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Harmonic Drive Mount for De-forked Meade LX200 8" OT

Astrophotography Cassegrain Mount Meade
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#1 dbernst

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Posted 02 March 2024 - 12:28 AM

This is my first post, so sorry if too many questions. I purchased a Meade Classic LX200 8" SCT 31 years ago, and after spending the best part of this year replacing capacitors and trying to fix it's GoTo function and tracking, have just de-forked the OT and mounted a Losmandy dovetail plate. I am fascinated by the ZWO AM5, have mostly heard great things, and am looking forward to not having to lift 73 lbs. to get my rig set up.

 

I understand that a 2000+ mm scope isn't going to be easy for a novice to do autoguiding for AP, but want to stick with this OT for now. I also plan to use my Nikon D800E for my initial foray into deep space AP, and later on purchase a good refractor. Here are few questions:

 

1. Are there other mount options I should consider? The biggest complaint I have heard about the AM5 is that it locks you into the ZWO ecosystem, however, I have been an Apple user since the Apple II days, so am OK with sticking with one manufacturer, as long as the ecosystem really works well. I would use an ASIAIR and ZWO cameras. Within this approximate price range, is there another harmonic drive mount worth considering? Since I also want to do some visual observing, I like the option to use as an Alt-Az mount as well.

 

2. I understand that an OAG (rather than guide scope) is best for this length OT, and that a larger mirror OAG (either ZWO or Celestron) is required. My question: can I use a guiding camera like the ASI220MM or do I need something with even larger pixels? I understand that I will need to also buy a small guide scope for use with my DSLR. I would rather save my $ to buy a better imaging camera.

 

3. One of the things I really don't like about the Meade is the focus-shift. I have considered adding a Crayford focuser. Will I have problems with back focus if I use a focuser and OAG? Will I have problems if I eventually add a filter wheel?

 

4. Any other recomendations would be much appreciated.

 

Thanks,

Dan B.


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#2 FRANKVSTAR

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Posted 02 March 2024 - 01:35 AM

 I used a 8 INCH Meade and a 8 inch Celestron both SCT scopes. I also used an upper dove tail to which I installed a guide scope both an lesser priced Celestron 80mm refractor and a Evostar 72ED refractor, both with a ZWO camera to guide. All this run with the help of ASIAIR PLUS and it worked well both at F-10 and with a reducer.

 I have in the past used a Crayford focuser to help with image shift, it worked well for me as you can get a close focus and fine tune with the other focus attachment. Never had used a OAG as if you use the guide scope and it,s firmly attached there is little issue with imaging with this setup. I am no expert but when I get back into the hobby after I leave for a while, I will be using either a 8in Meade or Celestron again.



#3 Celerondon

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Posted 02 March 2024 - 10:41 AM

This is my first post, so sorry if too many questions. I purchased a Meade Classic LX200 8" SCT 31 years ago, and after spending the best part of this year replacing capacitors and trying to fix it's GoTo function and tracking, have just de-forked the OT and mounted a Losmandy dovetail plate. I am fascinated by the ZWO AM5, have mostly heard great things, and am looking forward to not having to lift 73 lbs. to get my rig set up.

 

I understand that a 2000+ mm scope isn't going to be easy for a novice to do autoguiding for AP, but want to stick with this OT for now. I also plan to use my Nikon D800E for my initial foray into deep space AP, and later on purchase a good refractor. Here are few questions:

 

1. Are there other mount options I should consider? The biggest complaint I have heard about the AM5 is that it locks you into the ZWO ecosystem, however, I have been an Apple user since the Apple II days, so am OK with sticking with one manufacturer, as long as the ecosystem really works well. I would use an ASIAIR and ZWO cameras. Within this approximate price range, is there another harmonic drive mount worth considering? Since I also want to do some visual observing, I like the option to use as an Alt-Az mount as well.

 

2. I understand that an OAG (rather than guide scope) is best for this length OT, and that a larger mirror OAG (either ZWO or Celestron) is required. My question: can I use a guiding camera like the ASI220MM or do I need something with even larger pixels? I understand that I will need to also buy a small guide scope for use with my DSLR. I would rather save my $ to buy a better imaging camera.

 

3. One of the things I really don't like about the Meade is the focus-shift. I have considered adding a Crayford focuser. Will I have problems with back focus if I use a focuser and OAG? Will I have problems if I eventually add a filter wheel?

 

4. Any other recomendations would be much appreciated.

 

Thanks,

Dan B.

Hello Dan,

 

Welcome to Cloudy Nights!  I don’t use an SCT on my AM5 but I do have some tips regarding your plans.

  • The ZWO AM5 doesn’t tie its users into anything!
  • That SCT will work fine on an AM5 and you can take great pictures with that combination but you shouldn’t let it limit your development. 

The ZWO ASIAIR is the product that has limited compatibility with products from other manufacturers, not the AM5.  Even then the ASIAIR is compatible with most telescope mounts and DSLR cameras (and others) from several manufacturers. 
 

Just because your SCT will work on the AM5 doesn’t mean that you have to punish yourself by using it as your astrophotography training setup.  Although you seem to appreciate that it will be challenging to “do” autoguiding and astrophotography with this equipment combination, the big problem will be learning how to do these things with a long focal length behemoth like your SCT!  Small refractors and simple guide scope setups are surprisingly inexpensive.  In the beginning you could save money and grief by using a small refractor and reserving the big SCT for planetary images and visual use.  Later as your skills advance, you could dive into topics like OAG and mirror flop management. 
 

What do you think about these ideas?

 

Don

 

,


Edited by Celerondon, 02 March 2024 - 10:42 AM.

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#4 dbernst

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Posted 02 March 2024 - 12:40 PM

Thanks for the advice.  My thoughts would be to use the Meade mostly for planetary imaging at first to just get used to the ASIAIR system. That will allow me to also sharpen my skills with post-processing software. I was planning to use my DSLR for deep space initially, but am open to suggestions for a nice refractor that won't break the bank. If I have the DSLR (my longest lens is 400 mm) and the 2000 mm Meade, what focal length would be a good choice to add to these?

Thanks,

Dan



#5 Celerondon

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Posted 02 March 2024 - 01:37 PM

Thanks for the advice.  My thoughts would be to use the Meade mostly for planetary imaging at first to just get used to the ASIAIR system. That will allow me to also sharpen my skills with post-processing software. I was planning to use my DSLR for deep space initially, but am open to suggestions for a nice refractor that won't break the bank. If I have the DSLR (my longest lens is 400 mm) and the 2000 mm Meade, what focal length would be a good choice to add to these?

Thanks,

Dan

You should be fine then, Dan.  Many of us like the ASIAIR system and these AM-series mounts work well with it.  Apos between 400mm and 700mm would increase your range with options like reducer/correctors required if you don’t select Petzval optics. 
 

Don



#6 Deimos20

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Posted 02 March 2024 - 06:25 PM

Dan,

I have a Meade 8 inch SCT that I bought in the mid nineties and deforked a few years back. One of the mounts it rides on is a ZWO AM5 and it works just fine.  I use a ZWO OAG and the ASI 290 mini for guiding (pixel size 2.9um) and have a filter drawer rather than the wheel. I do use a .63 reducer/corrector on the back of the SCT which necessitates the requirement for a 105mm back-focus. I have no problem achieving focus using that setup or without the reducer when I do simple EAA and put a camera on the back of the scope with a standard 55mm T adapter.  I do have to adjust focus during the evening as temp and focuser creep do cause the image to shift after a while. I have an electronic focuser, but that is reserved for my main imaging gear which is a 115mm refractor. Cant help much on using Asair as I find NINA, PHD2  for imaging and Sharpcap for EAA more to my liking.  But as mentioned above, the Asair has a strong following and provided you want to standardize on ZWO cameras and accessories would be fine. I would also echo the comments above cautioning you on learning DSO astro photography with a 2000mm focal length scope.

 

Steve


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#7 dbernst

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Posted 02 March 2024 - 07:44 PM

Thanks!

 

I hear your cautions about trying to learn AP on this focal length scope. What about starting using my D800E and telephoto lens (ranging from 80 to 400 mm) mounted directly on the AM5? I checked and it appears that the ASIAIR supports this camera. Would that provide a good sense of all the workflow that I need to learn, or is working with a DSLR and telephoto lens different enough from working with a refractor (even of the same focal length) that it is worthwhile to get the refractor?

Dan



#8 Cliff Hipsher

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Posted 02 March 2024 - 09:38 PM

Dan,

 

The mount does not lock you into the ZWO ecology.  The ZWO ASI Air and its siblings do.  The mount is supported by ASCOM and I believe INDI as well.

 

Having said that, I have an old LX5 2080 SCT that worked fine on my GEM45 and an LXD75, but if I were to switch to an AM5 I would definitely get bigger/heavier tripod to stick it on.

 

An OAG is a whole 'nother ball game.  Back in the day I used (and still have) a Celestron Radial Guider that woked very well with AutoStar Suite and Envisage, but I have yet to try it with an ASI Air..

 

I did try using a ZWO OAG on my 130mm refractor but I could not get the camera to detect any stars so I switched to a 60mm f4 guide scope.


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#9 Deimos20

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Posted 03 March 2024 - 12:31 PM

Dan,

 If you are looking to see if astrophotography is right for you, then yes, using a DLSR is fine.  I started down this rat-hole using a Sony mirrorless camera with a  200mm lens piggybacked on top of  my LX50 before I deforked it. Initial investment was zero dollars. Stacked using DSS and stretched and processed in Photoshop. It proved to me that it was possible for me to do and I learned quite a lot about the workflow before investing in the proper equipment and software. Sounds like you are in a similar situation.

Also, I agree with Cliff in the above post about a heavier tripod.  I neglected to mention that my AM5 is mounted on a Meade field tripod that came with the SCT. Sounds like you could do the same as well if you still have it.

 

Steve



#10 dbernst

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Posted 03 March 2024 - 12:44 PM

Thanks. I still have the heavy weight Meade tripod for which I constructed a wooden version of Wheeley Bars, so it was more portable when I had the LX200 on top. Should be easy to add the proper size bolt to attach the AM5 when I get it. 
 

My thought is not to drop any more $ until Iearn whether I enjoy the workflow required to do good quality AP. Then, I’ll have more motivation to buy a nice refractor. 
 

Appreciate the advice. 
 

Dan




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