Altair Astro 72EDF arrived today

[StaceStar]

So my new scope arrived today, this is primarily why my 80ed is up for sale. Early days yet, but I'm hoping to get first light tonight. 

Such a good price point too, considering it comes with an optical test report. 

I'll try and get an in depth review up soon

[Louis D]

Is that basically the same scope as the Astro-Tech AT72EDII?  If so, I'm definitely interested in your thoughts on it since I have the original Astro-Tech AT72ED with FPL-51 glass.  It's great up to about 100x where unfocused color starts to show up on bright objects.  Above 125x, it's not really usable.  That's when I switch over to my 127 Mak on the other side of my grab and go setup.  If it doesn't show any color at those sorts of high powers, I might just trade up to it sometime.

My other question would be on the focuser tube.  My AT72ED doesn't allow a GSO 2" diagonal to be inserted all the way because the shiny receiver end of the tube is too short.  You'd think you could push past it, but the tube blackening further up is narrower than the receiver.

[Yawning Angel]

Lovely looking scope! You know it only suits ZWO and Primaluce accessories now ?

[StaceStar]

15 minutes ago, Louis D said:

Is that basically the same scope as the Astro-Tech AT72EDII?  If so, I'm definitely interested in your thoughts on it since I have the original Astro-Tech AT72ED with FPL-51 glass.  It's great up to about 100x where unfocused color starts to show up on bright objects.  Above 125x, it's not really usable.  That's when I switch over to my 127 Mak on the other side of my grab and go setup.  If it doesn't show any color at those sorts of high powers, I might just trade up to it sometime.

My other question would be on the focuser tube.  My AT72ED doesn't allow a GSO 2" diagonal to be inserted all the way because the shiny receiver end of the tube is too short.  You'd think you could push past it, but the tube blackening further up is narrower than the receiver.

Looks like it! Primarily I'll be using this for astrophotography...but I'll try and check out what it it is like at higher powers. I might even be lucky and get first light this evening

[John]

The figures on that test report are better than most Zeiss, Takahashi, Astro Physics and LZOS objectives. How do they manage that for the cost

In fact they are crazilly good - 1/13th wave PV if my calculation is correct and a practically perfect strehl !!!!!

Hope you have a lot of fun with it !

 

[StaceStar]

13 minutes ago, John said:

The figures on that test report are better than most Zeiss, Takahashi, Astro Physics and LZOS objectives. How do they manage that for the cost

In fact they are crazilly good - 1/13th wave PV if my calculation is correct and a practically perfect strehl !!!!!

Hope you have a lot of fun with it !

 

I must admit with the optical test report I am out of my comfort zone. That said I know the strehl value is crazy good!! 

If they are infact true...which I don't doubt they are ill be super happy. I reckon Altair know people will be scrutinising these results...so it's not in their interest to lie

I have a feeling these might go out of stock rapidly haha

[John]

It will be interesting to see if the high power star test looks like the simulated star test on the report.

[StaceStar]

1 minute ago, John said:

It will be interesting to see if the high power star test looks like the simulated star test on the report.

Noob question, do I pick a star and defocus?

[John]

9 minutes ago, StaceStar said:

Noob question, do I pick a star and defocus?

Use Polaris at around 150x or so.

The scope should be fully cooled. You examine the star image at sharpest focus then just inside and outside focus. Main thing to look for is concentric and circular diffraction rings around a small circular airy disk. At focus you should only see one or two rings on Polaris (more on a brighter star like Vega), either side of focus more diffraction rings appear. Ideally you want as close as possible the same concentricity and intensity of rings either side of focus but thats not always possible to discern if the seeing conditions are not good. 

A really good startest with a refractor should look something like this (outside focus --> at focus --> inside focus):

[StaceStar]

Silly me forgot to order a longer vixen dovetail...nearly balanced but not quite going to give it a go regardless

[StaceStar]

17 hours ago, John said:

Use Polaris at around 150x or so.

The scope should be fully cooled. You examine the star image at sharpest focus then just inside and outside focus. Main thing to look for is concentric and circular diffraction rings around a small circular airy disk. At focus you should only see one or two rings on Polaris (more on a brighter star like Vega), either side of focus more diffraction rings appear. Ideally you want as close as possible the same concentricity and intensity of rings either side of focus but thats not always possible to discern if the seeing conditions are not good. 

A really good startest with a refractor should look something like this (outside focus --> at focus --> inside focus):

Didnt get round to doing this yet, but I will at some point. All I can say is that this scope exudes quality

....especially when compared to my SW ED80. I did get an image of M31 last night, i'll post it up when I'm happy with my processing :) 

[John]

4 hours ago, StaceStar said:

Didnt get round to doing this yet, but I will at some point. All I can say is that this scope exudes quality

....especially when compared to my SW ED80. I did get an image of M31 last night, i'll post it up when I'm happy with my processing

Fair enough. It would be the first thing that I would do I reckon -just takes a few minutes once the scope is cool. You want to make sure that the star test does not look like the synthetic one on the test sheets I think.

[StaceStar]

18 minutes ago, John said:

Fair enough. It would be the first thing that I would do I reckon -just takes a few minutes once the scope is cool. You want to make sure that the star test does not look like the synthetic one on the test sheets I think.

I did take a look at the airy discs and diffraction rings briefly. I didn't spend an epic amount of time on it admittedly. But they looked much like the examples above 

[StaceStar]

Found this useful article too http://cameras.altairastro.com/2018/03/20/star-testing-a-fast-modern-ed-doublet-refractor/

[John]

My slight concern is that the optics on the test sheets look a little "pinched". If you look at the synthetic star test on the test sheet the 1st diffraction ring and the airy disk have a triangular aspect in terms of shape and illumination. The example that I supplied of a good star test has concentric circular diffraction rings, evenly illuminated around. I'm probably being a little paranoid but it's worth checking out

If the scope has a strehl ratio of .990 and is figured to 1/13th wave peak to valley then it should show a practically perfect star test under decent seeing conditions.

 

 

[StaceStar]

2 minutes ago, John said:

My slight concern is that the optics on the test sheets look a little "pinched". If you look at the synthetic star test on the test sheet the 1st diffraction ring and the airy disk have a triangular aspect in terms of shape and illumination. The example that I supplied of a good star test has concentric circular diffraction rings, evenly illuminated around. I'm probably being a little paranoid but it's worth checking out

If the scope has a strehl ratio of .990 and is figured to 1/13th wave peak to valley then it should show a practically perfect star test under decent seeing conditions.

 

 

I don't think it is pinched...though it certainly looks that way. The article above suggests it's spacers either way...for the price I cannot complain. Especially when it's scoring better than some taks ?

[John]

1 minute ago, StaceStar said:

I don't think it is pinched...though it certainly looks that way. The article above suggests it's spacers either way...for the price I cannot complain. Especially when it's scoring better than some taks ?

Does the scope use spacers ?. I can't see any in the objective photo you posted. A lot of refractors use rings to create the air space between the lenses now, particularly the ones aimed at imagers.

Anyway, what matters is that you enjoy the scope and it sounds like you are very happy with it

[GavStar]

1 hour ago, John said:

My slight concern is that the optics on the test sheets look a little "pinched". If you look at the synthetic star test on the test sheet the 1st diffraction ring and the airy disk have a triangular aspect in terms of shape and illumination. The example that I supplied of a good star test has concentric circular diffraction rings, evenly illuminated around. I'm probably being a little paranoid but it's worth checking out

If the scope has a strehl ratio of .990 and is figured to 1/13th wave peak to valley then it should show a practically perfect star test under decent seeing conditions.

 

 

John, what about this as a comparison?

 

[StaceStar]

Had it confirmed from Altair. My lens is the best of the batch I'll take that. Its a 1 in 500 lens. I better go put the lottery on ?

[John]

1 hour ago, StaceStar said:

Had it confirmed from Altair. My lens is the best of the batch I'll take that. Its a 1 in 500 lens. I better go put the lottery on ?

Congratulations !

No need to star test it now then.

 

[StaceStar]

36 minutes ago, John said:

Congratulations !

No need to star test it now then.

 

That's not what I was implying ... Just it's nice to hear I had a bit of luck

 

I will get round to star testing it eventually. I live in Birmingham where the seeing conditions aren't great anyway. I also need to dig out a green filter and read a lot more into it so that it's fair. First impressions though, this is an incredible scope and I can't believe my luck. 

[StaceStar]

The triangular 'pattern' on my lens is a polishing artefact. But the strehl score is real. A happy accident so to speak 

[Louis D]

4 hours ago, StaceStar said:

I don't think it is pinched...though it certainly looks that way. The article above suggests it's spacers either way...for the price I cannot complain. Especially when it's scoring better than some taks ?

You mention Taks.  I've read that Taks, APs, and other high end APOs have temperature compensating designs to hold the figure despite vast temperature variations.  That, and they usually have collimatable cells.  I'm thinking it probably matters little in our 72EDs to have this level of engineering built in, though.

[StaceStar]

14 minutes ago, Louis D said:

You mention Taks.  I've read that Taks, APs, and other high end APOs have temperature compensating designs to hold the figure despite vast temperature variations.  That, and they usually have collimatable cells.  I'm thinking it probably matters little in our 72EDs to have this level of engineering built in, though.

Exactly ? I honestly can't wait to take my scope out again. For the price our little 72s are fabulous

[StaceStar]

First light

57x60s

AA72edf, AA lightwave 0.8 reducer, AA hypercam 183c pro, Skywatcher Heq5 pro