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Equipment Discussions >> Cats & Casses

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Stardaug
professor emeritus


Reged: 08/03/08

Loc: Ontario, Canada
Re: SCT COLLIMATION - Much more than collimat'n screws new [Re: bilgebay]
      #5413672 - 09/10/12 04:24 PM

Hi - what CCD camera did you use for this image your posted showing flat field pin point stars in all corners? What size chip? Diagonally?

I've been reading this thread with interest since having obtained a Hyperstar 3 for my CPC800 (8"). I had coma in all corners in different directions.

I couldnt do everything you did not having access to any machine shop or skills in that area. But I did assume some things correct from the factory and centered my corrector and the secondary holder by measurements.

I then pulled all the push pins as you did so the Hyperstar was flat against the backing.

My test image after that was better. Coma was gone from corners but I now had the top left to right of image, stars out of focus while the bottom was better aside from the right bottom corner which showed elongated stars.

I havent had a chance to do adjustments to test anything further. I do know you can't collimate a Hyperstar with a defocussed star that much is true!

I was wondering since my QHY8L is a 28.4mm diagonal chip and the Hyperstar 3 being 27mm diagonal max, if this plays a major role in the problems with out of focus stars. If it did I would not expect these out of focus stars on the top part of the image, one side to the other side, to show out of focus leading so close to center of image. I am thinking maybe the corrector/secondary is not square with the primary mirror?

Thanks for posting all of this information. It has been very VERY useful.

Cheers.

Shawn / Canada


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bilgebay
Post Laureate
*****

Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: SCT COLLIMATION - Much more than collimat'n screws new [Re: Stardaug]
      #5415713 - 09/11/12 04:53 PM

Hi Shawn,

The camera is a Canon 550D, the sensor is 27mm diagonally.

I hope this helps.

Cheers

Sedat


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bilgebay
Post Laureate
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Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: SCT COLLIMATION - Much more than collimat'n screws new [Re: bilgebay]
      #5440104 - 09/25/12 03:30 PM Attachment (9 downloads)

Quote:

Let's continue from where we left.

The adjustment is finished now and I am showing how the secondary holder centering piece is smoothly being seated in to the holder:







Glenn, as you can see, I am verifying the alignment with the scope in vertical position.

If you are wondering the white stuff between the collimation piece and the shaft, it is a delrin bushing. The clearance between these two parts is so little that if I let the metal move on metal they would soon start seizing. I could have used bronze or similar bushing material but opted for delrin as it was what I had at the time of production.




Somewhere in this thread, I must have promised to give you further details on Hyperstar collimation I remembered this subject only when I noticed a thread going on about Hyperstar collimation on fastar yahoo group. Just to recap, I have quoted the above post from where we can continue now.

If you have followed me so far, you must be bold enough to take your Hyperstar unit apart When you do that, you will notice that there is a huge( in terms of our purposes of course) gap/play between the main lens holder body and the 2 rings that holds it in place on the secondary holder. However, there is nothing wrong with this if you consider the way the original collimation method is devised. In fact, without this gap you can not tilt and collimate the Hyperstar unit. With my method, I don't need this functionality and I need to make sure the lens is seated in alignment with my optical axis.

If your camera chip is not square to focal plane, you should take care of this on the camera side. I believe most cameras have a tilting mounting flange for this purpose.

Do not touch your Hyperstar collimation screws to correct for your camera chip's defects. Hyperstar should remain centered on your optical axis and parallel to the focal plane of the scope.


I produced a stepped bushing which can be seen in photo below, the one in the middle at the bottom.

Edited by bilgebay (09/25/12 03:36 PM)


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bilgebay
Post Laureate
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Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: SCT COLLIMATION - Much more than collimat'n screws new [Re: bilgebay]
      #5440116 - 09/25/12 03:40 PM Attachment (42 downloads)

This stepped bushing fits snugly with a swooshing sound on the lens body, with literally no play.

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bilgebay
Post Laureate
*****

Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: SCT COLLIMATION - Much more than collimat'n screws new [Re: bilgebay]
      #5440118 - 09/25/12 03:43 PM Attachment (41 downloads)

This is how it looks like when installed in place

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bilgebay
Post Laureate
*****

Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: SCT COLLIMATION - Much more than collimat'n screws new [Re: bilgebay]
      #5440120 - 09/25/12 03:45 PM Attachment (32 downloads)

.

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bilgebay
Post Laureate
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Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: SCT COLLIMATION - Much more than collimat'n screws new [Re: bilgebay]
      #5440125 - 09/25/12 03:49 PM Attachment (29 downloads)

another photo

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bilgebay
Post Laureate
*****

Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: SCT COLLIMATION - Much more than collimat'n screws new [Re: bilgebay]
      #5440129 - 09/25/12 03:50 PM Attachment (26 downloads)

+++

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bilgebay
Post Laureate
*****

Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: SCT COLLIMATION - Much more than collimat'n screws new [Re: bilgebay]
      #5440134 - 09/25/12 03:50 PM Attachment (23 downloads)

***

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bilgebay
Post Laureate
*****

Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: SCT COLLIMATION - Much more than collimat'n screws new [Re: bilgebay]
      #5440178 - 09/25/12 04:15 PM Attachment (25 downloads)

This was the first part only...now we can be sure that our Hyperstar body is perfectly centered within the 2 rings that attaches it to the secondary holder. But there is one more thing we should take care of....you know the lower ring is threaded on the secondary holder...if you take this ring in your hand and thread it on to the secondary holder you will notice that the thread is not tight fit either.. in my case the Hyperstar ring was not centering on its counterpart on the scope. So I developed a method of assembly and used the secondary holder centering tool for centering the Hyperstar base to the secondary holder.

If you check the photo below carefully, you can see what I am talking about.

Edited by bilgebay (09/25/12 05:03 PM)


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bilgebay
Post Laureate
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Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: SCT COLLIMATION - Much more than collimat'n screws new [Re: bilgebay]
      #5440193 - 09/25/12 04:27 PM Attachment (29 downloads)

So you are at the mercy of the coupling threads for centering the HS base. Well, I had the necessary tool already produced for this alignment. Starizona had the bore machined exactly to the same dimension of the secondary holder register which was a great help for this operation.

To cut a long story short let me share my HS assembly procedure with you:

1) Take the secondary mirror off and store it
2) Start threading the HS base on the secondary holder but don't tighten.
3) Just before it becomes snug, insert the centering tool, making sure it goes all the way in tho the secondary holder. Pls see photo


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bilgebay
Post Laureate
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Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: SCT COLLIMATION - Much more than collimat'n screws new [Re: bilgebay]
      #5440213 - 09/25/12 04:41 PM Attachment (12 downloads)

4) Tighten the HS base and take the centering tool out
5) Insert the bushing





6) Insert the HS collimation ring on the bushing





7) Tighten the collimation ring screws that fasten it to the threaded HS base.



8) Insert the HS lens body gently ( because it is not loose anymore)

Edited by bilgebay (09/27/12 02:29 AM)


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bilgebay
Post Laureate
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Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: SCT COLLIMATION - Much more than collimat'n screws new [Re: bilgebay]
      #5440216 - 09/25/12 04:44 PM Attachment (27 downloads)

.,

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bilgebay
Post Laureate
*****

Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: SCT COLLIMATION - Much more than collimat'n screws new [Re: bilgebay]
      #5440228 - 09/25/12 04:49 PM Attachment (19 downloads)

9) Rotate the lens body to your liking and tighten the "pull" screws. The push screws are gone for ever so you don't bother with them

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bilgebay
Post Laureate
*****

Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: SCT COLLIMATION - Much more than collimat'n screws new [Re: bilgebay]
      #5440234 - 09/25/12 04:52 PM Attachment (17 downloads)

You are free to make the visual check as shown on the Starizona video but I guarantee you will not find any faults if you have followed my method precisely.

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bilgebay
Post Laureate
*****

Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: SCT COLLIMATION - Much more than collimat'n screws new [Re: bilgebay]
      #5440257 - 09/25/12 05:00 PM Attachment (22 downloads)

There may be other and much better methods to achieve this task but this method was very easy for me to implement.

I am still seeing a lot of people complaining about the difficulty of collimating their HS system. Some are even on the verge of losing their faith in the system. Maybe this thread can help some of them in some ways.

Now go back to the first page of this thread and check the image I shared there.

Ok, here it is for your convenience.

Clear skies to you all.

Sedat


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robininni
scholastic sledgehammer


Reged: 04/18/11

Loc: Stephenville, TX
Re: SCT COLLIMATION - Much more than collimat'n screws new [Re: Stardaug]
      #5440478 - 09/25/12 07:23 PM

Quote:

I do know you can't collimate a Hyperstar with a defocussed star that much is true!






Whoa! I don't agree with that statement. I just did this the other night. I have a DSLR and, as anyone with Hyperstar knows, its shape makes using a defocused star just about impossible. HOWEVER, I got an adapter from Dean at Starizona to use my Orion StarShoot Autoguider on my hyperstar for one purpose---defocused star collimation. And I must say, it worked well. Not as easy as using the live view on the DSLR, but it worked using PHd as my imaging control and I was able to adjust the collimation screws to get that perfectly (well as good as my eyes can do) concentric donut star. After switching back to the DSLR...BAM! Excellent star roundness edge to edge.

Rob


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shrevestan
scholastic sledgehammer


Reged: 04/19/12

Loc: Shreveport, LA
Re: SCT COLLIMATION - Much more than collimat'n screws new [Re: robininni]
      #5442201 - 09/26/12 06:51 PM

Good idea on using the Autoguider to collimate. I wonder if using a donut to cover the DSLR shape would work as well. I typically just use the DSLR shape.

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tjensen
Carpal Tunnel


Reged: 02/16/05

Loc: Chapel Hill, NC
Re: SCT COLLIMATION - Much more than collimat'n screws new [Re: robininni]
      #5442270 - 09/26/12 07:44 PM

Quote:

I got an adapter from Dean at Starizona



Hey Rob,
What adapter? What can you do with the adapter/SSAG that you can't do with the DSLR in place? I haven't actually tried doing a defocused collimation. Next time I'm out I'll have a look.

Cheers


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robininni
scholastic sledgehammer


Reged: 04/18/11

Loc: Stephenville, TX
Re: SCT COLLIMATION - Much more than collimat'n screws new [Re: shrevestan]
      #5442561 - 09/26/12 10:17 PM

Quote:

Good idea on using the Autoguider to collimate. I wonder if using a donut to cover the DSLR shape would work as well. I typically just use the DSLR shape.




I have made a donut as well out of card stock, but the placement of it is the problem. It should be exacting and repeatable and easy to do and it isn't because:

1. I made the donut to fit around the secondary housing so I have to remove the hyperstar to place it and remove the hyperstar again to remove it after collimation. I don't like doing this.

2. The donut hole must be larger than the secondary housing to slip over it and thus there is some 'slop' because of this and the secondary housing cuts inward slightly where it meets the corrector plate if I remember correctly so the base of it is slightly smaller diameter. This allows for a couple of milimeters of movement once the card stock ring (donut) is in place. Depending on the position of the scope, this will lead to a near, but not perfectly symmetrical DLSR cover-up ring. Its pretty hard to get perfect collimation if your defocused star's hole is not exactly centered--but close. I have added some foam tape to snug it along 4 sides of the secondary housing but this still isn't exact.

The Orion Starshoot pro is totally symmetrical and even past this, is totally hidden behind my hyperstar III on my CPC1100. While I don't get "live view" (man I love that), it does work, although the stars are FAINT. I got my best collimation doing this. The you just remove the SSAG and the adapter and put your DSLR adapter back on the Hyperstar and attached that bad boy DSLR! All collimated!

Rob


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