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APM 140 Doublet Owners; What Do You Think?

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#26 chemisted

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Posted 23 February 2019 - 07:31 PM

I have to ask: are you comfortable with using your 10" dob with a 2X or 3X barlow for the smaller DSOs and your Mod-3C?  If so, I would go with the 140mm refractor.  I am only now getting into a careful comparison of my 140mm with the RC-10 (using the NVD Micro) so I may be making this recommendation prematurely.  I just think that there is something special about the 140mm class of refractor.  If I had to pare my herd down to one scope that would be it.  One thing that I have discovered is that there is an enormous resolution increase when I looked at a bright glob (M5) and went from f/12.5 to f/20.  It really transformed the appearance of the cluster, was fully competitive with the views I get with the RC-10 and was easily handled by the Micro.  I plan to make more comparisons like this in the coming months.


Edited by chemisted, 23 February 2019 - 07:37 PM.


#27 chemisted

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Posted 23 February 2019 - 07:48 PM

As far as conventional astronomy goes, I also think this class of scope is pretty hard to beat.  I was able to resolve 'the Pup' adjacent to Sirius ten years ago when they were still quite close.  There is enough light gathering that open star clusters glisten.  I routinely use my scope alt/az and carry it out as a single unit.  The scope itself is 16 pounds and it is on a TV Gibraltar mount.  I suspect the APM 140 could be configured to have a similar portability.



#28 Doug Culbertson

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Posted 23 February 2019 - 09:01 PM

I have to ask: are you comfortable with using your 10" dob with a 2X or 3X barlow for the smaller DSOs and your Mod-3C? If so, I would go with the 140mm refractor. I am only now getting into a careful comparison of my 140mm with the RC-10 (using the NVD Micro) so I may be making this recommendation prematurely. I just think that there is something special about the 140mm class of refractor. If I had to pare my herd down to one scope that would be it. One thing that I have discovered is that there is an enormous resolution increase when I looked at a bright glob (M5) and went from f/12.5 to f/20. It really transformed the appearance of the cluster, was fully competitive with the views I get with the RC-10 and was easily handled by the Micro. I plan to make more comparisons like this in the coming months.

Actually, I routinely use 2x and 3x Barlows when using NV in my dob. The best view of the Cat’s Eye and the Eskimo were using the Mod-3 with a 3x barlow.

I agree with you on all points regarding tha 140mm class of refractor. In spite of the additional light grasp of the Mewlon, I like the idea of no collimation and faster cool down that can only be had with a refractor.

While my setup won’t be out the door in one trip portable, it will still be easily transported in our RV or either car.

Thanks, I believe that you have convinced me.

BTW, sorry for the brevity of my reply, but I only have my iPhone available right now.

#29 Doug Culbertson

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Posted 25 February 2019 - 04:51 PM

I just placed my order. Thanks to everyone for your information!
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#30 junomike

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Posted 25 February 2019 - 05:35 PM

Great choice Doug!

Be sure to post pics when it arrives!


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#31 Doug Culbertson

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Posted 25 February 2019 - 05:45 PM

Thanks Mike, I’ll be sure to take photos. 

 

I’m afraid that it’s going to arrive well ahead of my AYO mount, but at least I can look at it. lol.gif



#32 Bomber Bob

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Posted 25 February 2019 - 06:44 PM

I seriously considered the 140, but wound up buying the 152.  APM's Black Friday sale made it cheaper than the 140, and I was going to use either on the same Meade StarFinder mount, so weight wasn't a concern.  Yes, the 152 is severely nose-heavy.  I added a pair of Bresser rings + bar & handle that carries a vintage Takahashi FC-50 -- used this kit last night on clusters & faint fuzzies.  The 152 showed more galaxy details than the very good Dakin 4" F10.  It shows more fine planetary detail than any other scope I own.

 

Nothing wrong with the 140.  But after owning a D&G 5" F10, it's amazing to have a 6" F8 that's shorter, lighter, and shows so much more -- with no false color.


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#33 aa6ww

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Posted 25 February 2019 - 08:04 PM

My friend and I both bought the APM refractors during this recent sell. I bought the 152 with the 3.7" focuser and my friend bought the 140 with the 3.7" focuser.

I thought the 140 was going to be a scaled down 152 but it isn't. Its just shorter but used the same tube, dew shield, tube rings, and focuser. On the 152Ed, this size is just right. For the 140ED, it seems oversized.

I wanted the 152 but really considered the 140 until I saw my friends 140ED. Its beautiful in every way, but could have easily been built with a smaller tube and dew shield and just scaled back in size. This to me would have made it an amazing Mid size lightweight potent scope.

 

Making more efficient use of the sizes of scopes seems very practical. As an example, for years I had 102mm refractors using the larger 114mm tube diameters. I never thought much about this size until I owned an AT-102 with the smaller 105mm tube. This is much more practical and seems to give up nothing to the larger tube except size and weight.

 

I think if the 140 would have been built on a smaller scale, using a common size like the 145mm tube vs the current 155mm tube, it could have been a lighter more practical scope and capable of being supported by mid size mounts easier.

 

Regardless, the 140ED as it is, seem to fill a needed size we don't have much selection in. I'm sure you will be impressed by the new 140. It is in a class by itself.

 

...Ralph


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#34 Bomber Bob

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Posted 25 February 2019 - 08:53 PM

I think if the 140 would have been built on a smaller scale, using a common size like the 145mm tube vs the current 155mm tube, it could have been a lighter more practical scope and capable of being supported by mid size mounts easier.

 

A smaller lighter 140...  might have fit my Takahashi EM-1S, and that could've made a big difference for me.  The Tak carries my 4" F10 & 4" F15, and I can pick & move the whole thing as needed.  I can't do that with the 152.  My StarFinder mounts are the only ones that can carry it.



#35 stryker66

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Posted 25 February 2019 - 10:16 PM

Mine will arrive tomorrow and I dont know why I cant find many DSO images taken with the 140mm, I will pair it with zwo 1600mm and for high magnification zwo ASI385MC. Will test Narrow band and RGB on DSO as soon as I have a clear sky..



#36 Steve Allison

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Posted 25 February 2019 - 10:29 PM

Wider tubes allow the use of effective light baffles. Narrow tubes are often just flocked inside. I don't know if one is really better than the other.


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#37 Jeff B

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Posted 26 February 2019 - 12:09 AM

I believe the lens and cell are available from Markus as well.  It would make for a nice ATM project and you can customize it to suit you.

 

Jeff


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#38 evan9162

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Posted 26 February 2019 - 02:01 AM

NGC7662 (Blue Snowball).  APM140, ASI224MC, 320x5s, enlarged 2x

 

 

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#39 evan9162

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Posted 26 February 2019 - 02:04 AM

M76 (Little Dumbbell) - APM140, ASI224MC, 58x60s

 

 

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Edited by evan9162, 26 February 2019 - 02:04 AM.

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#40 evan9162

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Posted 26 February 2019 - 02:06 AM

Core of M42 - APM140, ASI224MC, 400x0.5s

 

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#41 CvBadengoth

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Posted 26 February 2019 - 02:29 AM

I seriously considered the 140, but wound up buying the 152.  APM's Black Friday sale made it cheaper than the 140, and I was going to use either on the same Meade StarFinder mount, so weight wasn't a concern.  Yes, the 152 is severely nose-heavy.  I added a pair of Bresser rings + bar & handle that carries a vintage Takahashi FC-50 -- used this kit last night on clusters & faint fuzzies.  The 152 showed more galaxy details than the very good Dakin 4" F10.  It shows more fine planetary detail than any other scope I own.

 

Nothing wrong with the 140.  But after owning a D&G 5" F10, it's amazing to have a 6" F8 that's shorter, lighter, and shows so much more -- with no false color.

...you find it is nose heavy? Have the 152 too, and for me not nose heavy at all, its even light weight with respect to its size. A 125 triplet is heavier than the APM152 doublet...triplets are nose heavy.

For the APMs it depends how/where you install the rings with the handle. 

 

@Doug: The 140&152 are both awesome scopes, you will enjoy it :-))


Edited by CvBadengoth, 26 February 2019 - 02:59 AM.

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#42 aa6ww

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Posted 26 February 2019 - 03:11 AM

This may have been the case in 1960, but not any more. My AT-102 has numerous light baffles installed in it.

 

...Ralph

 

Wider tubes allow the use of effective light baffles. Narrow tubes are often just flocked inside. I don't know if one is really better than the other.



#43 Doug Culbertson

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Posted 26 February 2019 - 06:44 AM

This may have been the case in 1960, but not any more. My AT-102 has numerous light baffles installed in it.

 

...Ralph

Yes, I also have the AT-102 and it does indeed have several baffles. It’s a nice little grab and go scope.

 

Thanks for your comments. I did briefly think about the 152, since it’s the same price, but the 140 is really what I wanted. I honestly don’t think that the tube size relative to the objective is going to bother me too much. lol.gif


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#44 Jon_Doh

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Posted 26 February 2019 - 09:54 AM

Doug, I think you're going to enjoy this telescope.  It's a solid, well built refractor with excellent optics and it balances well.


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#45 Bomber Bob

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Posted 26 February 2019 - 09:59 AM

...you find it is nose heavy? Have the 152 too, and for me not nose heavy at all, its even light weight with respect to its size. A 125 triplet is heavier than the APM152 doublet...triplets are nose heavy.

For the APMs it depends how/where you install the rings with the handle. 

 

@Doug: The 140&152 are both awesome scopes, you will enjoy it :-))

Yes.  Compared to my D&G 5" F10, it is severely nose heavy.  1" aperture larger doublet, yet the unloaded balance point is way too close to the lens cell for even my 5' pedestal.  On the D&G, it was close to the middle of the OTA.  I don't use the handle.  My Bresser + Takahashi addition puts the 152's balance near the OTA's middle (and gives me an excuse to Milky Way sweep with a picture-perfect 50mm fluorite.)



#46 HydrogenAlpha

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Posted 26 February 2019 - 11:25 AM

Very nice images, Darin! 

 

I wonder, has anyone tried imaging with this scope and the Riccardi reducer? I wonder how well the CA is controlled at f/5.25. I know that APM has released sample images, but it seemed like whoever processed it was reluctant to stretch the curves. 



#47 evan9162

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Posted 26 February 2019 - 11:45 AM

Thanks.  I've only done short-exposure imaging with my ASI224MC at prime focus so far.  If we ever see clear skies again, I will connect my setup from my C80ED, which consists of a TS 0.79x reducer, 1.25" filter wheel, and ASI178mm camera.  That gives an image scale of 0.63"/px, which is pretty small given seeing conditions, and challenging for guiding.  Most nights I guide at 0.5" RMS, so I think it will work out.

 

You can see in my M42 image that there are blue halos around the brighter stars.  We know that the 140 stretches what's possible with an FPL53 doublet, and that deep blue light will definitely result in bloat at those wavelengths.  I replaced the protective window on my ASI224MC with the UV/IR cut window, but it lets in everything from 400nm to 675nm.  I may try my Baader UV/IR-cut which blocks below 420nm.  I also have a #8 light yellow filter on the way, which has a gradual cut-off around 480nm.  That may mess with color balance quite a bit, so I'll just have to experiment.  The other option is the Baader Fringe Killer, which blocks about 50% below 475nm.  That probably results in better color balance, with the trade-off of being less effective at reducing blue bloat.


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#48 Jeff B

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Posted 26 February 2019 - 01:27 PM

But Evan, you have shown everybody that you can indeed use the 140 F7 for deep sky imaging.  So what if you have to customize filtration and color balance a bit.

 

Jeff



#49 evan9162

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Posted 26 February 2019 - 01:53 PM

Sure.  I don't think it's significantly worse than any other F6/F7 ED doublet.  I even see blue halos around brighter stars in my C80ED.

 

The smaller physical size and FPL53 glass (for better correction across a wider range of wavelengths) are the reasons I went for the 140 over the 152.  I need some more camera time, but based on some of the design and test data, it seems like the 140 will be fantastic for narrowband imaging.  I'm going to try some H-a and O(III) imaging if the skies ever clear up.



#50 Steve Allison

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Posted 26 February 2019 - 05:18 PM

This may have been the case in 1960, but not any more. My AT-102 has numerous light baffles installed in it.

 

...Ralph

Are the baffle apertures the same or do they decrease in size from large to small as the light cone is followed?




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