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Ovni-m and askar fm180 combo

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#1 Gavster

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Posted 18 November 2020 - 08:35 PM

I received an ovni-m a week ago and have been having quite a bit of fun testing it out, despite being limited to very light polluted london skies. It’s the first time I’ve had an option to do prime nv (my existing kit is a pvs-14) so it’s been a bit of a learning curve.

I enjoy taking quick phone pics of my observations but with prime it’s harder than afocal to get my ems wide field shots. As a result I bought and received today a new Askar fm180 which should give me about a 6 degree fov for some nice big nebulae viewing.

More experiments with prime mode night vision with my new ovni-m this evening. This time I used a ridiculously small scope to try to get a larger fov than prime normally gives.
First impressions of the Askar are very positive. Given the in focus that the ovni-m needs in prime mode, I wasn’t expecting to be able to use the askar with its included reducer. However after a bit of experimenting I managed to get the light path down to a very short distance, by directly screwing in my Baader t2 prism. I like the fact that I can use a diagonal with this setup unlike camera lens.
I was very intrigued by what the quality of the stars across the large 6 degree field would be like and having taken a few phone pics this evening, this little askar scope is a quality piece of kit imo. A nice touch is that my 2 inch filters can be screwed directly into the front of the askar.
Here’s some shots of the setup itself and also some phone pics of Orion and horsehead, rosette, North America (with the added bonus of neighbours roof and television aerial), heart and soul and California.

The phone pics are washed out and lack detail due to being in London. Hopefully next month I can take some shots in much darker skies.

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Edited by Gavster, 18 November 2020 - 09:05 PM.

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#2 Gavster

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Posted 18 November 2020 - 08:36 PM

More phone pics

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Edited by Gavster, 18 November 2020 - 09:06 PM.

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#3 a__l

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Posted 18 November 2020 - 10:22 PM

I bought a used Nikkor 135 mm f/2.8 a few months ago and an F adapter.  It has a 52mm filter diameter and a 2" filter good install. I'm happy with it. Good field to edge. Good stars. A few days ago I bought a Nikkor 200mm f/4. It has the same filter thread. It will be 8x on my NV. Both cost for me ~$200 (with all adapters).



#4 GeezerGazer

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Posted 19 November 2020 - 10:09 PM

The Askar is definitely a compact objective!  And it is providing a really nice flat FoV... great stars right to the edge. It also looks like the Askar is providing full NV sensor illumination, as I see the upside down Heart Nebula remains consistently bright right through the edge of field.  And it looks even smaller than the RedCat, which does not provide enough back focus to use a diagonal.   Lots of good potential there.  Congratulations.   It looks like a plane with a blinking light flew through the long exposure image of the California nebula! 

 

I had looked at the Askar 72mm x 400mm Petzval as an alternative to my f:2.8 Nikon 300.  It would be great to have use of a diagonal... a LOT less neck strain! 

Ray


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#5 a__l

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Posted 19 November 2020 - 10:29 PM

I had looked at the Askar 72mm x 400mm Petzval as an alternative to my f:2.8 Nikon 300.  It would be great to have use of a diagonal... a LOT less neck strain! 

Ray

Probably just the problem of the zenith and close. The question of the lens price is the main one. Used Japanese lenses are cheap and of good quality.


Edited by a__l, 19 November 2020 - 10:32 PM.


#6 Gavster

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Posted 20 November 2020 - 01:59 AM

Probably just the problem of the zenith and close. The question of the lens price is the main one. Used Japanese lenses are cheap and of good quality.

The price of the Askar seemed pretty good to me at £350. As GeezerGazer says the main benefit to me of the Askar is the ability to use a diagonal which makes it much more comfortable to use on my mount. 


Edited by Gavster, 20 November 2020 - 02:05 AM.

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#7 Gavster

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Posted 20 November 2020 - 02:03 AM

It looks like a plane with a blinking light flew through the long exposure image of the California nebula! 
 

Ray

Ah you spotted that. I don’t think it’s a plane as the Heathrow flight path was closed at the time I took the photo. Actually I took a number of shots of the California and there were a number of these slow moving objects shown (one of my images had three in the fov). I was wondering if it was Starlink?

 

I can’t see any noticeable bandshift in the images which is also good considering I was using my 3nm chroma ha filter.


Edited by Gavster, 20 November 2020 - 02:07 AM.

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#8 nicknacknock

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Posted 20 November 2020 - 03:26 AM

Gavster, I would recommend you get a M48 extension and screw it on AFTER the 2" filter, so that you have a light shield in place and avoid reflections. Something like this or this.


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#9 nicknacknock

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Posted 20 November 2020 - 03:29 AM

Also, in cased more in-travel is needed, swap the T2 to 1.25" Clicklock with this one. Saves you 20mm in-travel!



#10 Gavster

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Posted 20 November 2020 - 04:33 AM

Gavster, I would recommend you get a M48 extension and screw it on AFTER the 2" filter, so that you have a light shield in place and avoid reflections. Something like this or this.

Thanks Nick. The chroma filter doesn’t have threads on the other side so the extensions won’t work. However I didn’t have issues with reflections in London so hopefully it won’t be a particular issue. If it is an astro friend had offered to 3D print a shield for me that can slip over the scope.

The barrel on the nv monocular is quite long so I need to be careful about not hitting the diagonal but useful to know for other scopes. I think I’m fine on in travel with this scope.


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#11 Joko

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Posted 20 November 2020 - 05:15 AM

Thanks Nick. The chroma filter doesn’t have threads on the other side so the extensions won’t work. 

The barrel on the nv monocular is quite long so I need to be careful about not hitting the diagonal but useful to know for other scopes. I think I’m fine on in travel with this scope.

Unfortunately most 2" h-alpha filters don't have thread at the front. 

About the barrel, it is made in 2 parts, so you can unscrew the bottom if you fear to hit the diagonal. And both parts are threaded for 1.25" filters. See pic attached.

Capture d’écran 2020 11 20 111201

Edited by Joko, 20 November 2020 - 05:19 AM.

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#12 Gavster

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Posted 20 November 2020 - 05:31 AM

Unfortunately most 2" h-alpha filters don't have thread at the front. 

About the barrel, it is made in 2 parts, so you can unscrew the bottom if you fear to hit the diagonal. And both parts are threaded for 1.25" filters. See pic attached.

Unscrewing the bottom would leave a very short barrel to clamp onto, I think a shorter 1.25 inch extension tube would be something to look for to get something in between.


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#13 Gavster

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Posted 20 November 2020 - 06:00 AM

Gavster, I would recommend you get a M48 extension and screw it on AFTER the 2" filter, so that you have a light shield in place and avoid reflections. Something like this or this.

Nick, I’m embarrassed to say that after looking again at my chroma filter I can see that it does have a small amount of thread on the sky side which would be fine to screw your suggested extension on (as does my Baader 685) so I’m going to order one - many thanks for the suggestion. :)


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#14 Astrojedi

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Posted 20 November 2020 - 11:01 AM

Nick, I’m embarrassed to say that after looking again at my chroma filter I can see that it does have a small amount of thread on the sky side which would be fine to screw your suggested extension on (as does my Baader 685) so I’m going to order one - many thanks for the suggestion. smile.gif

You can use one of the extensions that comes with the fra180 as a dew shield. That is what I do.


Edited by Astrojedi, 20 November 2020 - 11:01 AM.


#15 Gavster

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Posted 20 November 2020 - 11:47 AM

You can use one of the extensions that comes with the fra180 as a dew shield. That is what I do.

Just checked the extensions that came in my box and they are all

t2 extensions not m48.



#16 a__l

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Posted 20 November 2020 - 08:09 PM

The price of the Askar seemed pretty good to me at £350. As GeezerGazer says the main benefit to me of the Askar is the ability to use a diagonal which makes it much more comfortable to use on my mount. 

Gavster, I spent $52 for a used Nikkor 200mm f/4 and $17 for a new f ring-c-mount. Now everything is on the way, I hope everything will be fine.


Edited by a__l, 20 November 2020 - 08:11 PM.


#17 Gavster

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Posted 20 November 2020 - 10:53 PM

Gavster, I spent $52 for a used Nikkor 200mm f/4 and $17 for a new f ring-c-mount. Now everything is on the way, I hope everything will be fine.

Can you attach a diagonal to it?



#18 a__l

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Posted 21 November 2020 - 12:13 AM

No. But from experience with other lenses, it doesn't really bother me. Is that in summer Cygnus is at its zenith.



#19 Gavster

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Posted 21 November 2020 - 02:52 AM

No. But from experience with other lenses, it doesn't really bother me. Is that in summer Cygnus is at its zenith.

Ok, for me being able to use a diagonal is necessary to be able to mount it and take phone images with it.

However for handheld use I have followed your suggestion and got a fujinon 75mm f1.8 c mount lens with 49mm to 48mm adapter to attach 2 inch filters to the lens. The ovni-m is good in that the gain control and on off switch are offset a fair bit to the side so no problem attaching this lens.

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Edited by Gavster, 21 November 2020 - 02:56 AM.

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#20 GeezerGazer

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Posted 25 November 2020 - 01:30 AM

Gavster, how does the 75mm Fujinon perform compared to the 3x lens attached to the Envis lens?  The 3x does not change the fast f:1.2 focal ratio of the Envis.  The Fujinon is f:1.8.  So how do they compare for: 

1.   Brightness of image

2.   Vignetting w/o filter

3.   Full sensor illumination

4.   Vignetting caused by band shift

 

Any outstanding benefit of one over the other?  

Ray



#21 Gavster

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Posted 25 November 2020 - 04:18 AM

Gavster, how does the 75mm Fujinon perform compared to the 3x lens attached to the Envis lens?  The 3x does not change the fast f:1.2 focal ratio of the Envis.  The Fujinon is f:1.8.  So how do they compare for: 

1.   Brightness of image

2.   Vignetting w/o filter

3.   Full sensor illumination

4.   Vignetting caused by band shift

 

Any outstanding benefit of one over the other?  

Ray

Ray

I think the 3x afocal lens used with the pvs-14/envis is actually running at f1.5, ie does change the fast f1.2 - that is what is quoted by the dealer and also quoted in previous posts here I think. 
1. The afocal is marginally brighter as would be expected from the slightly faster speed but the impact is very small to my eyes

2. You can screw the 3x afocal into the pvs-14 which reduces vignetting to maybe only 5% of fov but it’s not possible to use filters in this manner (unless you buy a bespoke larger than 2 inch filter which will cost $$$). With the fujinon both with and without filters I can see maybe only 5% vignetting visually. With filters with the rafcamera adapter on the pvs14 and 3x afocal I get sever vignetting of maybe 40% of the fov - this really detracts from the view and makes it harder to use well, key reason I prefer the fujinon lens

3. Not sure, seems ok in both

4. not noticeable unlike when I use my pvs14 with the chroma 3nm in 1x mode.


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#22 chemisted

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Posted 25 November 2020 - 10:04 AM

With a little horse trading I was able to pick up a Nikkor 85mm f/1.8 lens recently for $30 out of pocket. Only a little use so far but I like it a lot. With adapter attached it fits well into my Micro utility bag.
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#23 gatorengineer

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Posted 25 November 2020 - 12:24 PM

Not as fast f1.73 but sharp to the edge filterable a nikon 105 f2.4 with a siebert 36.  Only 45mm of aperture. The afocal 3x...  Working on a much faster variant but not there yet.  Afocal with camera lenses is alot of fun. 

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#24 GeezerGazer

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Posted 25 November 2020 - 10:59 PM

Ray

I think the 3x afocal lens used with the pvs-14/envis is actually running at f1.5, ie does change the fast f1.2 - that is what is quoted by the dealer and also quoted in previous posts here I think. 
1. The afocal is marginally brighter as would be expected from the slightly faster speed but the impact is very small to my eyes

2. You can screw the 3x afocal into the pvs-14 which reduces vignetting to maybe only 5% of fov but it’s not possible to use filters in this manner (unless you buy a bespoke larger than 2 inch filter which will cost $$$). With the fujinon both with and without filters I can see maybe only 5% vignetting visually. With filters with the rafcamera adapter on the pvs14 and 3x afocal I get sever vignetting of maybe 40% of the fov - this really detracts from the view and makes it harder to use well, key reason I prefer the fujinon lens

3. Not sure, seems ok in both

4. not noticeable unlike when I use my pvs14 with the chroma 3nm in 1x mode.

Wow!  The filtered vignetting of the 3x @ 40% versus 5% on the 75mm Fujinon C-mount lens is huge.  Understandable why you prefer the Fujinon. Thank you.  A good benefit of camera lenses is that they can be used with 1.25" or 2" filters in the C-mount adapter without a hint of vignetting.  I sold my 3x add-on lens long ago... had forgotten about the severe vignetting when using filters.  But I also like my Computar 50mm lenses for their light weight and small size, especially when using them rigged together in Bino mode @ 2x.  They do vignette when using first surface 2" filters, compared to a Nikon lens with the filter behind the lens.  


Edited by GeezerGazer, 25 November 2020 - 11:09 PM.


#25 Astrojedi

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Posted 16 December 2020 - 01:27 PM

Just checked the extensions that came in my box and they are all

t2 extensions not m48.

You are right. I checked the 180 again and looks like I am using a M48 spacer from my pile of astro stuff. For some reason I thought it came with the scope. In case you don't have a m48 spacer a step down ring can also work.


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