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Something for nothing: Celestron C90

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#2226 Jim1804

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Posted 04 October 2018 - 06:56 PM

Wanted to get a quick look at a big, crescent Venus before it dips behind the Sun on Sunday - only problem? It’s very low in the sky and I don’t have a clear view looking west. The C90 to the rescue!

 

Loaded the scope and my zoom EP in the little backpack that came with the scope (pretty nice, but be careful removing it as the lens cap tends to get stuck and pop off as you’re pulling it out - don’t want any zippers near that corrector plate!). Threw my Meade lightweight alt-az tripod under one arm, and off I went. 

 

I hiked the 1 mile to the local ball field, with a nice clear western horizon. Watched the sun set as I got my scope together. Took a few minutes to find it, but I finally spied Venus among the wispy clouds and sunset glow. The seeing was horrible - less than 10degs altitude, and that big crescent was shimmering - but it looked good to me. I don’t think I’ve ever seen Venus this big - 49 arc seconds. Snapped a few iPhone photos, watched the planet descend u til it was lost in the clouds hugging the horizon, packed everything up as was back home less than an hour after I left. 

 

I would never ever have done this with a larger scope - the large, no CA view of Venus made it worth my time. I expect my C90 will mostly become a lunar scope once the summer of planets is over - at least until the next time around - but I have seen so much this summer that I never would have seen without this small, quality, no-nonsense slow telescope!

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#2227 Adun

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Posted 26 October 2018 - 01:08 PM

It seems the C90 is getting ready for holiday sales, since it's price has been ramped up to $215 on amazon ($200 on OPT/HPS).

 

Maybe it's getting ready for a "discount" during holiday sales, or ... tariffs or something.

 

If price doesn't drop to old levels, I'm going to treasure mine more.


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#2228 Steve Cox

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Posted 26 October 2018 - 01:30 PM

Ouch, I only paid $139 for mine last January.


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#2229 Steve C.

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Posted 26 October 2018 - 02:09 PM

It seems the C90 is getting ready for holiday sales, since it's price has been ramped up to $215 on amazon ($200 on OPT/HPS).

 

Maybe it's getting ready for a "discount" during holiday sales, or ... tariffs or something.

 

If price doesn't drop to old levels, I'm going to treasure mine more.

Tariffs kicking in?



#2230 PXR-5

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Posted 26 October 2018 - 07:55 PM

Yes, at $120-150, it was a good buy. Inflation can make one appreciate ones belongings more.

#2231 PXR-5

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Posted 26 October 2018 - 07:57 PM

It seems the C90 is getting ready for holiday sales, since it's price has been ramped up to $215 on amazon ($200 on OPT/HPS).

Maybe it's getting ready for a "discount" during holiday sales, or ... tariffs or something.

If price doesn't drop to old levels, I'm going to treasure mine more.


$189. At B and H

#2232 jeremiah2229

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Posted 26 October 2018 - 11:53 PM

Back when I grabbed the one here it was $149 to the door from B&H. Aptly fits the title of the thread.  :)

 

 

Peace...

 

Oh, check out B&H's odds n ends link or whatever it's called. Sometimes nice things pop up there.



#2233 redbaron12

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Posted 27 October 2018 - 07:22 AM

Also in keeping with this thread title, when I first stumbled on it and read the comments, I started looking for my "bargain" version of the C90.  After a while, I found mine on Ebay for $125 shipped AND it included a Celestron HD Alt/Az manual mount w/tripod for that price!  The only thing missing was the carrying bag.  Truly  befitting the title "Something for Nothing"!

 

Mike


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#2234 Reid W

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Posted 22 November 2018 - 10:20 PM

I've been enjoying my C90 over the past few weeks. 

 

What resurrected my interest was a collimation session that seemed to get things spot on.  It just took a fraction of a turn on one bolt.  

 

I also ran a two inch piece of flocking in the baffle tube.  It's no-where near the full length of the tube, but it has significantly improved the out-of-field brightening.  Earlier this week, I tested the flocking by placing Vega just outside of the field.  I tried in all four directions.  I could not see any brightening.

 

So, I'm having a good time seeing what this optic can do. I have other tubes that can show more,  but like Jim said, this optic is literally something for nothing.  


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#2235 photoracer18

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Posted 23 November 2018 - 06:10 PM

My choice for the 90mm class Mak is still the LOMO Astele 95. While working at Hands On Optics I looked thru a lot of Maks in that size range. I don't remember a single one from Celestron or Meade that was as good as the best LOMO 95, not even the 2 C90 telephotos I had.
They also made 133.5, 150, 180 , and 203mm ones, Rumaks mostly in the F10 range. I personally never saw one above 150mm and that one was fork mounted. I owned one of the 133.5 models and stupidly sold it to an AM friend in CA. We rapidly sold out of the 95 models we had left when some LR shooters found they could resolve 30 caliber holes in the black at 1K yards. I ended up having to search like mad and finally find one for sale on CL at $250 a couple of years later. Had to pay it as they don't come up very often. Still have it to this day. Never found one of the screw on dewshields but did latch onto one of the cute little high quality 5x25 finder scopes. Nice thing about these is the micrometer focuser shaft is on the right so they mount perfectly on a Nexstar single arm mount if you put a Vixen dovetail on the mount bracket. Mine is currently on an old NS5 using the custom Ray's Bracket from that era. Not quite as nice on some of the manual AZ mounts that use the clamp from the other side.

Oh and that Intes MN56 I got off AM for only $350 because the secondary holder was loose in the corrector plate. Did a few of those in my time.

Edited by photoracer18, 23 November 2018 - 06:16 PM.


#2236 Simon B

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Posted 24 November 2018 - 06:02 AM

Moonshot with Orion Starmax 90:

 

 

IMG 8499

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#2237 Jaimo!

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Posted 26 November 2018 - 11:27 PM

Gentlemen, let's try and stay on topic. 

 

Jaimo!



#2238 organge

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Posted 27 November 2018 - 03:54 PM

Guys, I read all of the pages in this topic over the last few days. At first I was thinking of getting SW 72ed as a quick grab and go but now I have C90 in the basket on a few online shops. C90 with my 18mm eyepiece and Baader barlow will give me 18mm ( 69.4x ), 13.8mm ( 90.6x ) and 8mm ( 156.3x ).

 

So what gives?


Edited by organge, 27 November 2018 - 04:02 PM.


#2239 Jaimo!

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Posted 27 November 2018 - 04:20 PM

Guys, I read all of the pages in this topic over the last few days. At first I was thinking of getting SW 72ed as a quick grab and go but now I have C90 in the basket on a few online shops. C90 with my 18mm eyepiece and Baader barlow will give me 18mm ( 69.4x ), 13.8mm ( 90.6x ) and 8mm ( 156.3x ).

 

So what gives?

They are about as different as telescopes can get...  The SW 72ED is an f/5.8 and the C90 is an f/13.8, and both have about the same light gathering capabilities after you subtract the central obstruction.  You will achieve much higher magnifications for a given eyepiece in the longer focal length; along these same lines, the C90 will be a little more forgiving on eyepieces.  

 

In a practical sense, the C90 will have a much more narrow field of view, great for planets, double stars, globs and planetary nebula; while the SW 72ED will excel on wider star clusters, like the Pleiades and the Double Cluster, which the C90 cannot frame the entire structures.  Also at f/5.8 the SW 72ED will be a much better choice for deep sky imaging, while the C90 will do better at planetary imaging, which requires a longer focal length.  Which one is better, depends on what you want to see on a given evening.  Many on this thread have tried to split the difference and add a 0.63x reducer to the C90 which gets you to about f/8.6.  I feel by the time to get all of the bits to make this work is becomes a little "Rube Goldberg-ey"... I have both the C90 and a WO 66SD, f/5.8, and use what ever scope is appropriate for the given evening.  For my Grab and Go observing I use the C90 easily 10:1 over the WO 66SD...

 

Good luck, it is hard to make a mistake given the two scopes,

Jaimo!


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#2240 organge

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Posted 27 November 2018 - 04:53 PM

I went from 102 mid (f6.5) achro to 102 shorter (f4.5) achro to 80 long (f11.4) achro to 80 apo to st80 to 102 mak. The closest to ideal from convenience and image at the eyepiece point of view for me was 102 mak. Cool down time really wasn't an issue. I left it outside on the balcony for an hour and it was all good. Even immediate image was okish after 5-10 minutes - the time it took me to properly align the mount. I also had best EAA sessions with the little mak. Could actually see M57 with it. It bothered me though that there was no way to collimate the scope. I had to send the first one back. I don't want to buy used ( old 102 had collimation screws ) so I am left with either C90 or 127 mak to choose from. I was thinking about 127 for a long time but got cold feet due to all the talk about cool down time since there are times when the weather clears and it needs to be ready in 5 minutes for a 30 minutes session.



#2241 Peter Besenbruch

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Posted 27 November 2018 - 09:57 PM

... It bothered me though that there was no way to collimate the scope. I had to send the first one back. I don't want to buy used ( old 102 had collimation screws ) so I am left with either C90 or 127 mak to choose from. I was thinking about 127 for a long time but got cold feet due to all the talk about cool down time since there are times when the weather clears and it needs to be ready in 5 minutes for a 30 minutes session.

My understanding is that the little Maks have 6 collimation screws. I just checked the images of the Skywatcher version of the 90 and 102mm Maks (as long as you avoid the Virtuoso 90) and the collimation screws are there. On the 4" Nexstar, I can't tell, but you can always go with the Skywatcher and their Orion twins.

 

The 5" Skywatcher Mak is quite a bit heavier than the 4". If you are worried about the size translating into slower cool down, check out the threads on insulating Maks and SCTs.


Edited by Peter Besenbruch, 27 November 2018 - 09:59 PM.

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#2242 Cajundaddy

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Posted 27 November 2018 - 10:06 PM

Guys, I read all of the pages in this topic over the last few days. At first I was thinking of getting SW 72ed as a quick grab and go but now I have C90 in the basket on a few online shops. C90 with my 18mm eyepiece and Baader barlow will give me 18mm ( 69.4x ), 13.8mm ( 90.6x ) and 8mm ( 156.3x ).

 

So what gives?

I agree with Jaimo! that the two scopes are as different as night and day.  For moon and planets in a jacket pocket telescope, the C90 is unrivaled at it's price point.  For wide field Milky Way sweeps, Andromeda, and some terrestrial birding and wildlife, I'll choose my AT72-ED.  Different tools for different uses.  The only realistic solution is to own both so I do.  ;)


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#2243 organge

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Posted 27 November 2018 - 10:45 PM

My understanding is that the little Maks have 6 collimation screws. I just checked the images of the Skywatcher version of the 90 and 102mm Maks (as long as you avoid the Virtuoso 90) and the collimation screws are there. On the 4" Nexstar, I can't tell, but you can always go with the Skywatcher and their Orion twins.

 

The 5" Skywatcher Mak is quite a bit heavier than the 4". If you are worried about the size translating into slower cool down, check out the threads on insulating Maks and SCTs.

New SW 102 maks with green dovetails have no collimation screws at the back.

 

Check this photo : https://nimax-img.de...i-GoTo-WiFi.jpg

 

The old ones can be collimated. Not really sure why they did this with the 'new' version.



#2244 Peter Besenbruch

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Posted 27 November 2018 - 11:31 PM

New SW 102 maks with green dovetails have no collimation screws at the back.

 

Check this photo : https://nimax-img.de...i-GoTo-WiFi.jpg

 

The old ones can be collimated. Not really sure why they did this with the 'new' version.

Bummer if true. Neither B&H, or Agena, have the updated pictures. Highpoint has scopes with the green dovetail, but with collimation screws. Hmmmm.



#2245 skyward_eyes

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Posted 28 November 2018 - 07:51 AM

New SW 102 maks with green dovetails have no collimation screws at the back.

 

Check this photo : https://nimax-img.de...i-GoTo-WiFi.jpg

 

The old ones can be collimated. Not really sure why they did this with the 'new' version.

 

That is not 100% accurate. The 102mm Mak included with the AZGTi kit is not collimatable. The 102mm Mak OTA on its own is. Both scopes have green dovetails as well. 

 

Why was this done? Not exactly sure but the 102mm Mak on the AZGTi is a lighter weight version of the standard 102 OTA. 


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#2246 PXR-5

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Posted 29 November 2018 - 01:30 PM

New SW 102 maks with green dovetails have no collimation screws at the back.

Check this photo : https://nimax-img.de...i-GoTo-WiFi.jpg

The old ones can be collimated. Not really sure why they did this with the 'new' version.


That's not the only difference, I dont see the O ring and the front cell looks different.

#2247 Peter Besenbruch

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Posted 30 November 2018 - 03:51 PM

That's not the only difference, I dont see the O ring and the front cell looks different.

Yes, they had been offering the scope earlier with a Dob like mount, called the Virtuoso. I don't know how much worse the cheapened version is, but I have this gut level desire of wanting the collimation screws. :/


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#2248 Simon B

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Posted 01 December 2018 - 05:08 PM

$157 on Amazon

 

C$240 on Amazon Canada

 

 

just a heads up : )


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#2249 Jim1804

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Posted 08 December 2018 - 12:15 AM

A common theme with me - guerrilla astronomy with the C90. Last night, the Mars-Neptune conjunction was completely clouded out - but tonight there was a small window of opportunity.

 

Clouds were closing in from all sides - no time to set up my bigger scope, and my richer field scopes wouldn’t show Neptune as anything but a point. This is a job for the C90!

 

Tube currents were crazy - no time for cool down with the clouds moving in. Mars was a boiling orange ball, while Neptune was a hard, almost stellar blue dot - not a point, but not quite a disk either in my 25mm Plossl. 

 

And just like thst, the clouds closed in. Yet another thing I never would have seen without this little guy - good thing, because I don’t have a couple of hundred years to spare. 

 

The attached screenshot from SkySafari shows a very similar view to what I saw - the circle represents the field of view. 

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#2250 Jaimo!

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Posted 06 January 2019 - 10:04 PM

While not nearly as impressive as images of the Moon, Sun, Jupiter, Saturn, Venus and Mars; I went out last night and was determined to image Uranus with the C90.  It is 45 stacked images (best 25%), 550 ms exposure, f/13.8, using a ASI224 color CCD.  While not impressive, that little blue dot is, according to SkySafari, 19.6 AU away from the earth or nearly 20 times the distance from the earth to the sun and it still appears as a disk in the little C90.  

 

Uranus_221616_g4_ap4.jpg


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