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Help Attaching ASI6200 to Meade 10in ACF SCT

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#1 justasecond

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Posted 17 January 2022 - 07:08 PM

I have a Meade LX600 10in F8 ACF telescope and hope to use it for remote DSO imaging. I am new to the hobby and having a few issues.
I have been struggling with a couple of questions about the scope's specifications (primarily back focus and field curvature). I don't know where to find the parts I need or even what those parts are supposed to be.  I have to be honest, when I purchased the scope, I had no clue what I was getting into, so those questions came as a challenge and I started  researching information about my Meade scope for remote imaging. The two biggest questions are - what is the published back focus for the scope (and by extension, what do I want to add to the image train to achieve the best result).  I would like to find and purchase an automatic focuser I can control remotely via pc or asiair.  Finally whether the scope produces a flat field for larger sensors (again, I have no experience with these scopes should i put some device to corrected for field curvature.

Currently my meade came with a 2" sct to 1 1/4 eyepiece holder adapter that screws on to the rear cell port.  Clearly this is not going to work. 
I want to attach my ASI6200MM camera.  The 6200 is a full-frame sensor (36 x 24 mm). This has the SONY IMX455 CMOS. 62 Mega Pixels. 9576*6388.
Basically.  I am hoping to attach a 4/3 sensor and achieving a fairly flat field. I don't know any other specifics - like if I am to be using a reducer or a flattener in their imaging train.
I would like to know if Meade has officially published the scope's back focus anywhere?  Is there is anything on Meade's website?
I have been told it's 105mm, I have read it does not matter, someone wrote it is 110mm, and I found this drawing.  Any help is appreciated.  Thanks.

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Edited by justasecond, 17 January 2022 - 07:09 PM.


#2 bobzeq25

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Posted 17 January 2022 - 07:22 PM

You're going to find it really difficult to start with such a big scope.  You'd be _far_ better advised to start with something no larger than an 80mm refractor, and learn the complicated techniques with that.  These experiences are far from outliers, they're the overwhelmingly common experience.

 

"After months of learning and overcoming challenges <with the SCT>, and finally buying a shorter FL APO refractor, I really really really wish I had listened to everyone on here and started learning the imaging basics on THAT frac instead of on the SCT.   Trust me."

 

"really really really" <smile>

 

15 minutes spent watching this YouTube could save you many hours of time.  Maybe save you years.

 

"I put together a video of my imaging rig along with some info on how I went from years of failure trying to image with a long focal length SCT, to achieving success on my first image." 

 

https://www.youtube....h?v=MNQU1hdqz4M

 

"I regret spending the first 6 months trying to learn imaging with an 8" Edge, with that scope it was a losing effort. Fortunately got a nice little refractor, and not only have the quality of my images improved but I'm actually enjoying the process of learning how to do it!"

 

This is nothing at all like visual astronomy.  It's _really_ unintuitive.  The mount (which you didn't mention) is more important than the scope.  A big scope presents all kinds of problems.  It's not impossible to learn on one.  But, it's a bad idea.

 

A really really really bad idea.  <smile>  You'll learn significantly faster/better/ cheaper on a small scope.  Think months, not weeks.

 

Good analogy.  Someone who's never driven trying to learn to drive with a modern Formula One car. 

 

When it comes to breaking into DSO AP, the following things are important.

 

Good mount.  Small refractor.

 

Breakfast of Champions.


Edited by bobzeq25, 17 January 2022 - 07:56 PM.


#3 mrlovt

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Posted 17 January 2022 - 08:31 PM

Bob's right, you've jumped into the deep end.  But with a very cool scope and camera!  You can learn with what you have. True, it's a much steeper and more expensive learning curve than with a widefield refractor.  But then, you didn't tell us what you wanted to image, or what your level of persistence is!  (All that to say that I jumped in the deep in too, long ago, and am still swimming and having fun!)

 

To your question(s) - first, hitting the perfect backfocus distance is excellent, but not vital at this stage.  But to get there, you'll get to do some calculations, some plumbing, and some experimenting.  The backfocus on the sensor of the ASI6200 is at 17.5 mm.  Presuming that your drawing is correct, and the backfocus of the OTA is approximately 115.8 mm, then you'll need to put the front of the camera at 98.3mm (3.87").  That could involve using an extension tube like these sold by this website's host, shorter extension of 1mm, 2mm, etc, to fine tune back focus, filter wheel, etc.  That's the plumbing.

 

Here's a brief thread discussing the topic.



#4 justasecond

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Posted 17 January 2022 - 08:43 PM

I appreciate you two opening up as experts and telling me I am over my head.  Ok.  Fine.  Im over my head.  An opinion.  That isn't an answer.  This isn't my first scope nor is it my only scope.  Just the one I am trying to get going at this time.  I never said that.  Please I realize you are trying to be helpful.


Edited by justasecond, 17 January 2022 - 08:56 PM.


#5 mrlovt

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Posted 17 January 2022 - 11:31 PM

Apologies - I was actually trying to be encouraging. 

 

Maybe someone can chime in with documentation from Meade giving you an exact back focus number.  It's not in the LX600 manual, though it certainly should be.  That's frustrating.

 

My opinion is that what you found will put you in the ballpark, and that thread would hopefully be a useful confirmation of the same.  You don't have to get it exact, but if you want to, use a combination of extension tubes and spacers to put the sensor of the camera out to 115.8 mm from where the threads end inside the visual back of the SCT.  Calculate that 17.5 mm is already taken up by the front part of the camera.  Also, if you are using any other accessories between the back of the scope and the camera, subtract the length they take up.  And if there are filters involved, they can change things.  So you may need to adjust by using spacers.  


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#6 justasecond

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Posted 18 January 2022 - 07:54 AM

Thanks mrlovt,   

 

What I have and want to accomplish is Camera --> Filter Wheel --> OAG (guider) --> spacer/???? --> Flattener/Or not --> ????? what attaches directly here to the cell port????   

 

Currently the adaptor is for the holding the small diagonal used for visual astronomy.   I need a larger diameter cell port adapter.46AB56EB-1D2D-4607-8FFD-DB2A58C053AD.jpg

 

 

Below is my Skywatcher setup for illustration.  I'm missing something to do same with Meade.....

 

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Edited by justasecond, 18 January 2022 - 08:03 AM.


#7 justasecond

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Posted 18 January 2022 - 10:04 AM

On another forum someone suggested astrophysics large SCT adapter.  



#8 mrlovt

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Posted 18 January 2022 - 10:44 AM

You can use the Meade adapter: https://www.meade.co...sct-models.html

 

Yes, the A-P adapter will work just fine.  Or I used this Eye Opener from Peterson Engineering:  https://petersonengi....com/eyeopener/

 

Those will let you use your 2" refractor imaging train, just adjust for proper back focus.  The ACF is "coma free" - so you don't need a field flattener.  You should be able to get pinpoint stars (or very close to pinpoint) to the edge of the field.  With that full frame sensor the closer you are to the ideal backfocus position the better.


Edited by mrlovt, 18 January 2022 - 10:45 AM.

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#9 justasecond

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Posted 18 January 2022 - 12:03 PM

The links to the vendors for the Meade adapter are all out of stock or no longer carry.  I purchase the A-P adapter.  Checking out the Peterson now.   Thanks.



#10 mrlovt

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Posted 18 January 2022 - 05:04 PM

Also check out the Baader Clicklock visual back:  https://agenaastro.c...sct-thread.html  I use it on my Celestron.  The male SCT threads are slightly different between Celestron and Meade.  I've heard of people using this on both.  The site says to use plumbing tape on the Meade.


Edited by mrlovt, 18 January 2022 - 05:05 PM.

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#11 justasecond

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Posted 19 January 2022 - 09:07 PM

So far here is my progress.  Nothing is set in stone.  Hoping to use an OAG to guide.   Still awaiting my larger Celestron CWX-L mount.  It has a much larger capacity than the Skywatcher EQ6.  At this point I am still considering what focuser to use.  Hopefully there is some way to use the ZWO focus controller so I can use my ASIAir.  No field flattener yet.  It hasn't arrived.  

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#12 carolinaskies

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Posted 20 January 2022 - 10:22 AM

So far here is my progress.  Nothing is set in stone.  Hoping to use an OAG to guide.   Still awaiting my larger Celestron CWX-L mount.  It has a much larger capacity than the Skywatcher EQ6.  At this point I am still considering what focuser to use.  Hopefully there is some way to use the ZWO focus controller so I can use my ASIAir.  No field flattener yet.  It hasn't arrived.  

The standard camera adapter may be OK though eventually given the backspacing with other accessories you may find it causing vignette issues at the corner.  It was originally conceived by Meade that adapter would be used with a T-ring directly to a film camera(from back of OTA or focal reducer screwed on the OTA).  Once you start using accessories the light cone can become clipped the further back the camera sits from this base position. 

Since you plan to use other accessories the SCT thread on the OTA is your starting interface. To give you an example..
When I was imaging with my LX200 8" 20 years ago I used the flip mirror system. We would set the eyepiece parfocal with the camera and the flip mirror screwed directly to the OTA via the standard SCT thread. 
This image from the web is typical of how we used them in the 90's. 
equip02.jpg

When I decided to manually guide, I swapped out for a Meade OAG similar to this picture another CN'r shared a while back. In this case he used a guide camera. I had no such luxury in the 90s. This would attach to the back of the OTA directly(he has a focal reducer in front of it), then a T-ring would attach to it and which-ever camera I chose to use.  I would have an illuminated reticule and guide by eye using the hand control buttons to guide my exposures.

 

post-33237-0-69561400-1418585143.jpg

 

 

The OAG guiders out today come in a few different configurations. If you plan that route, then choose one that isn't too thick and has a good size pick off-prism and adjustable helical focusing for the guide camera. I won't suggest a particular one and suggest reading reviews for each on CN to come to your own decision.  Be aware once you start looking at them you'll see how many ways there are to interface between accessories.

M48 & M42 are common thread size standards for connecting these accessories so you may want to look at buying a few adapters to have on hand for various situations to make them fit and space correctly.  That perhaps is one of the biggest hurdles when putting the systems together... finding and using the best combination for what accessories are chosen.  

 


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