80mm ed triplet

[hatflyer]

I thought it was a Photoline triplet. oops!
A good refractor, 2.5" R&P focuser.
Either refractor would work well for you.
If you can afford the triplet get it but if the doublet is easier on the banking account you will not be disappointed.

As to the corrector, the AP voodoo practitioners will have to comment on its worth.

What are the factors that make u suggest the triplet over the doublet?

[Lady Fraktor]

Only cost really, the most expensive has the Starlight Instruments focuser which is top of the line, the other has a good focuser as well but may require the occasional tweak.
Either refractor will work very well so initial output is what it comes down to. Telescope + needed accessories etc.

[Bigzmey]

I would stay away from obscure brands, otherwise getting 80mm ED/APO is very little risk. The technology is mature and doublet or triplet from any known brand would work just fine.

AstroTech doublets have great following, come with good quality R&P focuser and priced competitively. That would be my suggestion.

https://www.astronomics.com/telescopes. ... series=890

[hatflyer]

I would stay away from obscure brands, otherwise getting 80mm ED/APO is very little risk. The technology is mature and doublet or triplet from any known brand would work just fine.

AstroTech doublets have great following, come with good quality R&P focuser and priced competitively. That would be my suggestion.

https://www.astronomics.com/telescopes. ... series=890

What is the least loss of focal length a corrector can be for the AT72EDII? Is it 0.8?

[Lady Fraktor]

I would post that type of question in the beginner AP section.

[JayTee]

You need to distinguish between the two functions. Is it a field flatter or is it an FL compressor, or is it both? All three of these accessories exist. If all you want is a flat field (I have 2 of these), then a field flattener is what you need. It does not change the FL to a noticeable degree. Compressors are another story.

[hatflyer]

You need to distinguish between the two functions. Is it a field flatter or is it an FL compressor, or is it both? All three of these accessories exist. If all you want is a flat field (I have 2 of these), then a field flattener is what you need. It does not change the FL to a noticeable degree. Compressors are another story.

So is a compressor used to make it a faster, wider lens? Do most scopes accept flatteners that don't affect FL? I'd like to maintain as much reach as possible.

[JayTee]

So is a compressor used to make it a faster, wider lens? Do most scopes accept flatteners that don't affect FL? I'd like to maintain as much reach as possible.

A FL compressor called a focal reducer or just FR does just that. Typically they are expressed in a decimal value <1. So a .75 compressor will take an OTA with an FL of 800mm and compress it down to 600mm (.75 x 800). With this example, the aperture is still the same (let's say 100mm) but now we have a shorter FL which also means we have a smaller f/ (focal ratio). Our old f/ was f/8 (800÷100), now 600mm as your new FL gives you an f/ of (600÷100=6) so f/6. So this configuration for the OTA is now "faster" f/6 vs f/8 and the shorter FL means you see a larger chunk of sky for a given EP or camera sensor.

The field flattened also called an FF. It can be generic or linked to a certain f/ range (say f/9 to f/15) or to a specific manufacturer or even a specific OTA. So you need extra data before doing research on an FF.

Lastly, if you see an accessory labeled FF/FR it is the combo of both field flattener AND focal reducer.

Use this link to explore all the fun ways to express OTA plus optical train accessories characteristics.
https://astronomy.tools/calculators/field_of_view/ or
http://www.stargazing.net/naa/scopemath.htm

[Juno16]

Something else to consider if the scope will be used fir AP (as if there isn’t enough!).
That would be the sensor size of the camera that you plan to use.
I moved from a apsc (cropped) sensor dslr (Nikon D5300) to a dedicated astro camera (ASI533MC-P).

Check out this site to see the fov with different scope/camera configurations.

https://astronomy.tools/calculators/field_of_view/

The image below shows the different field of views between the ES 80mm APO and the Nikon D5300/ASI533.

The image below shows the different field of views between the ES 80mm APO and the ASI533 with and without a 0.8 FR.

Dedicated astro camera prices usually go up considerably with sensor size.

So, if AP is in your plans, camera choices and FR's should be considered.

[chris_g]

Just saw this 1 for saler - Sky-Watcher EvoStar 80mm f/7.5 Doublet APO Refractor ED80; focal length is 600mm, and FPL53. Thoughts?

My first scope, I paired it though with the .85 reducer/flattener. Changed the focal length to 530 and f/6.3. You can get just a flattener too if you want

I love it. My last image taken with it and a stock T3i

[hatflyer]

Something else to consider if the scope will be used fir AP (as if there isn’t enough!).
That would be the sensor size of the camera that you plan to use.
I moved from a apsc (cropped) sensor dslr (Nikon D5300) to a dedicated astro camera (ASI533MC-P).

Check out this site to see the fov with different scope/camera configurations.

https://astronomy.tools/calculators/field_of_view/

The image below shows the different field of views between the ES 80mm APO and the Nikon D5300/ASI533.


Capture.JPG


The image below shows the different field of views between the ES 80mm APO and the ASI533 with and without a 0.8 FR.


Capture1.JPG


Dedicated astro camera prices usually go up considerably with sensor size.

So, if AP is in your plans, camera choices and FR's should be considered.

I have the D5500. To see a notciable improvement, what would the lowest cost camera be?

[Juno16]

Something else to consider if the scope will be used fir AP (as if there isn’t enough!).
That would be the sensor size of the camera that you plan to use.
I moved from a apsc (cropped) sensor dslr (Nikon D5300) to a dedicated astro camera (ASI533MC-P).

Check out this site to see the fov with different scope/camera configurations.

https://astronomy.tools/calculators/field_of_view/

The image below shows the different field of views between the ES 80mm APO and the Nikon D5300/ASI533.


Capture.JPG


The image below shows the different field of views between the ES 80mm APO and the ASI533 with and without a 0.8 FR.


Capture1.JPG


Dedicated astro camera prices usually go up considerably with sensor size.

So, if AP is in your plans, camera choices and FR's should be considered.

I have the D5500. To see a notciable improvement, what would the lowest cost camera be?

Maybe I didn’t explain well enough.

My point was about sensor size and field of view and the need for a focal reducer.

[hatflyer]

Just saw I'm not in the right forum. But thought I would continue here.

Does anyone make a field flattener that doesn't reduce the focal length for the Astro-Tech AT72EDII? Maybe the Orion Field Flattener for Short Refractors? I'm down to the Apertura 72mm f/6 which has the 1:1 flattener and the AT72EDII.

Any opinions on the 2?

Thanks.

[JayTee]

Here are the two I own. The first one, the Astro-Tech says it's for TMB and astro-tech scopes but it works just fine in my ES APO, even better than the Hotech.

https://www.astronomics.com/astro-tech- ... ctors.html

https://www.highpointscientific.com/hot ... xwQAvD_BwE

[chris_g]

@JayTee , correct me if I am wrong. If I can get a flattener made for one refractor to properly mate with the tube of another, in theory it should work.

For example, I have an Orion .85 reducer/flattener with 56mm female thread used on a sky watcher 80ED no adapters. I can adapt it to a two inch nose piece. Then I put in the two inch adapter for my Z73 and insert. Now my 440 focal length is 374 and my focal ratio 5.9 is now 5.0

Obviously this affects other things that may or may not be relevant, such as image circle in my case, but it should work, correct?

[hatflyer]

Here are the two I own. The first one, the Astro-Tech says it's for TMB and astro-tech scopes but it works just fine in my ES APO, even better than the Hotech.

https://www.astronomics.com/astro-tech- ... ctors.html

https://www.highpointscientific.com/hot ... xwQAvD_BwE

The Astro-Tech seems unavailable. Are u saying the Hotech will do well with the AT72?

[JayTee]

Are u saying the Hotech will do well with the AT72?

From the Hotech website:
"HOTECH SCA Field Flattener: It accommodates f5 to f8 refractor telescope. You will see bright and sharp image across the entire field."

Since your AT72 is f/6, the answer is, it should.

[JayTee]

correct me if I am wrong. If I can get a flattener made for one refractor to properly mate with the tube of another, in theory, it should work.

A FF should work when it is installed in the optical train that keeps its f/ within the operating range of the FF's specs. Remember that where you put the accessory in the optical train is important because the light cone is ever-expanding after the focal point.

[hatflyer]

Does anyone know of a 1.0 field flattener for the TS-Optics Doublet SD-Apo 80 mm f/7 besides the TSFlat25DEL?


Impressions of this scope for AP?


Thanks.

[chris_g]

Does anyone know of a 1.0 field flattener for the TS-Optics Doublet SD-Apo 80 mm f/7 besides the TSFlat25DEL?

As @JayTee confirmed any flattener designed for a refractor that falls within it's focal ratio should work. You just have to be aware of where and how in the image train you are putting it. You might be better off finding another 1:1 flattener then asking for opinions on it.

Clear Skies,
Chris