Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Is a TEC 140 (or 160) a good upgrade from an FC100DL for visual planetary use?

refractor
  • Please log in to reply
95 replies to this topic

#76 gnowellsct

gnowellsct

    Hubble

  • *****
  • Posts: 18,190
  • Joined: 24 Jun 2009

Posted 12 October 2020 - 09:14 PM

I'm not looking to "cure" mediocre seeing. Just for something that will perform at least as well as my FC100DL in mediocre seeing. My C-8 does not. I have set it up on a variety of surfaces including asphalt, cement and yes grass. It performs poorly on any surface until it's cooled which typically takes three hours or more, even on grass, and in mediocre seeing it doesn't matter what surface it's on, the planetary performance has been less than mediocre. The one time it performed well on planets I had it set up on a second floor deck. And it was a mild evening in mid July with good seeing and a cloud layer moving in, so my viewing was unfortunately cut short. But the C-8 gave a brilliant view of Saturn before the clouds moved in. I don't think my FC100DL is "magic". I have seen my C-8 out perform it by a wide margin on occasion, but only rarely when the conditions were perfect which is rare where I live. My experience has been that the FC100DL out performs the C-8 on planets the vast majority of nights when set up on exactly the same surface. The FC100DL even performs well when it is set up on warm black asphalt. It's not "magic", it's just a non-folded unobstructed light path with a near perfect optical figure in a small tube that cools to ambient quickly and performs well in a variety of temperature and seeing conditions. I'm looking for something a little larger that maintains the performance of the FC100DL in less than ideal conditions.

It's unfortunate that real estate prices and massive fires from New Mexico up into Canada are convincing me not to retire to the west (where I grew up).  I would love to see my c8 take 3 hours to cool down because I have never ever seen that here in the NE.  But I hear it from west coast people with great regularity.  

 

I have a good friend who has a Ph.D. in materials science with whom I used to observe regularly.  Our discussions were about why the C14, which weighs 3x the c8, cooled down so *fast*, not why it cooled down so slow.   It was his observation.  As a practical matter most of my energies are put into heating the C8 and C14 up (to prevent dew); cooling down takes care of itself.

 

Nonetheless a 5 inch apo is a great thing.  Get one.  You can't go wrong with a TEC.  And I sometimes have a hankerin' to get a CFF 135 or 140.  That's when I think I would be wise to get out of this forum and cool down for a bit.  I have my reasons for wanting two 92mm apos, but I'm not sure I would want a GT130 and a 140 anything (TEC or CFF).

 

For sure you leave the domain of the GT130 and get a 140mm you're leaving the domain of an airline portable optic.  Well, maybe. Never say never. But it would take some thinking.

 

Spurred by the endless wisdom on the topic offered here, at the last NEAF I asked Roland whether there was any truth to significant difference in cooldown times for triplet oiled apos versus triplet air spaced.  He offered the view that it was part of the weird stuff out on the internet and that he didn't have an opinion about it either way.

 

Greg N


Edited by gnowellsct, 12 October 2020 - 10:03 PM.

  • Ihtegla Sar likes this

#77 StarAlert

StarAlert

    Viking 1

  • *****
  • Posts: 647
  • Joined: 11 Aug 2019

Posted 12 October 2020 - 09:20 PM

1.  So by this logic, a meal could not be optimized (a) to show off the talents of the chef and (b) to feed someone who was really really hungry.  But of course it could do both.  

 

2.  In this particular matter, if Yuri says it is optimized, it very likely is.   If I were to guess, which I would have to do as a non-owner of the famous TEC 140, I would say it is optimized for visual performance and also has a carefully planned ability to use a specific reducer/flattener for purposes of imaging.

 

Greg N

If there is no trade-off, then by all means, optimize both conditions until your heart is content. If there is a trade-off, then it's simply impossible to maximize both conditions. That's called constrained optimization. That's different from optimization. 

 

So if there are no tradeoffs between what optimizes the visual experience and what optimizes the CCD experience, then Yuri is correct. But I have to believe that the imagers would prefer that the TEC 140 was an f6 while the visualists (is that a word?) would prefer it was an f8. I don't know... maybe I'm wrong. Not that it matters what I think.


  • Ihtegla Sar likes this

#78 R_Huntzberry

R_Huntzberry

    Mariner 2

  • *****
  • Posts: 226
  • Joined: 03 Apr 2011
  • Loc: North Florida Lat 30.30

Posted 12 October 2020 - 10:06 PM

Were you the original owner? 

No, I purchased it from a gentleman named Thomas in Alaska who was the original owner.



#79 gnowellsct

gnowellsct

    Hubble

  • *****
  • Posts: 18,190
  • Joined: 24 Jun 2009

Posted 12 October 2020 - 10:09 PM

If there is no trade-off, then by all means, optimize both conditions until your heart is content. If there is a trade-off, then it's simply impossible to maximize both conditions. That's called constrained optimization. That's different from optimization. 

 

So if there are no tradeoffs between what optimizes the visual experience and what optimizes the CCD experience, then Yuri is correct. But I have to believe that the imagers would prefer that the TEC 140 was an f6 while the visualists (is that a word?) would prefer it was an f8. I don't know... maybe I'm wrong. Not that it matters what I think.

Visualist is an interesting suggestion, but the custom is to say "visual use" or "visual observers."  

 

The TEC 140 is f/7, which I think is a good visual focal length.  With the in-house focal reducer it is f/6.3.  They also sell a flattener.  

 

I don't own one, but it is among the most highly prized instruments for astro-photography.

 

Greg N


  • gozer and StarAlert like this

#80 StarAlert

StarAlert

    Viking 1

  • *****
  • Posts: 647
  • Joined: 11 Aug 2019

Posted 12 October 2020 - 11:14 PM

Visualist is an interesting suggestion, but the custom is to say "visual use" or "visual observers."  

 

The TEC 140 is f/7, which I think is a good visual focal length.  With the in-house focal reducer it is f/6.3.  They also sell a flattener.  

 

I don't own one, but it is among the most highly prized instruments for astro-photography.

 

Greg N

I'm adding visualist to my signature :) 


  • Ken Sturrock likes this

#81 MikiSJ

MikiSJ

    Apollo

  • *****
  • Posts: 1,179
  • Joined: 24 Feb 2006
  • Loc: San Jose, CA

Posted 12 October 2020 - 11:44 PM

I was leaning towards an APM 152 ED but then I read that they typically need 60 minutes or more of cooling.

I had an APM/TMB 152/1200 that I kept setup in my San Jose backyard. It cooled down nicely and I never noticed any substantial thermal noise.

 

APM-TMB 152 400px-2.JPG

 

I looked at the Trapezium through a TEC 140 and it rivaled the view I had with my 14.25" classical cass. The view through the TEC got me into the refractor side of our sport and it was the main reason to get rid of my C14. I ended up with a TAK 128 then a TAK 152 and finally the APM/TMB 152.

 

I REALLY, REALLY wish I had kept my APM and mortgaged the house for a mount like the Paramount ME. Alas, I traded the APM last December for a C11 EdgeHD/CGX combo.


  • gozer likes this

#82 MikiSJ

MikiSJ

    Apollo

  • *****
  • Posts: 1,179
  • Joined: 24 Feb 2006
  • Loc: San Jose, CA

Posted 12 October 2020 - 11:44 PM

I was leaning towards an APM 152 ED but then I read that they typically need 60 minutes or more of cooling.

I had an APM/TMB 152/1200 that I kept setup in my San Jose backyard. It cooled down nicely and I never noticed any substantial thermal noise.

 

APM-TMB 152 400px-2.JPG

 

I looked at the Trapezium through a TEC 140 and it rivaled the view I had with my 14.25" classical cass. The view through the TEC got me into the refractor side of our sport and it was the main reason to get rid of my C14. I ended up with a TAK 128 then a TAK 152 and finally the APM/TMB 152.

 

I REALLY, REALLY wish I had kept my APM and mortgaged the house for a mount like the Paramount ME. Alas, I traded the APM last December for a C11 EdgeHD/CGX combo.



#83 dedo

dedo

    Mariner 2

  • -----
  • Posts: 247
  • Joined: 04 Jun 2010
  • Loc: Italy, Rome

Posted 13 October 2020 - 01:39 AM

 Therefore the FL scope will give better visual images.  

 

Our samples of ED (from 2nd run) and FL (from last run) where absolutely undistinguishable visually on the planets.



#84 jmccown

jmccown

    Mariner 2

  • -----
  • Posts: 223
  • Joined: 22 Mar 2015

Posted 13 October 2020 - 07:53 AM

Your FC100DL is a F/9 refractor. if you can find a larger refractor that is closer to F/9 that would be ideal for visual planetary observation. The TEC 140 and 160 are both F/7 and are optimized for imaging. Since you mentioned CFF as another possibility you can always contact them and ask if they can produce a longer F ratio scope for you, I know that they offer slower refractors on special orders, I once asked TEC if they would make me a 160 FL f/9 the answer was NO.

.
I have a AP 155 EDT F/9 which I use primarily for Planets and the Moon, eveytime that I look at planets in this refractor the first question that comes up is how do people manage to do planetary observation with a 4"? Planets are so hopelessly tiny in my 6.1" that a 4" would be just too small, but that is my opinion of course.
.

Vahe

I have a couple of 4 inch achromats (not APOs, LOL) that are useful. But my main scope for planets and the moon is an AT80ED. It must be nice having a 6 inch Astro-Physics scope, but I couldn't begin to afford one. Many people have spent more on one eyepiece than I did on my OTA. 

 

So, I have to make do with my 80 mm somewhat-APO and I'm not the least bit disappointed. I've had some magnificent observing sessions of Venus, Mars, Jupiter, and Saturn with it. I'm sure the 36 inch Lick refractor or the Hubble space telescope would give much better views of the planets than a 6 inch Astro-Physics scope.



#85 vahe

vahe

    Surveyor 1

  • -----
  • Posts: 1,804
  • Joined: 27 Aug 2005
  • Loc: Houston, Texas

Posted 13 October 2020 - 09:28 AM

 It must be nice having a 6 inch Astro-Physics scope, but I couldn't begin to afford one. Many people have spent more on one eyepiece than I did on my OTA. 

 

 

My AP 155 EDT F/9, circa 1993, cost me $3195.00 new, since it is F/9 it is generally considered to be highly undesirable by the overwhelming majority of refractor fanatics who prefer F/6 to F/7 scopes. One just like mine appeared on CN classifieds last month and sold it in one day for $14,900.00.

I could not afford to buy a used one today despite its undesirability issues.

.

Vahe


  • jeremiah2229 likes this

#86 Ihtegla Sar

Ihtegla Sar

    Viking 1

  • -----
  • topic starter
  • Posts: 663
  • Joined: 02 Apr 2019
  • Loc: Pacific Northwest

Posted 13 October 2020 - 10:54 AM

It's unfortunate that real estate prices and massive fires from New Mexico up into Canada are convincing me not to retire to the west (where I grew up).  I would love to see my c8 take 3 hours to cool down because I have never ever seen that here in the NE.  But I hear it from west coast people with great regularity.  

 

I have a good friend who has a Ph.D. in materials science with whom I used to observe regularly.  Our discussions were about why the C14, which weighs 3x the c8, cooled down so *fast*, not why it cooled down so slow.   It was his observation.  As a practical matter most of my energies are put into heating the C8 and C14 up (to prevent dew); cooling down takes care of itself.

 

Nonetheless a 5 inch apo is a great thing.  Get one.  You can't go wrong with a TEC.  And I sometimes have a hankerin' to get a CFF 135 or 140.  That's when I think I would be wise to get out of this forum and cool down for a bit.  I have my reasons for wanting two 92mm apos, but I'm not sure I would want a GT130 and a 140 anything (TEC or CFF).

 

For sure you leave the domain of the GT130 and get a 140mm you're leaving the domain of an airline portable optic.  Well, maybe. Never say never. But it would take some thinking.

 

Spurred by the endless wisdom on the topic offered here, at the last NEAF I asked Roland whether there was any truth to significant difference in cooldown times for triplet oiled apos versus triplet air spaced.  He offered the view that it was part of the weird stuff out on the internet and that he didn't have an opinion about it either way.

 

Greg N

Greg,

 

If you are looking to retire in a place with bad seeing and hot clear days with cold nights with steadily declining temperatures all night, I'd be happy to take you on a tour of affordable Bortle 2 sky land that has clear skies more often than not.  If you stay far away from Portland and tourist trap cities like Hood River and Bend, the land east of the Cascades can be affordable.  In the area around where I have my dark site there are bargains to be had in the $1,500 to $2,500 per acre price range.   It's out on the steppe where there aren't enough trees (just prairie grass) for fire to do too much damage to a structure, and there was only a week or two this entire season when the smoke from the distant fires was much of a problem.

 

You have mentioned the CFF telescopes and I have been reading about them. They sound really well made.  If one of an appropriate size for me comes up on the used market before a TEC, I might just get one.  It sounds like I could be happy with either a CFF or a TEC.

 

It's interesting that Roland wouldn't take a position on the cooling properties of oil vs air spaced telescopes.  Does he make many oil spaced scopes?  Both Roland and Yuri make some interesting comments, with Yuri saying things like that the only real difference between the TEC 140 and 160 was the price.  Definitely has a good sense of humor and seems like the kind of guy who would be a lot of fun to go drinking with.



#87 t.r.

t.r.

    Fly Me to the Moon

  • ****-
  • Posts: 6,193
  • Joined: 14 Feb 2008
  • Loc: 1123,6536,5321

Posted 13 October 2020 - 11:41 AM

If I went drinking with Yuri I’d end up buying that 10” apo of his and be served divorce papers the next morning when I came clean with the misses!
  • ad701xx, daquad, astrophile and 2 others like this

#88 Ihtegla Sar

Ihtegla Sar

    Viking 1

  • -----
  • topic starter
  • Posts: 663
  • Joined: 02 Apr 2019
  • Loc: Pacific Northwest

Posted 13 October 2020 - 12:33 PM

Your FC100DL is a F/9 refractor. if you can find a larger refractor that is closer to F/9 that would be ideal for visual planetary observation. The TEC 140 and 160 are both F/7 and are optimized for imaging. Since you mentioned CFF as another possibility you can always contact them and ask if they can produce a longer F ratio scope for you, I know that they offer slower refractors on special orders, I once asked TEC if they would make me a 160 FL f/9 the answer was NO.

.
I have a AP 155 EDT F/9 which I use primarily for Planets and the Moon, eveytime that I look at planets in this refractor the first question that comes up is how do people manage to do planetary observation with a 4"? Planets are so hopelessly tiny in my 6.1" that a 4" would be just too small, but that is my opinion of course.
.

Vahe

Actually, the TEC 160 ED is f/8, not f/7.  The fluorite version is f/7, but the discontinued ED version that I am considering is f/8.  All things considered, I am like you and would prefer a slower scope, which puts us in a distinct minority.  Someone mentioned a 10 to 1 preference for shorter scopes.  Was that you?  I think that is accurate but mainly because people using refractors for AP seem to outnumber people who use refractors primarily for visual use (us "visualists") by a factor of 10 to 1.  

 

All of that said, I have an f/9 (FC100DL)  and an f/7 Tak (FC100DF) and I am hard pressed to notice any difference visually on planets or double stars.  Maybe if I were more experienced I could notice a difference.  Maybe.  But I have heard a lot of reports from experienced observers that they can tell either no difference or only a very very slight difference between a DL and a DF when used for visual observation.

 

I have a couple of 4 inch achromats (not APOs, LOL) that are useful. But my main scope for planets and the moon is an AT80ED. It must be nice having a 6 inch Astro-Physics scope, but I couldn't begin to afford one. Many people have spent more on one eyepiece than I did on my OTA. 

 

So, I have to make do with my 80 mm somewhat-APO and I'm not the least bit disappointed. I've had some magnificent observing sessions of Venus, Mars, Jupiter, and Saturn with it. I'm sure the 36 inch Lick refractor or the Hubble space telescope would give much better views of the planets than a 6 inch Astro-Physics scope.

I agree.  My four inch apo gives very fine views.  Definitely worthwhile and can give stunning views.  The only reason I am considering a larger scope is to get more of what the 4" provides.  Life is short and I am now in the situation where I could afford a larger scope, something that wasn't always in my budget ( I can afford $15,000 now a lot easier than I could have afforded $3,000 30 years ago).  So, I figured I would at least try something larger while I am still young enough to enjoy it.  But a small refractor with fine optics can certainly provide pleasant and worthwhile views of the planets.  I have an old 60mm f/15 achro that can give nice views of the planets.  Not quite the same as my four inch Tak but still very pleasurable.

 

If I went drinking with Yuri I’d end up buying that 10” apo of his and be served divorce papers the next morning when I came clean with the misses!

By the time you add tube rings and dovetail, that 10" costs as much as the 40 acres I bought for my dark site.  But land is an investment (at least in the area where I purchased), so that was an easy to sell to the spouse.  I expect that 40 acres to increase in value substantially in the next 20 years since it is adjacent to areas that are literally ten times more expensive due to urban pressure and that market pressure is expanding.

 

On the other hand, it sounds like a quality apo can be a good investment.  Vahe's $3,000 investment in a telescope 30 years ago is worth $15,000 today.  Maybe you can convince your wife that its a good investment?


Edited by Ihtegla Sar, 13 October 2020 - 12:45 PM.


#89 BKBrown

BKBrown

    Aurora

  • *****
  • Posts: 4,637
  • Joined: 22 Aug 2009
  • Loc: Under dark skies in central Virginia, USA

Posted 13 October 2020 - 01:09 PM

If I went drinking with Yuri I’d end up buying that 10” apo of his and be served divorce papers the next morning when I came clean with the misses!

funnypost.gif

 

Clear Skies,

Brian snoopy2.gif  



#90 astrophile

astrophile

    Viking 1

  • -----
  • Posts: 706
  • Joined: 30 Jun 2013
  • Loc: NoVA Yellow Zone

Posted 13 October 2020 - 09:16 PM

...  I have my reasons for wanting two 92mm apos, but I'm not sure I would want a GT130 and a 140 anything (TEC or CFF).

But of course you would.  The 140 for visual use in the light polluted back yard, and for planets.  The compact 130 for road trips to dark skies where wider-field apos really strut their stuff.  Honestly how do you manage without both  lol.gif

 

 

...  Does he make many oil spaced scopes?

Ummm...yes.  Many hundreds of Travelers, 130EDFs, 130EDTs, 130GTs, 155EDFs, and I think the 140s, 160s, and 175s (could be an exception or two in there).  AFAIK A-P did some air-spaced stuff early on, and then hardly anything but oil spaced triplets until the 130GTX and new Stowaway.


  • gnowellsct likes this

#91 gnowellsct

gnowellsct

    Hubble

  • *****
  • Posts: 18,190
  • Joined: 24 Jun 2009

Posted 14 October 2020 - 08:06 AM

But of course you would. The 140 for visual use in the light polluted back yard, and for planets. The compact 130 for road trips to dark skies where wider-field apos really strut their stuff. Honestly how do you manage without both lol.gif


How silly of me not to consider this

#92 Ihtegla Sar

Ihtegla Sar

    Viking 1

  • -----
  • topic starter
  • Posts: 663
  • Joined: 02 Apr 2019
  • Loc: Pacific Northwest

Posted 14 October 2020 - 10:47 AM

Ummm...yes.  Many hundreds of Travelers, 130EDFs, 130EDTs, 130GTs, 155EDFs, and I think the 140s, 160s, and 175s (could be an exception or two in there).  AFAIK A-P did some air-spaced stuff early on, and then hardly anything but oil spaced triplets until the 130GTX and new Stowaway.

In looking at their website, the Gran Turismo looks like something I would order in a heartbeat. Unfortunately AP is not taking orders from new customers for this or any other refractors at this time.  All waiting lists are closed and have been closed for a long time.   frown.gif



#93 Scott99

Scott99

    Fly Me to the Moon

  • *****
  • Posts: 5,307
  • Joined: 10 May 2007
  • Loc: New England

Posted 14 October 2020 - 01:46 PM

FWIW, if the manufacturer is honestly posting specs and color correction data I go there first.  Frankly, no, I don't put much stock into reports I read here on CN in comparison to specs posted by TEC, AP, and Tak.   Most of what I read here does not correspond to my viewing experience with the scopes I've owned.  People's attachment to the scope they currently own seems to influence what they see.   And who knows what eyepieces and diagonals they use, most eyepieces have lateral color error, so do prism diagonals.  We all have varying degrees of problems in our eyes that affect things.

 

For example I compared a Tak FC100DL to a new Tak FC76 and saw what I would consider to be a large difference in color correction.  In daytime viewing and star-testing on a bright star at high power the FC76 had plenty of false color visible.  The FC100DL was completely free of any color error I could see.  The difference in a 1st-magnitude star image was easy to see.  Yet most reports here equate the FC100-DL with the other FC f/7.5 scopes.

 

My AP Star12 ED was included in the comparison and it came in 3rd place in color correction.  It has .07% color error so that makes sense.  Regardless, it was my favorite of the three.   My visual results matched the posted specs from Takahashi 100%.   It's possible I would prefer the TEC160ED to the FL version just for the longer f/8 ratio.  But I'd expect the FL to have slightly cleaner views of planets and star images at high power.  

 

that 10 to 1 stat I mentioned for short f-ratio to long comes from the CFF website and the specs for the CFF160 and other scopes.  So that's just people buying CFF apos.  It doesn't necessarily extrapolate to other brands and telescopes.   The FC100DL seems popular, they made a 2nd run "back by popular demand" and APM/LZOS have had a popular 130 f/9 triplet in the lineup for years, so there are definitely fans of this type of refractor out there!  We are not alone! lol.gif


Edited by Scott99, 14 October 2020 - 01:58 PM.


#94 Ihtegla Sar

Ihtegla Sar

    Viking 1

  • -----
  • topic starter
  • Posts: 663
  • Joined: 02 Apr 2019
  • Loc: Pacific Northwest

Posted 23 October 2020 - 10:12 PM

Well, shoot. I'm sorry you missed it. Frankly, I was surprised it was "out there" for that long before getting snatched up.

"Well in addition to saying I was interested, I did ask a couple of questions about how old the scope was, how long he has had it and if he was the first owner. It's a lot of money to lay down for something sight unseen, just based on a few photos and a very brief description in an ad and I was hoping to get a little more detail on condition.
Is that a bad strategy? Can you tell the condition is excellent from the ad? Should I just send another message saying "Upon further reflection, my friends on CN convinced me this is the scope for me, so I'll take it"?

Well, sorry for being a bit cavalier and flip, especially with your money (!) My bad and I did not mean to offend and my apologies for not articulating what others quickly chimed in on. You really have no down side here with the TECs. I feel you are making the right choice with a TEC for what you're looking for. Yuri sold over 700 of the 140's for a reason. Of course, you can always post a "wanted" ad for either one too, which can give you multiple samples to choose from.

Once again, sorry, but also good luck in your search. waytogo.gif

Jeff


No need to apologize Jeff. Your initial advice to just get that TEC160ED was spot on and your follow up info was invaluable. In hindsight I should have jumped on that scope quicker, but I probably would have had to drive to San Jose to have had a good chance at getting it and a multi-day trip just isn't in the cards for me right now. But I've got my eye out for the next 140 or 160 ED that comes up for sale. Who knows, I might have to get both. Seems like you are happy with multiple refractors in that range. Right now I have two fine smaller refractors, a FC100DL and a DF, which are pretty much identical except for focal length, and I don't think I could part with either of them. Seems like the price of a new TEC160FL would just about pay for a used 140 ED and a used 160 ED. So I will just try to get whichever one comes along first, and in the meantime I will continue enjoying my smaller Taks.

Thanks so much to you and everyone in this thread for all the good information. The hunt for a TEC ED is on . . .
  • Jeff B and Paul Morow like this

#95 Voyager 3

Voyager 3

    Messenger

  • -----
  • Posts: 440
  • Joined: 20 Jul 2020
  • Loc: Near Bangalore, India

Posted 24 October 2020 - 08:26 AM

Sry this is going to be realllyyyy off topic but which one of your taks do you use more often for planetary? Sry for hijacking but a single word will make a newbie a bit knowledgeable flowerred.gif .


Edited by Voyager 3, 24 October 2020 - 08:27 AM.


#96 Ihtegla Sar

Ihtegla Sar

    Viking 1

  • -----
  • topic starter
  • Posts: 663
  • Joined: 02 Apr 2019
  • Loc: Pacific Northwest

Posted 24 October 2020 - 12:19 PM

Sry this is going to be realllyyyy off topic but which one of your taks do you use more often for planetary? Sry for hijacking but a single word will make a newbie a bit knowledgeable flowerred.gif .

Not really too off topic since this thread is about upgrading from a FC100DF or FC100DL for planetary work, so a discussion of what those scopes are capable of would be a good starting point to discuss benefits of an upgrade.

 

In a word, I typically use the DL more for planetary at home and take the shorter DF out to my dark site for viewing deep sky objects, since the DF is a little shorter and easier to load into the car with worrying about bonking it on things.  On paper, the DL is better for planets, but you have to look really hard to tell a difference.  You do need shorter eyepieces with the DF to reach the same magnification as the DL, but I have plenty of shorter eyepieces that are only rarely used.

 

I've never set the two up side by side but I have viewed the planets in both.  I have been viewing Mars a lot and a couple days ago I was tired when I set up and accidently grabbed the DF by mistake.  Didn't realize until I was outside, so I decided to go ahead and use it.  Both my Taks have stock focusers.  The DL came with a dual speed but the DF only has a single speed.  I was still able to achieve a good focus on Mars in the DF at about 150x, which was about all the seeing was supporting that night.

 

This season I have seen the polar ice caps every time I looked in either scope and have seen a great many identifiable albedo features, like syrtis major, sinus sabaeus,  the margarifer, hellas, mare cimmerium, etc. So you can see a lot of planetary detail with a good 4" scope.

 

But I did have one good night with my C-8 on Saturn last summer where the brightness and resolution were stunningly beyond anything I had seen in my FC100DL, but the moment only lasted a few minutes, as it was interrupted by clouds, and I have not been able to repeat the moment since.  Every other time I have set the C-8 up for planetary since then, it has disappointed with tube currents, cooling and seeing difficulties. So that's what has me looking for an upgrade.  

 

But to answer your question simply, I typically use the DL for planets but sometimes use the DF and I my local seeing conditions are not usually good enough to be able to tell a difference in their planetary performance.  Neither shows any false color to my eye, at least not any color that could be distinguished from the color produced by atmospheric distortion.




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics







Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics