Sky-Watcher Evostar 72ED DS-Pro

[Stub Mandrel]

I'm using an Equinox ED 66 lens. these are crops from the top corners using the OVL flattener without and then with a 1mm spacer, I think I need another 0.5mm (the Ha at bottom is in super pixel mode so they cover the same amount of sensor, more or less):

[Cozzy]

I got my ED72 and OVL flattener  from FLO a couple of weeks ago but did not have a EOS T2 adapter , which I now have, when I get the 'weather and work commitments to play ball'  I will test and let you know how things go.

Tim

Edited September 28, 2018 by Cozzy
typo

[alexbb]

I link this here too, maybe some will land here for results with the 72ED.

 

[Stub Mandrel]

I swapped my t-adapter. and went back to the thin spacer.

The star elongation got worse but the tilt and collimation error virtually disappeared (I can live with a 9 pixel collimation error!)

This means some of my problem was a loose bayonet fitting.

So, I've gone back to the ticker spacer and wait to try again. At least none of the practice runs are write-offs, they all are usable with a bit of cropping.

[calli]

1 hour ago, moise212 said:

I link this here too, maybe some will land here for results with the 72ED.

 

Can you just do a quick note how you connect the camera and which spacer and what not were used? The Thread gets a bit big to search this all.

Thanks,

Carsten

[alexbb]

8 minutes ago, calli said:

Can you just do a quick note how you connect the camera and which spacer and what not were used? The Thread gets a bit big to search this all.

Thanks,

Carsten

Yes, you can find more details here:

Stars still appear less round towards the corners, but this last image also had less than perfect tracking so you wouldn't see too much the aberrations.

[Susaron]

I will receive the TS reducer tomorrow, I hope to make a test along this week.

Meanwhile the 130PDS did the work last weekend shooting 3 objectives in one night.

[alexbb]

22 hours ago, Susaron said:

I will receive the TS reducer tomorrow, I hope to make a test along this week.

Meanwhile the 130PDS did the work last weekend shooting 3 objectives in one night.

The TS reducer should work best with 420mm FL at 65mm backfocus. I'm curious if you can reach focus.

[Susaron]

23 hours ago, moise212 said:

The TS reducer should work best with 420mm FL at 65mm backfocus. I'm curious if you can reach focus.

Due to the clouds I was not able to make an imaging test, but even at a distance of 65mm between the sensor and the reducer, because of the TS geometry I have gained around 27mm in-focus.

I did some measurements with the ED80 reducer and the FLO adapter, putting the sensor at a distance of 55mm from the reducer. The total length measured  from the focuser mouth to the sensor was 108mm.

With the TS reducer ( I got the one with 2'' barrel without the M54 thread), it inserts perfectly into the drawtube, having measured a total length from the focuser mouth to the sensor of 80mm, so even increasing the distance from the sensor from 55mm to 65mm I have improved the infocus travel around 18mm.

I am eager to make a test soon.

Edited October 10, 2018 by Susaron

[alexbb]

On RGB, the little scope is quite sharp. Blue is a bit bloated, but still sharp.

FWHM of 30x120s stacks from yesterday. R - 1.680px, G - 1.455px, B - 1.915px.

And an RGB STF tease of the fish-head.

[alexbb]

Another tease. This will take me a while to process properly.

 

[Susaron]

Dear all, finally I could test the TS x0.79 reducer with the ED72, my calculations where almost perfect. The focus point for my QHY168C with a distance between the sensor and the reducer of 64.5mm is around 17mm outwards so I got enough margin.

 

From my point of view this reducer shall be recommended for the ED72 accessories if you own an APS-C like sensor (ASI071 or QHY168C).

I took only fast pictures of Mirfak so I will check the stars at the squares this afternoon.

Cheers.

[alexbb]

2 minutes ago, Susaron said:

Dear all, finally I could test the TS x0.79 reducer with the ED72, my calculations where almost perfect. The focus point for my QHY168C with a distance between the sensor and the reducer of 64.5mm is around 17mm outwards so I got enough margin.

 

From my point of view this reducer shall be recommended for the ED72 accessories if you own an APS-C like sensor (ASI071 or QHY168C).

I took only fast pictures of Mirfak so I will check the stars at the squares this afternoon.

Cheers.

Could you post an image of the setup, please?

[Susaron]

This evening

[Susaron]

[calli]

25 minutes ago, Susaron said:

Looks a bit unballanced... From left to right.... Moneywise SCNR

[Susaron]

True, I need an extra 1kg at the nose, one of those from baader

[alexbb]

Looks good! Did you manage to check the frames? Can you share a stretched one?

[Susaron]

I just did a short test around Mirphak, as from my balcony I cannot see the Polaris, the stars looked good in 3 of the 4 squares, maybe the error comes from flexure or poor polar alignment.

Edited October 18, 2018 by Susaron

[alexbb]

On 18/10/2018 at 15:05, Susaron said:

I just did a short test around Mirphak, as from my balcony I cannot see the Polaris, the stars looked good in 3 of the 4 squares, maybe the error comes from flexure or poor polar alignment.

Looks good!

[alexbb]

According to this, it seems that the focal length with the 0.85x reducer/flattener for 80ED (at 60mm backfocus) is ~377mm, not 357mm. That means that the corrector reduces ~0.9x at 60mm backfocus.

[Susaron]

More test from yesterday night using an Optolong Halpha filter it also achived focus, so deal done with the TS reducer. 25x60s subs around Mirphak an Mel 20. Also the result from the aberration analysis at the squares from Pix. My polar alignment was non-existent so the guiding suffer (but not much as I was shotting at 332m).

Cheers.

Mario.

 

[Grumman]

I wish I have seen this post earlier before spending £170 on the SW Field Flattener....

I have fitted the FF to the scope and attached my Canon 100D DSLR on it with the correct T-ring and I am getting around 40% Curvature according to CCDInspector, where before without the FF I was having curvatures of around 130%!!! - So for starters it is doing something...

I have purchased some .5mm and 1mm thick spacing rings and I installed them between the FF and the T-Ring.

I have done some tests and with a 1.5mm ring the curvature increased to 44.6% which is the opposite of what I expected to see...

It seems like it needs a thinner T-Ring so the camera sensor can come closer to the FF .... ? 

Has anyone done any tests with a DSLR than can shed some light?

 

[Stub Mandrel]

8 minutes ago, Grumman said:

I wish I have seen this post earlier before spending £170 on the SW Field Flattener....

I have fitted the FF to the scope and attached my Canon 100D DSLR on it with the correct T-ring and I am getting around 40% Curvature according to CCDInspector, where before without the FF I was having curvatures of around 130%!!! - So for starters it is doing something...

I have purchased some .5mm and 1mm thick spacing rings and I installed them between the FF and the T-Ring.

I have done some tests and with a 1.5mm ring the curvature increased to 44.6% which is the opposite of what I expected to see...

It seems like it needs a thinner T-Ring so the camera sensor can come closer to the FF .... ? 

Has anyone done any tests with a DSLR than can shed some light?

 

Using an OVL flattener I'm creeping up on the right size spacer, but the results in CCD Inspector seemed to be heavily influenced by how well focused I was as well a the actual curvature.

Looking at the subs seems to tell a  more intuitive story than CCD I. I've 3D printed my MK4 spacer at 2mm and hoping that will be the one.

Check out the inside/outside diagrams and advice in this thread to see if you actually need to add or subtract spacer. From my experience I'd expect a much bigger change than 4.6% with 1.5mm of spacer. You may have gone past the 'sweet spot' with 1.5mm so I'd try 1mm or 0.5mm next.

 

[Grumman]

Thanks for the reply @Stub Mandrel!

I see what you mean... I might have gone too far with the 1.5mm and it started reversing the whole curvature...

I will try and do it in smaller steps and see if it makes any difference.

TA!