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Ho-tech SCT Collimator?

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#1 Raginar

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Posted 05 August 2014 - 06:03 PM

Anyone have one of these they wouldn't mind loaning/renting out?  I have a 12" LX200 that's out of collimation and I'm at my wits end... I'd like to avoid spending $455 bucks but a reasonable fee would work for me.

 

If you're interested, or just want to sell it, please send me a PM.

 

 


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#2 areyoukiddingme

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Posted 06 August 2014 - 01:31 AM

Why not try out a camera and meta guide? Even with a really good camera, you come out way ahead on the deal compared to the collimator, and you can use it for things other than collimation. . . 



#3 R Botero

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Posted 06 August 2014 - 03:40 AM

I would second the Metaguide route.  Just get your scope roughly collimated using an artificial star or just standing at focal distance in front of the mirrors and then use a webcam and Metaguide.  It'll get you spot on.  I do this with my f/20 250mm Mak which does not come to focus on an artificial star with the distances I have available at home.

Good luck!

Roberto 



#4 ur7x

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Posted 06 August 2014 - 03:50 PM

I third the metaguide suggestion,  easier, cheaper, better.


Edited by ur7x, 06 August 2014 - 03:50 PM.


#5 Raginar

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Posted 06 August 2014 - 04:00 PM

Well  :), I can't seem to figure it out. Anyone want to do a Google Hangout or Teamviewer? I have Metaguide and a compatible camera and tried it. I just can't figure it out :/.


Edited by Raginar, 06 August 2014 - 06:18 PM.


#6 areyoukiddingme

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Posted 06 August 2014 - 06:32 PM

I'd like to see a dummies guide myself. I have the gubbins, but haven't yet had the chance to learn how it works!  :)


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#7 dobsoscope

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Posted 07 August 2014 - 06:22 AM

interested as well at having a go at this


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#8 Raginar

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Posted 07 August 2014 - 05:48 PM

If you guys PM your email addresses, we can figure out a date to do it.  I'd like to do it on a weekend so I can stay up a little bit more.  I have a security camera feed I can give you access to in addition to utilizing a web cam at the computer in the observatory.  Maybe it would help to just talk through what I'm doing?



#9 areyoukiddingme

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Posted 07 August 2014 - 05:55 PM

Cool: PM sent.



#10 dobsoscope

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Posted 14 August 2014 - 05:35 AM

pm sent too



#11 dobsoscope

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Posted 15 January 2015 - 10:50 AM

has this ever happened?



#12 De Lorme

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Posted 15 January 2015 - 12:33 PM

Here's a great web site the made collimating my C14" so much easier.

 

http://www.asterism....als/tut14-1.htm

 

De Lorme



#13 JHub

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Posted 15 January 2015 - 03:26 PM

Okay guys, Metaguide is a term I haven't encountered before this. So, what is a Metaguide?

 

John



#14 rmollise

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Posted 15 January 2015 - 04:13 PM

A guiding program with provisions for using it as a collimation helper. ;)



#15 WebFoot

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Posted 15 January 2015 - 05:53 PM

I know I'm just an old fart too cheap to consider such a thing, but I seriously question why expensive aids are needed for something as simple as SCT collimation.  Newt (or, worse, RC) collimation is a different matter, but it takes just a couple of minutes to collimate an SCT to the limits of seeing, the old-fashioned way.


Edited by WebFoot, 15 January 2015 - 05:53 PM.


#16 leviathan

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Posted 16 January 2015 - 01:21 AM

On top of that, for me nothing is better and more accurate than star collimation. I guess these aids are more for some shops or collimation/tweaking services where they might have to collimate several scopes.



#17 areyoukiddingme

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Posted 16 January 2015 - 01:22 AM

I see the advantage being particularly for people with bad seeing, larger apertures, and those of us who want to futz about and try different techniques.

 

The bigger the aperture of your CAT, the harder it is to get fine collimation done, especially when seeing is merely so so. My C6 is a pleasant doddle to collimate. My 11 Edge is much more difficult, just b/c it is very hard to get seeing stable enough for stable diffraction rings to be seen.


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#18 dobsoscope

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Posted 16 January 2015 - 02:50 AM

And I guess stopping down the aperture does not make any sense for larger apertures as you would be exposing only a small part of the primary



#19 leviathan

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Posted 16 January 2015 - 05:43 AM

I see the advantage being particularly for people with bad seeing, larger apertures, and those of us who want to futz about and try different techniques.

 

The bigger the aperture of your CAT, the harder it is to get fine collimation done, especially when seeing is merely so so. My C6 is a pleasant doddle to collimate. My 11 Edge is much more difficult, just b/c it is very hard to get seeing stable enough for stable diffraction rings to be seen.

You can use artificial star.



#20 WebFoot

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Posted 16 January 2015 - 07:45 AM

I really still don't see why star collimation isn't any use.  By definition, you can ALWAYS star collimate to the limit of seeing.  If seeing only supports 100x, you can effectively collimate to 200x anyway; the diffraction rings are good enough for that.  The fact that your collimation at that point may not be perfect is irrelevant to the seeing you're experiencing at that point; by definition, you won't be able to tell the difference.

 

I have an Edge 11, and I find collimating it quite easy, so I don't understand the assertion about "larger" SCTs being difficult to collimate.

 

And artificial star collimation isn't much use on an SCT; the mirror will flop differently when pointed at the sky than when pointed parallel to the ground.


Edited by WebFoot, 16 January 2015 - 07:48 AM.

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#21 leviathan

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Posted 16 January 2015 - 08:10 AM

And artificial star collimation isn't much use on an SCT; the mirror will flop differently when pointed at the sky than when pointed parallel to the ground.

Put it somewhere above, on a roof of a building let's say.



#22 WebFoot

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Posted 16 January 2015 - 08:17 AM

 

And artificial star collimation isn't much use on an SCT; the mirror will flop differently when pointed at the sky than when pointed parallel to the ground.

Put it somewhere above, on a roof of a building let's say.

 

Whatever you do won't be nearly as good as star collimation.  If you live near a very tall building (having it on the roof of your house, 20 feet away, isn't going to help much), you can play with an artificial star during the day, but it's not as if seeing during the day, near the earth, is any good, either.

 

This can be useful for getting a really badly collimated scope into some decent collimation.  But there's no substitute for pointing your scope high in the sky, at an object essentially at infinity, for proper collimation.

 

And collimating an SCT really is easy.  Any SCT.



#23 areyoukiddingme

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Posted 16 January 2015 - 01:04 PM

 

I see the advantage being particularly for people with bad seeing, larger apertures, and those of us who want to futz about and try different techniques.

 

The bigger the aperture of your CAT, the harder it is to get fine collimation done, especially when seeing is merely so so. My C6 is a pleasant doddle to collimate. My 11 Edge is much more difficult, just b/c it is very hard to get seeing stable enough for stable diffraction rings to be seen.

You can use artificial star.

 

 

I don't find an artificial star to be particularly useful. They have to be a good distance away, and the SCT being the SCT, you need to really have it at some what of an angle to get the primary 'happy' on the baffle. And that's very difficult with an artificial star.



#24 areyoukiddingme

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Posted 16 January 2015 - 01:14 PM

I really still don't see why star collimation isn't any use.  By definition, you can ALWAYS star collimate to the limit of seeing.  If seeing only supports 100x, you can effectively collimate to 200x anyway; the diffraction rings are good enough for that.  The fact that your collimation at that point may not be perfect is irrelevant to the seeing you're experiencing at that point; by definition, you won't be able to tell the difference.

 

I have an Edge 11, and I find collimating it quite easy, so I don't understand the assertion about "larger" SCTs being difficult to collimate.

 

And artificial star collimation isn't much use on an SCT; the mirror will flop differently when pointed at the sky than when pointed parallel to the ground.

 

Star collimation is all that I use. But I am interested in trying other methods. I also don't think that the limit of seeing argument applies to most people. I want to do my collimation and leave it alone! I have collimated my 11 Edge perhaps 3 times. Also, seeing changes over time. Best to get the collimation nailed and leave it alone. Once it's there it'll stay for a good long while.

 

As to the assertiion about ease. . . it's all about the amount of energy that makes it into the diffraction pattern. My c6 puts a lot of energy into the first diffraction ring and that is easy to see. Much easier than the 11" which requires very high power and very stable seeing to get a stable diffraction ring when in focus. So to be more specific, out of focus collimation on the c6 and c11, no difference. Critical in focus collimation. . . definitely harder for the 11 than the 6.

 

The camera/meta-guide idea is to make getting that critical infocus collimation easier when the seeing isn't good enough for the in focus collimation.



#25 rgsalinger

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Posted 17 January 2015 - 12:46 PM

I bought the Hotech and I think that this thread doesn't accurately reflect what it's good for. The premise is that it's just as good as a star test, but that you can do it in your garage (not in the bright sun) at any time, more or less. One member of my club has proven this to his satisfaction and he's pickier than me by a mile. I have not personally proven it yet. Anyway, that's the idea. If it works and if your scope loses collimation frequently it's going to be really useful to have it and worth every penny. If your scope (like my old C11) seems to NEVER lose collimation it's a waste of money and some folks say that they can collimate their SCT in ten minutes anyway.The other thing that it does is to tell you if you have a centering problem with your secondary (not tip/tilt) and a tip/tilt problem with your focuser and this I can say is definitely correct as I verified the problem I had with a CCD Inspector run. My situation may be unique as The dark sky site I use is 90 miles from my house. I try to get out 4 times a month. That's enough travelling to put my RC8 out of collimation every other time.  So, I figured that I would eliminate needing to calibrate it at the dark sky site and just do it in the morning before I leave. Time will tell. 

Rgrds-Ross




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