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how often do you collimate your SCT?

collimation equipment SCT astrophotography
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#1 ManboneRidge

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Posted 07 December 2018 - 07:07 AM

Another rainy weekend here at Manbone Ridge so here come the rookie questions, UBI (useless bits of information) and trivia questions. 

 

Do you wait for symptoms in visual viewing, astrophotography or something else? Do you check collimation after so many hours of use? After years of astronomy do you have some kind of sixth sense for the collimation of your scope? Can you train your astronomy mascot (Manbone has a dog AND a cat) to warn you of bad collimation?

 

 



#2 Ishtim

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Posted 07 December 2018 - 07:59 AM

In general SCT's tend to hold collimation well.  The frequency needed to check and tune collimation is driven more by how the OTA is handled and sot so much by use as it is only the secondary mirror you would can tweak.  For instance, I have collimated mine maybe 3 or 4 times in 10+ years, but my OTA only travels from mount to house and back and unless I bump it or take it on a road trip, collimation holds up well and is left untouched.  I primarily use the SCT for planetary (f/20 and up) so I typically check collimation at the beginning of planetary "season" and tune it as required. 

 

A star test is your friend...as it is the best "teller" while in the field (or Obs) of when to do it, we don't have a dog or cat. 

 

Keep in mind this should be done on nights of good seeing.  There's a plethora of SCT collimation threads here on CN if and when you get the itch (or your pets tell you) to look at a defocused star near the zenith at high magnification on a night of good seeing.    


Edited by Ishtim, 07 December 2018 - 08:00 AM.

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#3 junomike

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Posted 07 December 2018 - 08:15 AM

Checking the Fresnel pattern on a Star will confirm Collimiation or the need for it.  On DSO's I find some mis-collimiation is acceptable, however I can almost always detect mis-collimation on Planets as It's the difference between razor sharp views and soft (even slight) views.


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#4 deepwoods1

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Posted 07 December 2018 - 08:26 AM

Within an observing session I’ll check on Polaris after the scope has sufficiently cooled. Infrequent need for collimation.


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#5 jgraham

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Posted 07 December 2018 - 08:30 AM

I check the colimation at the start of every observing session, but it rarely needs adjustment. I may tweak it once a year.
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#6 Migwan

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Posted 07 December 2018 - 08:38 AM

I don't colimate often, but do out of focus star tests as often as I get decent seeing.  On those rare nights that seeing is excellent (3-4 nights a year) , I look at in focus airy rings rather than out of focus tests.  I have touched it up twice in last two years on such nights with very good results.  No other tweaking has been necessary even with a trip out west and a few to dark sites.   jd   


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#7 WadeH237

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Posted 07 December 2018 - 09:02 AM

To answer the question in the title, I collimate my SCT whenever it needs it, which is not that often.

 

I don't do any special tests or anything to determine if it's time.  I can tell just in normal use.  Any time I adjust the focus, I can see what happens to the image, and that is enough for me to know.  Sometimes, if the seeing is worse than normal, I may tweak the focus a bit just to make sure that the collimation is still on.

 

When I go to star parties and look through other people's scopes, I can tell immediately as well.  It turns out that most scopes that I look through are just a bit off.  If I look through one that is more than a little off, I will offer to show the owner how to collimate it.


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#8 Exnihilo

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Posted 07 December 2018 - 10:04 AM

Yes, I'm like most here. I check mine every session, but don't need to recollimate very much.
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#9 rmollise

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Posted 07 December 2018 - 10:11 AM

Another rainy weekend here at Manbone Ridge so here come the rookie questions, UBI (useless bits of information) and trivia questions. 

 

Do you wait for symptoms in visual viewing, astrophotography or something else? Do you check collimation after so many hours of use? After years of astronomy do you have some kind of sixth sense for the collimation of your scope? Can you train your astronomy mascot (Manbone has a dog AND a cat) to warn you of bad collimation?

 

I check it periodically on nights of decent seeing, and collimate when it needs it. Last time my C8 needed adjustment? About three years ago. Admittedly, the Edge doesn't travel to many star parties anymore, but still... :)


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#10 baron555

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Posted 07 December 2018 - 11:14 AM

Another rainy weekend here at Manbone Ridge so here come the rookie questions, UBI (useless bits of information) and trivia questions. 

 

Do you wait for symptoms in visual viewing, astrophotography or something else? Do you check collimation after so many hours of use? After years of astronomy do you have some kind of sixth sense for the collimation of your scope? Can you train your astronomy mascot (Manbone has a dog AND a cat) to warn you of bad collimation?

I use my C-9.25 Edge strictly for AP.  I run CCD Inspector 2 continuously during calibration and imaging to check for proper collimation as well as change in focus.

I use the FT Micro Focuser along with a FocusLynx auto focusing system; the mirror locks are partially tightened.

The scope, with cameras and everything still attached, is moved as a unit, in and out of the adjacent garage for each imaging session.

 

I did a full blown collimation early this year and it has not changed one bit.  I also do not see any mirror flop issues.


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#11 Eddgie

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Posted 07 December 2018 - 11:31 AM

People that collimate frequently are probably chasing collimation do to poor technique.   Once properly collimated, an SCT can go months to years without collimatoin.

 

I think my C14 went 5 years without collimation.   I would check it every now and then, but it never changed (and should not change with normal handling).

 

Technique has a lot to do with minimizing the effects of mirror slop, which means always approaching final focus using CCW  turns of the focuser knob. 

 

Once collimated though, the scope should hold collimation for months to years, depending on handlng and transport. 


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#12 SeattleScott

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Posted 07 December 2018 - 04:50 PM

Of course there is going to be sample bias in these responses. I suspect half the SCT users out there have never collimated their scope!

I have never collimated my Mak after 6 years. A buddy got a used C8 a couple years ago and hasn’t collimated it yet. Another buddy has, let’s see, one, two, three, four, five Cats and hasn’t collimated any of them, although he got all of them within the last 2-3 years. As long as the views are good and collimation looks good, many people are lazy about getting it precisely dialed in.

Scott
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#13 Asbytec

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Posted 07 December 2018 - 05:24 PM

Check it every time, tweak it if or as needed. 


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#14 bbqediguana

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Posted 07 December 2018 - 06:28 PM

Check it every time, tweak it if or as needed. 

Another vote for check it every time, tweak as needed (which isn't often).


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#15 ManboneRidge

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Posted 07 December 2018 - 06:43 PM

I use my C-9.25 Edge strictly for AP.  I run CCD Inspector 2 continuously during calibration and imaging to check for proper collimation as well as change in focus.

I use the FT Micro Focuser along with a FocusLynx auto focusing system; the mirror locks are partially tightened.

The scope, with cameras and everything still attached, is moved as a unit, in and out of the adjacent garage for each imaging session.

 

I did a full blown collimation early this year and it has not changed one bit.  I also do not see any mirror flop issues.

CCD Inspector 2? Does this run inside one of the programs like Maxim. I have prowled around in Maxim pretty good and have not seen something like that. Of course, for me, Maxim is kinda like my brain. I have only discovered and use about 10-percent. 



#16 carolinaskies

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Posted 07 December 2018 - 06:43 PM

I haven't checked my 8's, 11 or 16 this season mainly because I haven't had good enough weather or time to get them out.   SCTs don't lose colimation at the drop of a hat simply by moving. Typically it's weather related to expansion/contraction so only need minor adjustment. 

There is just much less to cause miscolimation in an SCT vs newtonian.  A solid corrector plate holds the secondary precisely whereas a newt is often held on a very narrow stalk attached to thin spider veins bolted to either a secondary cage or an OTA tube of a different material where movement is far more likely in the system when the unit is mounted/dismounted. 



#17 Rovert9988

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Posted 07 December 2018 - 08:02 PM

With my Edge I collimate it maybe 2 times a year if that. Usually it's only after travelling with it that it needs a tweak.

I give it a quick check on a star every night still, but generally a SCT will hold collimation pretty well. If you don't travel with the scope you wouldn't have to collimate hardly at all once it was done initially.

#18 JHollJr

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Posted 07 December 2018 - 08:26 PM

I have Bob’s knobs on my C8i, but haven’t collimated it since 2007. I check with every use, but just haven’t seen the need to collimate.



#19 baron555

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Posted 07 December 2018 - 10:47 PM

CCD Inspector 2? Does this run inside one of the programs like Maxim. I have prowled around in Maxim pretty good and have not seen something like that. Of course, for me, Maxim is kinda like my brain. I have only discovered and use about 10-percent. 

Can't say.  It's a standalone program that I run along with TSX and others.  Check it out, it's great.



#20 Cfreerksen

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Posted 07 December 2018 - 11:37 PM

Whenever I go from Hyperstar and back. Pretty much just needs a touch up. SCT is very easy to do and only takes a few minutes after you have a bit of practice.

 

Chris



#21 choward94002

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Posted 08 December 2018 - 11:16 AM

Collimation means different things to different people and also depends on the scope and how you use it ... if you're doing something that doesn't demand high precision and you're treating your scope gently and it's not one that suffers from inherent design decisions that cause collimation errors [search for "collimation" and "mirror flop" here to better understand that] then you can do days/ months/ years/ decades ...

 

If you've got a scope that has inherent design decisions and you do meridian flips/ zenith transits, if your scope gets torn down/ set up frequently, if you're a "pixel peeper" or a comet hunter then you'll likely collimate daily (or at least check it!)

 

Collimation is one of those things that can make or break a session; if you're not collimated then it doesn't matter how dark the skies are or how good the seeing is or how well you're guiding ... you've wasted your time, might as well have been watching Oprah ... for some people it's that critical ...

 

I check collimation nightly before imaging using MetaGuide (takes a minutes and swapping out my imaging train for a Skyris to do, part of my setup checklist) as well as running the night's results through CCD Inspector to look for issues (part of my processing checklist).  If I find an issue then I'll schedule some time during the day to recollimate with my Hotech (another reason I like the Hotech, I can use daytime to collimate rather than burning clear night hours), do a final collimation with MetaGuide and CCD Inspector, mark my "down" position for the OTA and I'm off to the races!

 

Clear skies!



#22 bumm

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Posted 08 December 2018 - 11:46 AM

I've had my C8 for 41 years, but between pretty much routine poor seeing and my visual defects, ( I thought it was mainly astigmatism, but it turned out to be mostly cataracts,) I couldn't detect any mis-collimation needing tweaking or muster the self confidence to start twisting screws.  Even after gutting the thing once to repair my focusing mechanism.  A year or two ago, I made a Duncan Mask to get around both problems, and my old scope turned out to be very close.  Only one screw needed a very slight turn.  So, I'd guess I'd say I've collimated once about every 40 years. :)

                                                                                                                                             Marty



#23 whizbang

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Posted 08 December 2018 - 12:23 PM

Almost never.

 

I collimated my vintage C8 last spring, then took a 4800 mile raod trip down to Arizona, New Mexico and Colorado.  The C8 traveled in the back of our little RV and got bounced the whole time. 

 

It is still in collimation.  If that trip didn't bump it loose, the gentle handling I give it at home won't either.




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