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Should i buy this ?

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#1 TeeD

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Posted 08 November 2019 - 01:38 AM

Is this telescope any good for imaging?  I would highly appreciate for any example images and your thoughts.

 

Omegon 90/500 OTA

 

https://www.astrosho...500-ota/p,43767


Edited by TeeD, 08 November 2019 - 01:39 AM.


#2 eros312

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Posted 08 November 2019 - 02:27 AM

I have one just like that from Ebay https://www.ebay.com...redirect=mobile It's wonderful for low power wide field views of the heavens. Sure, you could use it for astrophotography, but it's a short focal length achromatic refractor. There will be a lot of chromatic aberration and field curvature. 


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#3 sg6

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Posted 08 November 2019 - 03:46 AM

Not really suited to AP. Achromat and short and fast so you will get a fair amount of CA and curvature caused by yhe short focal length.

 

Nice easy scope for visual and wide low power viewing. Should be good down to 8mm, 62x, eyepiece, unsure about a 5mm eyepiece 100x.


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#4 TeeD

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Posted 08 November 2019 - 03:50 AM

I have one just like that from Ebay https://www.ebay.com...redirect=mobile It's wonderful for low power wide field views of the heavens. Sure, you could use it for astrophotography, but it's a short focal length achromatic refractor. There will be a lot of chromatic aberration and field curvature. 

Ok thank you very much, I can live with CA , and if you don't mind me asking, how are the optics, is the image sharp?


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#5 TeeD

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Posted 08 November 2019 - 03:53 AM

Not really suited to AP. Achromat and short and fast so you will get a fair amount of CA and curvature caused by yhe short focal length.

 

Nice easy scope for visual and wide low power viewing. Should be good down to 8mm, 62x, eyepiece, unsure about a 5mm eyepiece 100x.

The problem is that i'm limited to 5 kg (+ guide scope,camera,) since i'm using the SkyWatcher GTi and i'm not that bothered by the CA


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#6 junomike

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Posted 08 November 2019 - 07:25 AM

The problem is that i'm limited to 5 kg (+ guide scope,camera,) since i'm using the SkyWatcher GTi and i'm not that bothered by the CA

CA may not bother you but it will bloat your stars during AP.  Something like an SV90T would be far more suitable but also quite a bit more expensive.


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#7 cst4

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Posted 08 November 2019 - 07:28 AM

Those fast achromats are kind of low power visual only scopes. Something like an Astro Tech 72ED would suit your photography wants a lot better if you can afford it. Much better visually too in my opinion even though it is less aperture. 


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#8 drd715

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Posted 08 November 2019 - 09:04 AM

About the only thing a short F# achromat of this type would be good for is as a finder or auto guiding scope. Achromat scopes work better at F-10 or longer. ED scopes are available in a doublet that may fill your needs , but under F-7 a triplet is better. For visual i would favor 90mm or more, but for imaging there are good scopes in the 76mm class. Short scopes are better for wide field objects. Not so great on planets (not enough magnification for details - imaging).

It will cost more for a good quality small well corrected scope. But your time and efforts put into the final image will be a thousand times better and more rewarding.

Consider a quadruplet if your imaging a short Fl scope. They have a nearly flat field by design. Otherwise you will probably have to spend a significant amount on a field flattener and the time to adjust it to the correct spacing.

It's possible you may be better off with a camera lens especially if you are strictly imaging and using a camera body.

My choice would be a short quadruplet for a lightweight travel scope in the 76mm (80mm) size. It is simple and won't require additional optical correction. Just get quality optics, you won't regret it.

When you bake a cake. It tastes better if the ingredients are better.

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#9 eros312

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Posted 08 November 2019 - 09:55 AM

Ok thank you very much, I can live with CA , and if you don't mind me asking, how are the optics, is the image sharp?

Optics are sharp at the low powers I use. This is the eyepiece that I mostly use https://agenaastro.c...piece-7743.html I've never run the power up and done a star test. 


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