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Focal reducer for Meade ACF 12" - help needed

catadioptric Meade reflector
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#1 ASTERON

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Posted 19 August 2020 - 01:48 PM

Is there any good focal reducer available for the Meade ACF series ?  I need something that will give good results for AP, which is tried and proved to work reasonably well. Any help will be greatly appreciated.  I currently have a moonlight two speed focuser at the back of my scope but I am willing to change focuser if the reducer necessitates this.


Edited by ASTERON, 19 August 2020 - 02:04 PM.


#2 audioengr

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Posted 19 August 2020 - 04:18 PM

There is this Meade product, but it does coma correction, so don't use it unless your scope has no coma correction.

 

If you have Meade ACF scope, then this might work well.  I am trying to get feedback on the forums from anyone that uses it.


Edited by audioengr, 19 August 2020 - 04:19 PM.

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#3 ASTERON

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Posted 20 August 2020 - 10:13 AM

There is this Meade product, but it does coma correction, so don't use it unless your scope has no coma correction.

 

If you have Meade ACF scope, then this might work well.  I am trying to get feedback on the forums from anyone that uses it.

Hi Audioengr,

Thanks for the help. People in the intermediate imaging forum advised me to find a 0.62X Optec Lepus telecompressor.

I checked their website and indeed it is designed to work on Meade ACF scopes.   Problem solved !!

Clear skies waytogo.gif  



#4 audioengr

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Posted 20 August 2020 - 02:17 PM

There is also this one that works with AFC, but harder to get.  I will look into the Lepus.



#5 dcaponeii

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Posted 20 August 2020 - 02:23 PM

I have used both my Meade f6.3 and f3.3 reducer corrector on my 12" LX600 ACF without any noticeable issues.  I'm using an Orion G-10 camera.



#6 audioengr

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Posted 20 August 2020 - 02:51 PM

I suppose if the moon is centered, that the edge distortion will be out of range and in the black.  Much cheaper to go with the Meade reducers.



#7 carolinaskies

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Posted 20 August 2020 - 07:12 PM

I have used both my Meade f6.3 and f3.3 reducer corrector on my 12" LX600 ACF without any noticeable issues.  I'm using an Orion G-10 camera.

Using the FR/Correctors is possible with smaller chips.  

Someone with an ACF should take photos of the same target with the different reducers/cameras to show the effects. 



#8 lmclouth

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Posted 20 August 2020 - 08:12 PM

I know Mike Weasner has the Meade 12" LX600 ACF and he did a review of the Optec 0.62x focal reducer.

http://www.weasner.c...ucer/index.html

 

I have the Meade 12" LX850 ACF OTA and already owned a couple Celestron f/6.3 focal reducer/correctors that I used with my Meade LXD55 SC-8.

With suggestion from this website:

https://stargazerslo...er-for-sct-acf/

specifically this post:

https://stargazerslo...comment=2703978

 

you can remove the field flattener from the Celestron or Meade f/6.3 reducer/corrector.  I did that (as you can see in the last post of that site) and it appears to work very well.  I first had the reducer glass in its original location but I was just short of reaching focus.  I think it's mostly because I'm using the original Meade OAG and it is not the most thin OAG out there.  Then I put the reducer glass closest to the camera end of the reducer and then I was easily able to reach focus.

I went from f/7.78 down to f/6.29 and the images were flat all the way to the edges when used with my APS-C Canon EOS 7D Mark II.

 

I plan to do some more experimenting sometime but anyway I was very happy I was able to use my existing Celestron focal reducer with the already flat field of the Meade ACF.

 

Lamar


Edited by lmclouth, 20 August 2020 - 08:36 PM.

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#9 ASTERON

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Posted 21 August 2020 - 01:23 PM

Lamar,

Thanks for the links, - very useful !  I'll either give the Lepus a try or try to remove the corrector from a Meade/Celestron  FR if I get one.



#10 Canis Miner

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Posted 21 August 2020 - 03:44 PM

Several years ago a similar thread had some comments that the Antares is really a reducer and not a corrector, in that case, shouldn't it work for an ACF?  That's my question as well and would like to hear from someone that has 1st hand experience.  Interesting is that looking at reviews for the Antares, the negatives are all that there is coma around the edges.  Hmmm



#11 HarveyDeckAstro

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Posted 28 February 2021 - 10:45 PM

Just got a Meade LX 85 8 AFC, wondering about what reducer to get.

So, is the Lepus the choice? How did it all work out @Asteron?

#12 barnold84

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Posted 01 March 2021 - 12:18 AM

Just got a Meade LX 85 8 AFC, wondering about what reducer to get.

So, is the Lepus the choice? How did it all work out @Asteron?

Hi,

 

I have the same optics and I purchased the AstroPhysics CCDT67. The results with the reducer look very good.

 

CS!


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#13 HarveyDeckAstro

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Posted 01 March 2021 - 06:23 AM

@barnold84. Thanks for the suggestions! Would you please also share how you connect the reducer to the OTA and the camera? I plan to buy ASI533MC to go with it.

#14 barnold84

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Posted 01 March 2021 - 06:28 AM

@barnold84. Thanks for the suggestions! Would you please also share how you connect the reducer to the OTA and the camera? I plan to buy ASI533MC to go with it.

Sure! I bought a 2" Crayford focuser which is directly attached to the SC thread at the end of the tube. The reducer goes directly into the 2" eyepiece holder of the focuser and is clamped there. The other equipment is connected to the reducer through it M48 male thread. In my case, the filter wheel/holder follows directly on the reducer. My camera has a T2 thread. Therefore I have a M48 (female) to T2 (male) adapter.

 

Please let me know if you need more details!


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#15 ASTERON

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Posted 01 March 2021 - 11:07 AM

Just got a Meade LX 85 8 AFC, wondering about what reducer to get.

So, is the Lepus the choice? How did it all work out @Asteron?

Hi Harvey,

I never got to buying the Lepus as there was a change of plans and change of priorities.

Maybe in a year or so I will have things work out to the stage that I  may buy the Lepus.  Stay tuned. smile.gif


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#16 HarveyDeckAstro

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Posted 01 March 2021 - 12:36 PM

Sure! I bought a 2" Crayford focuser which is directly attached to the SC thread at the end of the tube. The reducer goes directly into the 2" eyepiece holder of the focuser and is clamped there. The other equipment is connected to the reducer through it M48 male thread. In my case, the filter wheel/holder follows directly on the reducer. My camera has a T2 thread. Therefore I have a M48 (female) to T2 (male) adapter.

 

Please let me know if you need more details!

Hi Bjorn,

 

This is really helpful! So the Crayford focuser is something like

 

https://optcorp.com/...c4aAjqAEALw_wcB

 

Now the OTA has its own focuser. Does the Crayford make the OTA's focuser useless?

 

Harvey



#17 barnold84

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Posted 01 March 2021 - 01:06 PM

Hi Bjorn,

 

This is really helpful! So the Crayford focuser is something like

 

https://optcorp.com/...c4aAjqAEALw_wcB

 

Now the OTA has its own focuser. Does the Crayford make the OTA's focuser useless?

 

Harvey

Hi Harvey,

 

Yes, a focuser like this. I think you found the very same focuser that I have, just with a different label on it but probably the same Chinese factory. 

 

The OTA focuser won't be useless, as you would use it to coarse focus on the target and do the fine tuning with the Crayford. When I set my scope up, I extend the Crayford to 10mm and lock it there. Then I focus with the OTA focuser ending with a CCW movement to keep the mirror in position (at least as long as possible). The fine focussing afterwards with the Crayford. 

 

The focuser you found has a range of 30 or 40mm which is actually more than you need. If available, you can look out for one that is shorter and thus a bit lighter as you won't need this huge travel distance. As I said, it's for the fine tuning and thats a matter of a few millimeters and less.


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#18 HarveyDeckAstro

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Posted 01 March 2021 - 01:29 PM

Hi Harvey,

 

Yes, a focuser like this. I think you found the very same focuser that I have, just with a different label on it but probably the same Chinese factory. 

 

The OTA focuser won't be useless, as you would use it to coarse focus on the target and do the fine tuning with the Crayford. When I set my scope up, I extend the Crayford to 10mm and lock it there. Then I focus with the OTA focuser ending with a CCW movement to keep the mirror in position (at least as long as possible). The fine focussing afterwards with the Crayford. 

 

The focuser you found has a range of 30 or 40mm which is actually more than you need. If available, you can look out for one that is shorter and thus a bit lighter as you won't need this huge travel distance. As I said, it's for the fine tuning and thats a matter of a few millimeters and less.

Great solution! Yes, I will go with your system. Thanks for helping out!

 

Harvey


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#19 Oberon510

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Posted 04 March 2021 - 11:21 AM

You may want to also look at the Moonlite focuser solutions which include models to incorporate several FRs - they call them the Tall Focus Reducer profile models. https://focuser.com/products.php

 

The Astro Physics model is popular (attached document)

I went with the Lepus.

 

Attached Files


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#20 HarveyDeckAstro

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Posted 04 March 2021 - 01:47 PM

You may want to also look at the Moonlite focuser solutions which include models to incorporate several FRs - they call them the Tall Focus Reducer profile models. https://focuser.com/products.php

 

The Astro Physics model is popular (attached document)

I went with the Lepus.

The Moonlite focuser looks really nice and works well with the reducer.

 

How is the Lepus? Are you happy with it?

 

-Harvey



#21 Oberon510

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Posted 04 March 2021 - 05:26 PM

A couple of things why I decided on the Lepus over the AP :-

 

1) Seems to be designed to support the ACF style f/8 OTAs where the AP CCDT67 says f/9-f/10 and above (although AP says f/8 or f/9 as lowest in other documentation). Others seem to have no issue with it so this was just my decision thought.

2) Imaging train seemed a little more sturdy with everything screwed on - Lepus screws on to 2" rear cell and provides a good mix of camera adapter sizes (M42/T for me) to support various camera configurations to get to the recommended back focus (105mm - see attached)

3) Both Lepus and AP get good reviews so my decision was a combo of these three - maybe a little more personal choice though.

 

I am happy but I think there are a lot of people who like the AP so just offering up my two cents worth. I am using an LX850 f/8 10" OTA.

 

This was on the Lepus site too - https://lx850.tumblr...-telecompressor

Attached Files



#22 HarveyDeckAstro

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Posted 04 March 2021 - 06:47 PM

Thanks for the explanation! Indeed, OTP specified that Lepus works with Meade AFC. The screw-on does make all things secure. With the aim being imaging, the diagram is very straightforward. This is a very attractive solution too!

Perhaps someone with experience with both Lepus and AP on Meade AFC could provide more definitive comparisons.

Would a focuser as a part of the distance between the reducer and the camera still useful? Or it is unnecessary? I don’t know how bad the image shift would be for Meade LX85 8” with the stock focuser. I haven’t got a chance to test the OTA since my mount is sitting somewhere in a UPS facility for past week or so.

#23 barnold84

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Posted 04 March 2021 - 11:43 PM

Thanks for the explanation! Indeed, OTP specified that Lepus works with Meade AFC. The screw-on does make all things secure. With the aim being imaging, the diagram is very straightforward. This is a very attractive solution too!

Perhaps someone with experience with both Lepus and AP on Meade AFC could provide more definitive comparisons.

Would a focuser as a part of the distance between the reducer and the camera still useful? Or it is unnecessary? I don’t know how bad the image shift would be for Meade LX85 8” with the stock focuser. I haven’t got a chance to test the OTA since my mount is sitting somewhere in a UPS facility for past week or so.

Hi Harvey,

 

I cannot provide a comparison between Lepus or AP, as I only own the AP. Only a bit more of experience with the AP: I did some images recently again and the image quality is completely satisfying to me. Round and coma- free stars into the edges with the 16mm chip. APS-C is yet to be tested.

The nominal reduction factor with the AP starts at a back focus of 85mm, which I like as I don't need more space between reducer and camera. By increasing the working distance, I can "increase" the reduction factor from the nominal 0,67 to 0,63 or even less. However, I don't know how image quality changes if I deviate a lot from the 85mm. The last session, I shot at 92mm back focus.

 

For the focuser: I don't want to miss it. There are certainly a few methods to make finer adjustments with the included focuser but you won't get rid of the mirror flipping if you reverse direction, which I find extremely annoying. With the Crayford, the object stays perfectly in position and I can really focus on focusing.

 

Björn



#24 HarveyDeckAstro

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Posted 05 March 2021 - 06:39 AM

Bjorn,

Thanks for your detailed information about your results! Very helpful! I don’t plan to get a big chip camera, so 16 mm is very good!

Would you be able to upload a photo of your setup? Also, which focuser are you using? There are so many choices!

Harvey

#25 barnold84

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Posted 05 March 2021 - 11:44 AM

Hi Harvey,

 

I've uploaded a picture, where I had my scope assembled to test if I can balance it. From an imaging point of view this setup is a bit nonsense but I did that because the focuser is quite heavy and also I prepared to go into the mono shooting with filter wheel. The DSLR served just as a weight substitute for the mono camera which hadn't arrived by then. Also the placement of the reducer (it was with the Meade) is wrong. It would be after the focuser. Nevertheless, you might get an impression about the focuser's size. With all that stuff attached, the tube gets quite long. I'm not using an OAG mainly for the balancing purpose and tried it with the guide scope on top.

 

Setup.jpg

 

One more thing:

I've now determined the effective focal lengths. When I shot with the Meade attached directly to the tube (without Crayford), the reduction is about the 0,63 it's supposed to have.

Now with the Crayford and the AP reducer at the end, I'm not getting the nominal 0,67 but only 0,8. The effect comes from the Crayford since I need to change the FL of the SCT significantly to bring the focus point quite behind the tube. So instead of having 1300mm, I was shooting with 1600mm FL, making an f/8 out of my f/10. 

Nevertheless, I'm quite happy with the resulting image quality: https://astrob.in/rwezw6/C/ 

The image is cropped to emphasize the open cluster and due to some offset between the LRGB channels.

 

Tomorrow should be a good night and maybe I'll go for M1. Then I'll use the SCT and try another back focus to make the scope faster. I could make a photo of that setup and place it here as well.

 

Björn

 




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