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New ES 140mm f6.5 FPL-53 Scope - Pictures and Impressions

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#76 gnowellsct

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Posted 24 March 2019 - 07:32 PM

 

 

Hahahahahaha smile.gif So it looks like I'm good to go so long as I stay away from truck drivers who got beat up for their lunch money by Carl Sagan as a child. Point noted...

Yeah I think so.  Although upon reflection I realized that just because the screws are strong doesn't mean the *rings* are strong.  I imagine there is a big "pull out" difference between CNC machined aluminum rings and cast aluminum.  That said, I used my FS128 for I dunno, 8 or 9 years with cast aluminum rings and no incidents.  The rings are still in service on that Tak which is over at a friend's house.  GN


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#77 SkyHunter1

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Posted 24 March 2019 - 07:45 PM

That moon shot looks like a one degree field or so, implying a magnification of about 70x or 0.5x per mm of aperture.  To get a "tough" lunar limb color test you should push it to 2x per mm or about 280x.  Should be doable.  Or during the day find a distant tree branch against the bright blue sky.

 

This is a pricey triplet apo and it will, in my estimation, pass such color tests, but an almost-full moon in the field of view indicates this test did not push the optics hard. 

 

2x per mm of aperture corresponds to a 0.5 mm exit pupil in every scope, and the 50x per inch rule is just an Americanization of the measurement.  The 1x per mm of aperture is always a 1 mm exit pupil.  A 6.5 mm eyepiece in your scope will yield exactly 140x.  And although a 3.25 mm eyepiece might be hard to find a 3.5mm or 3.0 mm will be close enough to the 0.5 mm exit pupil or 2x per inch (280x).  

 

The idea of color testing at high magnifications is that the R G B don't come together at exactly the same point in an imperfectly corrected scope.    High magnifications are unforgiving in terms of getting exact placement of the eyepiece relative to the focal plane, and either all the color is exactly there or it isn't.  If it isn't, you get false color fringe.  At low magnifications the focus position is more forgiving, it is easier to find a sharp focus point for lunar features (for example) and more difficult to detect whether one color is coming to the focus point in front or behind of the others.  That is, it's harder to see false color.  In fact even f/5 or f/6 achromats at very low magnifications exhibit little false color on run of the mill star fields. 

 

The ES 140 triplet will do much better.  The 70x  test is like a ten minute mile for professional runners.  Anyone can do that (not me, but anyone who says he is a runner).  Closer to the three minutes-and-change mile is 2x per mm.  And yes, I'd say most real contenders have to be reliably below 4 minute miles these days, and most apos can do better than 2x per mm.  But at least you're in a zone that is acknowledged to be tough.

 

I doubt your 140 will give up anything at 280x, but you don't know till you try, and the full moon pic, while very nice to the eye, was not a color test.  Try to nail the limb at 280x.  Or a daytime branch in bright sun against blue sky.  If you're feeling nutso keep on pushing past  280.  

 

Greg N

Greg,

Thanks for all your advice. I appreciate you keeping me honest and making sure I test the scope enough to provide a fair test. I am pleased with the results so far with the ED140, but to highly experienced and knowledgeable members like yourself here on CN, I know I haven't pushed this scope enough to fairly access where this scope ranks with others in its class in terms of price, aperture and performance. I'm a noob :) I'm easy to please lol. 

 

I mentioned in an earlier portion of this thread that I have a buddy who I thought might might have stronger eyepieces. Unfortunately, his strongest eyepiece is 9mm. If I use my 2.5x powermate with the 9mm I think that brings me to about 250x. I was hoping not to have to introduce the powermate into the mix, but I don't have any access to anyone who has a high quality 3mm eyepiece or stronger. 

 

Any suggestions as to how I can give this scope a fair test? Is using the powermate not recommended? I'm not really sure how to perform proper testing given the equipment I have available. It seems a 9mm with a powermate at 250x is about the best I can do at the moment. Maybe you have an answer to my conundrum?

 

Regards,

Skyhunter1


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#78 gnowellsct

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Posted 24 March 2019 - 08:25 PM

Greg,

Thanks for all your advice. I appreciate you keeping me honest and making sure I test the scope enough to provide a fair test. I am pleased with the results so far with the ED140, but to highly experienced and knowledgeable members like yourself here on CN, I know I haven't pushed this scope enough to fairly access where this scope ranks with others in its class in terms of price, aperture and performance. I'm a noob smile.gif I'm easy to please lol. 

 

I mentioned in an earlier portion of this thread that I have a buddy who I thought might might have stronger eyepieces. Unfortunately, his strongest eyepiece is 9mm. If I use my 2.5x powermate with the 9mm I think that brings me to about 250x. I was hoping not to have to introduce the powermate into the mix, but I don't have any access to anyone who has a high quality 3mm eyepiece or stronger. 

 

Any suggestions as to how I can give this scope a fair test? Is using the powermate not recommended? I'm not really sure how to perform proper testing given the equipment I have available. It seems a 9mm with a powermate at 250x is about the best I can do at the moment. Maybe you have an answer to my conundrum?

 

Regards,

Skyhunter1

I think if you get to 250x you've done all that a man can do.  Who dares do more, is none.  Power mates are very good quality and stand out in the Barlow crowd.  Well they're not Barlows.  They're "telecentrics," which means they don't spread the light out (it is kept parallel).  That's a good thing and commands a premium in the market.  9/2.5=3.6, it's the equivalent of a 3.6 mm eyepiece.    To get *exactly* to 2x per mm you would need 1/2 of 6.5, or 3.25.  You're probably not going to hit that on the nose, and close is good enough.  A bit over, a bit under, what the hey. 

 

At f/6.5 with a good scope you're going to want, at some point, to get to the neighborhood 2x per mm of aperture.  You can use a power mate.  Incidentally I had occasion, doing a branch test on my CFF, to use a 4x powermate with a 3.5XW.  I wrote it up here.  At the time I calculated I was at over 726x in the scope or about 8x per mm of aperture.  This is ridiculous.  But if you have the stuff you can screw around with it.  No laws broken.  The point is that as I increased the magnification and reached for the power mates, they did not appear to introduce any color.  This means your 2.5x power mate should render good color free service, IMO.    And the reason I bring this up is that it is not uncommon for less expensive Barlows to introduce their own color in the optical train.

 

I also have a thought rumbling around my otherwise empty head that at some point pushing a color test with magnification is bound to fail because the image gets darker and therefore less able to render color, so even if you *were* seeing color you wouldn't see it, so to speak.  

 

If you like pushing your 140mm on the planets you might at some point want a 3.5-ish type of ocular.  I like the XWs but people here will be quick to offer other suggestions.  When I got my f/6.3 130 mm refractor I realized with some disappointment that my 3.5 mm didn't get me up to the 300x range which is nice planet territory in a 5 inch refractor on a good night. That's about 2.3x per mm.  A little overboard, but nothing outrageous.   For you a 2.5mm eyepiece would be 2.6x per mm, still not overboard, but wandering up there.  (8x per mm is insane.)  To do 300x now on the 130 mm I need to use the Power Mate on a 5mm or use the XO 2.5.  Usually I use the 2.5 because, well, it's there.  I get to say I'm using my planet killer eyepiece.  

 

Greg N


Edited by gnowellsct, 24 March 2019 - 08:27 PM.

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#79 SkyHunter1

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Posted 25 March 2019 - 11:02 AM

I think if you get to 250x you've done all that a man can do.  Who dares do more, is none.  Power mates are very good quality and stand out in the Barlow crowd.  Well they're not Barlows.  They're "telecentrics," which means they don't spread the light out (it is kept parallel).  That's a good thing and commands a premium in the market.  9/2.5=3.6, it's the equivalent of a 3.6 mm eyepiece.    To get *exactly* to 2x per mm you would need 1/2 of 6.5, or 3.25.  You're probably not going to hit that on the nose, and close is good enough.  A bit over, a bit under, what the hey. 

 

At f/6.5 with a good scope you're going to want, at some point, to get to the neighborhood 2x per mm of aperture.  You can use a power mate.  Incidentally I had occasion, doing a branch test on my CFF, to use a 4x powermate with a 3.5XW.  I wrote it up here.  At the time I calculated I was at over 726x in the scope or about 8x per mm of aperture.  This is ridiculous.  But if you have the stuff you can screw around with it.  No laws broken.  The point is that as I increased the magnification and reached for the power mates, they did not appear to introduce any color.  This means your 2.5x power mate should render good color free service, IMO.    And the reason I bring this up is that it is not uncommon for less expensive Barlows to introduce their own color in the optical train.

 

Greg N

Greg,

Thanks again. I wasn't sure if using the powermate would have been a mistake in terms of testing the scope. I didn't want to use it only to be told later that it shouldn't have been used for testing. I'll use the 9mm with the powermate next time out as per your advice. I didn't want to waste my time with improper testing, or post information that may be inaccurate due to my inexperience. I've owned many scopes, but none of this caliber and I've never done any testing of this type so your advice has been invaluable. 

 

Regards,

Skyhunter1



#80 SkyHunter1

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Posted 25 March 2019 - 04:10 PM

Glad you finally got it out, SkyHunter!  Im in the same boat here in upstate, NY.....its been just lousy out.  But, this weekend has a lot of potential so Im keeping my fingers crossed.  Love to get my triplet out too!  Not as big as yours though. smile.gif

 

Post more pics when you can, love to see them!!!! 

Thanks Mike, I'm doing my best to get out soon, but the weather is crap for the next couple of weeks again... Been trying to figure out good targets for the next shoot. Thinking Leo Triplet, M63 or M51. If I get anything good I'll definitely post. 

 

How has it been going with your new scope? Have you had a chance to get some views, AP? Happy with it so far?

 

Regards,

Skyhunter1



#81 AxelB

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Posted 25 March 2019 - 09:22 PM

Test it with the powermate. To really push it you would need to reach at least 280x but 250 is not half bad. As long as you’re able to see the diffraction ring around the Airy disk of a focussed star, it’s enough to assess the quality of optic. Higher magnification only make that easier to assess.
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#82 Mr. Mike

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Posted 26 March 2019 - 04:31 AM

Thanks Mike, I'm doing my best to get out soon, but the weather is crap for the next couple of weeks again... Been trying to figure out good targets for the next shoot. Thinking Leo Triplet, M63 or M51. If I get anything good I'll definitely post. 

 

How has it been going with your new scope? Have you had a chance to get some views, AP? Happy with it so far?

 

Regards,

Skyhunter1

I actually had a nice session last night even though I got cold! Did some star clusters in Cassiopeia, the double cluster in Perseus which was breath taking and then I did manage to get a glimpse of the Leo triplet.  They were faint smudges(really only could detect M65 and M66 as the NGC galaxy eluded me) and even though it was very clear last night the seeing was a little iffy so the view didn’t sit still all the time.  But, it was great nonetheless.  Very pleased with my scopes performance.  I got a "good one" as they say. 

 

No AP plans for me at this point.  Maybe down the road.  Next time it’s warmer and clear I’ll head to my buddies house about 15 mins away where it’s nice and dark.  Then, I’ll get more out of those galaxies and such.  And I won’t feel like an ice cube a half hour into it either! :)


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#83 SkyHunter1

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Posted 26 March 2019 - 03:09 PM

Test it with the powermate. To really push it you would need to reach at least 280x but 250 is not half bad. As long as you’re able to see the diffraction ring around the Airy disk of a focussed star, it’s enough to assess the quality of optic. Higher magnification only make that easier to assess.

Axel,

Thanks for the advice. At least I have some guidance from Greg and yourself as to how to proceed. I'll look for the diffraction ring as you indicate. Never tested a scope in this way so I want to make sure I do it right :) Thanks again and clear skies!

 

Regards,

Skyhunter1



#84 SkyHunter1

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Posted 27 March 2019 - 12:12 PM

Hey all,

Was finally able to get the interferogram test report today from ES smile.gif I don't know how to interpret the numbers but was wondering of anyone could make sense of them and tell me if this is good or bad. I'm hoping that this reflects what a $5000 scope should be reporting. Keeping my fingers crossed. Please be honest with your assessment :)

 

Thanks in advance to this amazing community!!!

 

Aperture:     140         
Focal Length:  910 mm         
Wavelength:  0.6328  
Points:   7538  
Aperture OD:  100 percent  
PV:    0.238  wave 
RMS:   0.043 wave

 

Regards,

Skyhunter1


Edited by SkyHunter1, 27 March 2019 - 01:40 PM.


#85 SkyHunter1

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Posted 27 March 2019 - 06:16 PM

I actually had a nice session last night even though I got cold! Did some star clusters in Cassiopeia, the double cluster in Perseus which was breath taking and then I did manage to get a glimpse of the Leo triplet.  They were faint smudges(really only could detect M65 and M66 as the NGC galaxy eluded me) and even though it was very clear last night the seeing was a little iffy so the view didn’t sit still all the time.  But, it was great nonetheless.  Very pleased with my scopes performance.  I got a "good one" as they say. 

 

No AP plans for me at this point.  Maybe down the road.  Next time it’s warmer and clear I’ll head to my buddies house about 15 mins away where it’s nice and dark.  Then, I’ll get more out of those galaxies and such.  And I won’t feel like an ice cube a half hour into it either! smile.gif

Glad you like the scope and that you got a good one :) Hopefully I'll get a view and some pics of Leo triplet soon. its been so windy and rainy and cold. I will have some more time in April so hoping I get a break in the weather this month. I know about feeling like an ice cube too lol. I was dressed real warm last time out but still the cold was getting to me. I think when things go smoother, the cold is much less of a factor, but when its not a good night (seeing, wind, equipment problems) then it seems so much worse...

 

Keep me posted on "Rodney" :)

 

Regards,

Skyhunter1


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#86 SkyHunter1

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Posted 29 March 2019 - 01:45 PM

After much research, it seems that my numbers are good and that I got a decent scope . Strehl calculates to about 93.0. I am happy with the scope so its all good.

 

One thing that still confuses me is that looking at a number of these ES interferometer reports, there is quite a variance in the numbers at times... All scopes from essential series to FPL-53 series seem to be diffraction limited (less than .25 PV). RMS varies quite a bit as well. I understand that sometimes you get a "good one" and there is variance, but if an essential series scope has close to the same numbers as an FPL-53 scope, is it for all intents and purposes the same?

 

I also assumed that the numbers would be linear, meaning that the numbers would always be better on with an FPL-53 scope over an FDC1 essentials scope (with a few VERY rare exceptions). Also, doesn't the glass make a difference as well even if the numbers are close between 2 scopes? If so, how?

 

My thought was always if you paid more for a scope with better glass, and the assumption that it is subject to more stringent manufacturing standards, it should always perform better than a scope that's 1/4 of the price. If I buy a 100K Mercedes, and get the worst one made, I don't expect that a Mercedes 1/4th of the price, even if its the best one made will be able to out perform me.

 

Maybe I'm over simplifying it, but it would seem to me that if you're going to buy a scope and especially if you're going to pay a lot of money, that you would buy used and get the report first.... I haven't seen a BAD report yet, but it seems like there is a LOT of variance between scopes.

 

Again, I may not be fully understanding all the variables involved, but it seems odd that someone could pay a lot less money for a scope by the same manufacturer and if they get lucky, get the same performance as a expensive scope from the same manufacturer.

 

Is this accurate or am I just a hopeless noob lol :)

 

Aperture:     140      
Focal Length:  910 mm      
Wavelength:  0.6328
Points:   7538
Aperture OD:  100 percent
PV:    0.238  wave
RMS:   0.043 wave

 

Regards,

Skyhunter1


Edited by SkyHunter1, 29 March 2019 - 01:54 PM.


#87 AxelB

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Posted 29 March 2019 - 05:08 PM

I got much better numbers on the report for my AR127. It only tells that at this exact frequency (in red), my lowly achromat performs better than your expensive triplet ;-).

These numbers don’t tell the whole story, of course. Unless someone intends to use it exclusively for that particular narrowband, your triplet is certainly a much better performer, mainly because it’s able to focus the whole visual spectrum at the same point, which my achromat can’t. This is where the type of glass make a huge difference.

Edited by AxelB, 29 March 2019 - 05:10 PM.

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#88 SkyHunter1

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Posted 30 March 2019 - 02:27 PM

I got much better numbers on the report for my AR127. It only tells that at this exact frequency (in red), my lowly achromat performs better than your expensive triplet ;-).

These numbers don’t tell the whole story, of course. Unless someone intends to use it exclusively for that particular narrowband, your triplet is certainly a much better performer, mainly because it’s able to focus the whole visual spectrum at the same point, which my achromat can’t. This is where the type of glass make a huge difference.

Axel,

Thanks for the explanation. That helps me understand better too. I love the scope so its not about being disappointed... Views so far have been amazing and I think it'll shine for AP too. It's just curious to me that there can be so much variance between scopes. 

 

Gonna so some focal reducer testing tonight from the loaner ES gave me. Hopefully I'll figure it out and it'll pair with this scope :) keeping my fingers crossed 

 

Regards,

Skyhunter1



#89 lionel

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Posted 30 March 2019 - 09:04 PM

A 1/4 20 screw is more than enough to hold a scope.  There is an advantage in that a single bolt in center ring can adjust its angle to the tube.  If you screw in two screws tight it is the tube that will have to adjust to the rings.  My GT130 is held on to the Losmandy dovetail by two rings, each with one screw.  This is also true of the top rail.  In fact if your top rail has four screws and your bottom rings are held in by 4 screws you now have the potential for slight misalignments to be working in opposite directions.  

 

My 2c....

 

I'm assuming I understand you correctly, that you want more than one screw in each ring rather than the center screw.  

 

GN

I see the issue of safely securing the OTA to the dovetail differently. To me redundancy here is a good thing.  I’m not worried about the holding strength of the bolts but if I only use one bolt on each ring then what happens if one of the two bolts holding the scope loosens over time or falls out?  I use a machined dovetail that attaches to each ring with two bolts...preferably a CNC machined ring. With quality rings and dovetails I've never heard of an OTA being misaligned or damaged because of a sloppy 4-bolt pattern securing the dovetail to the rings, but I suppose it's possible. The solution to this is to not overtighten the rings on the tube. They should just be snug enough to prevent the OTA from rotating or slipping.

 

I use a shorter 8” version of the machined William Optics Vixen-style dovetail to mount my 130GTX. It is well designed to allow full width contact between the plate and the base of the AP rings and is hollowed out in non critical areas to save weight. Here  is the current iteration of the design. Detailed dimensions and hole spacings are given in the specs.

https://williamoptic...-dovetail-plate

 

Lionel


Edited by lionel, 30 March 2019 - 09:33 PM.

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#90 John Fitzgerald

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Posted 31 March 2019 - 09:12 AM

Yeah I think so.  Although upon reflection I realized that just because the screws are strong doesn't mean the *rings* are strong.  I imagine there is a big "pull out" difference between CNC machined aluminum rings and cast aluminum.  That said, I used my FS128 for I dunno, 8 or 9 years with cast aluminum rings and no incidents.  The rings are still in service on that Tak which is over at a friend's house.  GN


I don’t trust the holding power of cast aluminum rings. I drilled the dovetail holes to 17/64, put the rings on the tube while loose on the dovetail, tightened the rings on the tube, then tightened the six 6mm bolts to the dovetail by hand, making sure no binding, then snugged them up with the allen wrench. Alignment seems perfect, no binding.

#91 dscarpa

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Posted 02 April 2019 - 01:01 PM

 Now on sale for $4,320.  The FT version isn't on sale. OPT is offering 0% financing for 1 year.  At first with my WO ZS110 I used a small dovetail  with one bolt with each ring.  It feels much more secure with a bigger bar and 2 bolts. David


Edited by dscarpa, 02 April 2019 - 01:08 PM.


#92 MCinAZ

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Posted 03 April 2019 - 12:30 AM

I don’t trust the holding power of cast aluminum rings. I drilled the dovetail holes to 17/64, put the rings on the tube while loose on the dovetail, tightened the rings on the tube, then tightened the six 6mm bolts to the dovetail by hand, making sure no binding, then snugged them up with the allen wrench. Alignment seems perfect, no binding.

  This is the correct procedure, in my opinion. I generally drill clearance holes in my mounting plates 1/32" oversize, but any clearance at all is sufficient if the holes in both the plate and the rings are where they belong. Using two holes on each ring stabilizes the plate as well, making for a very rigid assembly.



#93 25585

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Posted 03 April 2019 - 08:03 AM

I see the issue of safely securing the OTA to the dovetail differently. To me redundancy here is a good thing.  I’m not worried about the holding strength of the bolts but if I only use one bolt on each ring then what happens if one of the two bolts holding the scope loosens over time or falls out?  I use a machined dovetail that attaches to each ring with two bolts...preferably a CNC machined ring. With quality rings and dovetails I've never heard of an OTA being misaligned or damaged because of a sloppy 4-bolt pattern securing the dovetail to the rings, but I suppose it's possible. The solution to this is to not overtighten the rings on the tube. They should just be snug enough to prevent the OTA from rotating or slipping.

 

I use a shorter 8” version of the machined William Optics Vixen-style dovetail to mount my 130GTX. It is well designed to allow full width contact between the plate and the base of the AP rings and is hollowed out in non critical areas to save weight. Here  is the current iteration of the design. Detailed dimensions and hole spacings are given in the specs.

https://williamoptic...-dovetail-plate

 

Lionel

Switch to a longer & a Losmandy D dovetail. 2 or more bolts fastening a tube ring is good. 3 rings are good, so if one fails there are 2 others.

 

All fixings and securings need checking before any use, as for any type of apparatus, astronomical or not.



#94 John Fitzgerald

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Posted 03 April 2019 - 08:38 AM

  This is the correct procedure, in my opinion. I generally drill clearance holes in my mounting plates 1/32" oversize, but any clearance at all is sufficient if the holes in both the plate and the rings are where they belong. Using two holes on each ring stabilizes the plate as well, making for a very rigid assembly.

My drilling the holes to 17/64 is about 1/40th inch oversize for the 6mm SST socket head cap screws I used.  Plenty of wiggle room.

 

At any rate, no matter how many bolts, the holding power is still in the clamping of the dovetail. 

 

Before dovetails, we used to bolt the scopes onto the cradles.  I had an 8 inch f6 Newt that had the bolt heads countersunk into holes on the inside of the rings and bolted onto the cradle with either hand knobs or wing nuts.  Two 5/16 inch bolts held the entire OTA.  To break out of that, either the heads would have to pull through about 1/4 inch of aluminum, or the mount cradle would have to break.


Edited by John Fitzgerald, 03 April 2019 - 08:47 AM.


#95 Fernando134

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Posted 13 April 2019 - 01:48 PM

Dear all,

 

Is there a field flattner for this scope? I asked this question on ES website a couple of days ago and never got an answer.

 

Thanks in advance, Fernando


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#96 SkyHunter1

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Posted 20 April 2019 - 05:52 PM

Dear all,

 

Is there a field flattner for this scope? I asked this question on ES website a couple of days ago and never got an answer.

 

Thanks in advance, Fernando

Fernando,

The weather here in NY has been the worst ever... I've been running some tests in conjunction with a guy from skywatcher who is testing it on his ED120. So far so good with the testing on both scopes. I'm hoping to get some imaging time in next Saturday. So far forecast shows as clear to mostly clear and low winds at my imaging site. Gonna use the reducer and try Leo triplet with the 294mc and then use my friends DSLR to see if the .7 reducer will flatten on a full frame chip with this scope. That's really what ES wants to know....

 

Pray for me and some good weather lol :) I'll post any results i get...

 

Regards,

Skyhunter1



#97 CounterWeight

CounterWeight

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Posted 01 May 2019 - 08:41 PM

Full frame flat field are magic words with respect to imaging about any scope, I hope if it works well they will post some spot diagrams.



#98 Surfinash

Surfinash

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Posted 17 October 2019 - 05:30 PM

I recently got the 115mm FPL-53 CF from Explore Scientific with 3" Hex focuser. I think it is the same focuser on 140mm one. Has anyone tried using the baader clicklock with it? I did not see any scew-on capability on it.

 

Replacing it with feather-touch is a ~$1000 ask. Not sure it it is worth it (as the Hex focuser is solid and stiff.

 

Thanks.

 

AJ




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