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Something for nothing: Celestron C90

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#2351 Sarkikos

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Posted 20 April 2019 - 09:15 AM

I seem to recall some old saying about a picture is worth a thousand words...  shrug.gif

 

Bob F.  smile.gif

But that does depend on the picture.

 

:grin:

Mike


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#2352 johnhudson922

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Posted 13 June 2019 - 12:12 PM

Would this scope be a good way to get into Planetary astrophotography? I have a Canon 6d, not great for this, but can use BYEOS to run it all. I like the focal length...



#2353 Jaimo!

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Posted 13 June 2019 - 08:51 PM

Would this scope be a good way to get into Planetary astrophotography? I have a Canon 6d, not great for this, but can use BYEOS to run it all. I like the focal length...

While it it possible to do planetary imaging with the C90 (see LINK) the limiting factor with the C90 is aperture.  If you have a mount and you have the camera...  I'd recommend stepping up to a 127mm Synta Mak (Celestron, Orion, SkyWatcher) they can easily be found in the classifieds for ~$200.  I do enjoy imaging with the C90 because of the challenge, just like the name of this thread, I like to try and show that imaging can be done inexpensively.  Also, you might want to look into a dedicated planetary camera, the ZWO cameras seem to be leading the pack...  and the 120mc can be had for $150.  Go to the Solar System Imaging and Processing forum and look around, it is a wealth of information.  This video is informative, and his series on planetary imaging is very good.  But if you have any specific question about the C90 this is the place, do not hesitate to ask.

 

Clear Skies,

Jaimo!


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#2354 Messierthanwhat

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Posted 11 July 2019 - 09:10 AM

At 1250mm, the C90 Mak is also a bit short for good planetary imaging. I've tried mine on Jupiter a couple of times recently, using my Canon T2i in 640x480 "movie crop mode" (See Jerry Lodriguiss's article here). In that mode, the planet covers roughly 70x70 pixels. Using AutoStakkert2! and GIMP's "wavelet-decompose" sharpening, the best image I've managed to produce (attached) is not very exciting.

 

MVI_9686_pipp_pipp.jpg

I also tried the wavelet sharpening function of Registax 2, but it seemed to add more artifacts than the GIMP filter. Since that effort, I took some time to do very careful collimation, and notice huge improvement in image quality from just the tiniest nudges of the screws. But my schedule and the Arizona monsoon skies have not cooperated to give me a chance to try again. 

 

According to Jerry's article, the 6D also has a 1:1 live view mode that would, as I understand it, produce an image of the planet the same size, but just in a wider field of view. But it would require capturing the live view with a computer, rather than on the card. 


Edited by Messierthanwhat, 11 July 2019 - 09:14 AM.

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#2355 Adun

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Posted 12 July 2019 - 09:58 PM

At 1250mm, the C90 Mak is also a bit short for good planetary imaging. I've tried mine on Jupiter a couple of times recently, using my Canon T2i in 640x480 "movie crop mode" (See Jerry Lodriguiss's article here). In that mode, the planet covers roughly 70x70 pixels. Using AutoStakkert2! and GIMP's "wavelet-decompose" sharpening, the best image I've managed to produce (attached) is not very exciting.
 
attachicon.gif MVI_9686_pipp_pipp.jpg
I also tried the wavelet sharpening function of Registax 2, but it seemed to add more artifacts than the GIMP filter. Since that effort, I took some time to do very careful collimation, and notice huge improvement in image quality from just the tiniest nudges of the screws. But my schedule and the Arizona monsoon skies have not cooperated to give me a chance to try again. 
 
According to Jerry's article, the 6D also has a 1:1 live view mode that would, as I understand it, produce an image of the planet the same size, but just in a wider field of view. But it would require capturing the live view with a computer, rather than on the card.

 
 
From my post #8754628 on page 88 of this thread taken with a C90 and RT224 camera, and inexpensive SVBony 2x Barlow:
 
Jupiter image with C90 and IMX224

 

Saturn image with C90 and IMX224

 

Mars image with C90 and IMX224

 
Your Canon T2i has 4.3um pixels, which according to calculators (meant to help people match FLs/barlows/cameras), produces 0.71 arcsecs per pixel at 1250mm, which indeed is not great for planetary imaging, but it's not the fault of the 1250mm FL of the C90. 

 

One has to balance the pixel size, FL, aperture/resolution, and atmospheric seeing. Most people use barlows for planetary imaging, and choose carefully (between 1.5x, 2x, 2.5x, etc) to achieve this balance.

 

It's hard to find a 90mm telescope with longer FL than the C90, so I'd argue that in the 90mm class, the C90 is likely one of the better options for planetary imaging.

 

Did you use a bathinov mask? How did you achieve the best possible focus? 

How many (filtered, good) frames are stacked in your image? I got a real jump in quality when I went from dozens of frames to ~2000 (but be careful and keep videos shorter than the limit imposed by the planet's own rotation, and the az-mount field rotation).


Edited by Adun, 12 July 2019 - 10:02 PM.

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#2356 Orion68

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Posted 12 July 2019 - 10:24 PM

I had an orange c90 and was glad to re-sell it.
G

I had the same experience. Mine was way out of collimation so the images were pretty bad. Could not see any way to collimate it myself so I sold it to someone who insisted he could fix the collimation. Don't know if he succeeded or not.



#2357 Messierthanwhat

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Posted 18 July 2019 - 12:43 AM

 
 
From my post #8754628 on page 88 of this thread taken with a C90 and RT224 camera, and inexpensive SVBony 2x Barlow:
 

 

 

 

 
Your Canon T2i has 4.3um pixels, which according to calculators (meant to help people match FLs/barlows/cameras), produces 0.71 arcsecs per pixel at 1250mm, which indeed is not great for planetary imaging, but it's not the fault of the 1250mm FL of the C90. 

 

One has to balance the pixel size, FL, aperture/resolution, and atmospheric seeing. Most people use barlows for planetary imaging, and choose carefully (between 1.5x, 2x, 2.5x, etc) to achieve this balance.

 

It's hard to find a 90mm telescope with longer FL than the C90, so I'd argue that in the 90mm class, the C90 is likely one of the better options for planetary imaging.

 

Did you use a bathinov mask? How did you achieve the best possible focus? 

How many (filtered, good) frames are stacked in your image? I got a real jump in quality when I went from dozens of frames to ~2000 (but be careful and keep videos shorter than the limit imposed by the planet's own rotation, and the az-mount field rotation).

Thanks for the input. I guess blaming the C90's FL is a matter perspective, and it makes just as much sense to blame the camera. Since both are what I have, and I don't yet find planetary exciting enough to justify additional expenditure, I should probably just blame myself.

 

I did use a Bahtinov mask to focus on Antares, then slewed over to Jupiter. And the stack was of 40% of a little over 2600 frames. I have three different 2X Barlows, but when I tried imaging with any of them in place, the image seemed to degrade badly. That is, without a Barlow, my live view in movie crop mode looked much like the final result posted. With any of the Barlows in place, it really just looked like a muddy mess.

 

I am looking forward to another try since I was able to visibly improve collimation with very little effort. I got some really sharp lunar closeups the night I did the collimation, but just haven't been able to find time for another stab at Jupiter.



#2358 Adun

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Posted 18 July 2019 - 09:53 PM

Thanks for the input. I guess blaming the C90's FL is a matter perspective, and it makes just as much sense to blame the camera. Since both are what I have, and I don't yet find planetary exciting enough to justify additional expenditure, I should probably just blame myself.

 

I did use a Bahtinov mask to focus on Antares, then slewed over to Jupiter. And the stack was of 40% of a little over 2600 frames. I have three different 2X Barlows, but when I tried imaging with any of them in place, the image seemed to degrade badly. That is, without a Barlow, my live view in movie crop mode looked much like the final result posted. With any of the Barlows in place, it really just looked like a muddy mess.

 

I am looking forward to another try since I was able to visibly improve collimation with very little effort. I got some really sharp lunar closeups the night I did the collimation, but just haven't been able to find time for another stab at Jupiter.

 

For planetary imaging, I definitely need a 2x Barlow with the C90, and my camera has even smaller pixels than yours, so I'd say you need to find a way to use the Barlow.

 

It sounds like you added the Barlow after having already focused with the bathinov on Antares. If that was the case, you must focus with the Barlow on.



#2359 Jim1804

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Posted 20 July 2019 - 06:10 PM

Just for fun, an iPhone pic I took on the eve of the 50th Anniversary - C90 with Meade Zoom EP, around 1am EDT. 

 

I played with contrast and exposure on the iPhone - I set contrast really high because it looks cool smile.gif. I reversed the image to match naked-eye orientation, and marked the Apollo 11 landing site with an X.  I’m posting the original image too (original orientation) - the partially lit Mare Crisium made it look like the Deathstar - that’s no moon!

 

As before, with clouds moving in and lightning in the distance, guerrilla Astronomy gets no better than the C90!

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#2360 Starman81

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Posted 23 July 2019 - 03:08 PM

I do miss my C90 that I mentioned in this thread picking up back in 2015... One night I had it out with the 13 Ethos, so about 100x or so and I saw something very strange when I pointed it at the stars. This weird circular pattern with a ring around, eerily not moving at all, on all the stars.

 

I thought-- surely, there must be something wrong with this scope?? What I didn't realize is that I had near-perfect/perfect seeing that night and those were Airy disks and diffraction rings! So I'm thinking it had some really good optics maybe (?)


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#2361 Sarkikos

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Posted 23 July 2019 - 07:14 PM

I had a C90 years ago.  I sold it.  Within a year or so, I ended up buying another one.

 

Mike


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#2362 BillShakes

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Posted 25 July 2019 - 05:45 AM

Before the anniversary, when the moon was about first quarter, I tried to spot Tranquility Base with the C90.  Not the landing site, but rather the three honorific craters, Armstrong, Aldrin and Collins.  I had a still night and a good sun angle and convinced myself I could see Armstrong, but not Aldrin or Collins.  Armstrong is 4.6km across according to Rukl.  Could definitely see Molke (6.5km).  About 100X.  Was I kidding myself?  


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#2363 azure1961p

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Posted 25 July 2019 - 03:17 PM

No you weren't kidding yourself.  

 

Pete


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#2364 andycknight

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Posted 26 July 2019 - 08:37 AM

[snip...] I could see Armstrong, but not Aldrin or Collins.  Armstrong is 4.6km across according to Rukl.  Could definitely see Molke (6.5km).  About 100X.  Was I kidding myself?

 

It seems perfectly reasonable to me. The furthest I've pushed my little C90 was on small craterlets on Plato's floor. Using a 9mm eyepiece (140x) I spotted A and B (2.7 Km & 2.4 Km) as small faintly brighter spots. I even "hinted" at the C&D pair (suspected sighting but not confirmed).

 

I've never tried to spot Armstrong, Aldrin and Collins in the C90... Considering its 50 years since Apollo 11, I really should have go at these 3 ! If the weather co-operates - I'll give it a go. 

 

Regards

 

Andy.


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#2365 Binojunky

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Posted 27 July 2019 - 10:25 AM

I had a C90 years ago.  I sold it.  Within a year or so, I ended up buying another one.

 

Mike

Been there, done that, on my third now, due to the never ending LP I concentrate on the moon and planets, the C90 does everything I want it to do, not letting this one go,love.gif D.


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#2366 organge

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Posted 27 July 2019 - 10:56 AM

Been there, done that, on my third now, due to the never ending LP I concentrate on the moon and planets, the C90 does everything I want it to do, not letting this one go,love.gif D.

This is what my visual observing is reduced to as well. I add some double stars in the mix though.


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#2367 Sarkikos

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Posted 27 July 2019 - 10:58 AM

Double stars are decent under light pollution.  Though it's easier to star hop to them if the Moon isn't in the sky.

 

Mike


Edited by Sarkikos, 27 July 2019 - 10:59 AM.

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#2368 azure1961p

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Posted 07 August 2019 - 09:02 AM

[snip...] I could see Armstrong, but not Aldrin or Collins.  Armstrong is 4.6km across according to Rukl.  Could definitely see Molke (6.5km).  About 100X.  Was I kidding myself?

 

It seems perfectly reasonable to me. The furthest I've pushed my little C90 was on small craterlets on Plato's floor. Using a 9mm eyepiece (140x) I spotted A and B (2.7 Km & 2.4 Km) as small faintly brighter spots. I even "hinted" at the C&D pair (suspected sighting but not confirmed).

 

I've never tried to spot Armstrong, Aldrin and Collins in the C90... Considering its 50 years since Apollo 11, I really should have go at these 3 ! If the weather co-operates - I'll give it a go. 

 

Regards

 

Andy.

 

 

Nor I.  Knowing how tough they are in the 8 I've been dissuaded.  A very good map to know EXACTLY where to look could be the deal maker.  That casual looking around in a bigger scope works but here position is everything.

 

Oh BTW, saw the coolest double in Scorpius the other week: 

 

Xi Scorpi, multiple star system

 

Xi Scorpi C component at 7.5" clean but dim at 41x. Western of C slightly brighter by maybe .25 magnitude .    Fainter companion from alpha Xi Sco, dim like mag 8 seconds from primary. Primary pale cream with 6mm , slight elongation in discs and primary ring gave away the duplicity.  This was a toughy but with time and patience and 208x it worked out. Too quick a look and lower power and you'll miss it.

 

One of the best multiple systems out there. Surprised I missed it all these years.

 

Pete


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#2369 andycknight

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Posted 07 August 2019 - 03:19 PM

[snip...] A very good map to know EXACTLY where to look could be the deal maker.  That casual looking around in a bigger scope works but here position is everything.

 

Agreed... Normally when pushing to the limits on the Moon, I prepare an image or two to match the (diagonal reversed) view in a low and high power eyepiece. Then it's down to a lot of patience (and luck) for those brief moments of perfect seeing.

 

(Plus many other variables like magnification and different angles (and direction) of illumination.)

 

I had a look tonight (the first opportunity I've had frown.gif), but the wind was blowing hard and the seeing was terrible. Started off at Theophilus and then quickly spotted the Ritter/Sabine pair. Quite easy to find since Ritter has two smaller craters above and one below and is therefore stands out quite well. 

 

Ritter/Sabine point towards Moltke - an easy catch in the C90, but even this (relatively) large crater was fading in and out of visibility. During better moments of seeing I did catch a few glimpses of Aldrin, but Armstrong and Collins was out of reach tonight. (I'm puzzled here - I thought if I could glimpse Aldrin then Armstrong should have been possible...perhaps easier... Maybe just bad luck due to the poor seeing??) The Moon was now getting lower and passing over house roofs, so best to try again on a better night..

 

I fear tomorrow (weather forecast is again poor) the illumination angle will be getting too high - But you never know, because I just need some contrast between the surrounding area and [say] a brighter rim or floor. Craters that are too small to be resolved can be glimpsed this way. Odd angles of illumination sometimes creates a faintly brighter spot.

 

I used the finder image/chart: https://www.flickr.c...02/17044835299/ from a S&T article: https://www.skyandte...-landing-sites/ I performed a top/bottom flip to match my star diagonal view.

 

Regards

 

Andy.


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#2370 azure1961p

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Posted 14 August 2019 - 10:54 AM

Double stars are decent under light pollution.  Though it's easier to star hop to them if the Moon isn't in the sky.

 

Mike

Isn't that the truth.  Here's where a GOTO Mount really comes into its own.  Infact under a bright moon from a city sky to boot, it's just about necessary.  

 

Got a great Izars and Pi Booti last week but even on Xi... that's when the nearby gibbous moon makes even that a bit of work. I will say though, even under a darker sky the number of bright-enough doubles for this aperture is so starkly less than medium aperture.  Have too look harder for good-enough bright-enough pairs when around 1.0".

 

Oh, here's my Izar.

 

Pete

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#2371 pdxmoon

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Posted 18 August 2019 - 09:08 PM

My Mighty Mak Grab and Go....

How did you mount it from the side? I thought the dove was on the bottom?  Did you move the finder?



#2372 Jim1804

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Posted 18 August 2019 - 10:12 PM

How did you mount it from the side? I thought the dove was on the bottom?  Did you move the finder?

I have the same setup - C90 on a Twilight 1 mount. The dovetail on the scope is on the bottom - but the Twilight mounts from the side - you just put the scope in sideways, tighten it down, and rotate the diagonal. The arm for the mount needs to be on the left (it's moveable) if you want to use the finder - otherwise it'll be on the bottom of the scope - not very useful. 

 

Telescopes with diagonals on mounts are like celestial objects in the Universe - there is no true top or bottom - it all depends on your reference point :-).


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#2373 BFaucett

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Posted 19 August 2019 - 12:18 AM

I have the same setup - C90 on a Twilight 1 mount. The dovetail on the scope is on the bottom - but the Twilight mounts from the side - you just put the scope in sideways, tighten it down, and rotate the diagonal. The arm for the mount needs to be on the left (it's moveable) if you want to use the finder - otherwise it'll be on the bottom of the scope - not very useful. 

 

I just mount the scope and not worry about the position of the finder.  It may be in an unconventional position but it works fine for me.  The finder doesn't hit the mount.  YMMV.

 

Cheers!  Bob F.  smile.gif

 

 

gallery_230527_10968_825661.jpg

 

 

gallery_230527_10968_577423.jpg


Edited by BFaucett, 19 August 2019 - 12:21 AM.

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#2374 Sarkikos

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Posted 19 August 2019 - 09:20 AM

The C90 is short and light enough that you can mount it easily on a photo tripod.  The best for this purpose is one with built-in "counterbalance," i.e. a spring that can be engaged.  My 501HD is an excellent mount for the C90.

 

Mike


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#2375 Steve Cox

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Posted 19 August 2019 - 06:19 PM

The C90 is short and light enough that you can mount it easily on a photo tripod.  The best for this purpose is one with built-in "counterbalance," i.e. a spring that can be engaged.  My 501HD is an excellent mount for the C90.

 

Mike

That's almost exactly how I run mine, but on a 500AH head, which it timeshares with my 20x80 bino.  Excellent all-around setup for a C90, lightweight, portable, and flexible use between astronomy and a spotter.


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