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AP Stowaway or Tak FC-100DF ?

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#76 t.r.

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Posted 14 February 2020 - 09:21 PM

Kind of! It's difficult to find an exact match to the Tak paint off the shelf, so I chose something that was as close. It's kind of a half way house between the Tak and Vixen colour scheme. I just think its a bit nicer than the standard black.

Krylon Honeydew Melon is Tak green match.
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#77 dr.who

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Posted 14 February 2020 - 09:48 PM

How good is the Tak FC100DF for imaging?

It's pretty pricey for a 4" doublet, and...it's a doublet.  I know, I know; "triplets or nothing" when it comes to imaging, but...that's about as good a 4" f/7-ish doublet as they come.
 

Anyone use one for imaging?  I've seen some images on Astrobin, but I'm not sure what kind of post-processing headaches ED/fluorite doublet imagers may have had.

Clear Skies,

Phil

Nothing wrong with a well figured well matched quality glass doublet for imaging. The only thing you would run into would be that you might not get as tight a focus as you would with a APO because the third light band isn't focusing on the same place as the other two. Also you can correct for CA using a minus violet filter. APO's are usually recommended because they focus all three light bands in the same spot.



#78 turtle86

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Posted 14 February 2020 - 10:39 PM

 

As far as the scopes go, I'm with Alan, planetary and double star are best served by larger scopes. For the things a 3-4 inch scope does best, the Stowaway does them better than the Tak.
 
Of course, I'd argue that from an optical standpoint, the things a 3-4 inch scope does better than larger scopes, the NP-101 with its flat field and short focal length is a better choice than either of these two scopes.
 
But it's definite heavier than the other two.... 
Jon

 

 

+1  By the time my name came up on the Stowaway list, I decided that for my purposes (mostly rich-view, low-power viewing), the NP 101 was a better choice for me than the Stowaway—a little more aperture but with an even wider field of view, and one that is utterly flat to boot.  (To compare, a 31mm Nagler yields a 3.9 degree TFOV in the Stowaway, and 4.6 degrees in the NP 101.)  My choice was also influenced by the considerations that I already owned another AP refractor and that I was able to buy the NP 101 used at an attractive price.  

 

All that aside, had I decided to get the Stowaway anyway, I’m pretty sure that I would’ve been *very* happy with my purchase.  


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#79 giorgio_ne

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Posted 15 February 2020 - 03:58 AM

Get the AP first, then get the Tak and have a proper comparison between the two of them in your own backyard, your eyepieces and other equipment.

Your partner, family or friends feedback is also important.

 

After a couple of weeks keep that one you like.

 

With all due respect, for such a purchase, what you read here on CN cannot be compared to your own personal experience!


Edited by giorgio_ne, 15 February 2020 - 04:01 AM.

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#80 mikeDnight

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Posted 15 February 2020 - 04:00 AM

Hi Mike.  It looks like you have a nice place to observe from on a hill with a nice view.  Do you have  dark skies there?

 

Bill

Hi Bill,

Yes, they are dark enough for me to see the milkyway from my front doorstep on most clear nights, so not bad. There are some annoying lights that flood light a small football pitch not too far away, so I contacted the parks department of our local council and they turned off the lights that were aimed at me. 

In my small refractor, the faintest thing I've seen so far has been IC434, the nebula surrounding the horse head, so I'm very happy. grin.gif


Edited by mikeDnight, 15 February 2020 - 04:00 PM.

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#81 25585

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Posted 15 February 2020 - 04:09 AM

A truly portable imaging scope to compete with the AP would be a FSQ85 Tak. More expensive but a quadruplet. 


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#82 RogerLaureys

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Posted 15 February 2020 - 05:55 AM

I find the Ports II mount head perfectly capable and very stable for even a 4" f/8 like my TSA-102, which is more than 12 pounds with clamshell and finder, as long as you use other tripod legs than what the Porta-II comes with.

Is it possible to use  Skywatcher stainless steel tripod legs with the Porta mount?



#83 Astrojedi

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Posted 18 February 2020 - 10:12 AM

I own the Tak 76DCU, Tak 100DC and the AT92 (a very high optical quality sample). Here is my perspective. I would go for the Tak 100DC/DF for visual only high resolution observing.

 

The biggest issue I find with the AT92 which will be similar to the Stowaway is cool down time. For example last evening even after 45mins the triplet had not completely cooled down. Which is the most significant factor in high power observing. For lower power observing like star clusters and DSOs this is irrelevant.

 

I have found that both the Tak 76 & 100 can take insane magnifications and can get there very fast. Although there is the very slightest of CA out of focus at nonsensical magnifications (75x-100x / inch) on very bright blue targets like Vega and Sirius. But not perceptible in focus.


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#84 Paul G

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Posted 18 February 2020 - 11:08 AM

I own the Tak 76DCU, Tak 100DC and the AT92 (a very high optical quality sample). Here is my perspective. I would go for the Tak 100DC/DF for visual only high resolution observing.

 

The biggest issue I find with the AT92 which will be similar to the Stowaway is cool down time. For example last evening even after 45mins the triplet had not completely cooled down. Which is the most significant factor in high power observing. For lower power observing like star clusters and DSOs this is irrelevant.

 

I have found that both the Tak 76 & 100 can take insane magnifications and can get there very fast. Although there is the very slightest of CA out of focus at nonsensical magnifications (75x-100x / inch) on very bright blue targets like Vega and Sirius. But not perceptible in focus.

Interesting. Even here on the East coast I haven't found cool down time to be much of an issue in scopes that small, glass mass is so small. What kind of delta T do you have in So Cal?



#85 YAOG

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Posted 18 February 2020 - 11:58 AM

Interesting. Even here on the East coast I haven't found cool down time to be much of an issue in scopes that small, glass mass is so small. What kind of delta T do you have in So Cal?

Paul,

 

I'm a native Angeleno and outdoors person from the desert to the Alpine zone, life long experience tells me it depends. 

 

It depends on where you are and time of year. In a worst case scenario in the high desert it can easily run 115F daytime to high 20s low 30s F night time air temperature. As you might imagine it is quite a roller coaster ride as the air temps influence observation under extreme conditions like these. 

 

As soon as the sun is fully set the air temps fall sharply until the air temp matches the local thermal mass of sand, rock or parking lot paving you are on top of and that surrounds you. The local seeing hugely influences what you can observe undisturbed until all the local mass cools enough to stop generating wind currents and heat waves which have a large influence on the local seeing. This can last well into the night but by about 10-11PM seeing can get exceptionally good in the thermal equalibrium zone. 

 

Of course it is not always like this, usually the temperature swings are only 60F-70F and much less in the winter. But radiant energy from the sun can have a huge impact even in the winter and scopes must be cases and insulated for faster cool down. 


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#86 Paul G

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Posted 18 February 2020 - 12:11 PM

Paul,

 

I'm a native Angeleno and outdoors person from the desert to the Alpine zone, life long experience tells me it depends. 

 

It depends on where you are and time of year. In a worst case scenario in the high desert it can easily run 115F daytime to high 20s low 30s F night time air temperature. As you might imagine it is quite a roller coaster ride as the air temps influence observation under extreme conditions like these. 

 

As soon as the sun is fully set the air temps fall sharply until the air temp matches the local thermal mass of sand, rock or parking lot paving you are on top of and that surrounds you. The local seeing hugely influences what you can observe undisturbed until all the local mass cools enough to stop generating wind currents and heat waves which have a large influence on the local seeing. This can last well into the night but by about 10-11PM seeing can get exceptionally good in the thermal equalibrium zone. 

 

Of course it is not always like this, usually the temperature swings are only 60F-70F and much less in the winter. But radiant energy from the sun can have a huge impact even in the winter and scopes must be cases and insulated for faster cool down. 

Thanks, in my mind I was thinking balmy temps.



#87 Astrojedi

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Posted 18 February 2020 - 02:30 PM

Interesting. Even here on the East coast I haven't found cool down time to be much of an issue in scopes that small, glass mass is so small. What kind of delta T do you have in So Cal?

Chip put it well. Just to be more specific regarding that evening. I brought the AT92 from my garage to the backyard which is probably a 15-20 deg F delta. The garage was still warm from the day due to trapped heat - the day was 70 and sunny which is typical for San Diego but at night typically the temps fall rapidly after sundown where I am. That evening it was in the mid 40s at about 10PM (which is really too cold for me - yes we are soft here : ) ).

 

But climate aside, whenever you subject the 92mm triplet to 15-20 deg F temp difference, in my experience it takes at least  45m - 1 hour for the triplet to fully stabilize thermally. Of course falling temp make this worse. Again I am referring to high magnification viewing. For low powers the AT92 is usable right away.


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#88 YAOG

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Posted 18 February 2020 - 03:19 PM

Thanks, in my mind I was thinking balmy temps.

Hi Paul, no that's Florida! 


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#89 YAOG

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Posted 18 February 2020 - 03:39 PM

Chip put it well. Just to be more specific regarding that evening. I brought the AT92 from my garage to the backyard which is probably a 15-20 deg F delta. The garage was still warm from the day due to trapped heat - the day was 70 and sunny which is typical for San Diego but at night typically the temps fall rapidly after sundown where I am. That evening it was in the mid 40s at about 10PM (which is really too cold for me - yes we are soft here : ) ).

 

But climate aside, whenever you subject the 92mm triplet to 15-20 deg F temp difference, in my experience it takes at least  45m - 1 hour for the triplet to fully stabilize thermally. Of course falling temp make this worse. Again I am referring to high magnification viewing. For low powers the AT92 is usable right away.

Hey, 40F is COLD but people will never admit it.

 

I agree, triplets need time to reach their best, my SV80mm triplet needs at least half an hour to be ready for high mag use but much less for casual sweeping. My large heavy Parallax/AT130mm triplet needs at least an hour to be good and it gets better after another hour+ as the night goes on if it is cold outside and the day was warm. The Takahashi FC-100DL on the other hand leaps from the case and is ready to go very quickly, usually about the time I have the mount polar aligned or 15 minutes or so. The Tak FC-100DL tube and clamshell weighs less than 1/3 of what the Parallax/AT130 weighs. The SV80ST-25SV with hinged rings and "D" dovetail weighs a pound more than the Takahashi FC-100DL with Tak clamshell and Losmandy "D" dovetail. I think all this extra mass also has an influence on glass cool down just like the ground shedding its heat from the day the optical tubes also have to shed their retained heat for a scope to come into its best condition for observing. 


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