Askar 71F Flat Field Astrograph Review

[Roy Foreman]

Askar 71F Review

This is now the smallest telescope I own, beating my Skywatcher 72ED by just 1mm !  Like my other Askar telescopes the 71F is a high quality instrument, the deep blue accents making a welcome change to the red, gold, and green offerings that seem to have become so popular.  The fit and finish is first class, and once again Askar appear to have put a lot of thought into the design of both the telescope and the accessories that come with it.

I purchased the 71F to use as a high quality spotting scope as well as for astronomical use, and indeed Askar are promoting the terrestrial capabilities of this scope both in their promotional material, and by including an erect image diagonal and a couple of eyepieces in the package. As far as I know this is the only Askar scope that has this.

This is a handsome looking scope and includes such luxuries as a retracting dew shield, twin finder mounting shoes, a carry handle that can also hold additional accessories, a sensible length 230mm vixen style dovetail bar, CNC machined tube rings, and a rotating duel speed 2.4" focuser.

The included eyepieces are 8mm and 20mm plossls which seem to be of good quality if a little restrictive in their apparent field of view.  The erecting diagonal is a bit of a let down in that it is made of plastic - very un-askar-like - but it seems to do the job adequately.

A camera adaptor is also provided. It screws into the focuser in place of the eyepiece holder and terminates in a 48mm thread onto which you can attach a camera T-ring, or the barrel of a dedicated astro camera.  The 48mm threaded ring unscrews to reveal a larger 54mm thread, and the facility for mounting a single filter if required.  This arrangement is pretty standard for Askar scopes. Back spacing is not an issue, if you are in focus you are good to go.

Now to the optics, the heart of any telescope.  This is a four element flat field instrument that follows the same layout as in the more illustrious PHQ series, that is a triplet up front with a single field flattening element further back, the significant difference being that in the 71F there is only one ED element (of unspecified type) rather than two.  Having four lenses certainly adds the the weight of the system, and the OTA with its accessories weighs 3kg as compared to 2kg for Skywatcher's 72ED.

So how does the 71F perform? In a word, excellent.  In several words, very impressive indeed.  Using a 2" 40mm focal length wide angle eyepiece, details were sharp pretty much to the extremities, any minor aberrations probably due to my 25 year old eyepiece rather than the telescope.  Attaching a full frame DSLR and taking a series of short exposures in the region around Polaris showed nice round stars right across the frame and into the extreme corners.  And no nasty purple or red halos around bright stars, at least in the test images that I took.  This is indeed a flat field telescope doing exactly what it claims to do.  Nice.

Askar didn't quite get it all right though. The small screw that locks the focuser in position is not attached when the scope arrives, but is in a little bag packed away with the instructions and quality control certificate. When I tried to attach it to the underside of the focuser I found that I couldn't because the dovetail plate was in the way. Sliding the tube backwards in the rings cured this, but resulted in the dew shield not being able to retract fully, and with a heavy DSLR attached the balance point was off the rear end of the dovetail plate.  Raising blocks under the tube rings would cure this, but to be honest the focuser works so well without the little locking bolt in place that I just removed it.

Next point, the carry handle cannot be used as a carry handle. It it too short, at least for my stubby male hands, and there is not enough room between it and the tube to fit your fingers underneath it. More raising blocks required, perhaps.  To be honest though, the 71F is so good in every other way that I can forgive it these minor misdemeanours. It is a lovely little scope, well equipped, and very good value for money. An absolute winner in my book.

You might well compare the 71F to Skywatcher's ED72 which, at around £300, is half the price.  But factor in the cost of a flattener, two eyepieces, diagonal, carry handle, longer dovetail bar etc. and the cost difference diminishes.

Bottom line, the 71F comes highly recommended.

[Elp]

Thanks for the detailed input. It's an interesting alternative to, with more reach than the WO Redcat.

[lpalbou]

Hi Roy, I am very intrigued by this little scope. When you look at the spot diagram, it seems to perform even better than the 65PHQ.. and this is possible since it's a slower focal ratio. Could you share some test images in full frame ?

Once thing that I don't quite get however is.. what will be the interest of the 65PHQ ? The 71F also has the flattener.. there may be one ED glass difference.. but if the first ED glass is good, differences would be minimal, while the price difference isn't

[Elp]

PHQ 5 element 2 of which are ED Vs FF 4 element 1 ED. Askar aren't exactly forthcoming in the glass or coatings they use though.

Edited May 6 by Elp

[Roy Foreman]

15 hours ago, lpalbou said:

Hi Roy, I am very intrigued by this little scope. When you look at the spot diagram, it seems to perform even better than the 65PHQ.. and this is possible since it's a slower focal ratio. Could you share some test images in full frame ?

Once thing that I don't quite get however is.. what will be the interest of the 65PHQ ? The 71F also has the flattener.. there may be one ED glass difference.. but if the first ED glass is good, differences would be minimal, while the price difference isn't

I will try and post a test image later on.

Yes, I wondered about the similarities / differences between 71F and 65PHQ. The latter has an extra ED element and is faster, and has a dedicated reducer available which is supposed to enable it to still cover full frame. This is probably where the price difference lies.  For me the 71F seems much better value, and covers full frame, so why pay extra for the 65 unless you want to use it with a reducer ?

[Roy Foreman]

16 hours ago, lpalbou said:

Hi Roy, I am very intrigued by this little scope. When you look at the spot diagram, it seems to perform even better than the 65PHQ.. and this is possible since it's a slower focal ratio. Could you share some test images in full frame ?

Once thing that I don't quite get however is.. what will be the interest of the 65PHQ ? The 71F also has the flattener.. there may be one ED glass difference.. but if the first ED glass is good, differences would be minimal, while the price difference isn't

I've attached a test image taken with the 71F and a Nikon D810a full frame astro DSLR, on a Star Adventurer GTi.  Three x 60sec at ISO 6400, stacked manually in photoshop.  Bear in mind that this is a test image, only three frames, no autoguiding, and rough polar alignment.  Stars ae good and on the original there are even hints of IFN dust.  Not sure why there is an artifact on the bright star at the bottom - think it may be because only half of it was in the frame !  I have included a severe crop of the top left hand corner so you can judge star quality.  I think it is very good and has real potential.  Watch this space !

[lpalbou]

Thanks Roy, most aberrations seems nicely controlled. I am just a bit surprised by the relative star bloating, but this wouldn't be a first on Askar telescopes and it's usually well managed with a luminance filter (eg astronomic L3).

Any other tests with longer exposure in full frame ?

[TiffsAndAstro]

On 07/05/2024 at 14:21, Roy Foreman said:

I've attached a test image taken with the 71F and a Nikon D810a full frame astro DSLR, on a Star Adventurer GTi.  Three x 60sec at ISO 6400, stacked manually in photoshop.  Bear in mind that this is a test image, only three frames, no autoguiding, and rough polar alignment.  Stars ae good and on the original there are even hints of IFN dust.  Not sure why there is an artifact on the bright star at the bottom - think it may be because only half of it was in the frame !  I have included a severe crop of the top left hand corner so you can judge star quality.  I think it is very good and has real potential.  Watch this space !

Any tips on your phd2 settings?

[Roy Foreman]

8 hours ago, lpalbou said:

Thanks Roy, most aberrations seems nicely controlled. I am just a bit surprised by the relative star bloating, but this wouldn't be a first on Askar telescopes and it's usually well managed with a luminance filter (eg astronomic L3).

Any other tests with longer exposure in full frame ?

Any star bloating is probably due to the rubbish seeing that seems to prevail these days. Also I was using a DSLR which seems to be more prone to picking up red and violet halos than a regular astro cam.  A UV/IR cut filter would have helped, and one of these should always be used with refractive optics.

I don't have any additional images as there have been no clear skies since this test. I deliberately used short exposures to keep the stars small so that I could assess their shapes more easily.

[Roy Foreman]

7 hours ago, TiffsAndAstro said:

Any tips on your phd2 settings?

These were unguided exposures, but when I do use phd2 I just stick to the default settings and this works well. Sometimes I increase the star density tolerance as this can help in hazy skies which seem to prevail these days.

[TiffsAndAstro]

3 hours ago, Roy Foreman said:

These were unguided exposures, but when I do use phd2 I just stick to the default settings and this works well. Sometimes I increase the star density tolerance as this can help in hazy skies which seem to prevail these days.

Ty gonna reset phd2 start fresh