ASKAR FMA180 40mm aperture apochromatic telescope.

[Adam J]

4 hours ago, LaurenceT said:

Sorry for the newbie reply but how would I display a full resolution image, I've done so much processing of it?

I see the image as being 1000 X 1000 ish but it should be 3000x3000pixels from a IMX533. It's hard to assess stars on a resized image. 

[LaurenceT]

1 hour ago, Adam J said:

I see the image as being 1000 X 1000 ish but it should be 3000x3000pixels from a IMX533. It's hard to assess stars on a resized image. 

I understand, thanks, I will have to work out where in the  process it got reduced.

Edited November 26, 2022 by LaurenceT

[LaurenceT]

2 hours ago, Adam J said:

I see the image as being 1000 X 1000 ish but it should be 3000x3000pixels from a IMX533. It's hard to assess stars on a resized image. 

Image after processing and stretching in APP, exported to Dxo Photolab just for conversion to JPG. This is full size:

Edited November 26, 2022 by LaurenceT

[PadrePeace]

Seems that red/blue star fringing  you had in the first image has gone completely here. Have you done anything to achieve that or was it a conversion anomaly?

Edited November 26, 2022 by PadrePeace

[LaurenceT]

3 minutes ago, PadrePeace said:

Seems that red/blue star fringing  you had in the first image has gone completely here. Have you done anything to achieve that or was it a conversion anomaly?

It would seem that the fringing only appeared after my attempt at further processing!

[Adam J]

30 minutes ago, LaurenceT said:

It would seem that the fringing only appeared after my attempt at further processing!

Well one thing we would need to fix next before any further assessment is your back spacing as you don't have enough. Are you measuring 55mm from the back of the corrector or from the back of the extender that is matched to the corrector, it should be the latter. 

All in all a good first image though. 

Adam 

Edited November 26, 2022 by Adam J

[LaurenceT]

48 minutes ago, Adam J said:

Well one thing we would need to fix next before any further assessment is your back spacing as you don't have enough. Are you measuring 55mm from the back of the corrector or from the back of the extender that is matched to the corrector, it should be the latter. 

All in all a good first image though. 

Adam 

Thanks for the reply Adam, much appreciated. This is the setup I'm using:

[PadrePeace]

That’s bang on 55mm. But there is something going on in the corners. Is there UV/IR cut filter in your 11mm adapter? For any extra glass in the optical path you need to add 1/3 of its thickness to your BF.

Edited November 26, 2022 by PadrePeace

[LaurenceT]

2 minutes ago, PadrePeace said:

That’s bang on 55mm.

That's what I thought. I don't know if it's relevant to back focus but I got a perfect pattern on a bahtinov mask on Vega.

Perhaps there's something wrong with the scope?

[PadrePeace]

Back focus is different to the focus you achieve using a bahtinov. What AdamJ is seeing is the comet shaped stars flying outwards in each corner.

Edited November 26, 2022 by PadrePeace

[LaurenceT]

14 minutes ago, PadrePeace said:

Back focus is different to the focus you achieve using a bahtinov. What AdamJ is seeing is the comet shaped stars flying outwards in each corner.

So is there a mismatch between the scope and the flattener/reducer?

[PadrePeace]

This article explains Coma which is what this looks like. 
https://www.google.co.uk/amp/s/photographylife.com/what-is-coma/amp

 

Is your scope new?

[LaurenceT]

13 minutes ago, PadrePeace said:

This article explains Coma which is what this looks like. 
https://www.google.co.uk/amp/s/photographylife.com/what-is-coma/amp

 

Is your scope new?

I bought it used .

Edit: I've just checked the scope and the reducer wasn't absolutely screwed into the scope, there could have been a centimetre or slightly more of rotation 🙄

Edited November 26, 2022 by LaurenceT

[Adam J]

44 minutes ago, LaurenceT said:

I bought it used .

Edit: I've just checked the scope and the reducer wasn't absolutely screwed into the scope, there could have been a centimetre or slightly more of rotation 🙄

Rotation would not matter but if it's not fully tight that could give tilt. 

[Adam J]

3 minutes ago, Adam J said:

Rotation would not matter but if it's not fully tight that could give tilt. 

Try it now you are fully tight and submit the result here. If you still have that in the corner then try adding 1mm of backspacing. 

[LaurenceT]

10 minutes ago, Adam J said:

Try it now you are fully tight and submit the result here. If you still have that in the corner then try adding 1mm of backspacing. 

Will do, thanks Adam and @PadrePeace for your help.

[Adam J]

Looks like this is the end of the road for the original FMA180 as the FMA180 Pro has now been released with some upgraded features and potentially upgraded optics too although thats not 100% confirmed in my view. 

https://www.firstlightoptics.com/askar-telescopes/askar-fma180-f45-ed-apo-v2-astrograph-lens-reducer.html

However, its lost the modular construction which was a attraction.

Would be nice to try one out but am not sure that I can justify an upgrade. Wonder if they improved correction in the blue. 

 

Adam

[900SL]

It states that the optical train is the same. I see they are still posting that phoney correction ray trace. Goiod old honest Askar

 

[Adam J]

39 minutes ago, 900SL said:

It states that the optical train is the same. I see they are still posting that phoney correction ray trace. Goiod old honest Askar

 

True but the spot diagram has changed. Make of that what you will. 

Although still only goes down to 430 nm

OLD

NEW

Crossings are different too. 

Adam 

Edited February 15, 2023 by Adam J

[Space Oddities]

I had another tinkering session with the FMA180. I found a small dovetail bar lying around, and I thought it would be a perfect match for the scope's rings. Since they have 2 screws each, it's not easy to find a suitable Vixen dovetail bar... So I used the existing Arca-Swiss one to drill holes, and it works great!

Since I was drilling holes, I thought I could add a couple on top, to mount the autoguider. I drilled a 2.5mm hole in each ring, then used an M3 tap to add some threads. I reused a small Arca Swiss plate that came with ZWO's camera ring (which never fit my camera for some reason...), because it has holes that match perfectly Sky-Watcher's finder base (which I took off my Maksutov...).

With the ASI585MC, guide scope and filter slider, it now weighs 1.2 Kg ! Perfect for travelling light  

 

[Space Oddities]

I think I went to far... 😅

[Adam J]

A link to my latest image for my fellow fma180 fans! 

 

 

Adam J

Edited February 28, 2023 by Adam J

[LaurenceT]

I imaged M42 last night for the first time (imaging novice).

41 lights only each 120secs before I began to image trees! ASI533mcpro, Asiair Pro, no guiding.

so after some quick processing (APP and Photolab DXO3) here it is, there is blue fringing around stars so this needs to be addressed, the moon was very bright and quite close. There is another image with the sky not so darkened which shows an odd anomaly but I'll show that later.