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Air travel: 150mm f/5 achro vs 100mm binocular telescope?

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#1 wolfli

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Posted 23 January 2021 - 10:55 AM

Looking for a good air travel scope for dark sky lower power views.

 

I already have a 150mm f/5 achromat which is robust enough to survive the checked luggage. It has a nice 3.3* true FOV with ES 30mm 82 and a 6mm exit pupil. I have enjoyed it on several trips before.

 

Now I'm thinking about a binocular telescope like the APM series. The weight and bulk of the 150mm f/5 is similar to a 100mm APM. I would never put it in the checked luggage but its size seems to be marginally OK for carry-on... Wondering whether that would be an improvement over my existing setup. The max true FOV will be smaller @ 2.8* with a dimmer 4.4mm exit pupil, but two eyes are better than one.

 

Thoughts? 



#2 junomike

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Posted 23 January 2021 - 11:06 AM

Had both and compared them side by side keeping magnification the same .  I found the image a bit brighter in the Celestron 150 F5 Achro (due to larger exit pupil?),  however the darker background of the APM 100 (Semi Apo) seemed to make up for it. 

In the end I kept the Binoscope and sold the 150 F5.

 

Note that with both being F5 you can't match magnification and exit pupil at the same time. With magnification being more important to me, that was what I based my comparison on.


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#3 wolfli

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Posted 23 January 2021 - 11:13 AM

Had both and compared them side by side keeping magnification the same .  I found the image a bit brighter in the Celestron 150 F5 Achro (due to larger exit pupil?),  however the darker background of the APM 100 (Semi Apo) seemed to make up for it. 

In the end I kept the Binoscope and sold the 150 F5.

 

Note that with both being F5 you can't match magnification and exit pupil at the same time. With magnification being more important to me, that was what I based my comparison on.

Do you think being able to use both eyes made a bigger difference compared to the aperture? Also does the APM 100mm fit into a carryon case? 


Edited by wolfli, 23 January 2021 - 11:17 AM.


#4 junomike

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Posted 23 January 2021 - 11:41 AM

Do you think being able to use both eyes made a bigger difference compared to the aperture? Also does the APM 100mm fit into a carryon case? 

Using both eyes does make a big difference however overall aperture (in monomode) can't be ignored either.

 

Not sure about carry-on as they are constantly changing the regulations.

 

My case measure approx. 21.5"  X 11.75"

APM 100 Case.jpg


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#5 wolfli

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Posted 23 January 2021 - 01:43 PM

Thanks! This looks like the original version of APM and it indeed fits. The new one is a bit larger.



#6 junomike

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Posted 23 January 2021 - 02:06 PM

Thanks! This looks like the original version of APM and it indeed fits. The new one is a bit larger.

Yes the APM Semi Apo V.1

I'd suspect the case of the newer one's to be larger thus passing over the allowable length permitted (22").



#7 wolfli

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Posted 23 January 2021 - 03:41 PM

The light gathering power of the 100mm binoscope would be equivalent to a 141mm single objective, which is not all that far from 150mm. I think the main advantage of the 150mm is its huge true field of view. 




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