26 replies to this topic

[midwestastronomer]

Ok these are the scopes in my price range.
The Orion version uses FPL 53 glass but has a cheap focuser. The AstroTech version has a nicer focuser, costs $100 less but uses FK 61 glass. Both are ED doublets.

Looking for some advice here. Thanks.

Edited by midwestastronomer, 21 February 2021 - 01:05 AM.

[bobzeq25]

Advice.

 

Either scope will do just fine for learning the basics of DSO AP.  I'd go with the better focuser.  That's more of a factor for learning than slightly better glass.

 

But, you've got the cart in front of the horse.  <smile>  The most important thing is the mount, NOT the scope or the camera.  This ain't visual.  <smile>

 

Scroll down to the picture of the expert and experienced author of this book,  That's a $500 70mm refractor on a $1200 Sirius (aka HEQ5Pro) mount.  He did NOT pick those because he had them lying around.  <smile>   For $1700 + camera it's about the ideal setup for learning DSO AP.

 

http://www.astropix....bgda/index.html

 

Honest.

 

Too much money?  The workaround is to shorten the focal length a lot by using a camera lens instead of a scope, and a camera tracker.  That's a far better setup for learning than a scope on an inadequate mount.  Which is a mistake beginners make, seen all the time here.  It's just not intuitive how good a mount you need, and what a mount that good costs.

 

The book covers the camera tracker/camera/camera lens approach.

Edited by bobzeq25, 21 February 2021 - 01:23 AM.

[PirateMike]

I agree with Bob, the mount is the most important thing in AP and anyone doing it for even a short amount of time will most likely tell you the same.

 

But lets assume that you have the mounting all worked out.

 

The next most important thing in your setup probably is the focuser. I would put the quality of the glass as number 4 in importance.

 

Number 3 would be your level of perseverance. AP is not easy and it's really a life long adventure in learning (and spending). 

 

 

Miguel   8-)

 

.

Edited by PirateMike, 21 February 2021 - 01:57 AM.

[2112_Mike]

I sometimes think there is a little too much cork sniffing when it comes to whether or not FPL53 is better for AP than FK61, etc.  The majority if not most people out there that are going to look at and enjoy the pictures that you take are not going to have a clue about the different glass used in the scope and will not be able to tell any slight variation in color in your photos even if there is any.

I just took my first photo of the Orion Nebula with my 130EDT.  The photo was somewhat out of focus and there were some slight star trails.  Put it on Facebook and received numerous responses about how cool it was, even though I know I can do much better.  

On the other hand I do own the AT80 and love it but I have always heard that the Orion scope is an awesome bang for the buck...

[zirkel 2]

Optics first!
Optics alone give you the final image not the focuser 😁
Changing a focuser is easy and can be done later...
- Fpl-53 : 94.96 abbe number
- Fk-61 : 81.59 abbe number
Orion ED refractor is preferable, great optic, really.

[alphatripleplus]

You could also get the better focuser, and the FPL-53 glass if you are prepared to give up a little bit of aperture by going with the AT72EDII, which is what I did.

[Echolight]

TS Optics has the same scope as the AT80ED but with FPL-53 glass and a 2.5 inch focuser.

[2112_Mike]

More cork sniffing..haha!  

Will someone please show me a comparison photo of FPL53 vs FK61 through an 80mm scope and point out the differences...

Get the AT80...I have not read any disappointed posts on this telescope...

 

$100 cheaper, you can use that cash towards a decent finder, filter or eyepiece...

Faster FL

Comes with rings/dovetail

Better focuser

[Jon Isaacs]

More cork sniffing..haha!  

Will someone please show me a comparison photo of FPL53 vs FK61 through an 80mm scope and point out the differences...

Get the AT80...I have not read any disappointed posts on this telescope...

 

$100 cheaper, you can use that cash towards a decent finder, filter or eyepiece...

Faster FL

Comes with rings/dovetail

Better focuser

 

No photos but I have an 80 mm F/7 FPL-53 doublet, owned an ED-80  and have owned 72 mm F/6 and 102 mm F/7 FK-61 doublets and looked through 80 mm F/7 FK-61 doublets.

 

The difference is not slight. The analysis says it's about a factor or two and visually, I see the ED-80 as color free, the 80 mm F/7 FK-61 as showing some CA. A-P has a wider spectrum so it should show more.

 

Simple analysis says the FK-61 doublet has a chromatic blur 1.25x the Airy disk, the ED-80's blur is about 0.75 x the Airy disk..

 

You can upgrade the focuser.. you can't upgrade the optics..

 

Jon

[Jon Isaacs]

You could also get the better focuser, and the FPL-53 glass if you are prepared to give up a little bit of aperture by going with the AT72EDII, which is what I did.

 

I like this.. For beginners,  smaller is good. The good glass, the good focuser, what's not to like?

 

Jon

[2112_Mike]

The difference is not slight. The analysis says it's about a factor or two and visually, I see the ED-80 as color free, the 80 mm F/7 FK-61 as showing some CA. A-P has a wider spectrum so it should show more.

 

Jon - Still would like to see some astro photo comparisons...and what was the cost of the 80mm F/7 with FPL53?  Still within the OP's price range?  which seems to be right about $500...

[Jon Isaacs]

The difference is not slight. The analysis says it's about a factor or two and visually, I see the ED-80 as color free, the 80 mm F/7 FK-61 as showing some CA. A-P has a wider spectrum so it should show more.

 

Jon - Still would like to see some astro photo comparisons...and what was the cost of the 80mm F/7 with FPL53?  Still within the OP's price range?  which seems to be right about $500...

 

I too would like to see some raw, unprocessed photos taken with an 80 mm F/7 FK-61 objective.  The ED-80 is a known quantity.  I bought 80 mm F/7 FPL-53 doublet used about 15 years ago and it needed a better focuser.

 

I like the 72mm AT-72ED-2 suggestion.  I would like to see what Bob thinks.

 

And Bob points out the importance of the mount. It's not clear what mount Midwestastronomer will be using, hopefully something more robust than the Astroview listed in the equipment list.

 

Jon

[Redbetter]

I sometimes think there is a little too much cork sniffing when it comes to whether or not FPL53 is better for AP than FK61, etc.  The majority if not most people out there that are going to look at and enjoy the pictures that you take are not going to have a clue about the different glass used in the scope and will not be able to tell any slight variation in color in your photos even if there is any.

I would not expect the difference in the performance of the glass to be that subtle for visual at this ratio, and it would be even less so for imaging from what I have gathered.  I have a 110 ED f/7 with FPL-51, roughly the same class as FK61.  It puts up nice images and I am fond of it, but even stopped down to ~90mm with its longer focal length (for ~f/8.5 effective),  I can tell the difference in color compared with my ED80 f/7.5 with FPL-53. 

 

I like the color performance of the AT60 and AT72ED f/6 w/ FPL-53, so I would happily put an AT80 ED f/7 through its paces for visual, but it would be in a tough spot optically matching an ED80 f/7.5.  Imaging only makes matters worse as it shows color dispersion more readily than my eye.  Visually the difference might not matter that much depending on how the scope was used, but I would expect to seem some difference in planetary detail (and aesthetics.)

 

On the plus side, I would likely prefer the mechanicals (focuser/sliding dew shield) compared to my 2-speed ED80, and perhaps the baffling system (haven't compared them).  I would expect the AT80ED to be a considerably more compact/efficient arrangement.  Now make that an AT80EDII w/FPL-53 at f/7 and it becomes quite attractive for visual.  

[Echolight]

 Now make that an AT80EDII w/FPL-53 at f/7 and it becomes quite attractive for visual.  

https://www.teleskop...n-Objektiv.html

[Zubenelgenubi17]

The one thing I'd add to what's already been mentioned is to make sure you've got room for a flattener in your budget, particularly if you're using a DSLR or other medium to large sensor. Astrotech sells them for around $130‐$150 if I recall.

If you're comfortable with it, buying used can be a good way to save some money, or get more for your money depending on how you look at it. You can't be quite as picky about the specific make and model, but there do seem to be a fair number of small apos floating around out there in need of new homes.

[2112_Mike]

https://www.teleskop...n-Objektiv.html

 

$190 more than the AT80ED and  DHL  additional shipping charges.....$64 = $254 more...

 

I am not arguing that there are better 80mm scopes out there. But I stand by my thoughts that sometimes people get too wrapped up in this glass vs that glass.  If you are deeply devoted to AP you probably won't look at this scope anyway.  I can tell you that I really like mine and views through it are GREAT. 

What other new 80mm ED with the included mechanicals and accessories are there out there for $399 shipped to your door?  Any 'FPL53's'?

Edited by 2112_Mike, 22 February 2021 - 04:21 PM.

[Echolight]

https://www.teleskop...n-Objektiv.html

 

$190 more than the AT80ED and  DHL  additional shipping charges.....$64 = $254 more...

 

I am not arguing that there are better 80mm scopes out there. But I stand by my thoughts that sometimes people get too wrapped up in this glass vs that glass.  If you are deeply devoted to AP you probably won't look at this scope anyway.  I can tell you that I really like mine and views through it are GREAT. 

What other new 80mm ED with the included mechanicals and accessories are there out there for $399 shipped to your door?  Any 'FPL53's'?

It also has a 2.5 inch focuser.  But yeah, out of the stated price range.

Edited by Echolight, 22 February 2021 - 08:15 PM.

[Redbetter]

 

I am not arguing that there are better 80mm scopes out there. But I stand by my thoughts that sometimes people get too wrapped up in this glass vs that glass.  If you are deeply devoted to AP you probably won't look at this scope anyway.  I can tell you that I really like mine and views through it are GREAT. 

What other new 80mm ED with the included mechanicals and accessories are there out there for $399 shipped to your door?  Any 'FPL53's'?

You can stand by your thoughts, but that doesn't necessarily make them accurate depictions of the scope or of others' opinions which you have dismissed as "cork sniffing."  I am most interested in how a scope performs optically, rather than in what the glass is...but I have found that the glass is a big part of that, and through the wonders of algebra, one can estimate the impact.  By your same logic, one could just skip ED and go to an ST80 f/5 achro clone with 2" focuser upgrade for about $200 (I put mine together for less than that, but those focusers are gone now.)  Afterall, 80 f/5 achros are fine scopes for richest field viewing.  

 

I have learned to be wary when folks declare something is "great" without qualification of their statement, when my own calcs indicate it will have obvious color on bright objects, not severe, but visible.  (I have even had folks tell me they don't see color with an 80 f/5 achro, and I know what things look like through a good sample, and how much they have to be dialed back for max planetary detail.) Some folks just aren't sensitive to blue, and they often have lower expectations of planetary detail than I do.   What I have learned is that observable color blur is an indication of loss of some planetary detail and contrast near bright objects, the greater the blur, the greater the loss from a scope's potential.  (And, no, I haven't found that filters fix the detail by eliminating the blue.)

 

Visually, an 80 f/7.5 FPL-53, 72 f/6 FPL-53, and 60 FPL-53 are color free at focus to my eye.  What I have read in glowing reviews of the AT80 f/7 w/FK-61 is that it shows a little color on bright objects, confirming my calculations/expectations.  It is important that people be aware of that difference/qualifier, rather than to just pretend it is a non-factor and operate off vague superlatives.

 

The above is why Teleskop-Express lists the 80 f/7 FPL-53 as APO and the FK-61 as an ED, and the latter for 70.58 euros less (about $86 difference.)  Both of these have the 2.5" focuser so the price difference is purely in the glass.  

[zirkel 2]

 Visually, an 80 f/7.5 FPL-53, 72 f/6 FPL-53, and 60 FPL-53 are color free at focus to my eye.  What I have read in glowing reviews of the AT80 f/7 w/FK-61 is that it shows a little color on bright objects, confirming my calculations/expectations.  It is important that people be aware of that difference/qualifier, rather than to just pretend it is a non-factor and operate off vague superlatives.

 

I agree your words,  i have a same experience since a long time...

Edited by zirkel 2, 23 February 2021 - 02:56 AM.

[Jon Isaacs]

https://www.teleskop...n-Objektiv.html

 

$190 more than the AT80ED and  DHL  additional shipping charges.....$64 = $254 more...

 

I am not arguing that there are better 80mm scopes out there. But I stand by my thoughts that sometimes people get too wrapped up in this glass vs that glass.  If you are deeply devoted to AP you probably won't look at this scope anyway.  I can tell you that I really like mine and views through it are GREAT. 

What other new 80mm ED with the included mechanicals and accessories are there out there for $399 shipped to your door?  Any 'FPL53's'?

 

Optics versus mechanicals.  

 

I think if you were to compare the AT-80ED side by side with an otherwise identical FPL-53 doublet, you would see a noticeable difference.

 

Photographically color correction is more important than it is visually because a camera is sensitive over a broader spectrum, this increases the size of the defocused blur.

 

The AT-80ED is a very nice scope and a very good value but it probably isn't the best fit for A-P.

 

Jon

[Redbetter]

And the actual comparison from the same vendor is a much different cost basis than comparing to the AT here with 2" focuser:

Link:  Teleskop-Express 80 f/7 ED FPL-51 w/2.5" focuser

 

I suspect that we will eventually see a similar AT offering as the FPL-53 variant listed earlier.  It would be intriguing to me except that I got my ED80 f/7.5 FPL-53 with dual speed focuser second hand several years ago with case, rings, RDF, and 2" diagonal for $350.  Of course I could probably move that OTA on for considerably more than that now, minus the diagonal and RDF.  But I would want to run both scopes through their paces first on planets before determining which to keep.  The smaller size and wider FOV of the f/7 FPL-53, along with the sliding dew shield and likely somewhat better focuser (and likely baffling as well as fully illuminated field) would make it a real upgrade if the figure and planetary detail were equivalent.  

[zirkel 2]

I optimized my 80 ED in the same way with a 1/10 Lacerta microfocuser, since then it's perfect!

 

[2112_Mike]

Still my AT80 has great views. As far as qualifying that statement, if you remember a view through a telescope as having really made an impression on you, then I feel it has great views.  I viewed M42 a few weeks back and even though I have viewed it with much larger scopes in the past the view through this small scope is still with me.  It left an impression that I won't soon forget. Not everything comes down to math, it lies more in the user and their impression of what they feel is great.  I have not noticed any color but then I'm not striving to look for it as I am very satisfied with what this scope can show me. I have owned and do own achromats and this scope far surpasses those in terms of color correction. But I still love the views through my 6" achro as well, so...

The OP doesn't seem to mention AP as a primary concern and again, for the sum of $399 shipped I just don't see anything out there, this fact seems to be overlooked in this thread. 

So, if his budget is $400-500 he should get the Orion with FPL53, so goodness forbid he dare not see any color issues....

Edited by 2112_Mike, 23 February 2021 - 10:04 AM.

[Echolight]

Still my AT80 has great views. As far as qualifying that statement, if you remember a view through a telescope as having really made an impression on you, then I feel it has great views.  I viewed M42 a few weeks back and even though I have viewed it with much larger scopes in the past the view through this small scope is still with me.  It left an impression that I won't soon forget. Not everything comes down to math, it lies more in the user and their impression of what they feel is great.  I have not noticed any color but then I'm not striving to look for it as I am very satisfied with what this scope can show me. I have owned and do own achromats and this scope far surpasses those in terms of color correction. But I still love the views through my 6" achro as well, so...

The OP doesn't seem to mention AP as a primary concern and again, for the sum of $399 shipped I just don't see anything out there, this fact seems to be overlooked in this thread. 

So, if his budget is $400-500 he should get the Orion with FPL53, so goodness forbid he dare not see any color issues....

I agree with what you say.

 

The main issue is that "for AP" is in the title of the thread. And not visual.

This is why people are harping on the glass. While I can look past a purple halo around Jupiter when studying the detail on the planet through my 6 inch achro, that halo would stand out like a beacon on a photograph. Although false color on many DSO, including M42, is not noticeable to me through the same achro, I don't know what it would show if used for AP on the same objects.

Edited by Echolight, 23 February 2021 - 08:07 PM.

[Redbetter]

Yep, AP is in the title, so color consideration seems highly relevant.    

 

For AP-centric consideration of scopes in the U.S. market, the AT72EDII makes the most sense to me.  It is probably fairly close to the AT80ED f/7 for visual planetary, despite the aperture difference which should be worth about 0.23 mag.  Still, the better resolution of the larger aperture will be offset only slightly by a CA contrast hit, so it becomes a matter of how much.