Review of Astro-Physics 110 GTX scope and reducer

[gregbradley]

I have had my AP 110GTX now for a few months and done at least one image with it.

I just had 3 beautifully clear and dark nights at my dark site at a respectable 720 metres altitude. A site that has proven itself to have good seeing most of the time and tends to shed clouds around it so it is biased towards clear nights.

Freezing cold though.

I have data for 5 new images with it and will be posting these over the coming days.

In short these are the best optics I have ever used. Stars have great profile and look and appear 3Dish as spheres rather that flat points of light.

The images are very sharp. I am using it at F5 with the Lanthanum triplet compressor/corrector.

I also have an AP130 GT with the 3.5 inch focuser and I have the new F5 triplet Lanthanum corrector/compressor. This extends the range of correction of the 130 and the 110.

I really like the AP doveloc system which means I can loosen one or more of 3 large screws and the camera imaging train can be turned around easily to enable ideal framing. Takes literally a couple of seconds.

It's a beefy little scope and punches above its weight in terms of brightness of images light throughput. Very little vignetting.

I have used several scopes around the 110mm aperture - 2 FSQ's (one a fluorite FSQ106N and an EDX3), TEC 110 fluorite, Tak FS102, CFF105 F6 with 99.3 strehl (still have it).

Mechanically the AP is superior to all those scopes. The focuser is super strong and the drawtube is made of stainless steel not aluminium.

The dewshield has a tightening screw so it does not pull back from gravity.
The lens cap fits really well. It comes with a nice case but probably won't allow an electronic focuser to fit in the case.

Very tight FWHM values. When in focus it was achieving around 1.2 at the lowest I saw to about 1.6 as average and a few at 2.2 arc seconds. But more were under 1.6-1.7. Not that I monitor these numbers too much but I would say that is probably the lowest FWHM numbers I have seen from this site.

Easy to focus and it becomes quite clear when it is in focus. I am going to fit a ZWO electronic focuser. I have a couple of Feathertouch electronic focusers but they require another box and cable and I want to simplify my cabling.

How does it compare to its obvious competitor the FSQ106EDX?
Well mechanically the AP is better. Whilst I have not had an FSQ with a poor focuser there are plenty of posts of others who have. Similarly the rotating mechanism is better on the AP. Some replace the whole focuser unit with a large adapter to gain rigidity. No need with the AP.

The FSQ advantage is the Petsval lens means no need for backfocus calculations. Also it is natively flat field and does not need a compressor which is an extra cost. One disadvantage I noticed with my FSQ106EDX3 was the new mustard coloured coatings seemed to skew colours. Another person tested his for me and found the coatings inside the tube were biased to green. With digital processing that bias is minimised but I could tell FSQ106EDX images by this biased colour. Early days but I have not noticed colour bias with the 110GTX. Downloads from the AP have a vibrance about them which I have not seen with other scopes.

I would say just subjectively that the stars in both are very good but the latest Sony sensors with 3.76 micron pixels or smaller are handled without optical breakdown with the AP. The FSQ per Cloudy Nights forums starts to show chromatic aberration near the edges of the images with the FSQ.
So I would say the AP is better optically providing you have the correct spacing from the reducer. I don't have the flattener yet but have one for the 130 and want to see if that works on it.

As far as the appearance of the images are concerned I would say image quality is slightly superior to the FSQ but it may require pixel peeping to notice it. The images I have seen on the net showing FSQ chromatic aberration in the outer reaches of the image are not really that bad but the FSQ may be due a refresh of design to take it next level. I enjoyed using my FSQ EDX3 when I had it But that was with a 9 micron pixelled CCD.

If Tak ever made a TOA 110 it would be quite a scope but I doubt they would do that and risk their best seller the FSQEDX4.

My CFF 105 F6 scope does not offer a compressor/corrector but I do have a flattener for my Proline 16803 CCD. I'll be imaging with that in the coming months and can compare it's performance to the AP110GTX. Th A really nice scope. The CFF has a 3.3 inch FeatherTouch focuser, 99.3 strehl and a pretty pearl finish. They no longer make this size scope.

Of the scopes I mentioned I would rank them:

FS102 worst.
FSQ106N fluorite - a lovely scope but those dark crosses in bright stars is a major turn off.
TEC110 fluorite - better colour than an FSQ106EDX but the focuser was the worst I have ever seen but handleable with a workaround. Plus TEC rings can almost come with a guarantee they will scratch the tube! Poorly desgned. TEC scopes are designed to be optimised for green (visual use) and red correction tends to be poor. I had a TEC180 fluorite for several years and honestly only a few images using it made me happy. Good scope overall but TEC ain't AP.

FSQ106EDX3 overall a very nice scope and 106mm/F5 is a good sweet spot for 106mm - 110mm optics. 2nd best scope in this range.

The AP110GTX is the best.

So in conclusion, I would subjectively say given the various aspects of a scope on top of it's imaging strength, the AP110GTX is at the top of the pile
and well worth the cost. Roland Christen's genius and engineering and optical excellence is pushing the triplet APO into new territory.

If you want the very best then this is it. 110/F5 is a good imaging formula.

I'll be trying it out visually next trip. The 130GT is awesome with an APM 12.5mm eyepiece. Stars are colourful pinpoints.

Greg.

[strongmanmike (Michael)]

A great Bradley assessment, a few good scopes in that bunch .... made me, once again, think about finally unearthing my FSQEDX4 from Eagleview.....must do it soon...

Mike

[anj026]

Awesome review Greg, thank you for taking the time to share your thoughts and experience. I look forward to your visual assessment.

[NCRAW]

Whats the FS102 like for visual compared to the newer FC's?

[wavelandscott (Scott)]

Congratulations and I am glad you are happy and seem to truly appreciate the “AP Magic”…hope you get great use from it

[Peter Ward]

I had no doubts that the AP110 would be sublime.

Looking forward to seeing some IMX455 based imagery with it....

Problem I face is whether my better half would consider placing me in the house of the dog due my "needing" 5 AP scopes if I pulled the trigger on yet another one

[gregbradley]

Originally Posted by NCRAW

Whats the FS102 like for visual compared to the newer FC's?

Originally Posted by Peter Ward

I had no doubts that the AP110 would be sublime.

Looking forward to seeing some IMX455 based imagery with it....

Problem I face is whether my better half would consider placing me in the house of the dog due my "needing" 5 AP scopes if I pulled the trigger on yet another one

Hehe, yes it wasn't cheap. The Aussie dollar is very weak and then there is GST applied at entry.

Greg.

[Peter Ward]

Originally Posted by gregbradley

Hehe, yes it wasn't cheap. The Aussie dollar is very weak and then there is GST applied at entry.

Greg.

Not for the casual user for sure. With rings, reducer and flattener I estimate
the landed $A price to be around $17k. Ouch.

Then again, anyone looked at circa 600mm Canon L-series glass of late? pushing $A20k

[Leo.G (Leo)]

Then again, anyone looked at circa 600mm Canon L-series glass of late? pushing $A20k

A friend with a 5D MK4 has either a 600mm f4 or 800mm f5.6 lens which cost him $20,000 some years back new. He was going to try and rent it out I don't know how he's gone with it.
He loaned me his Mk4 for a couple of months (lovely camera had I not had so many old Nikon lenses (which worked fine with an adapter but I foolishly stuck with Nikon)) and he was upset when I rejected his offer to take the huge thing home. It should have come with it's own set of wheels. I would have loved to play with the big lens and will get the chance one day telling him I'd rather use it in his presence.
Something I could easily bump in the dark (he wanted me to take some astro shots) and damage, not unless I can either afford to replace it or insure it.
It is an amazing lens however!
Were he to buy an AP I may have a change of heart in what I'd be prepared to borrow.