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Criterion Dynamax

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#51 Stevegeo

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Posted 30 July 2020 - 05:24 PM

 I will try both at 20mm  then  , 12 and 9mm 

If weather permits..  and take pics using my cell phone adapter ( celestron)  .. 

Maybe pushing the dx to 200 plus will show difference ... but then who knows 

 This may take some time to sort out ... stay tuned ..

Stevegeo  



#52 tim53

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Posted 30 July 2020 - 11:17 PM

The one I bought from Chuck does decently on Jupiter up to about 200x.  Beyond that, my C-8s beat it without breaking a sweat.



#53 Stevegeo

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Posted 31 July 2020 - 08:41 AM

Yes I had the C8 and Dx8 last nite out looking at the moon .( No difference) at 20mm . Then swinging to Jupiter and dropping in my 12mm in each the DX started to blur a bit . The C8 sharp. Then swinging to Saturn the difference wasn't really that noticable until I dropped in the 8mm ..then the DX really showed it .
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#54 Bomber Bob

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Posted 31 July 2020 - 09:11 AM

Yep.  I got some sketch-worthy Jupiter views in my 1974 all-gray DX8 at ~ 185x in 8+ seeing.  BUT... my 1950s Edmund 4" F15 achro frac out-resolved it, due to the lousy corrector's induced blur...

 

IME, the DX8 is a very limited-use scope.

 

BIF:  How heavy is the SP-C8 kit?  Is it portable -- totable around the yard?


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#55 DAVIDG

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Posted 31 July 2020 - 09:35 AM

Yes I had the C8 and Dx8 last nite out looking at the moon .( No difference) at 20mm . Then swinging to Jupiter and dropping in my 12mm in each the DX started to blur a bit . The C8 sharp. Then swinging to Saturn the difference wasn't really that noticable until I dropped in the 8mm ..then the DX really showed it .

 This is  an example of what I have been saying for years. Unless you do a side by side test with a scope that has true 1/8 wave optics you don't realize what your missing. It also why  people will swear they are getting great views but  unknown to them  with poor optics. This also why manufactures of mass produced telescopes keep getting away with  making scopes with 1/2 wave  or worse optics. As I said many time 1/2 wave optics don't produce an image that is fuzzy mess at low to medium power so people don't question the quality. They believe they have 1/10 wave optics and  the lack of detail at high power is the seeing or the eyepiece etc.

 

             - Dave  


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#56 bobhen

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Posted 31 July 2020 - 10:01 AM

Yes I had the C8 and Dx8 last nite out looking at the moon .( No difference) at 20mm . Then swinging to Jupiter and dropping in my 12mm in each the DX started to blur a bit . The C8 sharp. Then swinging to Saturn the difference wasn't really that noticable until I dropped in the 8mm ..then the DX really showed it .

That pretty much matches up with my experience with my old 1978 DX8.

 

Certainly not as good as a modern C8 on the planets closer on the moon and no real difference on most deep sky objects. But the posts saying the DX8 showed nothing but mush probably means there is something else going on besides the rough corrector optics.

 

Bob



#57 Stevegeo

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Posted 31 July 2020 - 10:34 AM

Yes I had the C8 and Dx8 last nite out looking at the moon .( No difference) at 20mm . Then swinging to Jupiter and dropping in my 12mm in each the DX started to blur a bit . The C8 sharp. Then swinging to Saturn the difference wasn't really that noticable until I dropped in the 8mm ..then the DX really showed it
Stevegeo.

#58 Stevegeo

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Posted 31 July 2020 - 07:49 PM

Yes I had the C8 and Dx8 last nite out looking at the moon .( No difference) at 20mm . Then swinging to Jupiter and dropping in my 12mm in each the DX started to blur a bit . The C8 sharp. Then swinging to Saturn the difference wasn't really that noticable until I dropped in the 8mm ..then the DX really showed it
Stevegeo.

 

Yes I had the C8 and Dx8 last nite out looking at the moon .( No difference) at 20mm . Then swinging to Jupiter and dropping in my 12mm in each the DX started to blur a bit . The C8 sharp. Then swinging to Saturn the difference wasn't really that noticable until I dropped in the 8mm ..then the DX really showed it
Stevegeo.

Wanted to clarify  a bit more...I wouldnt call the image musch... I could see Jupiters  bans with both , and easily but being low in the sky I had to wait until much later , which i couldn't do , ( I HAVE A JOB) and get up at 4 am ...

I have tried my Celestron  zoom 8 to 24mm on both C8 and Dx8 both were about equall. 

Using individual  eyepieces the image difference  was noticable but only in high mag.

New York weather isnt what I aa would call ideal. Humidity, clouds, haze  continually plague  viewing . 

 

One comment I have yet to hear about is how smooth and light the DX  control is , the focus knob and both fork adjustments are first rate .. very fine at least mine are z, and super smooth . The C8s I have looked through ,all to me at least,  has courser threads ..control / adjustment then the Dx8 .. comparing fork mounts, not fork Gem mounts as I did last nite . My fork mount C8 which I now regret selling, never was as balanced or easy to adjust as the Dx .

Stevegeo 


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#59 Gil V

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Posted 02 August 2020 - 08:12 AM

Great thread, on point yet surprisingly polite.

To Dave’s point, you’re 100% right about most consumers misunderstanding about what good optics really can do.

As far as Steve’s question about what can be done to help? Mechanical and optical centering of the optical train. When I indicated that these telescopes were built by kids, I wasn’t kidding. It’s not hard to realign a Dynamax. It will help, but it will not improve a flawed piece of glass.

I remember when another user here gave me an 8” scope that he was frustrated with. As soon as I got the scope and swung it through RA, I could hear a clunk. Retaining ring on primary had loosened.

My measuring stick today for acceptability of a Dynamax telescope is a decent view in a 9mm eyepiece. If you’re expecting better than that, you’re going to have to be exceptionally lucky.

For me personally, that’s a compromise I can live with. I love everything else about the scope.

Edited by Gil V, 02 August 2020 - 08:17 AM.

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#60 starman876

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Posted 02 August 2020 - 10:32 AM

attachicon.gifIMG_20200716_121416.jpgI have a rather dumb question.. what other differences am I missing that the dx cant be improved to better quality image ?  I know the corrector plate issue , what else am I missing?  Mind you I'm doing just planetary with either.

Looking through  my C8 and my DX8 using the same eyepiece I see very little difference in image , both during the day and night . But maybe that's ME.

I recently had both out for comet viewing and  people I shared both scopes , about 12 in all,  told me they preferred the dx8  over the C8  for the comet, HOWEVER  turning both scopes 180 and checking out Jupiter , all said that the view was about equal, with very little differences .  I used two eyepieces, switching back and forth ..  20mm plossels and  24mm  ...I did not go any higher in magnification. 

 Just a little survey of my own ... I did notice that the dx plugged into 110 outlet on a wedge tracked much better then the C8 on GEM.. but that could be setup error .

Stevegeo  

Maybe the C8 has poor optics also??


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#61 Terra Nova

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Posted 02 August 2020 - 11:17 AM

Maybe the C8 has poor optics also??

Certainly wouldn’t be the first time. My problem has never been so much encountering poor optics as habitually encountering mediocre, ho-hum views.


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#62 bobhen

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Posted 03 August 2020 - 06:47 AM


My measuring stick today for acceptability of a Dynamax telescope is a decent view in a 9mm eyepiece. If you’re expecting better than that, you’re going to have to be exceptionally lucky.

 

That also pretty much (much less so on Jupiter maybe more so on the moon) matches my experience with my old DX8.

 

Bob




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