic Maris, was conducting annual "Majesty of the Night Sky" seminars in the Sierras, and the scope du jour at those events was the 80mm Stellarvue achromat. Though Stellarvue's offerings have grown and diversified over the intervening years, what Maris said back then about 80mm refractors still resonates today. Specifically Maris reasoned that 80mm was enough of a step up in aperture over the traditional 60mm that brighter DSOs become very interesting and planets share intriguing details not available in the smaller scope. Being an achromat, the 80mm f/6 post-copy-scopes remained relatively affordable for someone deciding whether they are really interested in astronomy. Being fast-ish, it is compact and easy to mount, and capable of wide fields making finding stuff on simple mounts easier. He was right; for most beginners the 80mm f/8 format is a better deal than the long focus 60mm format. But time change. Gone are the inexpensive 80mm achromats, having been replaced with 80mm doublets using some flavor of low dispersion glass. The prices climbed accordingly.

So, enter the 90mm Synta MCT. How does this format stack up to 80mm fast-ish doublets in the contest for beginning beginner attention? Quite well, I think. Here's why.

The C90 and its kin have no chromatic aberration. It is as compact if not more so than an 80mm f/6 or f/7.5 doublet. Though it is obstructed, it is not excessively so with a 31% CO. While it lacks the wide field capabilities of a fast 80mm refractor, it achieves higher magnifications using more comfortable, longer focal length eyepieces without the need for a Barlow. In terms of light grasp and resolving power it exceeds the capabilities of an 80mm refractor on both scores (the effective clear-aperture light grasp of a C90 once you account for transmission losses and obstruction, is 85mm). Most importantly, at under $200, it's cheaper than a refractor.

In conclusion, I'd say the 90mm Synta is a great starter scope, providing sufficient aperture for you to view many examples of each class of celestial object, but not demanding the monetary investment of alternatives. And even if you conclude that astronomy isn't for you, with an amici prism diagonal, you still have a solid little daytime spotting scope.

Regards,

Jim


#74 freelancer

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Posted 02 March 2012 - 11:29 AM

Just got my C90 a couple of days ago. As my first "real" scope, I was blown away by just how far affordable optics have come since I was a boy making cardboard-tube refractors. With the supplied 32mm Plossl, I was surprised get pin-sharp images without any purple fringing or color aberrations..

.. but I want more. Since I live in India and have to get "exotic" hardware transported at some cost, I'd like to get the forum's advice on what improvements would be the best bang/buck on the stock C90. Eyepiece? The 32mm Plossl is OK, and I did get an Orion 2x Barlow.. and while they're good, I can't help feeling the scope can give more than what these can extract.

Mostly for planetary/moon viewing, I think. This scope is perhaps too small for deep sky, and the moon and planets are more likely to get the kids hooked onto the habit.

How about the 11mm 80 degree UO ultrawide (http://www.universit...125inch.html#80)? Or one of the Explore Scientific 82's? (I have a lustful eye on the Ethoses.. some day, some day. But not today. She Who Must Be Obeyed would have a fit)

#75 jrbarnett

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Posted 02 March 2012 - 02:49 PM

Hello, and welcome to CN.

I think you'll really enjoy the C90.

If yours is the same C90 kit as mine, it came with a correct image amici-type prism diagonal. If so, the first thing I would do is obtain a 90-degree 1.25" star diagonal (prism or mirror).

The 32mm Plossl is a fine low power finder eyepiece for the scope. I'd keep and use it. It puts up almost 1.3 degrees of TFOV. To supplement the 32mm Plossl (11x per inch of aperture), you'll probably want two additional eyepieces in the 20x per inch (70x) and 30x per inch (105x) range (on the theory that, no matter what the seeing, these magnifications will always be useful). An ~18mm and a ~12mm eyepiece would fill these slots. The slowish MCT is gentle on eyepieces, so affordable, simple eyepieces like Plossls and Orthoscopics work well. Older generation wide fields, like Erfles or Konigs, that have poor edge performance in fast scopes, perform well in the C90 and don't cost very much compared to modern wide fields corrected for use in fast scopes.

A dew shade is an asset in humid or moist environments or seasons. You can easily make one yourself using black foam or cardboard painted flat black on the interior side or applying black felt or velvet to the inside of the cardboard.

An observing chair makes life more comfortable and convenient, too. Again no reason to pay a lot. For the short tubed C90, the range of placement for the diagonal when the telescope is pointed at different altitudes won't be so great that you need a huge range of seating positions. Instead I recommend making a LYBAR chair:

http://www.stark-lab...ybar/lybar.html

I've used one and it works surprisingly well. You straddle the top board like a bicycle seat in use.

As for deep sky versus the moon and planets, the C90 is actually a decent Messier chaser. Messier made most of his discoveries with a 4" telescope of modest optical quality. The C90 will present the brightest Messiers surprisingly well, and will at least detect the dimmer ones. It's true that the moon and planets are likely to get the children hooked, but there's also the fun of the hunt for DSOs. Make it an adventure. Show them the location of a "treasure" (i.e., Messier object) on a star chart and explain that they are going to help you find it and describe it. You might be surprised by their reaction.

One last item to think about - a solar filter might be interesting given that we've entered a new period of heightened solar activity. Sunspots show a wealth of detail and it is interesting to actually look at the surface of a star. You can make one using Baader solar film or buy one. For a C90 the filter shouldn't cost that much.

Clear skies, and enjoy your C90!

Regards,

Jim






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