Esprit 80 + TS Optics 0.79x Reducer

[Andyb90]

Hi everyone,

I'm tempted to try the TS Optics 0.79x reducer with my Esprit 80 as it would give f4. Has anyone tried the reducer with this scope? If so it would be good to know about your experiences. 

I'd also be interested to know if anyone has used another reducer with the Esprit 80 and what the results have been like.

Andy.

[Jkulin]

Is the reducer a flattener as well, as although I did use my 80 without a flattener whilst i was waiting for it to arrive, it was much better with one.

I found F5 fast enough and didn't want the aggro of continually altering my focus.

[Andyb90]

13 hours ago, Jkulin said:

Is the reducer a flattener as well, as although I did use my 80 without a flattener whilst i was waiting for it to arrive, it was much better with one.

I found F5 fast enough and didn't want the aggro of continually altering my focus.

I couldn't see on the TS website whether it's a flattener as well. I've emailed them to check.

So the faster the setup generally the more difficult it is to achieve and maintain accurate focus manually. Is that correct? I haven't got auto focusing setup at the moment. I use the star HFR readings in SGPro for focusing manually.

Andy.

[Jkulin]

Indeed the faster a scope the more susceptible it is to the temperature.

Only this week my mate Peter Shah sent me a curse as whilst he was chatting to me his F3.8 Newt had changed focus because the temp had changed marginally and he never checked his focus when he normally would.

I set SGP to refocus every 1 degree of temperature change and it is really is surprising how much difference it makes.

When you are ready the Lakeside worked out the best option for quality and price wise for autofocus and when you have used auto you will never go back to manual, it is just so accurate.

When I get a new setup or change a piece of kit and have to manually focus I use a Bahtinov Mask to get it as good as I can, then let autofocus take over, amazing difference.

[RayD]

9 minutes ago, Jkulin said:

I set SGP to refocus every 1 degree of temperature change and it is really is surprising how much difference it makes.

Spot on, John.  On my Tak I've actually just dropped this to 0.5 degrees (Esprit is still at 1 degree).

[RayD]

On 25/09/2018 at 22:13, Andyb90 said:

Hi everyone,

I'm tempted to try the TS Optics 0.79x reducer with my Esprit 80 as it would give f4. Has anyone tried the reducer with this scope? If so it would be good to know about your experiences. 

I'd also be interested to know if anyone has used another reducer with the Esprit 80 and what the results have been like.

Andy.

If you are referring to the Photoline 2" one (4 element) it is a corrector as well as reducer.

[Andyb90]

3 hours ago, Jkulin said:

Indeed the faster a scope the more susceptible it is to the temperature.

Only this week my mate Peter Shah sent me a curse as whilst he was chatting to me his F3.8 Newt had changed focus because the temp had changed marginally and he never checked his focus when he normally would.

I set SGP to refocus every 1 degree of temperature change and it is really is surprising how much difference it makes.

When you are ready the Lakeside worked out the best option for quality and price wise for autofocus and when you have used auto you will never go back to manual, it is just so accurate.

When I get a new setup or change a piece of kit and have to manually focus I use a Bahtinov Mask to get it as good as I can, then let autofocus take over, amazing difference.

Thanks for the information. I think I'm going to stick at f5 for now. As if I end up spending more time manually re-focusing that will probably negate (at least part of) the benefit of reduced f ratio. I think I'll re-visit using the reducer when I have auto focus setup with the scope.

Andy.

[Andyb90]

3 hours ago, RayD said:

If you are referring to the Photoline 2" one (4 element) it is a corrector as well as reducer.

Yes that's the one, thanks for confirming it corrects too.

Andy

[Ivan Hancock]

Hi all, So ! has anyone managed to try a flattener/reducer on the Esprit 80ED ? I also am very interested to know if there is such a thing available ?

I have no problems with focus shift so the thought of a reducer is very tempting 😋

I wait with anticipation 🤔

[ollypenrice]

On 28/09/2018 at 16:14, Andyb90 said:

I couldn't see on the TS website whether it's a flattener as well. I've emailed them to check.

So the faster the setup generally the more difficult it is to achieve and maintain accurate focus manually. Is that correct? I haven't got auto focusing setup at the moment. I use the star HFR readings in SGPro for focusing manually.

Andy.

Yes, the light cone has a steeper angle as in a capital X where the left hand half of the letter is the incoming beam and focus is at the point of crossover in the middle.  Because pixels have a finite size you have a little tolerance each side of the point of crossover but the steeper the light cone the less is that tolerance (or depth of field). Smaller pixels also give you less tolerance.

Your motivation seems to be to reach F4. If this is to make imaging faster a reducer may not do this. For the F ratio rule to work you would have to fix the focal length and add more aperture.* Reducing the focal length at the same aperture is not equivalent. The sound reason for using a reducer is to increase the field of view and if you actually want all that is in the new field you will get to an acceptable S/N ratio faster but at lower resolution.

Olly

* This is what happens in camera lenses and explains why the F ratio rule does work in this context.

Edited June 22, 2019 by ollypenrice
Footnote

[FaDG]

No experience with the Esprit 80, but I have TWO (*) TS Photoline 0,79 reducers (ok, I have the Tecnosky version, but it's exactly the same). 

Using it on a Sharpstar 72ED (same OTA as TS Photoline 72/400 f5.5), I can confirm that it's great on an APS-C chip. 

WARNING: I spent weeks to tweak the chip to reducer spacing, getting it right to 0.1 mm, and now always work at f4.5, and despite the T2 (M42) adapter, vignetting is not a big deal, can be corrected with good flats

@Ollyis right in that, at such an extreme f ratio, tolerances are very tight, and even the slightest tilt (in my case it was the camera sensor, but it can be the focuser or decollimation) will drive you mad. Finally I purchased a tilt adapter. 

Furthermore, major temperature changes need to be compensate by refocusing. 

But once you get the hold of it, it's just like magic! 

So, I can't say how it will perform on the Esprit, and you'll have to adapt backfocus, but if you are ready to stir the hornet's nest and survive, it could turn out great! 

Fabio

(*) Reason for having two is that I bought the first one used for cheap, as I didn't know whether it would work. When I had everything perfectly fit, I found a second used one for even less, and immediately grabbed it! 🤣 

 

[FaDG]

This is an example, shot with the above mentioned setup and an IDAS V4. 

I still get a wee of deformation on the stars in the extreme right side, but I can definitely live with it! 

And the Field of View at 320mm is gorgeous. 

 

Edited June 22, 2019 by FaDG

[Pompey Monkey]

I tried the TS279red with my Esprit 80 last year, including the special low profile M74 (?) to M48 adapter from Telescope Austria https://teleskop-austria.at/M74nM48p_M74neg-M48posFeingewinde-Adapter-um-den-TS-079x-Reducer 

However after many hours finding the correct backfocus distance, I then found that I couldn't move the drawtube far enough in to get focus!

YMMV, but for me, some things are just not meant to be

 

[newbie alert]

I can see this is an old post but what's everyone's back focus distance on their esprit 80,seen lots of different ones from 55 to 75mm..I'm talking about the distance from the flat part of the flattener to sensor..

[Jkulin]

55mm from the rear flat part of the flattener to the CCD, anything other causes odd shaped stars, add 0.6mm spacer for each 2mm filter in front of the Filter wheel and 1mm if using Chroma or Astrodon Filters as they are 3mm thick.

[newbie alert]

2 hours ago, Jkulin said:

55mm from the rear flat part of the flattener to the CCD, anything other causes odd shaped stars, add 0.6mm spacer for each 2mm filter in front of the Filter wheel and 1mm if using Chroma or Astrodon Filters as they are 3mm thick.

55mm from the rear of the flattener to sensor? 

[Jkulin]

Here's an image of my backfocus to the flange of the Esprit Flattener, mine added up to 54.57, so I added 2 x 0.5mm thin plastic spacers but might need to add a couple more as I use Chroma filters so I need an extra 1mm

Hope that helps?

[newbie alert]

On 01/07/2019 at 22:20, Jkulin said:

Here's an image of my backfocus to the flange of the Esprit Flattener, mine added up to 54.57, so I added 2 x 0.5mm thin plastic spacers but might need to add a couple more as I use Chroma filters so I need an extra 1mm

Hope that helps?

Yes, thanks for your reply

[RMercken]

On 22/06/2019 at 10:47, FaDG said:

No experience with the Esprit 80, but I have TWO (*) TS Photoline 0,79 reducers (ok, I have the Tecnosky version, but it's exactly the same). 

Using it on a Sharpstar 72ED (same OTA as TS Photoline 72/400 f5.5), I can confirm that it's great on an APS-C chip. 

WARNING: I spent weeks to tweak the chip to reducer spacing, getting it right to 0.1 mm, and now always work at f4.5, and despite the T2 (M42) adapter, vignetting is not a big deal, can be corrected with good flats

@Ollyis right in that, at such an extreme f ratio, tolerances are very tight, and even the slightest tilt (in my case it was the camera sensor, but it can be the focuser or decollimation) will drive you mad. Finally I purchased a tilt adapter. 

Furthermore, major temperature changes need to be compensate by refocusing. 

But once you get the hold of it, it's just like magic! 

So, I can't say how it will perform on the Esprit, and you'll have to adapt backfocus, but if you are ready to stir the hornet's nest and survive, it could turn out great! 

Fabio

(*) Reason for having two is that I bought the first one used for cheap, as I didn't know whether it would work. When I had everything perfectly fit, I found a second used one for even less, and immediately grabbed it! 🤣 

 

Hi,

Did you bought the 2" or the 3" version?

[newbie alert]

On 01/07/2019 at 17:00, Jkulin said:

55mm from the rear flat part of the flattener to the CCD, anything other causes odd shaped stars, add 0.6mm spacer for each 2mm filter in front of the Filter wheel and 1mm if using Chroma or Astrodon Filters as they are 3mm thick.

As this thread has been resurected  I did indeed use 55mm spacing, wasn't sure that the stars looked correct or not, caused drop off from my filter like a vignette.. investigated further and depending on what age/version of 80mm esprit  you have skywatcher recommend either 61or 66mm backfocus..

At 66mm it did correct the vignette issue,  although I'm not quite there on the spacing, near enough 

 

[FaDG]

On 01/11/2020 at 11:32, RMercken said:

Hi,

Did you bought the 2" or the 3" version?

Sorry for the late reply, I've been offline for some time. 

I have the 2" version. Very, very limited amount of vignetting on an APS-C sensor at f4.5. 

Had to use a lot of backfocus at 400mm focal length. 

Edited December 11, 2020 by FaDG