Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

C5 SCT as a travel/grab n' go scope?

Visual SCT Reflector Catadioptric Cassegrain
  • Please log in to reply
136 replies to this topic

#26 RCLARK28

RCLARK28

    Messenger

  • -----
  • Posts: 400
  • Joined: 19 Feb 2023
  • Loc: Columbus, Ohio

Posted 04 October 2023 - 10:31 AM

I would probably still use a tripod only because I don't want to have to worry that much about what to set the scope on. I don't really see personally how that is any kind of convenient but maybe I'm wrong since I have never tried a tabletop scope of any kind

That setup he is using is amazing. Good for GnG and traveling. I love our tripods too, but some sessions call for different hardware. Fun to just get out and use your equipment. The key is to just get out and view with the hardware you have.

Good luck and clear skies to you.


  • Echolight and Rayje1997 like this

#27 Bob Campbell

Bob Campbell

    Aurora

  • ****-
  • Posts: 4,676
  • Joined: 17 Sep 2004
  • Loc: Scottsdale, AZ

Posted 04 October 2023 - 10:51 AM

This is what I love about my AZGTi. I don't have to do anything with it, except get it reasonably level. I don't even have to polar align it (though I typically do a quick "eyeball it", rough alignment). I turn it on, manually slew my scope to an object I want to view, and tell my mount to track it, especially if it's like a planet at high power with my 90mm Mak.

 

It would easily handle a C5. It handled my deforked ETX125 with a Wegat back, rings and accessories that weighed in at 12.4 lbs. I'm actually thinking about getting a C5. I've owned a C6 and the C5 looks just about right for me. 

 

Otherwise, if I'm just out with my AT72EDII and a 40mm WA EP star gazing, I don't even turn my mount on. Manual control, Point and Track, or full GoTo. It's a super small, lightweight do-it-all mount.

 

Now if I could just get it to brew a pot of coffee for me...

mount-1.jpg

 

I also put the mount on a very lightweight surveyor's tripod, but I often put it on my deck pier. 

 

ETX90-new-finder2.jpg

If you get a good one, the az-gti is outstanding for the price. I love mine, and so far so good.

 

Bob


  • MarkMittlesteadt, Dpasqa, Rayje1997 and 1 other like this

#28 Nicole Sharp

Nicole Sharp

    Soyuz

  • *****
  • Posts: 3,651
  • Joined: 12 Jun 2018
  • Loc: Cumberland, Maryland, USA

Posted 04 October 2023 - 11:59 AM

You have a fair point if I was really looking for an upgrade, but what I'm really looking for is a more portable scope and the C5 was attractive there due to its diminutive size. I 100% agree that if I was looking specifically for a planetary viewer I would go after one of the many 127mm maks

Personally I would rather have a 1250/90 MCT than a 1250/127 SCT but I am biased against SCTs.  Any small Mak is an excellent travel 'scope.

 

A 1000/90 MCT will be a good replacement for a 900/90 achromatic refractor.  Much smaller and lightweight and it removes the chromatic aberration.


Edited by Nicole Sharp, 04 October 2023 - 12:00 PM.

  • Rayje1997 likes this

#29 Rayje1997

Rayje1997

    Viking 1

  • -----
  • topic starter
  • Posts: 555
  • Joined: 07 Jan 2022
  • Loc: Chilhowie, VA, USA

Posted 04 October 2023 - 12:11 PM

Personally I would rather have a 1250/90 MCT than a 1250/127 SCT but I am biased against SCTs.  Any small Mak is an excellent travel 'scope.

 

A 1000/90 MCT will be a good replacement for a 900/90 achromatic refractor.  Much smaller and lightweight and it removes the chromatic aberration.

I feel like to replace my 90mm refractor I would want something more like a 100mm scope to accommodate the central obstruction but that's not a bad suggestion.



#30 MarkMittlesteadt

MarkMittlesteadt

    Fly Me to the Moon

  • *****
  • Posts: 5,548
  • Joined: 08 Oct 2013
  • Loc: Weston, WI. USA

Posted 05 October 2023 - 09:02 AM

As far as portability, I own both an AT72EDII apo and it is really small and light, and also a deforked ETX90, a 90mm Mak. The AT72EDII at f6 (420mm fl) gives me nice wide field views with my 40mm WA EP, but the 90mm Mak (f13.8 (1250mm fl) gives me very sharp detail at much higher power. It's actually smaller than my AT72EDII.

 

ETX90-AT72EDII.jpg


  • Rayje1997 likes this

#31 Rayje1997

Rayje1997

    Viking 1

  • -----
  • topic starter
  • Posts: 555
  • Joined: 07 Jan 2022
  • Loc: Chilhowie, VA, USA

Posted 05 October 2023 - 10:01 AM

As far as portability, I own both an AT72EDII apo and it is really small and light, and also a deforked ETX90, a 90mm Mak. The AT72EDII at f6 (420mm fl) gives me nice wide field views with my 40mm WA EP, but the 90mm Mak (f13.8 (1250mm fl) gives me very sharp detail at much higher power. It's actually smaller than my AT72EDII.

 

ETX90-AT72EDII.jpg

Nice, what do you find that 90mm Mak to be good at? 


  • MarkMittlesteadt likes this

#32 MarkMittlesteadt

MarkMittlesteadt

    Fly Me to the Moon

  • *****
  • Posts: 5,548
  • Joined: 08 Oct 2013
  • Loc: Weston, WI. USA

Posted 05 October 2023 - 10:27 AM

Nice, what do you find that 90mm Mak to be good at? 

The Moon and Planets is all I use it for. Narrow FOV but takes much higher power than any good to great night of seeing could ever allow. At 1250mm focal length with my 2X Barlow and Baader 8-24mm zoom, I can get as high as 312X. The seeing is never that good, but the scope and EP can go that high. 

 

The other night the seeing would allow for maybe 150X at rare moments. I could see only two distinct cloud bands on Jupiter, but also some subtle coloration differences on the planet. All four of the largest moons were easily seen and one was super tight to the edge of the planet and I watched its occultation with Jupiter. No small feat with Jupiter being so bright. 

 

The craters and ridges along the Moon's terminator were stunningly crisp and detailed. Again despite the questionable seeing conditions.

 

Planets would be brighter and larger in a C5, but the 90mm is so small that it makes a great grab'n'go, that would even fit in a small camera backpack. It's only 12" long (with the diagonal internally built in). When I use it, I only go out with the 90mm Mak, my 2X Barlow and 8-24mm Zoom.

 

Putting it on my 6 lb. AZGTi and using a nice lightweight tripod makes for a very small and light grab'n'go set up. The scope, EP's, finders and mount combined only weighs a total of about 10 lbs. max. A small back pack could easily carry the ETX90, EP's, Finders and AZGTi mount, leaving only a small tripod to carry.


Edited by MarkMittlesteadt, 05 October 2023 - 10:38 AM.

  • Bob Campbell and Rayje1997 like this

#33 Rayje1997

Rayje1997

    Viking 1

  • -----
  • topic starter
  • Posts: 555
  • Joined: 07 Jan 2022
  • Loc: Chilhowie, VA, USA

Posted 05 October 2023 - 11:03 AM

The Moon and Planets is all I use it for. Narrow FOV but takes much higher power than any good to great night of seeing could ever allow. At 1250mm focal length with my 2X Barlow and Baader 8-24mm zoom, I can get as high as 312X. The seeing is never that good, but the scope and EP can go that high. 

 

The other night the seeing would allow for maybe 150X at rare moments. I could see only two distinct cloud bands on Jupiter, but also some subtle coloration differences on the planet. All four of the largest moons were easily seen and one was super tight to the edge of the planet and I watched its occultation with Jupiter. No small feat with Jupiter being so bright. 

 

The craters and ridges along the Moon's terminator were stunningly crisp and detailed. Again despite the questionable seeing conditions.

 

Planets would be brighter and larger in a C5, but the 90mm is so small that it makes a great grab'n'go, that would even fit in a small camera backpack. It's only 12" long (with the diagonal internally built in). When I use it, I only go out with the 90mm Mak, my 2X Barlow and 8-24mm Zoom.

 

Putting it on my 6 lb. AZGTi and using a nice lightweight tripod makes for a very small and light grab'n'go set up. The scope, EP's, finders and mount combined only weighs a total of about 10 lbs. max. A small back pack could easily carry the ETX90, EP's, Finders and AZGTi mount, leaving only a small tripod to carry.

That sounds like a really solid grab n go setup, I like it lol. I do like to do some DSO observing is one reason I was leaning towards something with between 4-5 inches of aperture since that would make viewing at least bright DSOs a little easier. Though, I suppose I would just stick with yee olden Orion ST80 if DSOs are what I'm after with such a setup


  • MarkMittlesteadt likes this

#34 MarkMittlesteadt

MarkMittlesteadt

    Fly Me to the Moon

  • *****
  • Posts: 5,548
  • Joined: 08 Oct 2013
  • Loc: Weston, WI. USA

Posted 05 October 2023 - 11:19 AM

That sounds like a really solid grab n go setup, I like it lol. I do like to do some DSO observing is one reason I was leaning towards something with between 4-5 inches of aperture since that would make viewing at least bright DSOs a little easier. Though, I suppose I would just stick with yee olden Orion ST80 if DSOs are what I'm after with such a setup

I've had a 125mm Mak and while it is about as large as the C5 it was just more than I wanted size-wise, but the C5 sure would do better on DSO's than the Mak (especially if you use a focal reducer, widening the FOV, but keeping the 5" aperture). Maks don't do well with reducers. That's partially why an SCT is so versatile. 

 

And almost nothing is going to do wide field like the ST80. That's what it excels at, even though it's aperture limited. 


Edited by MarkMittlesteadt, 05 October 2023 - 11:20 AM.

  • Rayje1997 likes this

#35 Rayje1997

Rayje1997

    Viking 1

  • -----
  • topic starter
  • Posts: 555
  • Joined: 07 Jan 2022
  • Loc: Chilhowie, VA, USA

Posted 05 October 2023 - 11:33 AM

I've had a 125mm Mak and while it is about as large as the C5 it was just more than I wanted size-wise, but the C5 sure would do better on DSO's than the Mak (especially if you use a focal reducer, widening the FOV, but keeping the 5" aperture). Maks don't do well with reducers. That's partially why an SCT is so versatile. 

 

And almost nothing is going to do wide field like the ST80. That's what it excels at, even though it's aperture limited. 

I agree with the statement of the ST80 and wide field viewing. I hadn't really considered using a focal reducer with the C5 but that's a good idea since I guess what I'm looking for here is a jack of all trades scope so that I don't have to carry more than one scope when travelling. I thought about a Mak of the same size, but ended that train of thought for the same reasons you mentioned 


  • Bob Campbell and MarkMittlesteadt like this

#36 MarkMittlesteadt

MarkMittlesteadt

    Fly Me to the Moon

  • *****
  • Posts: 5,548
  • Joined: 08 Oct 2013
  • Loc: Weston, WI. USA

Posted 05 October 2023 - 11:38 AM

I agree with the statement of the ST80 and wide field viewing. I hadn't really considered using a focal reducer with the C5 but that's a good idea since I guess what I'm looking for here is a jack of all trades scope so that I don't have to carry more than one scope when travelling. I thought about a Mak of the same size, but ended that train of thought for the same reasons you mentioned 

While I don't own a C5 (yet?) it really seems to be the sweet spot for SCT's (or Maks) while still being more versatile and small.


  • Bob Campbell, Bill Barlow, Midnight Dan and 2 others like this

#37 Doug Culbertson

Doug Culbertson

    Voyager 1

  • *****
  • Posts: 11,765
  • Joined: 06 Jan 2005
  • Loc: N. Florida

Posted 05 October 2023 - 12:12 PM

If choosing between the C5 and a SkyWatcher 127mm Mak, keep in mind that the Mak has been widely reported on CN to actually only have 119mm aperture. In these small sizes millimeters matter.
  • Rayje1997 likes this

#38 Nicole Sharp

Nicole Sharp

    Soyuz

  • *****
  • Posts: 3,651
  • Joined: 12 Jun 2018
  • Loc: Cumberland, Maryland, USA

Posted 05 October 2023 - 12:27 PM

If choosing between the C5 and a SkyWatcher 127mm Mak, keep in mind that the Mak has been widely reported on CN to actually only have 119mm aperture. In these small sizes millimeters matter.

This is misleading.

 

The total aperture diameter of the Synta MC127 is 127 mm whereas the total aperture diameter of the Celestron C5 is also 127 mm.

 

The difference is in the central obstruction.  The MC127 has a central obstruction diameter of 39 mm whereas the C5 has a central obstruction diameter of 52 mm.

 

The clear aperture diameter (t-stop effective aperture diameter) for the MC127 is 121 mm whereas the clear aperture diameter of the C5 is only 116 mm.

 

So the MC127 has an additional 5 mm of clear aperture diameter as compared to the C5 due to the smaller central obstruction.

 

The contrast-adjusted aperture diameter for the MC127 is 88 mm whereas the contrast-adjusted aperture diameter of the C5 is only 75 mm.

 

So the MC127 has an additional 13 mm of contrast-adjusted aperture diameter as compared to the C5.

 

The relative central obstruction diameter of the MC127 is 31% whereas the relative central obstruction diameter of the C5 is 41%.  What this means is that the MC127 will have 1.3 times better contrast than the C5.  This is particularly important for planetary, Lunar, and Solar viewing.

 

The t-stop of the MC127 is about t/13 whereas the t-stop of the C5 is about t/11.  The f-stop of the MC127 is about f/12 and the f-stop of the C5 is about f/10.

 

Overall, the MC127 is a much better optical system than the C5.  It has a smaller central obstruction, a larger aperture, better contrast, and lets in more light.  There is also the fact that the C5 suffers from comatic aberration whereas the MC127 is coma-corrected.

 

The only advantages of the C5 are its smaller size and weight, the slightly faster t-stop/f-stop, and it is easier to use focal reducers with.

 

The advantage in t-stop is minimal: exposures are approximately the same between the MC127 and the C5 (only a 1.4X increase in exposure time is needed).  Between needing 1.4X longer exposure times versus not having coma correction and a 1.3X loss in contrast, it is better to have the coma-corrected optics with the improved contrast, especially for Terrestrial, Lunar, and Solar viewing.  Coma correction is less important for planets or "faint fuzzies".

 

For Solar System observing, the MC127 is the better choice.  However, if you are primarily looking for DSOs, then the C5 can be the better choice, especially when combined with a reducer-corrector.


Edited by Nicole Sharp, 05 October 2023 - 12:44 PM.

  • Bob Campbell, MarkMittlesteadt and Rayje1997 like this

#39 Rayje1997

Rayje1997

    Viking 1

  • -----
  • topic starter
  • Posts: 555
  • Joined: 07 Jan 2022
  • Loc: Chilhowie, VA, USA

Posted 05 October 2023 - 12:50 PM

This is misleading.

 

The total aperture diameter of the Synta MC127 is 127 mm whereas the total aperture diameter of the Celestron C5 is also 127 mm.

 

The difference is in the central obstruction.  The MC127 has a central obstruction diameter of 39 mm whereas the C5 has a central obstruction diameter of 52 mm.

 

The clear aperture diameter (t-stop effective aperture diameter) for the MC127 is 121 mm whereas the clear aperture diameter of the C5 is only 116 mm.

 

So the MC127 has an additional 5 mm of clear aperture diameter as compared to the C5 due to the smaller central obstruction.

 

The contrast-adjusted aperture diameter for the MC127 is 88 mm whereas the contrast-adjusted aperture diameter of the C5 is only 75 mm.

 

So the MC127 has an additional 13 mm of contrast-adjusted aperture diameter as compared to the C5.

 

The relative central obstruction diameter of the MC127 is 31% whereas the relative central obstruction diameter of the C5 is 41%.  What this means is that the MC127 will have 1.3 times better contrast than the C5.  This is particularly important for planetary, Lunar, and Solar viewing.

 

The t-stop of the MC127 is about t/13 whereas the t-stop of the C5 is about t/11.  The f-stop of the MC127 is about f/12 and the f-stop of the C5 is about f/10.

 

Overall, the MC127 is a much better optical system than the C5.  It has a smaller central obstruction, a larger aperture, better contrast, and lets in more light.  There is also the fact that the C5 suffers from comatic aberration whereas the MC127 is coma-corrected.

 

The only advantages of the C5 are its smaller size and weight, the slightly faster t-stop/f-stop, and it is easier to use focal reducers with.

 

The advantage in t-stop is minimal: exposures are approximately the same between the MC127 and the C5 (only a 1.4X increase in exposure time is needed).  Between needing 1.4X longer exposure times versus not having coma correction and a 1.3X loss in contrast, it is better to have the coma-corrected optics with the improved contrast, especially for Terrestrial, Lunar, and Solar viewing.  Coma correction is less important for planets or "faint fuzzies".

 

For Solar System observing, the MC127 is the better choice.  However, if you are primarily looking for DSOs, then the C5 can be the better choice, especially when combined with a reducer-corrector.

All good information, for me I think the C5 is going to be a better choice when combined with a focal reducer since I am interested in both planetary and DSO viewing. I recognize that no one scope can be good at everything, but I do have other scopes that are good at certain things if I am at home. I am willing to sacrifice some performance in certain areas to have a scope that is "okay" at several things


  • MarkMittlesteadt likes this

#40 Doug Culbertson

Doug Culbertson

    Voyager 1

  • *****
  • Posts: 11,765
  • Joined: 06 Jan 2005
  • Loc: N. Florida

Posted 05 October 2023 - 12:56 PM

Here’s a pretty good discussion of the smaller aperture in the Mak: https://www.cloudyni...atcher-127-mak/

FWIW, I agree that the Maksutov is a better design than the SCT, particularly for the much flatter field, but your examples of where the SCT is better; i.e. weight, faster focal ratio and ability to use reducers are hard to ignore depending on the intended purpose of the telescope.

FWIW, I am considering a 180mm Mak, but I’m also considering a C5.
  • Bob Campbell, Echolight and Rayje1997 like this

#41 Bill Barlow

Bill Barlow

    Fly Me to the Moon

  • *****
  • Posts: 6,311
  • Joined: 03 Dec 2007
  • Loc: Overland Park KS

Posted 05 October 2023 - 04:14 PM

Given the SW 127 Man has a true aperture around 119mm and a CO around 40%, the C5 has more clear aperture with 127mm and a CO of 37%.  Plus it weighs 2 pounds less.  I like mine a lot..very sharp.

 

Bill


  • Bob Campbell, Doug Culbertson, Echolight and 1 other like this

#42 Midnight Dan

Midnight Dan

    James Webb Space Telescope

  • *****
  • Posts: 15,815
  • Joined: 23 Jan 2008
  • Loc: Hilton, NY, Yellow Zone (Bortle 4.5)

Posted 05 October 2023 - 05:52 PM

There is also the fact that the C5 suffers from comatic aberration whereas the MC127 is coma-corrected.

The C5 is a reflector so should not have any chromatic aberration with the exception of any that is possibly introduced from the corrector plate.  In my C5, I've never seen a hint of CA.

 

-Dan


  • Echolight likes this

#43 Nicole Sharp

Nicole Sharp

    Soyuz

  • *****
  • Posts: 3,651
  • Joined: 12 Jun 2018
  • Loc: Cumberland, Maryland, USA

Posted 05 October 2023 - 07:35 PM

The C5 is a reflector so should not have any chromatic aberration with the exception of any that is possibly introduced from the corrector plate.  In my C5, I've never seen a hint of CA.

 

-Dan

Comatic not chromatic.


  • Bob Campbell and Midnight Dan like this

#44 Bob Campbell

Bob Campbell

    Aurora

  • ****-
  • Posts: 4,676
  • Joined: 17 Sep 2004
  • Loc: Scottsdale, AZ

Posted 05 October 2023 - 07:35 PM

The C5 is a reflector so should not have any chromatic aberration with the exception of any that is possibly introduced from the corrector plate.  In my C5, I've never seen a hint of CA.

 

-Dan

She is talking about coma, not color.  

 

Bob



#45 Nicole Sharp

Nicole Sharp

    Soyuz

  • *****
  • Posts: 3,651
  • Joined: 12 Jun 2018
  • Loc: Cumberland, Maryland, USA

Posted 05 October 2023 - 07:50 PM

She is talking about coma, not color.  

 

Bob

Though catadioptric chromatic aberration is an interesting discussion.  The thicker corrector on the MCT technically produces more chromatic aberration than the thinner corrector on the SCT.  If you are doing infrared astronomy, then an SCT can be a better choice than an MCT but I think the difference is still quite small.  If going for infrared or multi-band, you're better off with a 1000/130 astrographic Newtonian but that is a bit heavy.


Edited by Nicole Sharp, 05 October 2023 - 07:53 PM.

  • Bob Campbell likes this

#46 Midnight Dan

Midnight Dan

    James Webb Space Telescope

  • *****
  • Posts: 15,815
  • Joined: 23 Jan 2008
  • Loc: Hilton, NY, Yellow Zone (Bortle 4.5)

Posted 05 October 2023 - 08:21 PM

Comatic not chromatic.

Gotcha.  My mistake.

 

-Dan



#47 Bob Campbell

Bob Campbell

    Aurora

  • ****-
  • Posts: 4,676
  • Joined: 17 Sep 2004
  • Loc: Scottsdale, AZ

Posted 05 October 2023 - 09:05 PM

Though catadioptric chromatic aberration is an interesting discussion.  The thicker corrector on the MCT technically produces more chromatic aberration than the thinner corrector on the SCT.  If you are doing infrared astronomy, then an SCT can be a better choice than an MCT but I think the difference is still quite small.  If going for infrared or multi-band, you're better off with a 1000/130 astrographic Newtonian but that is a bit heavy.

Yes. I discovered this when I was trying to image cloud structure  on Venus with a C6. You can tease some out, but it's far from optimal. 

 

Bob



#48 mayhem13

mayhem13

    Mercury-Atlas

  • *****
  • Posts: 2,549
  • Joined: 10 Jan 2021
  • Loc: New Jersey

Posted 06 October 2023 - 05:40 AM

I too had a C5 for about 2yrs as a travel scope…..it’s been on many a plane ride with me. We also used it as a spotter during the day in places like Utah, Montana and such to view wildlife and birds. Alt/az tripod mount is the way to go.

 

The optics of the C5 are really something special once collimated. 


  • Bob Campbell, Doug Culbertson, Bill Barlow and 2 others like this

#49 Rayje1997

Rayje1997

    Viking 1

  • -----
  • topic starter
  • Posts: 555
  • Joined: 07 Jan 2022
  • Loc: Chilhowie, VA, USA

Posted 06 October 2023 - 07:17 AM

I too had a C5 for about 2yrs as a travel scope…..it’s been on many a plane ride with me. We also used it as a spotter during the day in places like Utah, Montana and such to view wildlife and birds. Alt/az tripod mount is the way to go.

 

The optics of the C5 are really something special once collimated. 

I hear lots of great things about the optics on these little SCTs. What is the reason for their sharpness? Are they really exceptionally sharp or is it just that people don't expect sharp images from such small scopes?



#50 Bill Barlow

Bill Barlow

    Fly Me to the Moon

  • *****
  • Posts: 6,311
  • Joined: 03 Dec 2007
  • Loc: Overland Park KS

Posted 06 October 2023 - 10:32 AM

Maybe the smaller mirror and corrector lens are easier to get a smoother figure.  
 

Bill


  • Rayje1997 likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics





Also tagged with one or more of these keywords: Visual, SCT, Reflector, Catadioptric, Cassegrain



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics