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Balancing the APM152ED

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#1 J_D_Metzger

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Posted 16 March 2020 - 03:07 PM

I bought the APM152ED a while back, and although I love the scope, it was causing a problem in my observatory because of how front-heavy it is.  In order to balance it on my AP900GTO mount, I had to slide it quite far back in the rings, which left me very little room between the eyepiece and the observatory wall when observing in any direction except north (left in the pictures).  I decided to add weight to the rear of the OTA.  I ordered a ring to fit the OTA from APM, and a dovetail counterweight with two 3.5# weights from ADM.  As you can see in the "before & after" pictures below, I was able to move the OTA about 8" forward in the rings, which gave me the clearance I needed from the walls.  Luckily, the APM152 has a sliding dewshield, so there was no problem with roof clearance.

 

It's a little hard to see, but the new ring and counterweights are just in front of the focuser.  Comparing the pictures, you can see how much the OTA was moved.  Observing is now much more comfortable...  smile.gif

 

(and it looks better, too!)  

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  • Before and After.jpg

Edited by J_D_Metzger, 16 March 2020 - 03:09 PM.

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#2 photoracer18

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Posted 16 March 2020 - 03:46 PM

I have done that in the past also. I currently have such a ring on my SVA-130EDT.



#3 Astrojensen

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Posted 16 March 2020 - 03:58 PM

Odd, I never felt that my APM 152 was all that front heavy. Granted, it has the big 3.7" focuser, but so does yours. 

 

 

Clear skies!
Thomas, Denmark



#4 Kunama

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Posted 16 March 2020 - 04:02 PM

I am in the process of doing the same for my 6" refractor, I added an optical finder though I generally don't use one, just that extra weight moved the scope up 2".

Trying to find a 170mm tube ring at a reasonable price, though I expect I will end up making one....



#5 J_D_Metzger

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Posted 16 March 2020 - 04:43 PM

Odd, I never felt that my APM 152 was all that front heavy. Granted, it has the big 3.7" focuser, but so does yours. 

 

 

Clear skies!
Thomas, Denmark

Actually, it is the 2.5" focuser.  Perhaps that is why yours is not so front-heavy...


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#6 Bomber Bob

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Posted 16 March 2020 - 05:41 PM

Can't believe I'm coming up on 3 years with my APM 152ED...  Like yours, it has the 2.5" focuser, and is extremely nose-heavy.  I solved the balance issue by adding a pair of Bresser rings + handle + my Tak FC-50:

 

APM ED 152 S076 (Meade SF Restore).jpg

 

Perfectly balanced with 2" accessories as pictured -- I don't even have to use the DEC clutch to keep it steady while tracking.  And, the eyepiece is at a good height for seated observing at / near the zenith.


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#7 J_D_Metzger

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Posted 16 March 2020 - 05:46 PM

I have to agree - the best balancing aid for a telescope is another telescope!!  lol.gif waytogo.gif


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#8 SteveG

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Posted 17 March 2020 - 04:30 PM

APM should make a heavy steering wheel for these 6” tubes. It would be popular!


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#9 hfjacinto

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Posted 17 March 2020 - 09:48 PM

I motorized the focuser (I have the 3.7” also) that made it much better balanced. But I also use mint for imaging, and that adds weight to the back. Also put on a large finder.

#10 beanerds

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Posted 18 March 2020 - 05:14 AM

My Saxon 150mm f8 achro with Chromocor fitted was the same until I epoxied about 5lbs of lead fishing sinkers into the adapter piece that holds the focuser .

 

Like you , this made a huge difference in viewing pleasure .

 

Nice looking scope and mount you have by the way .

 

Beanerds 

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#11 CvBadengoth

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Posted 18 March 2020 - 05:29 AM

....add heavy camera and filterwheel, a lot of cables.....and more cables....will balance that thing..... X-)

 

DSCF8382.jpg


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#12 fred1871

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Posted 19 March 2020 - 02:38 AM

Interesting. I have the APM 140 doublet, and in bare form (OTA plus tube rings) it's also very front-heavy. It has the 2.5" focuser.

 

When I've added a 2-inch diagonal and 50mm finder, plus an eyepiece of the middle-weight kind (think Pentax 10mm XW, not Nagler 31) the balance is much better, near-enough central. Because it's a scope I swap in and out on the mounting, the weight for lifting on and off matters. So I don't want to be adding kilos of counterweights on the tube to balance it; then it's heavier so I become clumsier lifting on and off.

 

I was surprised by the amount of front heaviness when I got it. My various other scopes, including a Vixen 140 refractor have much better balance. Weighing the two tube assemblies in similar accessories, they're very close in weight. But lifting the APM it feels heavier because of the imbalance. No way to cure it, really, other than adding the observing bits. Unless taking off the sliding dewshield, and using a lightweight one similar to the foam style I use on my C9.25, would reduce weight/improve balance. Of course, if I left it permanently set up, no weight or balance issues need be there.

 

Given the larger cell and glass in the objective with the 152 (same tube), I expect it's further out of balance than the 140, as well as longer.


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#13 CHASLX200

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Posted 19 March 2020 - 05:36 AM

6lbs of weight in the back did the trick on mine and the SW150ED.  Same for a CR6 achro.


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#14 Bomber Bob

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Posted 19 March 2020 - 03:56 PM

APM should make a heavy steering wheel for these 6” tubes. It would be popular!

I'd buy it.  I have a bad habit of grabbing the diagonal to move the scope.  A steering wheel like the one on the vintage Lafayette Arcturus would really come in handy!



#15 BillP

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Posted 19 March 2020 - 04:25 PM

APM should make a heavy steering wheel for these 6” tubes. It would be popular!

Not heavy as this is made of rubber...but makes pointing-repositioning the scope very easy.

 

Lunt 152 +Handle.jpg

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#16 SteveG

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Posted 19 March 2020 - 05:23 PM

Not heavy as this is made of rubber...but makes pointing-repositioning the scope very easy.

 

I remember seeing that when you posted a while back. Very nice!

 

Are they still available?



#17 BillP

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Posted 19 March 2020 - 08:02 PM

Should be.  Contact Ted Hauter - tedhauter@aol.com.  He makes them.


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#18 chuckscap

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Posted 20 May 2020 - 10:52 PM

I bought the APM152ED a while back, and although I love the scope, it was causing a problem in my observatory because of how front-heavy it is.  In order to balance it on my AP900GTO mount, I had to slide it quite far back in the rings, which left me very little room between the eyepiece and the observatory wall when observing in any direction except north (left in the pictures).  I decided to add weight to the rear of the OTA.  I ordered a ring to fit the OTA from APM, and a dovetail counterweight with two 3.5# weights from ADM.  As you can see in the "before & after" pictures below, I was able to move the OTA about 8" forward in the rings, which gave me the clearance I needed from the walls.  Luckily, the APM152 has a sliding dewshield, so there was no problem with roof clearance.

 

It's a little hard to see, but the new ring and counterweights are just in front of the focuser.  Comparing the pictures, you can see how much the OTA was moved.  Observing is now much more comfortable...  smile.gif

 

(and it looks better, too!)  

 

Very nice!   I too have an AP900 and have been looking at the APM 152 ED with the 3.7" focuser.   Right now I've swapped off my Orange C14 and have a TV-101 on the mount.   Your APM 152 looks just right on it.  I am so tempted.



#19 J_D_Metzger

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Posted 21 May 2020 - 12:12 AM

Chuck,

 

The 3.7" focuser is apparently quite a bit heavier than the 2.5", so the scope isn't as front-heavy.  You may not need additional counterweight...

 

The 152 would be a nice step up from the 101, but of course quite a ways from the C14!   I really like my 152, it has an almost perfect star test, and M13 the other night was superb.  smile.gif


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#20 Kunama

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Posted 21 May 2020 - 04:12 AM

I am in the process of doing the same for my 6" refractor, I added an optical finder though I generally don't use one, just that extra weight moved the scope up 2".

Trying to find a 170mm tube ring at a reasonable price, though I expect I will end up making one....

I did end up making a counterweight , 172mm ID and 200mm OD x 60mm

 

https://www.cloudyni...-today/page-190

 

 

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Edited by Kunama, 21 May 2020 - 04:15 AM.

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#21 J_D_Metzger

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Posted 21 May 2020 - 10:56 AM

I did end up making a counterweight , 172mm ID and 200mm OD x 60mm

Beautiful!  What does the c/w weigh? 

 

I have added another 1.75# weight, so now, with the existing two 3.5# weights, I have a total of 8.75# of c/w, not counting the ring and dovetail/rod.  Probably close to a grand total of 10# of weight.  I was able to move the OTA another inch or so forward.  The consequence is that I've had to move the mount counterweights all the way to the end of the c/w shaft.  It's a short shaft, so not so much of a problem...



#22 Kunama

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Posted 21 May 2020 - 03:51 PM

Thanks JD, I worked out first that I needed a 1.4 kilo aluminium ring to get the balance where I wanted it, by the time I finished machining it and added the screws it came to 1.385kg.

#23 J_D_Metzger

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Posted 21 May 2020 - 04:14 PM

Thanks JD, I worked out first that I needed a 1.4 kilo aluminium ring to get the balance where I wanted it, by the time I finished machining it and added the screws it came to 1.385kg.

About 3#, not nearly what I have.  But that Feather Touch and binoviewer probably add quite a bit.... smile.gif



#24 Kunama

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Posted 21 May 2020 - 09:38 PM

About 3#, not nearly what I have.  But that Feather Touch and binoviewer probably add quite a bit.... smile.gif

The FT3545 and attached APM finder on FT bracket do a good job of adding weight to the bottom end, the extra 3# meant improved tripod clearance that allowed me to shorten the tripod extension by 80mm and that means the tripod fits into a cupboard in my motorhome (RV to US guys?)




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