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C5 spotter, 2" visual back.Aftermarket focuser.

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#1 Binojunky

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Posted 15 November 2019 - 12:11 PM

Just wondering the C5 spotter has a 1.25" visual back, any adavantage fitting a 2"one? also what about after market focusers , worth while upgrade to get around twiddling the knob,are they available in 2" or even 1.25' sizes ?,many thanks for your patience on  questions that must have been asked many times before, Dave.



#2 fcathell

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Posted 15 November 2019 - 12:49 PM

Because of the narrow diameter center baffle tube, a 2" visual back will not buy you anything.  Best bet is to get an F/6.3 focal reducer and use it with your lowest power 1.25" eyepieces if you are looking for a wider FOV. The focus knob works just fine on the C5.  Adding a rear focus would be redundant, and unless being a dual speed, it would have less focus resolution. If you are thinking about getting the C5 spotter, why not use it as is, get familiar with it, then decide if you need modification accessories.

 

Frank


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#3 Binojunky

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Posted 15 November 2019 - 01:24 PM

Because of the narrow diameter center baffle tube, a 2" visual back will not buy you anything.  Best bet is to get an F/6.3 focal reducer and use it with your lowest power 1.25" eyepieces if you are looking for a wider FOV. The focus knob works just fine on the C5.  Adding a rear focus would be redundant, and unless being a dual speed, it would have less focus resolution. If you are thinking about getting the C5 spotter, why not use it as is, get familiar with it, then decide if you need modification accessories.

 

Frank

Thanks, I have the chance of a brand  new Skywatcher 127 Mak OTA this has a 2'' focuser and diagonal, eyepiece in the package for only $350 Canadian, torn between getting this or upgrading my C5? I,m mainly luner and planetary visual, will think about it over the weekend, D


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#4 plyscope

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Posted 15 November 2019 - 02:58 PM

From what I have read online the Maksutov will be better for lunar and planetary.

 

http://scopeviews.co.uk/SW127Mak.htm

 

The C5 may be the better option for daytime spotting and deep sky.

 

http://scopeviews.co...estronC5XLT.htm

 

They are both interesting scopes.



#5 fcathell

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Posted 15 November 2019 - 03:02 PM

I've had both scopes and no complaints with either, but the 2" visual back on the 127 is even more "wasted" because its primary baffle tube is even smaller than the one in the C5. The C5 is probably a better all around scope but the 127 will have a slight edge on planetary assuming similar optical quality in both. I would upgrade the C5, OR go one step up and get the the 150 Mak if  you can afford it. 

 

Frank


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#6 photoracer18

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Posted 15 November 2019 - 03:47 PM

If you want to use 2" you will need either a 6" SCT or 6" MCT at a minimum to get anything out of it. I have owned both the C5 F10 and the C5 F6. Both have their pros and cons depending on the use you want them for.


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#7 stevew

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Posted 16 November 2019 - 05:17 AM

I thought that the Synta made 5 inch Maks actually test out closer to 118mm -120 mm rather than the 127mm that they are listed as.


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#8 Bowlerhat

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Posted 16 November 2019 - 08:38 AM

the mak will have longer focal length and heavier than a c5.

 

Some people still debating wether it's worth it to upgrade a 2" focuser: it's rather heavy and with the small baffle, the onger focal length makes it even dimmer. 



#9 KerryR

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Posted 16 November 2019 - 11:01 AM

I thought that the Synta made 5 inch Maks actually test out closer to 118mm -120 mm rather than the 127mm that they are listed as.

This is the result most of us get when we do the flashlight test, the more accurate beam expanded laser test, and/or the pinhole test, and some other more complex tests. There are, however, some folks who attest that none of those tests are accurate, and there are some very long and heated threads on the subject, most of which specifically address the Synta 127 Mak. Mine tests out at 118mm.

While the (possible/probable) sub-aperture thing is annoying to some of us, the Synta 127 Maks are still great little scopes. For me, the bigger issue is that they're pretty heavy for their size, and this seems to force the use of a beefier mount than would be needed with the lighter C5. Not a deal-breaker, but, if you have to tree-dodge it's nice to have the lightest possible setup for a given aperture.


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#10 MrRoberts

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Posted 16 November 2019 - 12:57 PM

My C-6 now has a F-0.63 FR, Baader SC-T2 adaptor and a T2-1.25" CL clamp that now supports my new Baader 1.25" prism diagonal. The FR and prism diag. made this scope visually outstanding when using my 13 Ethos or MOD 3. l tried my original C-8 2" diag on the C-6 and really didn't notice any improvement. 

I really don't know if these pcs would work with the C-5.

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#11 fcathell

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Posted 16 November 2019 - 01:12 PM

The Synta 127 Maks do test out with the flashlight test at about 120mm, but they are still excellent scopes.  I did test one against a good C5, and when at the same power on the same star field, you could notice the C5 was a little brighter due to the extra 7mm of aperture. However, on Jupiter and Saturn, I think the Mak was sharper due to contrast. Inexperienced observers may not be able to catch the difference.

 

Frank



#12 Hugh Peck

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Posted 16 November 2019 - 01:19 PM

A two inch diagonal and eps vignetted on my C-5+. Worked with the C-6. I would think you would have the same problem with a 5" Mak. My Meade ETX had a rather small opening. Never tried to add 2" accessories to it. If 2" is improtant I would go to a used C-6.

 

C-6-8.jpg


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#13 Jon Isaacs

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Posted 16 November 2019 - 01:35 PM

Just wondering the C5 spotter has a 1.25" visual back, any adavantage fitting a 2"one? also what about after market focusers , worth while upgrade to get around twiddling the knob,are they available in 2" or even 1.25' sizes ?,many thanks for your patience on  questions that must have been asked many times before, Dave.

 

I have had a few C-5s.  A 2 inch visual back and diagonal is workable even if there is vignetting. 

 

But a 2 inch focuser with a 2 inch diagonal, I think you'd eat up too much backfocus and the effective aperture would be reduced.

 

My 127mm Starmax had a 48-49mm secondary baffle, that works out to a 40% CO if the effective aperture is 120mm. The c-5 has a similar sized CO. It's not a refractor.

 

Jon


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#14 oldtimer

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Posted 27 November 2019 - 01:15 PM

Just sent my check in to a CNer here for a a C-5 spotter.. Looking around in my 50 year collection of spare parts I found a SC visual back with external threads for something. I took the barrel off my 2" diagonal and as luck would have it the diagonal threaded directly into the visual back so the back focus will be very small. I plan to use a 30mm 72 degree eyepiece which the math indicates will give me 41.7X , a 1.7 degree FOV with an exit pupil of 3mm.  Anxious to see what really happens.

 

Gary



#15 Jon Isaacs

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Posted 27 November 2019 - 01:58 PM

Just sent my check in to a CNer here for a a C-5 spotter.. Looking around in my 50 year collection of spare parts I found a SC visual back with external threads for something. I took the barrel off my 2" diagonal and as luck would have it the diagonal threaded directly into the visual back so the back focus will be very small. I plan to use a 30mm 72 degree eyepiece which the math indicates will give me 41.7X , a 1.7 degree FOV with an exit pupil of 3mm.  Anxious to see what really happens.

 

Gary

 

I think you'll be pleasantly surprised. You'll probable see some vignetting but it will be surprisingly little.

 

That was my experience with a 32mm, 65 degree eyepiece.

 

Jon



#16 Sarkikos

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Posted 27 November 2019 - 02:10 PM

The rear opening of the C5 is 24.5mm, measured by a digital caliper.  Compare that with the field stop of an eyepiece to get a rough idea whether it will vignette or not.  But your eye is the final arbiter.

 

Mike


Edited by Sarkikos, 27 November 2019 - 02:12 PM.


#17 photoracer18

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Posted 27 November 2019 - 04:46 PM

I have both a C-5 and a 6" Mak that came with a 2" focuser (fixed optics). 2" works on the 6" but not really on the 5". 6" and up cats are really the bottom of the range for 2" eyepiece use. Not to say you can't put a 2" focuser on the back just don't bother with 2" eyepieces.



#18 Bill Barlow

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Posted 28 November 2019 - 10:44 AM

If I bought a C5 I would use a blue fireball 1.25” visual back with a Tak 1.25” prism diagonal.  These prism diagonals are very sharp.

 

Bill




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