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Mak Collimated?

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34 replies to this topic

#26 RajG

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Posted 27 July 2021 - 06:14 PM

I'm no expert but that pic (esp of Jupiter's moons) looks more like mount shake/drift rather than bad optics to me. It is overexposed, so the exposure is too long. Try a shorter exposure perhaps? 


Edited by RajG, 27 July 2021 - 06:15 PM.


#27 vidrazor

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Posted 27 July 2021 - 06:40 PM

Your collimation images don't look bad, pretty close.  Maybe you got a C90 with not so good optics, no matter how good the collimation is.

Yeah that would be a drag LOL. I think I'm gonna pull on the bottom screw a bit, I see a bit of compression there. Then cross my fingers. grin.gif

 

I'm no expert but that pic (esp of Jupiter's moons) looks more like mount shake/drift rather than bad optics to me. It is overexposed, so the exposure is too long. Try a shorter exposure perhaps? 

I thought that as well, I'm going to make one more adjustment, and try some more tests. Weather has not been cooperating lately, and I'm also dealing with wildfire smoke. Tonight looks like T-storms. The Jupiter shot was made through fairly high humidity and wildfire smoke. We'll see.



#28 jesco_t

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Posted 28 July 2021 - 03:20 PM

Your Jupiter shot was way overexposed, don’t worry.

For planets the exposure time is in the low millisecond regime. It’s her different to DSO exposures. Planets are really bright.

Jesco

#29 vidrazor

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Posted 03 August 2021 - 01:37 PM

OK well, continuing to play whack-a-mole with my C90's collimation, I've come to this point. This was knocked out of focus just enough for me to see some rings, and then I brought it back almost into focus. How does this look like to you folks?

Thanks

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  • collimation test 3.jpg

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#30 Bill Barlow

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Posted 04 August 2021 - 10:28 AM

Looks pretty good to me.  Maybe a slight fattening of the rings at the 7 o’clock,position, but very slight.  Test it with some in focus looks of various stars or double star systems to see how it performs.  Try a little less de focusing to see how the diffraction rings look. 
 

Bill



#31 vidrazor

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Posted 05 August 2021 - 10:25 AM

Looks pretty good to me.  Maybe a slight fattening of the rings at the 7 o’clock,position, but very slight.  Test it with some in focus looks of various stars or double star systems to see how it performs.  Try a little less de focusing to see how the diffraction rings look. 
Bill

Yeah it seems pretty decent I think I tried less defocus, but it started to look like a blob. Both of these defocused images are fairly magnified.
 

I remember coming across references to two different software programs here on CN for accurate collimation, but unfortunately their terminology and use is over my head. It seems they would allow you to get perfect collimation however.



#32 CassGuy47

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Posted 05 August 2021 - 12:22 PM

I've owned a couple of C90's going back to the 1980's, and I've also looked through more recent copies of the scope.  In my experience, I've never come across a C90 with optics that are so bad that they can't produce a useable image.  Even if your collimation is off a tad, a C90, or any MAK for that matter, won't suddenly turn into a milk bottle bottom!

 

As has already been pointed out, your Jupiter image is severely overexposed, and the tracking isn't the best either.  Your focusing may also be off, and when observing planetary detail, accurate focus is critical.

 

How does Jupiter look visually?  How about the moon?  If the moon appears featureless, it's definitely not a collimation problem.  It could be a defective diagonal, a defective eyepiece, or user error.  I'm having difficulty understanding how the scope could be that bad unless someone kicked it for a field goal.



#33 cytan299

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Posted 05 August 2021 - 01:01 PM

Hi Vidrazor,

 

You might want to have a look at my post here:

 

https://www.cloudyni...-goodbad-is-it/

 

I think your collimation is probably ok, but needs to be focused in more to be sure.

 

cytan


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#34 vidrazor

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Posted 05 August 2021 - 01:56 PM

I've owned a couple of C90's going back to the 1980's, and I've also looked through more recent copies of the scope.  In my experience, I've never come across a C90 with optics that are so bad that they can't produce a useable image.  Even if your collimation is off a tad, a C90, or any MAK for that matter, won't suddenly turn into a milk bottle bottom!

As has already been pointed out, your Jupiter image is severely overexposed, and the tracking isn't the best either.  Your focusing may also be off, and when observing planetary detail, accurate focus is critical.

How does Jupiter look visually?  How about the moon?  If the moon appears featureless, it's definitely not a collimation problem.  It could be a defective diagonal, a defective eyepiece, or user error.  I'm having difficulty understanding how the scope could be that bad unless someone kicked it for a field goal.

I bought this used for astrophotography and it didn't come with eyepieces. I suspect it may have been knocked out by the former owner and/or in shipping. I deliberately overexposed Jupiter because I was really trying to get the smaller point size of the moons. However performing these collimation tests indoors with a pinhole light I came to realize I was getting mirror flop movement from my D5300. I had the scope set up on a SkyGuider Pro when I took those Jupiter shots, and I think the setup may be too susceptible to vibration. Testing indoors I switched to my mirrorless Olympus E-M10 Mk II to take these shots. I'm going to retest outside with the Olympus, I may have to use the C90 exclusively with the Olympus when it's mounted on the SkyGuider Pro, which is fine because vignetting is high even on the APS-C D5300 sensor, so I'll kill two birds with one stone.

 

Hi Vidrazor,

You might want to have a look at my post here:

https://www.cloudyni...-goodbad-is-it/

I think your collimation is probably ok, but needs to be focused in more to be sure.

cytan

Yeah, that stuff is right over my head, I don't understand any of that. I also don't really know how close to actual focus I need to be for analyzing. I'm pretty new to dealing with mirror scopes, I'm not entirely sure of what I'm doing and whether I'm going about it right. smile.gif I'll try making a series of images covering a range right through the focus point and post them here to see what you folks think.

I also think that it's looking pretty decent now. I just need to try it out outside to see what I get. Tonight may clear up enough to try some new tests.
 


Edited by vidrazor, 05 August 2021 - 02:00 PM.


#35 luxo II

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Posted 06 August 2021 - 07:53 PM

How does this look like to you folks?

Excellent !




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