5 replies to this topic

[CLJLF]

Hello, I have recently obtained a P8079HP cascade tube and plan to make it into a sky watching device.

I have looked at other people's builds and they often seem to use fast CCTV lenses. Would image projection size be a problem if I use CCTV lenses or TV zoom lenses (For 1/1.8", 1/2" and 1/2.8" sensors)? Since in photography, these lenses seem to be already causing vignette problems on Super-16 sensor cameras (Which only have a diameter of 14.33). The P8079HP usable cathode screen diameter is 25mm.

 

Am I worrying to much since this doesn't apply to night vision or are most people only using half of their tube's area? Being able to use TV zoom lenses would be very helpful since they're very fast,cheap and have a large focal distance range. The wacky mounts won't be a problem because I will 3D print the housing for the tube. I also have a f/3.8 70-300mm zoom lens on order for more zoomed in observation. 

Edited by CLJLF, 02 November 2024 - 03:09 PM.

[Lambda]

Hi CLJLF.

 

Great tube you have, a venerable underdog when compared to more modern tube. 

With a fast lens (F/1.2 or fster, tipically) you will have a nice sky spotting device.

 

Indeed, using a CCTV lens, commonly designed to be used with small sensor, with a P8079HP will generate tons of vignetting. Only a small central fraction of the whole photocathode (PC)'s surface will be illuminated and used.

 

The main advantage of this configuration is that you would use the more distortion free part of the PC, but at the cost of resolution because you would have to use a high magnifying eyepiece for obtaining from the P8079HP's screen a decent apparent field of view sufficiently confortable for your eye: the resolution provided by the P8079HP is typically 40lp/mm, if you use only a small area of few mm diameter from the PC, after the unavoidably necessary magnification of the image through the strong eyepiece, the resulting image will not be sharp for sure....

 

If, on the other hand, you tolerate the classical peripheral distortion provided by th P8079HP, try to find a fast lens which would provide a generous image circle covering the whole PC's surface (notice that with an adequate eyepiece, you can reduce this distortion effect on the resulting image).

 

It seems you can customize a mount, it means that you may use a large choice of lenses, even if not originally designed to be used with a camera.

Therefore, in this case, try to acquire for instance this kind of lenses (non exhaustive list):

- "Redenstock"/"De Oude Delft"/"Kowa"/... lens (F/1 or even faster F/0.75)

 

Here is some personal examples of what you may obtain with this kind of lens:

 

https://www.youtube....h?v=cWyKyCNPnwo

https://www.youtube....h?v=gx-zke9fsCI

 

 

- some vintage projector lens "LOMO"/"MEOPTA"/... (quite often F/1.2, but sometime faster)

 

Nevertheless a more camera compatible solution may be used....

- a current "MEIKE"/"7ARTISANS" (for instance, for "MEIKE", a 35mm/0.95) camera lens for APS-C sensor would be also a good candidate

 

A zoom is always a charming solution, but because it would be good to work with a lens as fast as possible, a F/3.8would be a bit too "s low" IMHO for using with this kind of tube.

 

Just some thoughts for food.

 

Good luck for your project.

 

Cheers.

Lambda

Edited by Lambda, 02 November 2024 - 04:16 PM.

[CLJLF]

Hi CLJLF.

 

Great tube you have, a venerable underdog when compared to more modern tube. 

With a fast lens (F/1.2 or fster, tipically) you will have a nice sky spotting device.

 

Indeed, using a CCTV lens, commonly designed to be used with small sensor, with a P8079HP will generate tons of vignetting. Only a small central fraction of the whole photocathode (PC)'s surface will be illuminated and used.

 

The main advantage of this configuration is that you would use the more distortion free part of the PC, but at the cost of resolution because you would have to use a high magnifying eyepiece for obtaining from the P8079HP's screen a decent apparent field of view sufficiently confortable for your eye: the resolution provided by the P8079HP is typically 40lp/mm, if you use only a small area of few mm diameter from the PC, after the unavoidably necessary magnification of the image through the strong eyepiece, the resulting image will not be sharp for sure....

 

If, on the other hand, you tolerate the classical peripheral distortion provided by th P8079HP, try to find a fast lens which would provide a generous image circle covering the whole PC's surface (notice that with an adequate eyepiece, you can reduce this distortion effect on the resulting image).

 

It seems you can customize a mount, it means that you may use a large choice of lenses, even if not originally designed to be used with a camera.

Therefore, in this case, try to acquire for instance this kind of lenses (non exhaustive list):

- "Redenstock"/"De Oude Delft"/"Kowa"/... lens (F/1 or even faster F/0.75)

 

Here is some personal examples of what you may obtain with this kind of lens:

 

https://www.youtube....h?v=cWyKyCNPnwo

https://www.youtube....h?v=gx-zke9fsCI

 

 

- some vintage projector lens "LOMO"/"MEOPTA"/... (quite often F/1.2, but sometime faster)

 

Nevertheless a more camera compatible solution may be used....

- a current "MEIKE"/"7ARTISANS" (for instance, for "MEIKE", a 35mm/0.95) camera lens for APS-C sensor would be also a good candidate

 

A zoom is always a charming solution, but because it would be good to work with a lens as fast as possible, a F/3.8would be a bit too "s low" IMHO for using with this kind of tube.

 

Just some thoughts for food.

 

Good luck for your project.

 

Cheers.

Lambda

Thanks for the info! apparently there are some TV lenses made for 1' sensors, which projects images of around 20 diameter. I'll get one and see how it goes since the difference isn't very big. 

Do you think that I can use a 25mm telescope eyepiece reversed to make an afocal setup with a telescope? I can get a PVS 14 lens on aliexpress but it's quite expensive. 

Wondering if I keep the scope pointed at stars for a while, would it be able to burn in and damage the tube? I see that these tubes have streaking, just worried that I'll have to keep moving the scope to avoid dots of burn from stars. (especially when trying to look at flame nebula/horsehead nebula which is right next to a magnitude 1.77 star)

Edited by CLJLF, 04 November 2024 - 08:16 AM.

[cnoct]

1" sensor format lenses are typically designed to cover a diagonal of ~ 16mm, a carry over from the 16mm film era.  The longer the focal length usually is more forgiving and usually have larger coverage than lenses with short focal lengths i.e. 75mm 16mm/1" lens will have greater coverage than a 25mm 16/1" lens. 

 

Aside from those that Lamda has listed, take a look at 35mm film camera lenses, there's some relatively fast (f/1.2) vintage 35mm lenses that can be had.  Since you'll likely be fabricating a lens mount, you can also go with short flange  lenses used on mirrorless cameras. 

 

Lamda is a great resource so I'd default to him. 

[Lambda]

Thank you cnoct,.... 

Just a simple hobbyist a bit curious, i am.

 

CLJLF, cnoct gave to you interesting details which should enlarge your possible selection and allow you to find your happiness !

Sometimes flea markets are your best friend !

 

Please share with us your project when the time will come.

 

Best regards.

Stéphane Lachaud

[highfnum]

p8079 have pinched optic field

you can reduce a "pinch" with a "barrel"

aspheric lens

reduces a lot (not all) the "pinch"