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EAA and SCT Collimation

EAA SCT Collimation
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#1 Ezzz

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Posted 12 May 2021 - 09:25 PM

Hey Folks,

Silly question, but the thought just occurred to me... I was planning on selling my TV eyepieces and using the funds to get into EAA. Since I have a C8, how does one collimate an SCT if they have no eyepieces? Is there some kind of new funky apparatus or program I am unaware of?

Thanks!



#2 Sky King

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Posted 12 May 2021 - 09:31 PM

Use your camera and zoom in on a bright star which is out of focus.... or if you prefer, keep an eyepiece for visual and collimation.

 

Second.jpg


Edited by Sky King, 12 May 2021 - 09:34 PM.

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#3 Ezzz

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Posted 12 May 2021 - 09:50 PM

Use your camera and zoom in on a bright star which is out of focus.... or if you prefer, keep an eyepiece for visual and collimation.

 

attachicon.gifSecond.jpg

Thanks Sky King! 


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#4 Eclipsed

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Posted 12 May 2021 - 10:37 PM

I actually prefer collimating my 8 EdgeHD SCT using using a small pixel planetary camera.  It seems easier to fiddle with the three secondary mirror screws (or bobs knobs if you have them), while viewing an image on a laptop screen, versus peaking through an eyepiece which is at the opposite end of the scope.


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#5 Noah4x4

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Posted 13 May 2021 - 12:47 AM

I actually prefer collimating my 8 EdgeHD SCT using using a small pixel planetary camera.  It seems easier to fiddle with the three secondary mirror screws (or bobs knobs if you have them), while viewing an image on a laptop screen, versus peaking through an eyepiece which is at the opposite end of the scope.


Take this a stage further for greater convenience.....

I was uncomfortable collimating my SCT using an eyepiece and a sharp pointed Phillips screwdriver. I found Bob's Knobs were always too wobbly and loose. But now, Collimation is vastly easier having instead installed Allen Key bolts and using a camera & screen. The Allen Key fits into the bolt and will stay there (no hands). Gives you chance to stand back and work out which bolt to adjust (using point with pencil technique.
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#6 SanjeevJoshi

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Posted 13 May 2021 - 01:06 AM

Use a small pixel camera, a near infra red filter and two cheap tools - tri bahtinov mask and Duncan mask.   Final airy if seeing allows.


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#7 roelb

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Posted 13 May 2021 - 06:46 AM

I also prefer to also incorporate a 2x Barlow
Magnifying the airy disk.
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#8 alphatripleplus

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Posted 13 May 2021 - 07:02 AM

Yep, lots of variations on using a camera and no need for an eyepiece. There is also a collimation routine using Metaguide and a camera, but I have not used it.


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#9 GaryShaw

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Posted 13 May 2021 - 08:13 AM

About just using an ‘artificial star’ tool to give a perfect stable star for the airy disk adjustments?

Gary


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#10 Eclipsed

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Posted 13 May 2021 - 09:48 AM

Oh, a final thought -  I found that reasonably bright stars that are really high up work way better.  Atmospherics can destroy those cool looking out of focus stars and really mess with the Airy disc when doing the final tweaking.


Edited by Eclipsed, 13 May 2021 - 09:49 AM.

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#11 SanjeevJoshi

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Posted 13 May 2021 - 11:29 AM

I use Polaris at my location and that seems to work really well for me.   Its not too bright, but bright enough.   It is impacted a bit more by seeing but is away from the moon - a real blessing for collimation even under a bright moon.   And finally, it moves very slowly around a small axis, so it is easy to recover the centering when your collimation adjustments make the star almost disappear or disappear from your FoV.   Recovering can be a bit more challenging when bigger slew adjustments are needed.


Edited by SanjeevJoshi, 13 May 2021 - 11:30 AM.

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#12 alphatripleplus

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Posted 13 May 2021 - 12:07 PM

Yes, Polaris is good as it is easy to recentre when making those collimation adjustments.


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#13 Ezzz

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Posted 13 May 2021 - 03:08 PM

Thanks very much for your input! This is very reassuring. Though the idea of selling my TV eyepieces still scare me, I feel much more confident to take the plunge into EAA. I think it will all be a much more enjoyable experience for the kids looking at a screen rather than through the small lens of an eyepiece. Plus, I like to buy new things....

Eric 



#14 alphatripleplus

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Posted 13 May 2021 - 03:28 PM

A lot of us like to buy new toys things.lol.gif


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#15 Ezzz

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Posted 13 May 2021 - 03:34 PM

A lot of us like to buy new toys things.lol.gif

Scientific apparatuses... to help better humanity. tongue2.gif


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#16 SanjeevJoshi

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Posted 13 May 2021 - 03:40 PM

Thanks very much for your input! This is very reassuring. Though the idea of selling my TV eyepieces still scare me, I feel much more confident to take the plunge into EAA. I think it will all be a much more enjoyable experience for the kids looking at a screen rather than through the small lens of an eyepiece. Plus, I like to buy new things....

Eric 

You won’t miss your eyepieces except when there is a special event like the Dec conjunction.   That one was quite special and required manual daytime set up.  No go to set up, no stars to align on - just nominal planetary tracking rate, manual find and focus, and getting wowed by the right eyepiece.

 

I still keep my C8 Edge HD on Evo Alt Az mount and a few choice eyepieces and the Celestron RACI finder (it’s actually nice) for anything special like that.

 

Cameras and computers do their magic for DSO’s / for the rest with EAA.   Even the moon is amazing with EAA.


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#17 Ezzz

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Posted 13 May 2021 - 05:28 PM

You won’t miss your eyepieces except when there is a special event like the Dec conjunction.   That one was quite special and required manual daytime set up.  No go to set up, no stars to align on - just nominal planetary tracking rate, manual find and focus, and getting wowed by the right eyepiece.

 

I still keep my C8 Edge HD on Evo Alt Az mount and a few choice eyepieces and the Celestron RACI finder (it’s actually nice) for anything special like that.

 

Cameras and computers do their magic for DSO’s / for the rest with EAA.   Even the moon is amazing with EAA.

Thanks Sanjeev!



#18 nic35

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Posted 14 May 2021 - 11:06 AM

Eyepieces !  We don't need no stinking eyepieces.  (apologies to Humphrey Bogart).

 

I found collimation of my SCT difficult at best - polaris, artificial star, metaguide, etc.  Never happy.  So I paid somebody $$ to do so, but that resulted in other problems - the spinning secondary holder issue..  Eventually I found a used hotech advanced CT collimator in the classifieds.  Hotech was great - recollimated one of the lasers gratis !

 

It took a while to master it, but I am now happy with my collimation. Not for everyone, but it works.

 

j


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