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Need a bit of help deciding

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#1 Chris1485

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Posted 10 February 2020 - 10:07 AM

Hi,

I have the offer of a Altair Astro102mm ED (FPL51 version) and wondered whether this would replace my 127 Mak and my ED80?

I am an occasional observer but do like to do Planetary imaging when I get time.

Do you think the 102mm with FPL51 objective to be a step up from the 80mm FPL53 scope and equal to the 127 Mak?

 

Many thanks,

 

Chris (UK)



#2 cst4

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Posted 10 February 2020 - 12:08 PM

I have a Lunt 102ED with FPL51 glass and the Altair Astro is likely the same optics.  It is an absolutely wonderful visual scope and I love it, but I wouldn't recommend it for astrophotography of any kind due to the little bit of chromatic aberration present.  I'm not an AP guy, but I have played around with taking some DSO shots with it and all the brighter stars come out red from the camera sensor picking up the CA.  A triplet or a doublet with FPL53 glass is noticeably better photographically.  Visually, the CA is so mild that it is practically unnoticeable on most all targets, but unfortunately it remains pretty obvious on Jupiter because it is so bright.  It is quite a bit better than a long achromat but the CA is still a little distracting to me.  Saturn looks great in it though with no noticeable false color... I actually often see a little more detail in the 102ED on Saturn than I do in my 8" cass.  So overall my guess is that the 102ED is a step up from the FPL53 80mm in image brightness but not quality and it maybe has a little more contrast than the Mak but the CA would likely keep it from surpassing it in my opinion.  Now if the choice was a true APO around 100mm then I would consider it to be an upgrade all around, but just not for the 102ED with FPL51 glass.


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#3 Chris1485

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Posted 10 February 2020 - 03:49 PM

Many thanks for the advice.

The fact that it won't replace the 127 Mak may be a decider.

I may wait until I can afford a better 100mm apo, at least something with FPL53 glass.



#4 cst4

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Posted 10 February 2020 - 05:53 PM

No problem.  But I will admit I have never looked through a 127mm mak, I've just read up on several comparisons between 4" APOs with 5" maks.  There are many threads on this subject here on CN if you need more opinions.  Most say they are very comparable on the planets with the consensus of the APO having better contrast and the mak having a brighter image.  I was trying to decide between these two last year to max out the capacity on my AZ-GTI and decided to go with a refractor for the option of wider views and quicker cool down.  If I had an ED80 already I would have went with a mak.  I do not regret my decision of going with a refractor as I absolutely love this size scope, however, I am still kicking myself for choosing to save a couple hundred dollars with a used 102ED rather than splurging and getting the Stellarvue Access 102 while it was on sale.  The 102ED is great, but I think it would have been worth the extra money to get completely color free views.... especially since I wouldn't mind getting into AP eventually.  If you think you can afford a better APO then yes I do suggest waiting.  



#5 Chris1485

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Posted 11 February 2020 - 03:15 AM

Thanks again, good advice.

I think I'll stick with what I have for now.



#6 F.Meiresonne

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Posted 13 February 2020 - 02:57 PM

As you are an owner of a 127 mm Mak i don't think a 100 mm FPL 51 is an advantage...

 

 

Cst4 gave a pretty good consensus about that  imo.

 

A big newt could be a step up like 10" or 12". Even at F/5 or F/6 they can give exquisite images of planets, but are a bit vulnerable to seeing and the image might be also a bit less stable due the open tube design.

 

Best views i ever had, seeing cooperating were in my 18 incher newt. Saturn and Jupiter can be exquisite...knocking your socks off ...



#7 Chris1485

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Posted 17 February 2020 - 04:42 AM

Thanks, I think you are both right, an FPL51 objective 102mm is not going to be a replacement for my Mak.

A much larger Dob would be great and is something I'm considering but I would need to keep it in my garden shed, which isn't the dryest place. It gets quite damp this time of year.

An 8" Dob would be nice though, cheap enough and light enough to move about.

Thanks again for the advice,

 

Chris (UK)




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