Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

New AT 6" and 8" Classical Cassegrain

  • Please log in to reply
1407 replies to this topic

#1326 quilty

quilty

    Mariner 2

  • -----
  • Posts: 230
  • Joined: 07 Oct 2019

Posted 24 July 2021 - 08:25 AM

I'll check. But if it is the case, we've won nothing by removing the ring. When you perform the torchtest I hope you use an eyepiece focused at infinity. I use an ordinary torch


Edited by quilty, 24 July 2021 - 08:36 AM.


#1327 Russkiy

Russkiy

    Explorer 1

  • -----
  • Posts: 61
  • Joined: 10 Feb 2021

Posted 24 July 2021 - 12:49 PM

Yes, we didn't win anything. But at least I have studied the internal structure of this telescope and am not afraid to disassemble it to the last detail)) I put the locking ring back. Moreover, I removed the secondary mirror from the cup. It looks like it was glued a little crookedly - when I combine the central mark of the secondary mirror with the center of the Cheshire eyepiece, I see that one edge of the cup is skewed. Adjusting the main mirror didn't help here. I'll just try to fix the secondary mirror with a ring, without glue. Although maybe that's not the point. I also fixed the main mirror, it was not fixed and made sounds when the pipe was turned.



#1328 quilty

quilty

    Mariner 2

  • -----
  • Posts: 230
  • Joined: 07 Oct 2019

Posted 24 July 2021 - 05:39 PM

That's what I like about these scopes. The assembly is simple and plain to see. My secondary looks exactly like yours in No. 1313 with a gap of 3 mm between the cylinder and socket.  When you've removed the secondary mirror could you exactly read its diameter and the inner diameter of the fixing ring? My 50 / 49 mm aluminated was just a guess.



#1329 Russkiy

Russkiy

    Explorer 1

  • -----
  • Posts: 61
  • Joined: 10 Feb 2021

Posted 25 July 2021 - 01:48 AM

Unfortunately, I didn't think to measure the secondary mirror... And I have already assembled a telescope.

Attached Thumbnails

  • 0_IMG_20210724_203254.jpg

Edited by Russkiy, 25 July 2021 - 01:49 AM.


#1330 Russkiy

Russkiy

    Explorer 1

  • -----
  • Posts: 61
  • Joined: 10 Feb 2021

Posted 26 July 2021 - 03:18 PM

Вот что у меня есть))

Attached Files

  • Attached File  CC6.pdf   33.04KB   49 downloads

Edited by Russkiy, 26 July 2021 - 03:18 PM.


#1331 quilty

quilty

    Mariner 2

  • -----
  • Posts: 230
  • Joined: 07 Oct 2019

Posted 27 July 2021 - 02:37 AM

Good drawing. Thanksfor sharing. The fruit of perseverance. Only thing that makes me nervous is your 322.4 mm mirror distance in combination with the fact that you said you don't use an extension ring at all. My distance is 325 mm and I need 1 inch extension with 2 inch diagonal. That doesn't quite fit.


Edited by quilty, 27 July 2021 - 02:41 AM.


#1332 Russkiy

Russkiy

    Explorer 1

  • -----
  • Posts: 61
  • Joined: 10 Feb 2021

Posted 27 July 2021 - 03:05 AM

This scheme was sent to me by the GSO at my request



#1333 quilty

quilty

    Mariner 2

  • -----
  • Posts: 230
  • Joined: 07 Oct 2019

Posted 27 July 2021 - 03:13 AM

Nevertheless perseverance. Then I'm free to criticise. The 322 mm mirror distance are indeed 325 mm, the 153mm primary mirror are indeed 150 mm but what they got right is their true aperture of 136,4 mm which they sell as 6 inch though knowing better. And their 0.9 arcsecs of waveoptical definition fits as well


Edited by quilty, 27 July 2021 - 03:17 AM.


#1334 Russkiy

Russkiy

    Explorer 1

  • -----
  • Posts: 61
  • Joined: 10 Feb 2021

Posted 27 July 2021 - 03:19 AM

150 mm is the diameter of the reflective layer. And the diameter of the main mirror glass is 153 mm. So they are right about this.



#1335 Russkiy

Russkiy

    Explorer 1

  • -----
  • Posts: 61
  • Joined: 10 Feb 2021

Posted 27 July 2021 - 03:23 AM

How did you measure the distance between the mirrors? And - is the bowl with the secondary mirror slightly unscrewed? By adjusting this distance (within a few mm), the aberration is eliminated. But in fact, I don't know yet whether these millimeters have a strong effect on aberration. And I don't know if I need to return the secondary mirror to its original position.



#1336 quilty

quilty

    Mariner 2

  • -----
  • Posts: 230
  • Joined: 07 Oct 2019

Posted 27 July 2021 - 03:33 AM

I read the distances baffle rim - secondary and baffle rim - primary mirror (centre). I don't think the effect on aberration is visible, I would stick to maximum possible distance. Maybe my secondary baffle is unscrewed for 3 mm but I didn't try too hard to remove the baffle it is really fastened



#1337 Russkiy

Russkiy

    Explorer 1

  • -----
  • Posts: 61
  • Joined: 10 Feb 2021

Posted 27 July 2021 - 03:47 AM

You do not need to remove the frame of the secondary mirror to change the distance between the mirrors. You do not need to disassemble the telescope for this. You need to tighten the fixing ring on the frame of the secondary mirror as much as possible and then tighten the bowl of the secondary mirror itself tightly to this ring.

Attached Thumbnails

  • 0_IMG_20210727_115023.jpg

Edited by Russkiy, 27 July 2021 - 06:31 AM.


#1338 Russkiy

Russkiy

    Explorer 1

  • -----
  • Posts: 61
  • Joined: 10 Feb 2021

Posted 27 July 2021 - 03:56 AM

<p>Вот ответ Telescope service:&nbsp;the distance between primary and secondary is a problem. because when you change it even if of 1mm, the spherical aberration and astigmatism (if present) will change. you have to bring the secodnary mirror in a decent position where you will see the best star shape.</p>

#1339 quilty

quilty

    Mariner 2

  • -----
  • Posts: 230
  • Joined: 07 Oct 2019

Posted 27 July 2021 - 05:27 AM

you keep me movin. Yes, thanks fpr your perseverance. I did one or two more mm of distance and got rid of the last 1 inch extension. But due to my undexterous hands I had to remove the front ring and a belt to unscrew the extension which left ugly scratches. But maybe another mm of more aperture and reduced swinging inertia. Will see about aspheric correction, if there's anything visible. Another collimation session anyway.


Edited by quilty, 27 July 2021 - 06:00 AM.


#1340 Russkiy

Russkiy

    Explorer 1

  • -----
  • Posts: 61
  • Joined: 10 Feb 2021

Posted 27 July 2021 - 06:30 AM

Did you make a scratch on the case? And I made a scratch on half the width of the main mirror)) Experience requires sacrifices!)) While there are doubts, it is impossible to calm down. We need to check everything. Now I have put one extension ring of 2.5 cm - just in case. Although in my opinion, it is not necessary for most eyepieces. Please let us know if you notice a deterioration in the image quality after increasing the distance between the mirrors.



#1341 quilty

quilty

    Mariner 2

  • -----
  • Posts: 230
  • Joined: 07 Oct 2019

Posted 27 July 2021 - 08:18 AM

. Please let us know if you notice a deterioration in the image quality after increasing the distance between the mirrors.

I'm not at all an expert at that, think they call it over- or undercorrection and increasing the distance while not changing mirror curvature might yield overcorrection but I doubt that I will notice anything. Did the daylight pre-collimation, the primary mirror was off as well a bit (because removing of the extension ring needed a big effort) the rest will be done at polaris. And it's 140 mm aperture now


Edited by quilty, 27 July 2021 - 08:48 AM.


#1342 Russkiy

Russkiy

    Explorer 1

  • -----
  • Posts: 61
  • Joined: 10 Feb 2021

Posted 27 July 2021 - 10:59 AM

And it's 140 mm aperture now

How did you measure this?



#1343 quilty

quilty

    Mariner 2

  • -----
  • Posts: 230
  • Joined: 07 Oct 2019

Posted 27 July 2021 - 11:29 AM

magic torch test. what else?



#1344 Russkiy

Russkiy

    Explorer 1

  • -----
  • Posts: 61
  • Joined: 10 Feb 2021

Posted 28 July 2021 - 02:29 AM

I was just asking. Have you done the star test yet?



#1345 quilty

quilty

    Mariner 2

  • -----
  • Posts: 230
  • Joined: 07 Oct 2019

Posted 28 July 2021 - 04:38 AM

Weather is dreadful at moment, yesterday's seeing unsteady but I did my best for collimation. For split seconds Epsilonlyrae were beautifully split (therefore the name "split second" :-). My first impression is: overcorrection (or undercorrection) makes it harder to decide at what point exactly to focus. But that needs further study

Guess my mirror distance is now 5 mm longer than the GSO drawing displays. Magnification is reduced by some% as the focal length which I think is noticeable.


Edited by quilty, 28 July 2021 - 05:36 AM.


#1346 Russkiy

Russkiy

    Explorer 1

  • -----
  • Posts: 61
  • Joined: 10 Feb 2021

Posted 28 July 2021 - 08:52 AM

Yes, the focal length decreases with increasing distance between the mirrors. And I still can't check my telescope.



#1347 quilty

quilty

    Mariner 2

  • -----
  • Posts: 230
  • Joined: 07 Oct 2019

Posted 29 July 2021 - 07:27 PM

Just watching Jupiter, seeing is quite good. Moon shadow really sharp. Epsilonlyrae split again like rarely before with this scope. So I can't tell that the aspherical correction has suffered by the mirror distance shift.



#1348 Garyth64

Garyth64

    Fly Me to the Moon

  • *****
  • Posts: 6,052
  • Joined: 07 May 2015
  • Loc: SE Michigan

Posted 29 July 2021 - 08:54 PM

FYI, the double double can be split with a 3" scope.

 

And, here's what a 8" CC can do:

 

https://www.cloudyni.../#entry11258712



#1349 Russkiy

Russkiy

    Explorer 1

  • -----
  • Posts: 61
  • Joined: 10 Feb 2021

Posted 29 July 2021 - 10:30 PM

And I still haven't gone anywhere with the telescope outside the apartment. And from the apartment window, all objects are not sharp. But they write that changing the distance between the mirrors leads to a change in the spherical aberration by 0.1 wavelength. I don't know how accurate this figure is. But I was told from the Telescope Express that the distance between the mirrors is a problem.



#1350 Russkiy

Russkiy

    Explorer 1

  • -----
  • Posts: 61
  • Joined: 10 Feb 2021

Posted 29 July 2021 - 10:32 PM

FYI, the double double can be split with a 3" scope.

 

And, here's what a 8" CC can do:

 

https://www.cloudyni.../#entry11258712

Отлично!




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics