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New member with my first SCT....a Dynamax 8

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#1 Pjacob77

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Posted 19 August 2019 - 05:52 PM

Well I got my first classic scope yesterday. I was able to pick up a Dynamax 8 with the tripod in pretty good shape. Even came with the original trunk and the bag for the tripod. I know the reputation of this but at $100 I couldn’t pass it up. It’s only my second scope and I can’t wait to see how it compares to my explore scientific ed80.

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#2 fcathell

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Posted 19 August 2019 - 06:00 PM

Actually, some of these performed pretty well. If the optics are even mediocre, it will do well as a low power DSO scope. For $100 it is a killer bargain! The tripod and wedge are worth more than that. If you star test it and find some issues, don't hesitate to try rotating the corrector by 60* increments, re-collimating (if necessary) and then re-testing. Make sure you index the original orientation! It's time consuming but it may help.

 

Frank

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#3 rolo

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Posted 19 August 2019 - 06:01 PM

Here we go again lol.gif


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#4 fcathell

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Posted 19 August 2019 - 06:30 PM

Now, now, Rolo!  LOL!

 

Frank


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#5 starman876

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Posted 19 August 2019 - 06:37 PM

Here we go again lol.gif

think positive Rolo.  


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#6 rolo

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Posted 19 August 2019 - 06:40 PM

I've got nothing but love for the DX8...I've owned 8 of them including a DX6waytogo.gif


Edited by rolo, 19 August 2019 - 06:44 PM.

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#7 Gil V

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Posted 19 August 2019 - 06:43 PM

If you are near CT, I can provide any and all service the scope requires.

I’ll bet you didn’t know that the Criterion Dynamax came with a lifetime warranty.

My lifetime. LOL
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#8 Russell Smith

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Posted 19 August 2019 - 06:44 PM

I would have jumped all over it for $100.
Known issues and all.
Just saying.
Congrats Pjacob77, and welcome to the classics forum.
Russ
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#9 clamchip

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Posted 19 August 2019 - 08:12 PM

I'm waiting for one to show up in my neighborhood, when it does 

I won't hesitate to buy it. 

 

Robert 


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#10 Bomber Bob

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Posted 19 August 2019 - 08:23 PM

Welcome to The Classics!

 

I can’t wait to see how it compares to my explore scientific ed80.

 

I predict that your ES 80ED will be sharper on the Moon & planets at 200x than your Dynamax 8.  


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#11 Chuck Hards

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Posted 20 August 2019 - 07:27 AM

The later, pretty blue and light grey ones actually have the worst imagery.  The early, dark grey and black-trimmed ones have been giving the better images.  Not great, but better than the later models.

 

The tripod alone is worth what you paid for the whole setup so you did good regardless.

 

Good luck!


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#12 Augustus

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Posted 20 August 2019 - 08:00 AM

If you are near CT, I can provide any and all service the scope requires.

I’ll bet you didn’t know that the Criterion Dynamax came with a lifetime warranty.

My lifetime. LOL

Criterion has the best customer service of any company... the company itself is defunct and there's still customer support! Thank you Gil!


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#13 terraclarke

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Posted 20 August 2019 - 08:47 AM

That was a bargain! Just consider it your light-bucket and you’ll be fine! ;)

 

And welcome to CN Classics!


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#14 apfever

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Posted 20 August 2019 - 09:38 AM

Hi Jacob,

 

Here's the story you don't have.  Criterion made the first few of these scope front lens plates using a system patented by Celestron.  There were very few of these early scopes because Celestron sued Criterion in court for infringement on the front corrector manufacturing process. Celestron won the suit and Criterion had to change the process they used to make the corrector plate. Criterion never did get very good results after the law suit and the optical performance definitely suffered. The scopes are useable but not great in general for optical performance.  Like any telescope model from any manufacturer, some will be better than others. In the BIG picture, the Dynamax 8 averages out at not so hot for what it should be against 8" Schmit Cass scopes in general.  

 

The regulars in this forum have a ton of experience, lots of bench testing, star testing, mechanical critique, analysis of scopes etc.  The experience here can lead to a focus on upper end performance with scopes that tend to perform above average in general. The Dynamax is NOT one, and will tend to get slammed here, and honestly just not have great optical reviews in general. However, for the general public (much lower experience and expectations that what's generated in this forum) the Dynamax is typically useable while a particularly bad one might be.....questionable to a novice.  Experienced opinions usually give them an OK for lower power which is up to around 100X, lets just say keeping the power in the double digits range. I've owned two, not that great, and I could get bigger and better images on a typical night that could squeak in at over 100X before deciding to back off for best view. Less experience than mine would probably still ooooh and aaahhhhh at a higher power and bigger image.  

 

Use it. Enjoy it. Find a local astronomy group and take it to a star party. Get some experienced people to give you an opinion. You'll probably find people very happy to check it out, and likely some one very happy to do a side by side with their 8" Schmit Cass.  Your tripod and wedge alone are worth more than what you spent. Seriously you could get your money back on those and then some in the used market, even in an ad here in Cloudy nights for just the tripod and wedge.  So go enjoy the scope - the entire telescope/fork/mount/trunk and accessories are essentially free for the cost of the tripod and wedge in your case.  By the way, the tripod is known to be pretty robust and is called the 'Golden Pyramid' by name. Plenty of people would love to have that tripod.


Edited by apfever, 20 August 2019 - 09:41 AM.

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#15 Augustus

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Posted 20 August 2019 - 09:49 AM

Hi Jacob,

 

Here's the story you don't have.  Criterion made the first few of these scope front lens plates using a system patented by Celestron.  There were very few of these early scopes because Celestron sued Criterion in court for infringement on the front corrector manufacturing process. Celestron won the suit and Criterion had to change the process they used to make the corrector plate. Criterion never did get very good results after the law suit and the optical performance definitely suffered. .

The forks on Jacob's scope are blue. The older scopes had gray forks.


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#16 DAVIDG

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Posted 20 August 2019 - 10:16 AM

 Minor correction to this " Criterion made the first few of these scope front lens plates using a system patented by Celestron."  They never made a corrector using the exact  Celestron method. They made them with their own version but that version infringed on  Celestron  patent,  hence the lawsuit. 

 

 

                       - Dave 


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#17 Chuck Hards

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Posted 20 August 2019 - 10:21 AM

The forks on Jacob's scope are blue. The older scopes had gray forks.

The older models had black forks.  Dark grey tubes.


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#18 Boom

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Posted 20 August 2019 - 11:39 AM

 Minor correction to this " Criterion made the first few of these scope front lens plates using a system patented by Celestron."  They never made a corrector using the exact  Celestron method. They made them with their own version but that version infringed on  Celestron  patent,  hence the lawsuit. 

 

 

                       - Dave 

 

How did Celestron find out?  Industrial espionage?  


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#19 fcathell

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Posted 20 August 2019 - 12:19 PM

Very interesting story on the Dynamax 8 which I had not heard. This certainly explains why these SCTs were typically substandard optically.  I believe Celestron made their correctors by placing the glass blank on a vacuum table where the glass was supported on the edge.  A vacuum was pulled on the blank such that it was deformed slightly and then the glass was polished by a special technique.  When the vacuum was released, the glass would go back to its normal form but now it would have the required shape/figure due to the polishing. I hear it didn't take much polishing to create this corrector figure.  Very clever!

 

The Criterion Company did make a couple of very nice Newtonians that I had a chance to observe through many years ago.  The Dynascope 6 and 8 were considered very affordable Newtonians at the time, and they came with motor driven EQ mounts. 

 

Frank

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#20 highfnum

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Posted 20 August 2019 - 12:41 PM

i added "bobknob" like thumb screws for easy adjust  M3 11mm long

 

and my setup  

DAVIDG and I talked about this scope up at stellafane 

interesting issues about the corrector plate

 

dyna2.jpg

dy8sec.jpg

 


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#21 davidc135

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Posted 20 August 2019 - 05:05 PM

Pjacob77 Good luck with your new acquisition. A DX-8 on a golden pyramid still looks magnificent even with its likely limitations- and for 100 dollars! There was so much good that went into these instruments to be undone by that poor corrector plate. If that could be replaced.... but it's not easy or cheap.

 

David


Edited by davidc135, 20 August 2019 - 06:44 PM.

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#22 Pjacob77

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Posted 20 August 2019 - 06:21 PM

Love all the information this site can provide!

with all the clouds around Chicago the past few nights I haven’t gotten to look at night yet but I figured I would try a comparison to my ED80.

with a big rainstorm the humidity is pretty high so it’s a little hazy out. These were taken with a t mount adapter directly into the dx8 and I used 2 2x Barlow’s with the ED80. The refractor was definitely a crisper image but with the Barlow’s not to much light was getting in compared to the DX8.

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#23 davidc135

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Posted 20 August 2019 - 06:39 PM

The Dynamax's image is much softer but much of that might be due just to poor collimation. I'd check that first (when the stars appear) and very likely there'd be a noticeable improvement.   David


Edited by davidc135, 20 August 2019 - 06:45 PM.

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#24 davidc135

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Posted 20 August 2019 - 07:50 PM

Adding to the above you could do a rough check anytime by taking out the diagonal and eyepiece and looking up the primary baffle. Adjust the three screws in the centre of the corrector until the secondary is centered in the baffle tube. It would be a useful first step followed up later by more precise adjustment using a star and high power eyepiece.

I wonder if you have a cover plate secured by the three slot headed screws because my DX-8 has Allen screws?   David


Edited by davidc135, 20 August 2019 - 07:56 PM.

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#25 rolo

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Posted 20 August 2019 - 08:44 PM

Adding to the above you could do a rough check anytime by taking out the diagonal and eyepiece and looking up the primary baffle. Adjust the three screws in the centre of the corrector until the secondary is centered in the baffle tube. It would be a useful first step followed up later by more precise adjustment using a star and high power eyepiece.

I wonder if you have a cover plate secured by the three slot headed screws because my DX-8 has Allen screws?   David

All those tips won't do much to address the real problem....bad corrector plates. I've wasted hours of tweaking, rotating, correctors, rotating secondaries, cooling, adjusting, aligning, collimating and even praying with no avail. The DX8 is what it is and should be appreciated that way. 


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