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Would you get a 400mm lens or a telescope that's similarly priced.

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Sir Canon

Sir Canon

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hi, so i think that id like to get a well corrected refractor in the 400mm range since ive found my 800mm newtonian to be constricting in terms of focal length as well as overall optical performance. ive found 2 similarly prices options in the 400ish mm range the first being the canon 400mm f5.6 l lens which can be had used for around 750 dollars and the other thing would be this small scope from Teleskop Service when adding a field flattener it will come to about the same price as the lens.

what are your recomendations on what to get. and if i get the scope should i get a focal reducer corrector (which will put me a 376mm) or just a field flattener

thanks for your thoughts
 
Have you considered a fast 300mm lens with ed glass and use of a teleconverter when needed?

Nate
 
I think the TS scope is a generic version of the Astrotech's AT80EDT triplet. I think for 400mm fl, I would rather consider this well corrected Quadruplet (AT65EDQ). It gives a real flat field and does not need a corrector (nor is it desirable to add a focal reducer to the already flat field). I think one saves the significant shipping charges TS charges to ship from Germany, Most US vendors will offer free shipping within continental US on big ticket items like a scope.

AT65EDQ is a 6.5 f ratio scope, so you get 422mm focal length, so just about where you want to be. I think a dedicated scope rather than a lens would be my choice. I don't like the 8 or more diffraction spikes one gets when one has to stop down a camera lens to avoid/reduce coma ..... Anil
 
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A few things to consider.

APS-C or FF camera? Small refractors usually do not illuminate a 44 mm image circle.

If getting a small refractor:

1) the reducer will also reduce the fully illuminated field, usually covering APS-C

2) several field flatteners cover a 44 mm image circle but read the text before ordering!

If using the lens for astro and wildlife then the 5.6/400 mm lens might be fine. This lens is also a bit more compact than most refractors if size and weight matter.

One fellow here has posted a few images taken with this Canon lens - might be worth a closer look. Also take a look at AstroBin and search for images taken with this lens.

And ... happy shopping! ;-)
 
Sir Canon said:
hi, so i think that id like to get a well corrected refractor in the 400mm range since ive found my 800mm newtonian to be constricting in terms of focal length as well as overall optical performance. ive found 2 similarly prices options in the 400ish mm range the first being the canon 400mm f5.6 l lens which can be had used for around 750 dollars and the other thing would be this small scope from Teleskop Service when adding a field flattener it will come to about the same price as the lens.

what are your recomendations on what to get. and if i get the scope should i get a focal reducer corrector (which will put me a 376mm) or just a field flattener

thanks for your thoughts

--
I tend to overdo things
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No clue as to which is better but I can tell you that my big white Canon 400mm 5.6L is very sharp! I've used it quite a bit with a Kenko 2x teleconverter and it is still sharp. And of course it works well on both my cropped and my FF cameras. Hope that helps.

--
Jack Swinden
W5JCK, amateur radio operator
An astrophotography hobbyist and amateur radio instructor and examiner. Sony a7 and Sony a6000. https://www.flickr.com/photos/jackswinden/albums
 
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BlackgumNate said:
Have you considered a fast 300mm lens with ed glass and use of a teleconverter when needed?

Nate
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I don't have fast 300mm lens money haha. If I did believe me if have one!
 
anilketkar said:
I think the TS scope is a generic version of the Astrotech's AT80EDT triplet. I think for 400mm fl, I would rather consider this well corrected Quadruplet (AT65EDQ). It gives a real flat field and does not need a corrector (nor is it desirable to add a focal reducer to the already flat field). I think one saves the significant shipping charges TS charges to ship from Germany, Most US vendors will offer free shipping within continental US on big ticket items like a scope.

AT65EDQ is a 6.5 f ratio scope, so you get 422mm focal length, so just about where you want to be. I think a dedicated scope rather than a lens would be my choice. I don't like the 8 or more diffraction spikes one gets when one has to stop down a camera lens to avoid/reduce coma ..... Anil
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That looks like a much better version for a similar price.
 
anilketkar said:
I think the TS scope is a generic version of the Astrotech's AT80EDT triplet. I think for 400mm fl, I would rather consider this well corrected Quadruplet (AT65EDQ). It gives a real flat field and does not need a corrector (nor is it desirable to add a focal reducer to the already flat field). I think one saves the significant shipping charges TS charges to ship from Germany, Most US vendors will offer free shipping within continental US on big ticket items like a scope.

AT65EDQ is a 6.5 f ratio scope, so you get 422mm focal length, so just about where you want to be. I think a dedicated scope rather than a lens would be my choice. I don't like the 8 or more diffraction spikes one gets when one has to stop down a camera lens to avoid/reduce coma ..... Anil
Click to expand...
i did a search on both the 400mm lens and the scope on astrobin. i did not find a single image from the 400mm lens where i went wow! i think that somewhat in part to the fact that many beginners are using it on mounts that are wayy to small for it. however there were many nice images from the scope. ill probably get the scope.
 
Sir Canon said:
i did a search on both the 400mm lens and the scope on astrobin. i did not find a single image from the 400mm lens where i went wow! i think that somewhat in part to the fact that many beginners are using it on mounts that are wayy to small for it. however there were many nice images from the scope. ill probably get the scope.
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W5JCK said:
Sir Canon said:
i did a search on both the 400mm lens and the scope on astrobin. i did not find a single image from the 400mm lens where i went wow! i think that somewhat in part to the fact that many beginners are using it on mounts that are wayy to small for it. however there were many nice images from the scope. ill probably get the scope.
Click to expand...
Click to expand...
 
I recently bought a Orion ED80T. It has a 480mm FL @f/6. I couldn't be happier with it. If you use a crop sensored camera like my Sony a6300 it comes out to 720mm. An Orion ED80 will run you about $650 in the US. Just my 2 cents tho.

Bryan

My Site
 
Hi,

As Trollmanx & others have said, the EF 400 5.6 lens does great double duty for birds as well as astro.

Here is a recent work in progress image with this lens - with 1.4x TC.

a814fec2131d4e79bc77b1e5030c0d0b.jpg

I am quite happy with the sharpness and good star shapes right up to the corners on mine.

The only time I have struggled with this was on really bright stars like the Pleiades where I got some very noticeable uneven halos, probably because of some imperfections or light leakage from the diaphragm blades (even when full open).

I plan to try a front aperture mask by next year and see if can get around the issue.

Hope this helps.

Regards, Vishy
 
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Vishy_b said:
Hi,

As Trollmanx & others have said, the EF 400 5.6 lens does great double duty for birds as well as astro.

Here is a recent work in progress image with this lens - with 1.4x TC.

a814fec2131d4e79bc77b1e5030c0d0b.jpg

I am quite happy with the sharpness and good star shapes right up to the corners on mine.

The only time I have struggled with this was on really bright stars like the Pleiades where I got some very noticeable uneven halos, probably because of some imperfections or light leakage from the diaphragm blades (even when full open).

I plan to try a front aperture mask by next year and see if can get around the issue.

Hope this helps.

Regards, Vishy
Click to expand...
great image!! im fairly confident that either ota will produce great images in the right hands

--
I tend to overdo things
 
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