686 replies to this topic

[ZX12]

Keep in mind 185mm Askar need lot to cooldown.

For me its approx 4-5 hours minimum, and then it provide maximum of his performance.

If cooled less than 4 hours, image is still not as sharp.

Denis,

 

 Are you bringing your 185 from inside a warmer environment and needing 4-5 hours cooldown?

 

My 185 sits in the observatory with ambient temps, so once I open the roof and take off the lens cover it takes 30-45 minutes at most to reach optimal image quallity.

 

During the coldest part of this winter I spent quite a bit of time observing and imaging with the 185, and was impressed at how well it performed in temperatures well below freezing.

I use a dew heater to prevent frost on some nights, keeping it at a low setting.

 

Mike  

[denis0007dl]

Yep, from inside to outside.

Holding it outside is best for temperature difference.

You sayed emperatures well below freezing, what temperature in Celsius it was approx? ...and wondering if there are any signs of pinched optics then?

I dont have such low temp here, but was wondering about pinched optics in Askar 185, how much it can hold it dont happen.

[ZX12]

Denis,

 

Temperatures here are not extreme cold due to the ocean being nearby, but typical nights in January without the wind chill can range from -5 to -12C.

 

The wind is fairly consistent here at night so wind chill can go down to -20C or lower. 

 

Mike

[denis0007dl]

Auuuu, THATS very cold

[denis0007dl]

Anyhow, Mike, did you used Askar 185 at temperature -5 Celsius and lower? (if you know lowest tem?)

...and if you do, did you notice pinched optics?

[ZX12]

Denis,

 

 I was out several nights when it was around -12C and I did not see any sign of pinched optics with the 185. 

 

My APM150SD BT shows slight pinching from the tight O ring seals that keep moisture out. They fit slightly tighter than my 150ED, so that anytime it gets near freezing I start to see subtle spiking around stars.

I solved the issue by using dew heaters around both objective housings when its cold. 

 

Mike

[denis0007dl]

Awsome, thanx for infos Mike!

Which eyepieces you using most in your binos?

[ZX12]

I use the following pairs with the 185;

 

24 Pan's

18 Tak AO

12.5 Tak AO

9 ES62

5.5 ES62

 

I don't care for the tight eye relief and narrow field of the shorter focal length Tak's.

 

Mike

[peleuba]

Paul, interesting suggestion about the Askar 1x corrector.  I did perform an early test (not DPAC) using my ZWO ASI2600MM camera (1x1 bin, 3.76 u pixels, RGB subs and then combined into a single RGB image) with and without the corrector and stars appear to be both a bit sharper and less chromatic aberration when using the 1x corrector - imaging cameras .  A DPAC test with and without corrector would provide some valuable insight.

 

Anecdotally, and not directly related to the Askar APO's specifically, my Asian contacts told me a couple of years ago (just after testing the StellarVue SVX180 Gen 1) that a sub-aperture reducer/flattener existed which pulled the overall correction to a more neutral wavelength (green) then what I found in the SVX180 Gen1.  So, its certainly possible and doing so would "tighten" up the stars, especially for visual.

 

Some additional minutia only tangentially related...   The Gen 2 of the SVX180 is a totally different design that uses two ED elements and is similar (same?) as some other 180/181 offerings on the market available lots of places.  I've been told by a friend in the APO business that the SVX180 Gen2 has better correction then another US made 180mm scope using Fluorite. 

Edited by peleuba, 22 March 2025 - 04:50 PM.

[Scott in NC]

 …then another US made 180mm scope using Fluorite. 

So I guess that would be the TEC 180FL? I can’t think of anything else that that could be.

[peleuba]

So I guess that would be the TEC 180FL? I can’t think of anything else that that could be.

 

The SVX180 Gen2 is a very nice lens with dual ED elements.  Its a very good design.

[VNA]

Hello, can't wait for nicer weather, it is getting a little much: clouds and more clouds  and it is no fog-anyway is my CGX mount to carry The Askar 185? It is not a light tube, the rings that open makes it relatively easy.

I am not a good judge of color firings, but from last session back. . .way back in October I was blown away.

Thank you for this thread as it is reassuring.  ;- )