ASKAR FMA180 40mm aperture apochromatic telescope.

[Adam J]

5 hours ago, 900SL said:

Apologies Adam, here's the stack of 11 images, 30s ISO 400 D5600. Center is pretty good, top and bottom right inward coma, Full size jpg

I would say you need a little more spacing 0.5 - 1mm and that you have a little tilt on the right too side too, tilt is not uncommon on a DSLR though and is usually caused by poor fitting t-adaptors. To get rid of the purple you will need to us a narrow UV IR filter, the key being to cut the blue end at 420nm or more. All in all I would not say this is a disaster. 

Edited September 4, 2021 by Adam J

[PadrePeace]

Agree with AdamJ. This diagram is handy for reference. 

[900SL]

Thanks, gents. This is a great forum. Appreciate the feedback

[PadrePeace]

Clearly if you have tilt included which may improve or degrade corners further you need to play tunes on the two images above

[900SL]

How do you adjust backfocus? Are there shims available for the M42 T mount? I'm a novice  

[Adam J]

43 minutes ago, 900SL said:

How do you adjust backfocus? Are there shims available for the M42 T mount? I'm a novice  

I recommend these:

https://www.firstlightoptics.com/adapters/baader-t2-fine-adjustment-rings-aluminium.html

I strongly advise against the cheaper plastic set. 

They need to be placed after the 0.8x flattener on the camera side. 

Adam

Edited September 4, 2021 by Adam J

[900SL]

On 29/01/2021 at 03:07, Adam J said:

I have been doing some testing with a Astronomik L-3 Luminance filter to see if this mild filter is able to remove the small blue bloat that the FMA 180 has.

I have heard that people have used the baader semi-apo and the finge killer filters with this scope to good effect in reducing the blue fringes on brighter stars.

However, it has been my belief that such filters are unnessasarily harsh for this scope and more than is required to remove the amount of bloat I have been seeing. Hence I have tried a combination of Astronomik L-3 in line with my Baader filters to slightly clip either end of the spectrum.

Here are my results for the blue channel with and without an Astronomik L-3 filter in line with my Baader Blue CCD filter.

First with Baader Blue Filter only:

And then with the Astronomik L-3 and Baader Blue Filters in series. (2 inch L-3 on the nose and 1.25 inch in the filter wheel).

I would call that quite a dramatic effect / improvement!

You lose a little bit of signal in the blue channel and less in the lum channel in comparison to without the L-3 filter, but not that much so I see it as a worth while trade off given Green and Red are vertually uneffected.

Just increase blue channel exposure by about 25% and keep L,G,R channel exposures the same, colour balance remains good.

Target was M44. Clearly a large crop this being presented at greater than 1:1.

I expect that this would produce a good improvement in a OSC camera too.

Star FWHM is now extreamly close across all four LRGB channels and so I am hopeful of some good perfomances to come.

Hope this is usefull to my fellow ASKAR FMA 180 users.

Adam

 

 

 

Hi @Adam J Would this be a filter (the L3 UV/IR M48 thread) that I could use with my DSLR D5600? I assume this screws into the far end of the FMA 180..

[900SL]

On 04/09/2021 at 21:43, Adam J said:

I recommend these:

https://www.firstlightoptics.com/adapters/baader-t2-fine-adjustment-rings-aluminium.html

I strongly advise against the cheaper plastic set. 

They need to be placed after the 0.8x flattener on the camera side. 

Adam

I'm looking at a Baader varilock 29-46  (I'll swap out the 28mm tube) with a thin solid T ring to the Nikon. Should work?

[Adam J]

32 minutes ago, 900SL said:

Hi @Adam J Would this be a filter (the L3 UV/IR M48 thread) that I could use with my DSLR D5600? I assume this screws into the far end of the FMA 180..

Yes will work. 

[Adam J]

30 minutes ago, 900SL said:

I'm looking at a Baader varilock 29-46  (I'll swap out the 28mm tube) with a thin solid T ring to the Nikon. Should work?

Personally I would go with the spacers as I have tried the varilock an it's too fiddly for me. 

[900SL]

Thanks Adam, appreciated

[Adam J]

Just a little test image to get the bugs out of the new ASKAR FMA180 mounting system. 

[900SL]

Nice work Adam.

 

My FLO package should arrive today, L3 filter 2" , shims etc. I made a shim up from a 1mm plastic disk and that significantly improved the tangential coma on testing.

The Askar spacer actually measures around 0.6mm short of spec. I also ordered an M48/0.75 T adaptor and the Askar M48 to T2 spacer. Should be able to get correct backfocus and a rigid mount hopefully 

https://www.firstlightoptics.com/askar-telescopes/askar-m42-to-m48-photo-adapter-for-fma180.html

 

Edited September 25, 2021 by 900SL

[Adam J]

Just a HARGB test Shot of an interesting area 30min RGB per channel in 20second subs and 34min of Ha in 240second subs, this is all about getting things running smooth for when I can eventually do a imaging trip further south with the mobile rig.

The thing I like about the FMA180 as opposed to most lenses at this focal lengh is that it is sufficiently sharp such as the stars do not merge into each other and for the most part are resolved as indevidual points. Although it has to be said that it fairs less well without the L3 filter.

Adam

Edited October 3, 2021 by Adam J

[900SL]

First attempt at Andromeda. Fornax LT /FMA 180 / D5600

1mm shims seem to have improved the backfocus and I used an M48 adaptor

L3 doesn't help much with the blue bloat, it's a hassle to deal with when stretching, I had to use Lightroom eyedropper to remove purple fringing, but its a handy little scope and I'm looking forward to Orion

 

[Adam J]

4 hours ago, 900SL said:

First attempt at Andromeda. Fornax LT /FMA 180 / D5600

1mm shims seem to have improved the backfocus and I used an M48 adaptor

L3 doesn't help much with the blue bloat, it's a hassle to deal with when stretching, I had to use Lightroom eyedropper to remove purple fringing, but its a handy little scope and I'm looking forward to Orion

 

I don't think that blue bloat is the issue rather a more general colour balance issue. Have you attempted to naturalise the background and align the histograms of the RGB channels? 

Apart from that the image detail looks good. Maybe just a tad more spacing as you say. 

Adam

[900SL]

Thanks Adam, yes it's strange how the colour balance appears more pronounced once uploaded, I'll revisit the image and keep a better eye on RGB drift during stretching etc.

I've removed the blue bloat as best as I can using lightrooms purple fringe eyedropper, Ill post a 'before' example to show the issue.

It could also be focus, I notice that it drops off sharply close to exact focus so I'll play around with that a little 

   

 

[Adam J]

4 hours ago, 900SL said:

Thanks Adam, yes it's strange how the colour balance appears more pronounced once uploaded, I'll revisit the image and keep a better eye on RGB drift during stretching etc.

I've removed the blue bloat as best as I can using lightrooms purple fringe eyedropper, Ill post a 'before' example to show the issue.

It could also be focus, I notice that it drops off sharply close to exact focus so I'll play around with that a little 

   

 

Yes you need to be bang on focus, I use an auto focuser with mine so you are pretty much guaranteed accurate focus. But at F4.5 i would think that a focusing mask would be a minimum requirement. If you look at my star field above you will not see much bloat. 

Adam 

[rnobleeddy]

Great thread - I'm looking for something with a focal length in this range and this seems like great value when compared with other scopes and even other Askar products.

 

Wondering if anyone has direct experience of this vs the Samyang 135mm f/2? I know they're slightly different beasts, so whilst I can't imagine the Samyang is better, the advantages of the Samyang for me are that it doubles as a camera lens, and there's a realistic chance of finding a 2nd hand one. I'll dig through the Samyang thread too, but with so many variables in play, it'd be great if anyone has direct experience of both?

[900SL]

I have both. The Sammy is a great lens. The image quality at f2.8 is very good and the exposure fast, so more data. I find it a bit too wide though.

The FMA is much simpler in construction, narrower FOV, lighter, slower, decent image although CA is clearly evident and needs addressing. 

[Adam J]

10 hours ago, rnobleeddy said:

Great thread - I'm looking for something with a focal length in this range and this seems like great value when compared with other scopes and even other Askar products.

 

Wondering if anyone has direct experience of this vs the Samyang 135mm f/2? I know they're slightly different beasts, so whilst I can't imagine the Samyang is better, the advantages of the Samyang for me are that it doubles as a camera lens, and there's a realistic chance of finding a 2nd hand one. I'll dig through the Samyang thread too, but with so many variables in play, it'd be great if anyone has direct experience of both?

I cant speak for the samyang apart from having seen many images from it and noting that for me it just seems to just miss that ~200mm sweet spot for resolution and FOV. If you really want speed go for the samyang, but if you want a detailed image the ASKAR is better. You will want to budget for an L3 filter with it though due to the CA, that aside I am really very happy with mine. 

 

What I would say to ASKAR though is that as most people are laying down another £100 for a filter to sort out the CA, a more premium ED glass might work better and on only a 40mm lens be cheaper than the combined cost with a filter. Hence I would encourage a change of design moving to FPL53, FCD100 or FLP55 even if it adds another £100 to the cost of the scope. 

 

Adam 

Edited November 25, 2021 by Adam J

[rnobleeddy]

13 hours ago, Adam J said:

I cant speak for the samyang apart from having seen many images from it and noting that for me it just seems to just miss that ~200mm sweet spot for resolution and FOV. If you really want speed go for the samyang, but if you want a detailed image the ASKAR is better. You will want to budget for an L3 filter with it though due to the CA, that aside I am really very happy with mine. 

 

What I would say to ASKAR though is that as most people are laying down another £100 for a filter to sort out the CA, a more premium ED glass might work better and on only a 40mm lens be cheaper than the combined cost with a filter. Hence I would encourage a change of design moving to FPL53, FCD100 or FLP55 even if it adds another £100 to the cost of the scope. 

 

Adam 

 

19 hours ago, 900SL said:

I have both. The Sammy is a great lens. The image quality at f2.8 is very good and the exposure fast, so more data. I find it a bit too wide though.

The FMA is much simpler in construction, narrower FOV, lighter, slower, decent image although CA is clearly evident and needs addressing. 

Thanks both. Based on a quick look on eBay, there aren't many used Samyangs, so cost is similar apart from the L3 filter.

I'll do some research at the weekend - I'd guess the longer focal length will be my preference, but there are plenty of good images with the Samyang too.

[Adam J]

On 25/11/2021 at 23:36, rnobleeddy said:

 

Thanks both. Based on a quick look on eBay, there aren't many used Samyangs, so cost is similar apart from the L3 filter.

I'll do some research at the weekend - I'd guess the longer focal length will be my preference, but there are plenty of good images with the Samyang too.

There is not really a right answer, but another benefit of the askar is the ample backfocus. 

[PadrePeace]

My latest effort with the Askar180. Still mounted on the iOptron SGP with a mono Atik 460EX and EFW loaded with NB filters. It’s just over 23hrs of integration. Enjoying this wonderful little scope a lot.

[Adam J]

4 hours ago, PadrePeace said:

My latest effort with the Askar180. Still mounted on the iOptron SGP with a mono Atik 460EX and EFW loaded with NB filters. It’s just over 23hrs of integration. Enjoying this wonderful little scope a lot.

Fantastic presentation of a lesser know region. Wish I could consistently turn out quality images as often as you do. 

Adam