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My experience using two 80-millimeter long-focus refractors

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#26 starmason

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Posted 26 December 2019 - 02:03 PM

I  enjoyed this comparison of 80mm F11 refractors as I was one of the lucky owners of the Burgess-TMB Planet Hunter 80mm refractors.  The optics were superb and the single speed chinese focuser was okay.   I agree with your assessments of planetary viewing with this fine refractor.  I was lucky to meet Mr. Tom Back at NEAF just before the Planet Hunter was offered.  The Burgess-Planetary eyepieces were being sold then for a wonderful discount at NEAF also.  My 30mm TMB Paragon eyepiece is a very nice design also.   Mr. Back impressed me - what a Great person -  and his passing was a tremendous loss to all of us.  Imagine all of the amazing cost effective designs he would have continued to present to us if he were still with us. 

I recently purchased the Starbase 80 F10 "long" focal length achromatic refractor system and must say that the Burgess-TMB had better glass.  Not a lot better, but I remember viewing Saturn, Jupiter and the Moon with similar eyepieces that I use, now, in the Starbase 80 and being very impressed with the sharpness, excellent contrast and coatings of the B-TMB.  The SB80, while a premium grade F10 achromat, is not "quite" that good -probably due to it's shorter focal length.  Still if is a very impressive retro telescope system and enjoyable to observe with - and the mounting system is very stable.

I wish I still had the Burgess-TMB Planet Hunter as I would mount it on my SB80 alt az and be a "happier" camper.  That's not going to happen so I'll just keep enjoying the views I have with the SB80. Not many very good long FL achromats out there now.  Too bad.

Clear skies, George NY.



#27 caussade

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Posted 26 December 2019 - 04:35 PM

I  enjoyed this comparison of 80mm F11 refractors as I was one of the lucky owners of the Burgess-TMB Planet Hunter 80mm refractors.  The optics were superb and the single speed chinese focuser was okay.   I agree with your assessments of planetary viewing with this fine refractor.  I was lucky to meet Mr. Tom Back at NEAF just before the Planet Hunter was offered.  The Burgess-Planetary eyepieces were being sold then for a wonderful discount at NEAF also.  My 30mm TMB Paragon eyepiece is a very nice design also.   Mr. Back impressed me - what a Great person -  and his passing was a tremendous loss to all of us.  Imagine all of the amazing cost effective designs he would have continued to present to us if he were still with us. 

I recently purchased the Starbase 80 F10 "long" focal length achromatic refractor system and must say that the Burgess-TMB had better glass.  Not a lot better, but I remember viewing Saturn, Jupiter and the Moon with similar eyepieces that I use, now, in the Starbase 80 and being very impressed with the sharpness, excellent contrast and coatings of the B-TMB.  The SB80, while a premium grade F10 achromat, is not "quite" that good -probably due to it's shorter focal length.  Still if is a very impressive retro telescope system and enjoyable to observe with - and the mounting system is very stable.

I wish I still had the Burgess-TMB Planet Hunter as I would mount it on my SB80 alt az and be a "happier" camper.  That's not going to happen so I'll just keep enjoying the views I have with the SB80. Not many very good long FL achromats out there now.  Too bad.

Clear skies, George NY.

An interesting story, and I truly wish I had the pleasure of meeting Mr. Back in person like you did.  Living and working in an island as I do is enjoyable and I don't complain, but sometimes it can be challenging to keep up with events and happenings in the US mainland.  I am very fortunate that professional commitments have allowed me to travel widely throughout the US and around the world, but I wish it were easier for me to travel just for pleasure and attend the big star parties and conventions in the mainland.

 

And yes, Mr. Back's passing was an inmense loss; I recall reading the news at the time (twelve years ago) and I just could not believe it.  Also, your mention of the Starbase 80mm f/10 astronomical telescope (labeled by some as "Takahashi") is quite opportune; amazingly I had never heard about this telescope until a couple of months ago, but caught sight of it on the Astronomics website while doing online research for my article.  A beautiful instrument that must surely stand on its own, and I appreciate you doing this comparison.


Edited by caussade, 26 December 2019 - 04:47 PM.


#28 REC

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Posted 28 December 2019 - 04:47 PM

So glad I read your review today, learned a lot and well written as others have said. Also I am enjoying all the feedback from other members as well!

My back started bothering me a ways back and I don't take out my 10" Dob or 8" SCT because of that. I have a C80ED 600mm f/7 that I bought to complement my Meade 8" SCT and it became my most used grab and go scope. When Celestron closed out their C102 f/1000mm f/9.8 tube, I jumped at it. Upgraded the focuser with a 10:1 crayford and now that scope has become my most used scope. I can't believe the optics are so good from that scope. It has very little AR color and don't see any on a general star field. Baader makes some filters that will calm down the color on the moon and Jupiter, but otherwise it's not a problem on the terminator features. I'll have to do some star testing that you did if I can figure out how other that just doing a donut shape i and out of focus. One last thing, I live in a red zone LP and the seeing is seldom over 3/5 and a few 4/5, so I can't get the high magnifications that you do.

 

Clear Skies and Happy New Year!

Bob



#29 caussade

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Posted 29 December 2019 - 12:07 AM

So glad I read your review today, learned a lot and well written as others have said. Also I am enjoying all the feedback from other members as well!

My back started bothering me a ways back and I don't take out my 10" Dob or 8" SCT because of that. I have a C80ED 600mm f/7 that I bought to complement my Meade 8" SCT and it became my most used grab and go scope. When Celestron closed out their C102 f/1000mm f/9.8 tube, I jumped at it. Upgraded the focuser with a 10:1 crayford and now that scope has become my most used scope. I can't believe the optics are so good from that scope. It has very little AR color and don't see any on a general star field. Baader makes some filters that will calm down the color on the moon and Jupiter, but otherwise it's not a problem on the terminator features. I'll have to do some star testing that you did if I can figure out how other that just doing a donut shape i and out of focus. One last thing, I live in a red zone LP and the seeing is seldom over 3/5 and a few 4/5, so I can't get the high magnifications that you do.

 

Clear Skies and Happy New Year!

Bob

I appreciate your comments, Bob, and the Celestron 102mm f/10 is indeed a nice instrument; have seen a couple of them in the past and they never fail to impress.  I have also heard wonderful things about the Celestron 80 ED, but sadly have never seen one in real life.  The star test is explained in amazing detail by Harold R. Suiter's in his book, but I suggest that you seek a knowledgeable colleague as the test results can be hard to interpret.  I wish you steady skies, and happy new year also!


Edited by caussade, 29 December 2019 - 05:43 PM.

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#30 BigC

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Posted 29 December 2019 - 02:52 PM

GREAT report.



#31 REC

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Posted 29 December 2019 - 03:46 PM

I appreciate your comments, Bob, and the Celestron 102mm f/10 is indeed a nice instrument; have seen a couple of them in the past and they never fail to impress.  I have also heard wonderful things about the Celestron 80 ED, but sadly have never seen one in real life.  The star test is explained in amazing detail by Harold R. Suiter's book, but I suggest that you seek a knowledgeable colleague as the test results can be hard to interpret.  I wish you steady skies, and happy new year also!

One think I really like about using the C102 is binoviewing with it. I picked up a used William Optic's heavy duty crayford focuser which had more back focus and that allowed me to get to focus without using a barlow lens. That allowed me to keep the native focal length. I get beautiful views of the moon in it. The C80ED is a great performer and give a perfect star test in and out of focus. I can get 4* FOV with it with a low power, wide angle EP at 17x. I got it used for $250!



#32 caussade

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Posted 29 December 2019 - 05:40 PM

GREAT report.

Thanks!



#33 caussade

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Posted 29 December 2019 - 05:43 PM

One think I really like about using the C102 is binoviewing with it. I picked up a used William Optic's heavy duty crayford focuser which had more back focus and that allowed me to get to focus without using a barlow lens. That allowed me to keep the native focal length. I get beautiful views of the moon in it. The C80ED is a great performer and give a perfect star test in and out of focus. I can get 4* FOV with it with a low power, wide angle EP at 17x. I got it used for $250!

Wow, $250 for the celestron 80 ED!  That's what I call a real bargain.


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#34 Astro-Master

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Posted 01 January 2020 - 07:20 PM

Thanks for your detailed report on your refractors.  I bought my first and only refractor about 6 years ago, its a Stellarvue 105mm triplet F7 with a Feathertouch 2" focuser.  I also have several fine barlows, a 2" Astro-Physics convertible, and a Celestron Ultima 1.25" triplet from Japan.  

I've often wondered what a 4" F12 or F15 would be like, so I used the 2x barlow, and noticed a flat field to the edge, and a little better resolution, its like having a long focus refractor with a short tube.



#35 caussade

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Posted 01 January 2020 - 10:50 PM

Thanks for your detailed report on your refractors.  I bought my first and only refractor about 6 years ago, its a Stellarvue 105mm triplet F7 with a Feathertouch 2" focuser.  I also have several fine barlows, a 2" Astro-Physics convertible, and a Celestron Ultima 1.25" triplet from Japan.  

I've often wondered what a 4" F12 or F15 would be like, so I used the 2x barlow, and noticed a flat field to the edge, and a little better resolution, its like having a long focus refractor with a short tube.

You're welcome, and that is an interesting observation.  A Barlow can indeed be used to increase the effective focal length of a telescope, and in turn its focal ratio.  The issue that I have encountered, after much experimentation with different telescopes, is that many Eyepiece-Barlow-Objective combinations will introduce an appreciable amount of vignetting that is obvious at the eyepiece, even bothersome.  But then, my tests have only involved shorter-length Barlows (specifically, the classic University Klee 2.8× and the classic Celestron Ultima 2×, both of which I own) and there is evidence that long-tube Barlows could be less invasive.  And also, vignetting—like field curvature—is extremely subjective, so what appears bothersome to my own eyes may not even be apparent to another observer.  So, while not useful for me, I accept they can sometimes be effective.



#36 dknott

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Posted 06 January 2020 - 02:07 PM

Thanks for the insights Armando.   Purchased a Vixen Super Polaris 80mm after reading your article.  



#37 caussade

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Posted 06 January 2020 - 04:59 PM

Thanks for the insights Armando.   Purchased a Vixen Super Polaris 80mm after reading your article.  

You're welcome, and I know you will enjoy it.  I also see that you've already included the scope as part of your signature.  Thanks for chiming in!



#38 jrbarnett

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Posted 23 January 2020 - 08:18 PM

Fantastic effort Armando!  And great insight into your background and academic efforts to proliferate an interest in astronomy among college-aged students.  



#39 Dave Mitsky

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Posted 23 January 2020 - 10:26 PM

Well done!



#40 caussade

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Posted 24 January 2020 - 10:07 PM

Fantastic effort Armando!  And great insight into your background and academic efforts to proliferate an interest in astronomy among college-aged students.  

Much appreciated, jrbarnett.  I have read your prolific postings in the forums and have learned a lot from your insights.  Thanks for chiming in!

 

 

Well done!

Very grateful, Dave.  It is an honor to get praise like this from a moderator.



#41 nato

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Posted 28 January 2020 - 04:27 PM

     Armando, A wonderful readable review, just the right blend of technical and personal observations. I  fully agree about long tube /F Ratio small refractors. The main telescope that I have used since the 1970's is an Edmund Scientific 4" F 15 refractor that has gone to thousands of public Star Parties most put on by the Salt Lake Astronomical Society. The scope drive has been modified to battery DC drive (three AA batteries) but everything else is original. See photos in my gallery under Nato. Again thanks for a great review.                                                                                    Nate Goodman. Salt Lake , Utah.



#42 fcathell

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Posted 29 January 2020 - 03:20 PM

Excellent review!  I too am a fan of "minimalist", long focus telescopes in the 80 to 125mm aperture range, but have been more a fan of Maks than other scope types. This is due to the short tube length and short moment arm of the scope as compared to refractors.  I admit better planetary views in equivalent aperture refractors, however, the long moment arm and any trace of wind or breeze causing vibration is a personal show stopper for me. The Maks definitely resolve this latter issue. After 40+ years of amateur astronomy and the use of many types and sizes of scopes, I have come to the unavoidable conclusion (for the most part) that the amount of observing one will do is inversely proportional to the size/weight of the scope! And although aperture definitely wins on DSOs, many amateurs grossly underestimate the potential of a small aperture scope with good optics for planetary/lunar observing.

 

Frank

Tucson, AZ



#43 caussade

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Posted 29 January 2020 - 08:22 PM

     Armando, A wonderful readable review, just the right blend of technical and personal observations. I  fully agree about long tube /F Ratio small refractors. The main telescope that I have used since the 1970's is an Edmund Scientific 4" F 15 refractor that has gone to thousands of public Star Parties most put on by the Salt Lake Astronomical Society. The scope drive has been modified to battery DC drive (three AA batteries) but everything else is original. See photos in my gallery under Nato. Again thanks for a great review.                                                                                    Nate Goodman. Salt Lake , Utah.

Very grateful for your comment, Nate, and I just saw the images on your gallery.  That is a beautiful, eye-catching telescope, and I can imagine the people approaching you during star parties.  My friend Guido Santacana, a Cloudy Nights member who I refer to in my article, owns a 102-millimeter f/13 refractor with (what I believe) is a Japanese Carton-made lens.  And I can share the anecdote that, right after concluding the star test that I also refer to, he allowed me to view the Orion Nebula through the 102 mm scope—a setup similar to yours.  The views were simply amazing, and this accounts for us staying late in the evening as the story explained.

 

 

Excellent review!  I too am a fan of "minimalist", long focus telescopes in the 80 to 125mm aperture range, but have been more a fan of Maks than other scope types. This is due to the short tube length and short moment arm of the scope as compared to refractors.  I admit better planetary views in equivalent aperture refractors, however, the long moment arm and any trace of wind or breeze causing vibration is a personal show stopper for me. The Maks definitely resolve this latter issue. After 40+ years of amateur astronomy and the use of many types and sizes of scopes, I have come to the unavoidable conclusion (for the most part) that the amount of observing one will do is inversely proportional to the size/weight of the scope! And although aperture definitely wins on DSOs, many amateurs grossly underestimate the potential of a small aperture scope with good optics for planetary/lunar observing.

 

Frank

Tucson, AZ

Thanks, Frank.  I certainly agree on every point, and my experience with mid-size telescopes of the Maksutov-Cassegrain type is similar to yours.  Mak tube assemblies are more manageable, and the views on a good Mak are truly refractor-like.  Your comment on the inverse proportionality of observing time versus the size/weight of the scope is right on target.  That was exactly what I was trying to convey with my review, and your choice of words could not have been better.



#44 nato

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Posted 11 February 2020 - 04:14 PM

Frank, I do have to agree that wind on a long Focal Length Refractor Tube mounted on a medium weight or lighter weight mount does some times cause a problem with image shake, but most of the time this is not a problem for me. Nate Goodman (Nato).

#45 dan boyar

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Posted 13 February 2020 - 01:20 AM

Great article! Interesting read.  I would add 3 benefits to the long focal length achromats (and for that matter long focal length reflectors as well): 1. Greater depth of focus (mentioned) means better performance in unsteady seeing conditions as compared to short F.L. instruments. 2. "Built in amplification" (due to long F ratio) yielding higher powers and less optical aberrations using easier to use longer F.L. eyepieces. 3. Darker sky background because extraneous (non-target light) does not reach the eyepiece end as easily as with a shorter FL system.  Regards, Dan B, Florida


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#46 caussade

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Posted 16 February 2020 - 07:45 PM

Great article! Interesting read.  I would add 3 benefits to the long focal length achromats (and for that matter long focal length reflectors as well): 1. Greater depth of focus (mentioned) means better performance in unsteady seeing conditions as compared to short F.L. instruments. 2. "Built in amplification" (due to long F ratio) yielding higher powers and less optical aberrations using easier to use longer F.L. eyepieces. 3. Darker sky background because extraneous (non-target light) does not reach the eyepiece end as easily as with a shorter FL system.  Regards, Dan B, Florida

Grateful for the compliments and I agree 100% on the added benefits you mention.  I particularly enjoy no. 2, the "built-in" magnification factor that allows a 5-to-6 millimeter eyepiece to achieve maximum magnification on my refractors.  Thanks!



#47 Tru_Colours

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Posted 23 February 2020 - 04:02 PM

Thank you for the very informative review.  I am new to backyard astronomy since retirement (and more free time) and this information is very helpful.

Best of wishes, Ron



#48 caussade

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Posted 24 February 2020 - 10:18 AM

Thank you for the very informative review.  I am new to backyard astronomy since retirement (and more free time) and this information is very helpful.

Best of wishes, Ron

You're welcome, Ron.  Glad that you liked my article, and I wish you all the best in your journey into backyard astronomy.



#49 BigC

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Posted 09 April 2020 - 07:49 PM

Since weight is an issue along with size I endorse the Celestron GT102/1000 as occupying a sweet spot if you can find one.
The XLT102 f10 is heavier.
Also worthy of consideration is 90/900 or 90/1000.

If the weather would synchronize with my days off it would be interesting to compare the TMB80 vs Tasco 80 vs Celestron 80 vs Meade 80 vs Towa 80 here. I haven't found the CA of 80f11 objectionable .
And quite surprised TMB80

#50 BigC

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Posted 09 April 2020 - 07:49 PM

Are so few.

Edited by BigC, 09 April 2020 - 07:50 PM.



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