22 replies to this topic

[Dave Novoselsky]

Having recently gained possession of a Skymax 180,  and after reviewing several older threads at this forum, I am wondering what the current view is to upgrading the focuser on this scope?

 

As far as I can tell, there are two basic schools of thought: first, replace the existing system with a GSO Crawford. The second is to use a micro focuser such as sold by telescope express, and several other sources.

 

The price differential is not that great but the question is what is a more effective upgrade.

 

Your thoughts would be appreciated.

[SoCalPaul]

I am not familiar with this specific scope, but I have experience with different types of focusers on SCTs.

 

In my experience, the Crayford type focusers that attach to the rear are best for imaging, because they help eliminate focus shift and potentially allow the primary to be locked down to avoid mirror flop.

 

However, they add a considerable amount of weight to the rear of the scope, which is a consideration for balancing the OTA in the dec/alt axis.

 

They might also increase the length of the optical path. For Cassegrain systems, increasing the length of the optical path also increases the system's EFL. As I understand it, SCTs are optimized for a certain focal plane position, so extending this out might increase some aberrations. Not sure about Mak-Casses though.

 

For visual, I prefer the dual-speed, replacement knob types, because they add hardly any weight at all and do not impact the length of the optical path.

 

Clear skies,

Paul

[Dave Novoselsky]

That seems sensible and I am 100% visual.  Anyone have any experience on this particular Mak and also what are the various available replacement knobs?  I am only aware of the lacerta (?) offered through Telescope Express.

[edsmx5]

That seems sensible and I am 100% visual. Anyone have any experience on this particular Mak and also what are the various available replacement knobs? I am only aware of the lacerta (?) offered through Telescope Express.

I just installed a Lacerta two speed upgrade to the Crayford focuser on my xt10. It's a smooth operating, solid, we'll built unit. The install was easy.



DavidAstro in Canada has them in stock

Edited by edsmx5, 06 December 2024 - 01:56 PM.

[SoCalPaul]

For SCTs, the gold standard are the Starlight Instruments Feather Touch Micro focuser replacements. I don't know if they make anything for the Skymax.

 

However, this does bring to mind a different solution, which is a larger focuser knob. This enables you to achieve finer rotational movements.

 

I think Starlight makes such larger knobs. There are also many inexpensive options available, e.g. https://www.etsy.com...b-for-8-and-925

 

You can also DIY these, such as this one made from a peanut butter jar lid:

 

 

Clear skies,

Paul

Edited by SoCalPaul, 06 December 2024 - 02:04 PM.

[Dave Novoselsky]

Again, my thanks

[vidrazor]

The simplest and best solution is to add a focusing motor. Trying to focus a 2700mm optic by hand is an exercise in futility. You can get and inexpensive Gemini focus motor that can be controlled via ASCOM, INDI, and comes with a wireless hand remote, and even a temperature gauge, at Ali Express for $75 and $13 shipping. I have two so far, one for my 102 f/7 and one for my C5.

 

They also have mounting kits that fit several scopes, and Buckeyestargazer can make 3D printed EAF mounts. While he presently doesn't list one for the Skymax, if you give him requested specs he'll easily print one out for your Skymax.

 

I honestly can't see wasting my time trying to focus such a monster by hand, especially if you're going to throw an eyepiece on top.

[bobhen]

Having recently gained possession of a Skymax 180,  and after reviewing several older threads at this forum, I am wondering what the current view is to upgrading the focuser on this scope?

 

As far as I can tell, there are two basic schools of thought: first, replace the existing system with a GSO Crawford. The second is to use a micro focuser such as sold by telescope express, and several other sources.

 

The price differential is not that great but the question is what is a more effective upgrade.

 

Your thoughts would be appreciated.

What are you goals?

 

If you want to improve focus sensitivity and eliminate image shift, then it's the Crawford.

 

If you want improve focus sensitivity and keep the weight to a minimum, then it's the micro focuser. But the micro will not eliminate image shift, which I find to hinder finding best focus and is just plain annoying.

 

Bob 

[Dave Novoselsky]

That is pretty succinct and answers what I wanted to know.  As usual Bob, you are the Man.

[Orion 3]

I installed a GSO Dual Speed Crayford Focuser for SCT on my Orion 150 mak to help with imaging at the suggestion of a few people on this forum. It works great, I do a rough focus with the mak knob and then fine focus with the Crayford. I bought it at Agena Astro for $150. It was a nice upgrade that wasn't too expensive, there are other premium focusers out there that are more expensive that could work also.

Tony

https://agenaastro.c...-telescope.html

[Cpk133]

Don’t forget the often suggested Baader diagonal with helical fine focus.  Fine focus without image shift or extra weight.  I should get one.

[CHASLX200]

Having recently gained possession of a Skymax 180,  and after reviewing several older threads at this forum, I am wondering what the current view is to upgrading the focuser on this scope?

 

As far as I can tell, there are two basic schools of thought: first, replace the existing system with a GSO Crawford. The second is to use a micro focuser such as sold by telescope express, and several other sources.

 

The price differential is not that great but the question is what is a more effective upgrade.

 

Your thoughts would be appreciated.

Mine was fine from the factory. But not as sharp as a 150 SW Mak jack i had.

Attached Thumbnails

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[Dave Novoselsky]

Chas, is there any scope you did NOT have?  You are my idol, obsessed even beyond me at my maniacal prime

Edited by Dave Novoselsky, 07 December 2024 - 08:31 AM.

[CHASLX200]

Chas, is there any scope you did NOT have?  You are my idol, obsessed even beyond me at my maniacal prime

Only stuff i never had was 2 big or 2 rich for me like AP's.

[Dave Novoselsky]

That’s okay, you are still my inspiration.

[Oldfracguy]

Unlike the smaller Skymax scopes which are all f/12-f/13, the 180 is an f/15 with a pretty long 2,700 mm focal length.  Adding a long dual-speed GSO Crayford will force the primary mirror to be moved closer to the secondary in order to create a narrower light cone in order to push the image plane farther out from the back of the scope.  That increases the focal ratio even more.  With that long 2,700 mm focal length you will probably want to use 2" eyepieces.  If you want to stick with 1.25" eyepieces, even a 32mm or 40mm Plossl, one way to avoid the problems with "mirror flop" or "image shift" when reversing the focuser direction--and this gets worse the larger these Maks get--would be to do what was suggested back in Post #11.  That's what I do with all the Maks and SCTs I end up with.  Here is one of those Baader T2 Prism diagonals with the 1.25" Helical Focusing Eyepiece Holder on a C8:

 

 

 

The idea is to approach focus as closely as possible from one direction only using the scope's focuser knob, preferably the direction that pushes the primary mirror toward the front of the scope, thereby supporting it from below when the scope is pointing upward.  Then just rotate the Helical Focusing Eyepiece Holder a little one way or the other to arrive at the precise best focus.

Edited by Oldfracguy, 11 December 2024 - 04:59 PM.

[Dave Novoselsky]

Just unloaded the 7” Mak on a friend who really liked it.  I decided that it was okay but the boat didn’t float the way I hoped it would and it was a tad too weighty for my age and health conditions.  Replaced it with a used but excellent condition 8” Meade LX 85 ACF, a lot lighter and, for what I want, should deliver just as well.

Edited by Dave Novoselsky, 11 December 2024 - 05:17 PM.

[Oldfracguy]

Just unloaded the 7” Mak on a friend who really liked it.  I decided that it was okay but the boat didn’t float the way I hoped it would and it was a tad too weighty for my age and health conditions.  Replaced it with a used but excellent condition 8” Meade LX 85 ACF, a lot lighter and, for what I want, should deliver just as well.

That's one way to upgrade.

[CHASLX200]

Just unloaded the 7” Mak on a friend who really liked it.  I decided that it was okay but the boat didn’t float the way I hoped it would and it was a tad too weighty for my age and health conditions.  Replaced it with a used but excellent condition 8” Meade LX 85 ACF, a lot lighter and, for what I want, should deliver just as well.

They all vary as well as SCT's do. My 180 was better than my very good Meade 8" LX50 by a hair blare.  But my SW150 Mak was much better and had one past nuts freaky insane sharp U.S. made 125 ETX that was just nuts it was so good. I have a 125 now and it is much better.  

[maniack]

For SCTs, the gold standard are the Starlight Instruments Feather Touch Micro focuser replacements. I don't know if they make anything for the Skymax.

 

However, this does bring to mind a different solution, which is a larger focuser knob. This enables you to achieve finer rotational movements.

 

I think Starlight makes such larger knobs. There are also many inexpensive options available, e.g. https://www.etsy.com...b-for-8-and-925

 

You can also DIY these, such as this one made from a peanut butter jar lid:

 

peanut butter lid focuser.jpg

 

Clear skies,

Paul

I have 3D printed knobs for fine focus on my SCTs - I just push them onto the existing knob. I'm 100% visual so my needs are very limited. Having the larger knob makes focusing much easier.

 

I also have a similar solution on my ST80 - a large 3D printed knob that replaces one of the stock knobs.

[Dave Novoselsky]

I just couldn’t deal with 19 pounds versus the a hair under 12 for the LX85.  I could no longer handle my larger refractors but thought I could handle the weight as the Mak was much more compact etc.  I was wrong. The much lighter and more compact Meade with the built in carry handle floats the boat, at least at this time.

[maniack]

I just couldn’t deal with 19 pounds versus the a hair under 12 for the LX85.  I could no longer handle my larger refractors but thought I could handle the weight as the Mak was much more compact etc.  I was wrong. The much lighter and more compact Meade with the built in carry handle floats the boat, at least at this time.

I love the maksutov design and I really miss the 5" I used to have. But SCTs are so much lighter that it's hard for me to justify the mak over a similar aperture SCT. As the OTA gets heavier the rest of the system also needs to scale up, so the overall kit weight increases dramatically.

 

That's why I have 5" and 8" SCTs. The C5 is much easier to mount than the 127 mak, and the 8" SCT is a bit lighter than a 6" mak.

[lakeorion]

1.25" Feather Touch (FTF1575BCR) with SCT thread adapter.

To complete the set add a ZWO EAF.