User Experiences ASKAR 120 APO Askar 120APO · Niels_L · ... · 59 · 2517 · 12

Alexn 12.25
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Adam Cox:
IMO the SW200P provides better resolution and contrast, which it should at F5 Vs F7 and 1000mm Vs 840mm focal length. However for the ease of use and consistent performance, I'd choose the Askar 120.


Thanks Adam!  Those photos are very helpful!
Indeed there is the difference in resolution but I do agree that the ease of use will play a big role for me, as still a newbie in the field.  I probably won't get the same quality out of a reflector (I already had trouble getting my 8SE SCT perfectly collimated...) as a refractor.

Only just read this post, but I think its certainly worth me mentioning that if you're a newbie, the Askar 120 APO is not really a 'newbie friendly' scope...

Whilst yes, a refractor has less points of failure than a 6 or 8 inch newtonian.. I really can't stress enough the number of complications that arise from having a 1.2m long moment arm... The 120APO is NOT a small scope. It is very long, and although balancing is not critical on harmonic mounts, trust me you will want to get this thing close to perfectly balanced, even on a harmonic mount. I balanced mine by putting a pencil on my kitchen bench top, and balancing the OTA across the pencil, then making a mark on the dovetail in the location where the OTA would balance on the pencil.... Then you need to consider, not only the moment arm and the amount of torque that is applying to the mount, but the length of the OTA and whether or not it's going to clear your tripod legs.

I'm certainly not trying to discourage anyone from enjoying the hobby in any way they would like to, but a 5" or larger APO will bring heartache to an unsuspecting user who's making the step up from a 60mm refractor or a camera lens, thinking 'well its just a bigger lens, how much harder can it be?' - because the answer to that is 'Much'. Askar_120APO_SetUp.jpg
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Googong_Observatory 1.20
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Alex Nicholas:
Adam Cox:
IMO the SW200P provides better resolution and contrast, which it should at F5 Vs F7 and 1000mm Vs 840mm focal length. However for the ease of use and consistent performance, I'd choose the Askar 120.


Thanks Adam!  Those photos are very helpful!
Indeed there is the difference in resolution but I do agree that the ease of use will play a big role for me, as still a newbie in the field.  I probably won't get the same quality out of a reflector (I already had trouble getting my 8SE SCT perfectly collimated...) as a refractor.

Only just read this post, but I think its certainly worth me mentioning that if you're a newbie, the Askar 120 APO is not really a 'newbie friendly' scope...

Whilst yes, a refractor has less points of failure than a 6 or 8 inch newtonian.. I really can't stress enough the number of complications that arise from having a 1.2m long moment arm... The 120APO is NOT a small scope. It is very long, and although balancing is not critical on harmonic mounts, trust me you will want to get this thing close to perfectly balanced, even on a harmonic mount. I balanced mine by putting a pencil on my kitchen bench top, and balancing the OTA across the pencil, then making a mark on the dovetail in the location where the OTA would balance on the pencil.... Then you need to consider, not only the moment arm and the amount of torque that is applying to the mount, but the length of the OTA and whether or not it's going to clear your tripod legs.

I'm certainly not trying to discourage anyone from enjoying the hobby in any way they would like to, but a 5" or larger APO will bring heartache to an unsuspecting user who's making the step up from a 60mm refractor or a camera lens, thinking 'well its just a bigger lens, how much harder can it be?' - because the answer to that is 'Much'. Askar_120APO_SetUp.jpg

Hi Alex, 

Good point on balancing and the inertial moment arm. The early challenges with learning how to use my WO Z81 refractor are all still there.... but now amplified on the Askar 120 APO. 

I went to the effort of hypertuning my EQ6-R Pro when I was trying to make my experience with my 8" Newt more user friendly. This made balancing a more accurate and quicker process as friction was significantly reduced in both RA and DEC axis. The other lessons learnt from that experience (e.g. careful balancing in 3-axis and positioning counterweights as close to the center of the mount as possible) definitely has benefited me with my Askar 120 APO experience.


Cheers,
Adam
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StewartWilliam 5.21
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John Stone:
Here's are some stacked masters from my Esprit 100 with both a mono APS-C camera and an APS-C OSC camera,   I don't believe my star shapes are particularly bad. 

https://drive.google.com/drive/folders/1v_9pME4EA_evx6oFNm82iwqNmpddU3lz?usp=drive_link

Pixinsight gives me an FWHM of ~2.0 and eccentricity of ~0.39 for the OSC data and FWHM of ~1.7 and eccentricity of ~0.4 for Mono for my images.

Pixinsight measured the above Askar 120 APO image as FWHM of 4.138 and eccentricity of 0.5004.

Are you seeing something different in your Esprit 100ED?

Yes I am, here is a small stack, it’s the best I can get from my esprit, if you zoom into the corners mainly the top right top left and bottom right you will se a bit of elongation, this is totally uncropped and straight from the camera, the elongation is not due to flattener distance as the elongation is in different directions from one side to the other, also tilt has been removed. The best HFR I can get in NINA with my 2600 cameras, is 2.6 🤷🏼‍♂️

https://drive.google.com/file/d/1LRJt4ANeT0NWHBsqQC3LRtcYDwx8ZK6d/view?usp=drivesdk
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kevinkiller 2.11
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Adam Cox:
The other lessons learnt from that experience (e.g. careful balancing in 3-axis


Adam,

I'd really like to learn more about 3-axis balancing.   How can you do that when there's only 2 axes on the mount and only 1 place to put counterweights and one place to slide the scope back and forth on the dovetail.

Very interested in learning more....

Thanks.
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kevinkiller 2.11
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AstroShed:
Yes I am, here is a small stack, it’s the best I can get from my esprit, if you zoom into the corners mainly the top right top left and bottom right you will se a bit of elongation, this is totally uncropped and straight from the camera, the elongation is not due to flattener distance as the elongation is in different directions from one side to the other, also tilt has been removed. The best HFR I can get in NINA with my 2600 cameras, is 2.6 🤷🏼‍♂️

https://drive.google.com/file/d/1LRJt4ANeT0NWHBsqQC3LRtcYDwx8ZK6d/view?usp=drivesdk


I think I may know what's going on here.   I had a similar problem when I got my Esprit and for me it turned out that the drawtube had tip/tilt/slop in it because the drawtube tensioners were not tight enough to support it. 

Maybe this is your problem too.

 I tightened them up and carefully created the best balance of tension between the 4 screws by feel while racking the focuser drawtube in and all out the way to try to square it up.   It's a delicate balance between too much tension/binding and too little/flop.

What ever you do NOT loosen these too much or the teflon pad they press on will fall out and you be up a creek without a paddle.

After I did this then I adjusted camera tilt using Nina Hocus Focus and now I'm getting the results you see in my images.
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StewartWilliam 5.21
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John Stone:
Adam Cox:
The other lessons learnt from that experience (e.g. careful balancing in 3-axis


Adam,

I'd really like to learn more about 3-axis balancing.   How can you do that when there's only 2 axes on the mount and only 1 place to put counterweights and one place to slide the scope back and forth on the dovetail.

Very interested in learning more....

Thanks.

You may be interested in my video here then with 4 axis balancing, but for a CEM mount…

https://youtu.be/Gatkmt7BFew?si=XXCATO1tRSQalMoQ
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StewartWilliam 5.21
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John Stone:
AstroShed:
Yes I am, here is a small stack, it’s the best I can get from my esprit, if you zoom into the corners mainly the top right top left and bottom right you will se a bit of elongation, this is totally uncropped and straight from the camera, the elongation is not due to flattener distance as the elongation is in different directions from one side to the other, also tilt has been removed. The best HFR I can get in NINA with my 2600 cameras, is 2.6 🤷🏼‍♂️

https://drive.google.com/file/d/1LRJt4ANeT0NWHBsqQC3LRtcYDwx8ZK6d/view?usp=drivesdk


I think I may know what's going on here.   I had a similar problem when I got my Esprit and for me it turned out that the drawtube had tip/tilt/slop in it because the drawtube tensioners were not tight enough to support it. 

Maybe this is your problem too.

 I tightened them up and carefully created the best balance of tension between the 4 screws by feel while racking the focuser drawtube in and all out the way to try to square it up.   It's a delicate balance between too much tension/binding and too little/flop.

What ever you do NOT loosen these too much or the teflon pad they press on will fall out and you be up a creek without a paddle.

After I did this then I adjusted camera tilt using Nina Hocus Focus and now I'm getting the results you see in my images.

Hmmm, I checked the focuser when it arrived, and was pretty solid, so left it alone, also if the focuser was sagging at all, surely the stars would be bad across the whole image, and not just the corners, as it would be the same as having tilt in the imaging train…
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Googong_Observatory 1.20
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John Stone:
Adam Cox:
The other lessons learnt from that experience (e.g. careful balancing in 3-axis


Adam,

I'd really like to learn more about 3-axis balancing.   How can you do that when there's only 2 axes on the mount and only 1 place to put counterweights and one place to slide the scope back and forth on the dovetail.

Very interested in learning more....

Thanks.

Hi John, I should of clarified when I refer to the third axis I mean the offset RA axis (Y2) of the telescope tube in its rings. I found it necessary to rotate the tube whenever my EFW was not aligned straight up or down in the 12 or 6 o’clock position e.g. when it is rotated 90 degrees to the 3 or 9 o’clock position in relation to the scope. Without some fine rotation in B2I would always have the scope pull left or right.


Cheers,
Adamimage.png
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Googong_Observatory 1.20
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AstroShed:
John Stone:
Adam Cox:
The other lessons learnt from that experience (e.g. careful balancing in 3-axis


Adam,

I'd really like to learn more about 3-axis balancing.   How can you do that when there's only 2 axes on the mount and only 1 place to put counterweights and one place to slide the scope back and forth on the dovetail.

Very interested in learning more....

Thanks.

You may be interested in my video here then with 4 axis balancing, but for a CEM mount…

https://youtu.be/Gatkmt7BFew?si=XXCATO1tRSQalMoQ

Thanks Stewart,

I must admit I was guilty of only checking a couple of positions when I first started out.... now I know better

BTW now subscribed and well done on the 1k subscribers.


Cheers,
Adam
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StewartWilliam 5.21
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Adam Cox:
AstroShed:
John Stone:
Adam Cox:
The other lessons learnt from that experience (e.g. careful balancing in 3-axis


Adam,

I'd really like to learn more about 3-axis balancing.   How can you do that when there's only 2 axes on the mount and only 1 place to put counterweights and one place to slide the scope back and forth on the dovetail.

Very interested in learning more....

Thanks.

You may be interested in my video here then with 4 axis balancing, but for a CEM mount…

https://youtu.be/Gatkmt7BFew?si=XXCATO1tRSQalMoQ

Thanks Stewart,

I must admit I was guilty of only checking a couple of positions when I first started out.... now I know better

BTW now subscribed and well done on the 1k subscribers.


Cheers,
Adam

Thanks very much, glad you enjoyed and thanks for subscribing…appreciated..👍🏻
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