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Here I Sit Broken Hearted, C5+ Arrived Now Wait For Clouds To Be Parted!

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#1 RalphMeisterTigerMan

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Posted 08 January 2020 - 12:05 AM

Thought that I would use that old "pay toilet" limerick and put a bit of a more modern Amateur Astronomer spin on it. 

 

Yes, it basically started raining when the C5+ package arrived, a few days before Christmas. Looks like it probably won't let up for at least a week or more. But it's okay, because I know how to cope and deal with these types of situations. But I have to admit that I've been getting an overwhelming urge to take up ancient carpentry and animal husbandry with an advanced courses in Vetrinanrian basics. Do you know that there is a lot of information that can be fouind on the internet regarding constructing Large box-shaped, unpowered Wooden boats.

 

The really tricky part will be dividing up the various decks into animal pens of just the right size for a certain animals....Animals?  When did animals enter this bizzare psychotic break of mine. Also, Can't seem to find "Gopher wood" and the proper water-proofing "pitch".

 

I believe there must have been somesort of "jail break" at several zoos and game farms because have been seeing the more and mre wild animals who are definitely NOT indiginous to my local.

 

Enough with the bizzare halucinations that I have been experiencing. I have been thinking, planning and scheming about different ways to possibly imporove the various optical components. If you happen to be a member of the "RalphMeisterTigerMan" fan club, and you should be! LOL! than you have most likely been following my SCT posts that have been popping up in various forums.

 

As many of you know, I have an extremelyn vivid, over active imagination. And Imaging is something that I am very good at and spend a lot of time doing.

 

So, here are some of the things that I have been checking out on the interent:

 

I have noticed that many amateurs are complaining that there is no way to replace a broken SCT corrector plate. Well, I have found an Italien optical company by the name of NOSCANO. They apparently have the ability to fabricate any Corrector Plate for most popular commercialy built SCTs. They were actually able to give me a quote to replace my current C5+ soda-lime, star-bright coated corrector plate with a BK7, broadband coating New corrector plate.

 

I have also been researching optical companies that can put New life into your old SCT Optical Tube Assembly. One company in particular which caught my attention (found about it here on cloudy nights) is Optical Wave Labs located in California.

 

OWlL offers several packages to make your SCT work like new, or even better if you wish and have the money to do so. OWL can dis-assemble the OTA, clean the entire thing including the optics and replace any shims or gaskets or any thing else that might need replacing. They will then re-assemble the scope and collimate it and ship it back to you in "shiny new condition".

 

If you request it, the optics can be tested to see if they are worth refiguring. Only the primary and secondary. They cannot and will not do anything for the corrector except a cleaning service.

 

If you get the optics tested and they turn out to be not what you hoped, they can strip the old coatings, refigure and then re-coat with your choice of regular aluminum, enhanced aluminum and even protected Silver that will last much, much longer than any of the "silver" coating fails that we all have read about.

 

Also, the inside of the tube and the interior of the secondary baffle can be lined with "flocking paper". And, while you are getting all this work done anyway, why not pay a bit more and get a Starlight instruments feather-touch focuser of the size you want (1.25" or 2") and the options you want, 2-speed rotating and a longer focuser travel.

 

 

Now, you are probably all wondering what the above has to do with me and my C5+. Honestly, I'm not sure yet. Doing all the research looking for possible ways of improving the current OTA helps to keep me from going completely Coo-coo for Co-co-puffs. And no one wants that!!!!

 

I can also imagine what many of you must be thinking. "Is seriously considering pouring hundreds if not more into a 27 year old SCT telescope?"

 

Truthfully, while I am contemplating and considering ways to make the C5+ optically better so that I can get more enjoyment out of it, I have many things to consider:

 

1. I am currently 59 years of age and my health isn't exactly the greatest. So, that means that I have a finite amount of time to enjoy the views through the C5+.

 

2. I cannot see myself replacing this telescope since it has all the features that I have been looking for: small, light-weight, portable, easy to move around and set-up. Also, 5-inches of aperture will obviously not compete with the big "light-buckets" that I have owned and looked through. And because of my current health concerns are out of the question, but a 5" scope is enough to enjoy some nice Solar, Lunar and Planetary views. As for DSO's, I live in an area of Abbotsford with moderate light pollution making viewing faint fuzzies very challenging.

 

3. Now this is an important consideration. Can I afford it financially and is it wise to pour that kind of money into a scope with only about 38mm more aperture than the iconic and venerable Questar 3.5?

 

So, here is the dilema: If I decide NOT to do any improvements at all and and save what-ever money that I may have spent, I will still have a pretty good Telescope that many, many amateurs have enjoyed as is. 

But, I will spend what-ever time that I have left wondering "what-if?".

 

Now, if I save enough money and sell a few things that I no longer need (10-inch, Skywatcher collapsible tube f/4.3 dobsonian on a manual mount. Which I now find difficult to move around) it is financially and economicaly possible and feasible that I could do the above modifications and hopefully be able to enjoy a C5+ with even better optics than it has now for hopefully and long time.

 

I do not know how muach time I have left. But I keep hoping and praying to be able to enjoy Amateur Astronomy and observing the night sky for years to come...with a telescope that has really nice optics.

 

I know that many of you will have some very strong opinions on this thread which I have started. I look forward to reading what-ever thoughts, feelings, opinions you have...the good, the bad and the ugly. LOL!

 

Here's hoping for clear skies!

RalphMeisterTigerMan

 


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#2 erin

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Posted 08 January 2020 - 08:09 AM

Absolutely do it up! Sounds like the perfect scope for you so why not? Congrats and enjoy waytogo.gif



#3 andycknight

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Posted 08 January 2020 - 09:26 AM

Congrats on the new scope.

 

Personally before spending money on improving any scope, I would thoroughly test it out. You never know it could be just fine as it is. You could stop down your dob to 5" and do a comparison. Also if the images look ok to you, why think what-if? Suppose they came back and said it is 1/4 wave - would that really tell you anything??... Sure a Questar might be 1/8, but unless you look through "known" 1/4 and 1/8 wave optics on that perfect night - How can one justify how much money was worth spending on such an upgrade?

 

An interesting point to note is a 1/4 wave 10" has the same resolution as a 1/8 wave 5". So a little 3.5" Questar has to be very good to beat a 5". I have a C90 and a C5 and its no surprise that the C5 is clearly better on the Planets than the C90.

 

Now my little C90 is clearly no Questar, but I seen plenty of detail on Jupiter / Saturn / Mars /Moon with it. Ed Ting has a review comparing a ETX90 and C90 against the Questar 3.5. These new Chinese C90 Scopes are not as bad as many think!!

 

http://scopereviews....0mmComparo.html

 

I'm guessing if it is a C5+, it's a white tube? My C5 is the white tube 'spotter' version purchased back in the late 90's.

 

Something worth noting about mine... When I first got it, I thought it had real lousy optics. Despite very careful collimation, images were really soft. I was going to send it back, but then I read an article in S&T about an undersized corrector plate.

 

Mine had the same issue, the corrector plate was undersize by ~6mm. Under gravity (and careful handling during shipping grin.gif) it had moved to one side and totally ruined the optical performance. Centring the corrector plate (a 2 minute job), totally transformed the scope. A blurry 50x view became nice and sharp at 250x!

 

I don't think I've ever purchased a scope without the weather punishing me - so I know the pain you are going through!! - Just stay away from the coco pops, otherwise all that excess sugar will prevent you from getting a steady view! lol.gif

 

If you don't mind me asking, how much was a BK7 C5 corrector Plate??

 

There are lots of posts on CN from people with broken or real nasty corrector plates, it would be good to know if it is an affordable option.

 

Regards

 

Andy.


Edited by andycknight, 08 January 2020 - 09:27 AM.

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#4 RalphMeisterTigerMan

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Posted 08 January 2020 - 10:39 AM

Hey Andycknight. Yes, it is a 1993 C5+, white tube, single fork equatorial with a wedge and the deluxe latitude adjuster. 

 

You do make some excellent points. While I am contemplating some upgrades nothing has been written in stone yet as my personal stone carver is on vacation. LOL! I have read many good reviews about the C5+ and most owners seem to be very happy with their scopes.

 

Once the weather gets better I hope to be able to see for myself. Since it's been approx. 30 years since my last SCT, it will take some time to get re-aquainted with a fork-equatorial and the optical abilites of a SCT. My last one was a "Halley Era" Meade 10" LX5 2120 and I can definitely say that I have never before, or since, have I been so disappointed with the optics of a telescope! While it wasn't bad on DSO's, the planets showed extremely little detail. The favourable opposition of Mars in Oct. 1988 should have been memorable and a delight, instead every other telescope that I looked at Mars with for that opposition completely outclassed the Meade. Seriously, all I could see through the eyepiece was a featureless orangey/red disk.

 

Now I am certain that my new C5+ will NOT be a repeat of the Meade 10". In fact, I am looking forward to some satisfying views...once the clouds have parted.

 

Clear skies!

RalphMeisterTigerMan


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#5 Axunator

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Posted 08 January 2020 - 11:22 AM

 

An interesting point to note is a 1/4 wave 10" has the same resolution as a 1/8 wave 5".

Errrrr.... I’m afraid it does not work quite that way. Even 1/4 wave is already diffraction limited, and 10” diffraction limited aperture will definitely have higher resolution (and contrast as defined by modulation transfer function) than the most perfect 5” in the world (when all other parameters than aperture and wavefront error remain constant).

 

There’s a very nice simulation page about this stuff by Damian Peach here. Please compare images on Part 5 of that page: A - 1/10th wave 10 cm vs. C - 1/4th wave 20 cm. The brute force of aperture is pretty revealing... (ignoring seeing effects etc. of course).


Edited by Axunator, 08 January 2020 - 11:26 AM.

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#6 andycknight

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Posted 08 January 2020 - 11:32 AM

Axunator, on 08 Jan 2020 - 4:22 PM, said:

Errrrr.... I’m afraid it does not work quite that way. Even 1/4 wave is already diffraction limited,

I was referring to 1/4 wave peak to valley i.e. 1/2 wave on wavefront.

 

Regards

 

Andy



#7 Axunator

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Posted 08 January 2020 - 11:58 AM

I was referring to 1/4 wave peak to valley i.e. 1/2 wave on wavefront.

 

Regards

 

Andy

OK, agreed then. That’s of course a pretty bad scope already, and should be put out of its misery immediately lol.gif


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#8 Axunator

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Posted 08 January 2020 - 01:15 PM

Ralph,

I remember drooling over C5+ ads in Astronomy and S&T in the early nineties. It was so darn cute and cool-looking at the same time! Of course, I was a poor young university student at the time and couldn’t afford anything like that (not to mention that I would have had to import it from abroad myself, which, at that time, wouldn’t have been a trivial procedure).

I understand your desire to modify a new-to-you old scope (a very familiar urge!), but please, try to make acquaintance with it first in its present state (well, collimation recommended of course), especially before doing any irreversible mods. It might pleasantly surprise you ;-)

Edited by Axunator, 08 January 2020 - 01:22 PM.

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#9 epee

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Posted 08 January 2020 - 01:32 PM

When I acquired my C5+, it had internal fogging that plagued many Celestrons of that era. I carefully removed the corrector plate and a quick clean up of its interior surface was all that was needed to make the little scope's optics glisten like new. I did notice that the corrector plate was "undersized" compared to the retaining ring, and that the factory cardboard centering shims had not aged well. I replaced these with plastic card stock from a craft store (I determined the thickness by measuring the corrector and the opening it was supposed to fit into) and used calipers to center both the corrector plate and secondary cell.

 

I can't say how much difference this made to the images as I was determined to clean the optics before using the scope, and all the other "repairs" were preformed then. I will say that my C5 gives a very clear and sharp image, so I don't think I did any harm.


Edited by epee, 08 January 2020 - 01:34 PM.

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#10 andycknight

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Posted 08 January 2020 - 02:10 PM

My C5 (purchased new in the late 90's) did not have any cardboard shims fitted (perhaps that's why some have a de-centring issue and not others?). Like you I used a pair of (internal) callipers to accurately re-centre the plate against the outside cell (which only took a few minutes as I did not need to touch the secondary housing).

 

I used some 3mm OD Earth sleeving (which squishes down nicely as you tighten the retaining ring) to keep it centred.

 

If it had not been for the S&T article - I would never have guessed the cause of the really bad optical performance was such an easy fix. It would have been returned for a refund and I would have probably hated all C5's for the rest of my days wink.gif lol.)

 

Never had a problem with outgassing though - Perhaps my C5 has a different type of grease on the baffle tube.

 

Regards

 

Andy.


Edited by andycknight, 08 January 2020 - 02:13 PM.

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#11 gfstallin

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Posted 08 January 2020 - 03:04 PM

Congrats on the new scope! I pined, literally pined over the C5+ in Sky and Telescope and Astronomy magazine ads as a young teen growing up, particularly in 1992-1993. I finally managed to buy one used in 2001, but I had to sell it within months because I had way too much going on at the time. I still wish I had it, though I did recently buy a C5 OTA that I will hold on to. 

 

There's lots of good advice here. I would echo waiting to see how the scope performs before sending it off anywhere to improve it. Clean if needed, collimate (likely needed after shipping), and check it out. Recoating and refiguring might not yield results that are easily visible if the optics are already decent. Still, by all means, if it makes you feel better about the purchase, trick out out C5+! Ship it off for a recoat. Get it gold plated! You are certainly in the wrong place if you're looking for folks to tell you to save your money for more frivolous purchases like lunch for a month or three. laugh.gif

 

Now, perhaps this is a function of my generation, but if I were tricking out a C5+, I would get a push-to computer and encoders from JMI/Farpoint. Add on the biggest finder scope the C5+ mount can easily handle, and you will have the very portable telescope I dreamed about on Saturday afternoons while sitting in at the public library by my home. Great stuff and congrats again! 

 

George


Edited by gfstallin, 08 January 2020 - 03:08 PM.


#12 Paul Hooper

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Posted 08 January 2020 - 03:14 PM

Do you know that there is a lot of information that can be fouind on the internet regarding constructing Large box-shaped, unpowered Wooden boats.

Here, this looks interesting:  https://www.diy-wood...mall_Boats.html

 

cloudy.gif 


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#13 charlesgeiger

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Posted 08 January 2020 - 10:03 PM

I would advise to think about just trying the scope out.  It is rare to very rare you hear of anyone finding bad optics in a C5.  As mentioned above, you need to have good collimation and relatively good centering of the corrector plate.  The corrector and the secondary mirror are the most important parts of any SCT.  Remember, the secondary is matched to the primary on each scope at the factory.  The corrector plates need to be made properly and that can be an issue if you were to replace the corrector.  No matter what type of glass or coating on the corrector you would not be able to perceive any difference visually as long as the corrector is made properly.  Spending money on another corrector plate would not provide any advantage in my opinion.  In fact, you might get something that will detract from the scope's performance.  Remember too that each primary is glued to the primary baffle and when the instrument is put together, the final optics touch up and allignment are based on the primary's exact orientation and placement on the baffle tube.  And remember the secondary must be alligned to the corrector and the corrector has to be in the exact right orientation in the tube for your set of optics   If you look through the forums you will find that 'recoated' SCT primary and secondary mirrors reinstalled into scopes from various

vendors have had devastating results.  Regluing the primary just doesn't work in most cases.  You will see that Celestron itself will replace the complete optics set rather than recoat or replace any part of it.  Even if the result was good (which odds are highly against) coating with 99% transmission on all parts would probably not be discernable visually in a scope of this size (if the existing coatings are in good condition). 

I would say if you are not happy with the result when you get your scope, you would be way better off just getting a new replacement optical tube from Celestron. 

I would put any extra money budgeted into a better tripod if what you get is a weak point.  The C5+ we had did have an upgrade tripod which made a wonderful difference in stability.  Also, I would get the reducer corrector.  You might want some good quality 68 to 70 degree oculars.  On my particular C5, I have run everything up to 6mm with good results.  I don't think you would need a barlow but if you have just one or two eyepieces you might consider a good one such as the powermate.

My health is not great either so I know what you mean about remaining observing time and wanting something that is workable with great optics.  If you get a C5+ that has not been tampered with, you should have a great scope!  Concerning the drive with a C5+, you may want to check that your motor drive (ours was a spur gear system with a 9 volt battery) motor does not have a slipping gear on the motor shaft.  That did occur with ours.  I am not sure if any had a worm gear drive but ours was the spur gear with one motor.  The older SCT's had a spur gear drive with two motors.  I believe what caused the slipping small gear on the motor shaft was a person trying to move the tube in RA with the RA drive lock on.  You will need a good dew shield (perhaps heated).  These were truly great SCT's and as you know, extremely portable.  In a truly dark sky, I can resolve M13 to the core.  I have seen 5 stars in the trap in the city of Portland.  Rigel is easily split...on and on.

I am not trying to dampen your enthusiasm in any way, I am just suggesting some things to consider before making expensive changes which might end up in disappointing you. Best wishes and hoping for great optics for you!

 

Charlie


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#14 stevew

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Posted 08 January 2020 - 11:44 PM

Ralph, you haven't even had it out under the stars yet, and your talking about refiguring it?

The rain must be getting to you...



#15 stevew

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Posted 08 January 2020 - 11:45 PM

I's actually clear at the moment in the Lowermainland.

Hopefully your outside with your new scope....



#16 RalphMeisterTigerMan

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Posted 09 January 2020 - 10:42 AM

 Charlie and SteveW, you are absolutely correct! I will take the scope on a "test drive" a minimum of 5 - 7 times before I make any decisions about making any drastic changes. Since I only have the 24mm Pan at the moment, oculars are at the top of my list. I'm thinking about the 13mm Nagler T6, the 9mm Nagler T6 and a high quality 2X barlow for now.  

 

I have had good experiences with a 2" UHC in the past, but that was with a decent sized Dob. Just wondering if a 1.25" O-III would be of any benefit to a 5" SCT? I'm also going to switch to Bob's knobs for the collimating screws, should make collimating a little easier.

 

Perhaps the Hyperion Mark IV would be nice also, expecially for day time viewing.

 

Thanks for all the input.

RalphMeisterTigerMan



#17 andycknight

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Posted 09 January 2020 - 01:02 PM

Some people have a good experience with Bob's knobs, but I am not one of them.

 

I guess it depends on previous experiences with various good & bad samples of SCT's, but I find unless I really bump the tube about - I don't need to perform frequent collimation.

 

Both my C5 and C8 hold collimation very well. Over the last ~26 years (C8) and ~23 years (C5) - I have probably needed to re-collimate a total of around 4~5 times (its hard to exactly remember since its so infrequent).

 

My main concern with Bob's knobs, is it is very difficult to get them tight enough by hand. Loose screws are a nightmare for holding collimation (and note a loose undersize corrector could be another reason). Another concern is that it makes damage to the corrector plate more likely if the tube gets a bump to the front as they poke out more.

 

You also need to be quite careful when replacing the screws (the golden rule is to only do one at a time and tighten it up before changing out another).

 

Some people recommend changing the Phillips screws for Allen head types. I can fully understand that since poking around the corrector lens at night with a sharp Phillips screwdriver and 'worn out screw heads', can be a recipe for a scratched or even cracked corrector. An Allen Key is so much safer and better to judge the amount of torque applied.

 

Having said that I'm still using the original Phillips screws. They are not worn and I have a screwdriver that grips the heads really well. Collimation is so infrequent that there is no need for me to bother changing them. But if your heads are worn, I would definitely change them out before making any adjustments!!

 

It is very difficult for me to describe "how tight" they should be - I have never used a torque wrench, but just used common sense. If I had to describe it, I would say about fingertip tight using my screwdriver with a 30mm diameter handle. If using a Allen key - again fingertip tight when finger and thumb are spaced about 30mm apart.

 

Hopefully a good starting point will be to feel how tight they are before undoing them.

 

Having said all the above - If by some good luck collimation is OK, then I would not touch anything until you have a problem. It's very easy to "test" collimation. I always do this without the diagonal fitted. I then add the diagonal afterwards and if it affects the results I would either collimate the diagonal or get a better one. I normally use Polaris since is does not move much as the Earth rotates. Or you can use an artificial star in the daytime. Make sure the star is exactly centred in the eyepiece.

 

1st step : Is to throw the image way out of focus to get a nice big "doughnut" (the eyepiece FL is not critical). The doughnuts hole should be exactly in the centre. If it is clearly not then collimation is really bad. If it looks ok (or you can't really tell) then assume its ok and move on to the 2nd step . Don't attempt to "re-centre the doughnut" if it looks ok!

 

2nd step : This is the only step I ever have to do. This should be done "In focus". Use something like a 6mm to 9mm Eyepiece so you can clearly see the airy disk and first ring. This ring should be perfectly symmetric and complete. If seeing is bad or the scope has not cooled down then you can not collimate.

 

Note adjustments should only be made to one screw at a time. A typical adjustment would be about 1/4 of a turn for the first step and 1/10th to 1/20th of a turn for the second step. VERY IMPORTANT!! - Re-centre the star after an adjustment before accessing what difference it has made. Always adjust by tightening the screws. (Only if the screws are too tight then loosen the other 2 by half the amount) - But ensure the last adjustment is made by tightening a screw.

 

I have only given a very brief description of collimation above, so have a look in the user manual and on the web for more info. But don't believe the dodgy websites that say you only need to centre the hole in the doughnut!! Some sites suggest putting a finger in front of the scope to know which screw to turn. This can save a lot of time but beware this can cause some confusion if a diagonal is (or is not) fitted.

 

Regards

 

Andy.


Edited by andycknight, 09 January 2020 - 01:06 PM.

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#18 epee

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Posted 10 January 2020 - 09:18 AM

I have allen head screws on mine. It was that way when I bought it, so I don't know if they were replacements or if production shifted.

 

Bob's Knobs on an SCT don't seem wise to me. I've read horror stories here about how they contact the dust cover and so will directly transmit shock to the corrector. It is also worth considering how tight "finger tight" will be using three closely-spaced small knobs; especially with aging fingers.

 

The best innovation I've seen for SCT collimation is three allen keys of the proper size, with tape wrapped around the long shafts to prevent scratching; think of them as removable knobs.


Edited by epee, 10 January 2020 - 09:18 AM.

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#19 Jeff Lee

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Posted 10 January 2020 - 09:33 AM

I've used Bob's Knobs for close to 20 years, no issues here. I've just ordered a set for my new to me C5 White Spotter. However I will wait for two things:

 

1. Collimation to be off

2. conditions good enough to collimate, which is the big issue. Had a hubble star, but it would only get me close.

3. It's no big deal, but just like cleaning a corrector, you need to take care and do it right. If you are in a club as someone to help you the first time.



#20 andycknight

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Posted 10 January 2020 - 01:20 PM

Jeff Lee, on 10 Jan 2020 - 2:33 PM, said:Jeff Lee, on 10 Jan 2020 - 2:33 PM, said:

[snip...] Had a hubble star, but it would only get me close.

I have heard this many times before, so its clearly an issue. However I found when collimating in the daytime (which I prefer) and then double checking at night on Polaris, it was still spot on.

 

I can only assume that it's something to do with the temperature difference or maybe the tube/primary flexing/moving when aimed at a different altitude (or maybe an out of alignment primary baffle tube). 

 

The only thing I did spot once was putting a cold tube on a warm mount. (I often put my tube outside [say] a hour before I observe, but this time the mount was left indoors) I put the C8 tube on the mount had a quick look at a few things then focussed on Polaris with a 9mm eyepiece and noticed collimation was clearly off.

 

Anyway I went inside to get the screwdriver, but ended up having a chat, cup of tea, something to eat etc... About half an hour had passed. I went back outside to collimate but it was now spot on. I can only guess that the "room temperature"  mount had warmed up one side of the tube affecting the collimation??

 

Regards

 

Andy.


Edited by andycknight, 10 January 2020 - 01:23 PM.



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