Convert Hoya 200mm prime lens into a scope

[uk_friendly_fire]

Has anyone tried this? I'm on a really tight budget now 5 years into retirement and still after a compact lightweight go anywhere rucksack kit.

I've seen a YouTube video suggesting you can simple wide field AP with such a lens and DSLR. I will use my SW az gti lightweight mount.

I just bought lens from Ebary for £20, not delivered as yet. It has an M42 thread and have many questions

1)  what do I need to connect to my Nikon d5300

2) a 1.25" lens

3) can a Barlow lens be used

4) would it be better to use a SV305 or my D5300?

Any help much appreciated 

Edited September 14, 2022 by uk_friendly_fire

[vlaiv]

1) not possible without special optical adapter.

M42 lens have 45.46mm flange focal distance while Nikon F-mount has 46mm, so you are 0.5mm short. You won't be able to focus properly at infinity.

When lens has longer flange focal distance than camera - solution is to add spacers, but when it has shorter flange focal distance - one can only use special adapters with optical elements that move focal plane of the lens further out.

Something like this:

https://www.bhphotovideo.com/c/product/995104-REG/fotodiox_m42_nk_pg_pro_nikon_f_mount_lens.html

That one uses x1.4 corrector lens embedded - and thus changes focal length of the lens as well.

Btw - you would need fully manual lens as these sort of adapters don't have electrical connections so no auto focus or automatic aperture control

2) No way, or at least no sensible way.

You would need M42/T2 adapter and then T2 to 1.25" adapter. These all need to have shorter optical path than said 45.5 mm and then you stand a chance focusing with lens focusing mechanism. If total path is longer - you won't be able to focus at infinity.

It also depends where focal point of 1.25" eyepiece is. There is no standard position, so some eyepieces will work and some might not.

Your best bet is to try any particular eyepiece by holding it against the lens and seeing if you can get the focus by moving eyepiece slightly back and forth (requires steady hands)

3) probably not for the same reasons as above - issue with mounting and distance

4) Dedicated astronomy cameras are easiest to attach to a lens. You only need M42/T2 adapter and some spacers. Astronomy cameras have small back focus so there is plenty of "room" in those 45.5mm for adapters / spacers.

Having said that - SV305 is probably the worst choice of camera to pair with such lens. It is very small sensor with small pixels.

Small sensor + longer FL of lens means: too narrow field of view.

Small pixels with any kind of lens - means blurry image. Lenses are not optimized to work with small pixels and provide sharp stellar images. Your best bet is to bin data to get larger pixels and then you loose pixel count.

You will end up with something like 640x480 image - covering small portion of the target.

 

[scotty1]

I use my Pentax DSLR and camera lenses for basic wide field astrophotography, and occasionally to photograph comets. I use a a standard tripod without any tracking,  although I can use the astrotracer GPS on my camera for longer exposures. 

This is one of the lightest and simplest setups for astrophotography. 

I think you will either use a DSLR and camera lenses. Or a telescope and astro camera. 

You can find good used lenses that fit straight onto your Nikon D5300. This is simpler than using lens adapters.

A fairly heavy sturdy tripod is essential also, as a lightweight tripod will not hold the equipment sill enough.

 

 

 

 

 

Edited September 14, 2022 by scotty1

[uk_friendly_fire]

Thank you both for your answers. Looks like I may have made a mistake. I need budget buy recommendations if I'm going to heat my house this winter.

Here is a link for the YouTube that set me off on the quest 

 

 

 

[Mandy D]

1 hour ago, uk_friendly_fire said:

Thank you both for your answers. Looks like I may have made a mistake. I need budget buy recommendations if I'm going to heat my house this winter.

Here is a link for the YouTube that set me off on the quest 

 

You ciuld try a Tamron 70-300 zoom. Inexpensive and works well. Even cheaper if you can find a used one. Have a look at the used lenses at Park Cameras, Castle Cameras and MPB.

An interesting alternative and super cheap, if you can find one, is a mirror lens. I have an 800mm f/8 Samyang with M42 thread and a Nikon adapter.

[vlaiv]

1 hour ago, uk_friendly_fire said:

Here is a link for the YouTube that set me off on the quest 

He seems to be using Canon DSLR in that video?

Both Canon EF and Canon EF-S lens mounts have 44mm flange focal distance and can easily adopt M42 lens. I used Helios 58mm F/2 lens on my Canon like that.

This adapter solves it for example:

https://www.bhphotovideo.com/c/product/843885-REG/vello_la_cef_m42_lens_mount_adapter.html

(note absence of any optical elements because light path does not need to be extended).

 

[uk_friendly_fire]

26 minutes ago, Mandy D said:

An interesting alternative and super cheap, if you can find one, is a mirror lens. I have an 800mm f/8 Samyang with M42 thread and a Nikon adapter.

Was looking at 500mm mirror lens but got put off when I saw the video as mirrors were 3 to 4x the cost and look much heavier. Do Samyang go under other brand names?

[Mandy D]

11 hours ago, uk_friendly_fire said:

Was looking at 500mm mirror lens but got put off when I saw the video as mirrors were 3 to 4x the cost and look much heavier. Do Samyang go under other brand names?

My Samyang 800mm cost £135 new, whereas my 300mm f/4 Nikon prime lens was around £1200 new. I've just done a quick weight comparison and reckon the mirror lens is around half the weight of the 300mm. Samyang lenses do get sold under other brand names, but I cannot recall which ones.

Mirror lenses are not popular with photographers because of the unusual donut shaped bokeh, soft contrast due to a large central obstruction, fixed wide aperture and manual focus. However, for astro-photography they can be quite good. They can be a little tricky to focus and take a while to cool. I find the results poor until they reach ambient temperature, but telescopes are pretty much the same.

The nice thing with mirror lenses is how compact they are due to the folded optical design. My 800mm is only 145mm long including the Nikon mount and 110mm in diameter.

[Ratlet]

This will fall into the 'just because you can doesn't mean you should' bracket but, depending on the lens you might be able to fit a diagonal inside the lens, using a modified lens cap to hold it in place.  Focus is controlled by the usual way of focusing the camera.

http://bobatkins.com/photography/technical/Lens-scope-adapter.html

Sounds like it's got no guarantees.  I'm going to give it a whirl because I've got a telephoto which isn't good enough for astro and a spare diagonal.

[scotty1]

I found this on wikipedia about Samyang.  

https://en.m.wikipedia.org/wiki/Samyang_Optics#:~:text=Samyang products are also sold,%2C Vivitar%2C Phoenix and Quantaray.

It says their lenses are sold under these brands.

Rokinon, Bower, Opteka, Vivitar, Phoenix and Quantaray.

Edited September 15, 2022 by scotty1

[uk_friendly_fire]

I bought the M42 Nikon adapter it arrived this morning with the Hoya lens arriving the day before.  I'll have a go and see what happens. Sorely tempted by Mandy's idea on mirror lens. But funds need replacing first. Thank you all for your replies, the details provided have helped immensely in this somewhat daunting hobby. It's also dangerous to the bank balance watching YouTube videos first without consulting here first!

[Second Time Around]

To make a telescope from a camera lens I use a Tamron Wide Field Tele-View. This is a 20mm/70 degree eyepiece connected to an Amici prism, so it gives a correct way up, non-reversed image that's much more comfortable to look through.

It attaches to any of Tamron's Adaptall camera lenses, although I haven't tried it with any long focus lenses. Instead I've been using it to make RACI finders.  

The Tele-View is long discontinued now, but does come up fairly often on eBay, as do the Adaptall lenses.

Below is a picture showing my 35-80mm f/2.8-3.8 lens attached to the built-in tripod adapter on the Tele-View. As you can see, I've fitted it with finder rings - a metal screw-in lens hood helps with this. 

With the lens set at 35mm it gives 1.75x magnification with an aperture of 12.5mm and a 40 degree field of view. At 80mm it becomes a 4x21 with a 17.5 deg FOV.

Amongst the other lenses I use are a 35-210mm f/3.5-4.2. This again can be a RACI replacement for a Telrad, giving the same 1.75x magnification with a 40 deg FOV but with an aperture of 10mm. Set at 210mm it becomes a 10.5x50 with a 6.66 deg FOV. It is of course heavier though. 

I've fitted my Tele-Views with crosshairs (the eyepiece screws out with a bit of force).

I've bought 3 Tele-Views, 2 of which have a 49mm internal thread and so with a 42mm step down ring may also take a T thread lens. When I find a suitable one I'll check if it'll reach infinity focus when set up like this. It does of course do so with Tamron's Adaptall lenses.

There's a wide range of these zoom and fixed focal length Adaptall lenses available, including telephotos that would make higher powered scopes.

 

[DaveL59]

You did used to be able to buy an adaptor for M42 lenses, but they're pretty rare to find nowadays

[RT65CB-SWL]

Hi @uk_friendly_fire and a belated welcome to SGL. 

I have an old Phota/Paragon 400mm/f6.3 telephoto prime lens. I have attached a T2 helical focuser... https://www.firstlightoptics.com/adapters/baader-125-t2-helical-focuser.html to it and it nearly achieves focus with a cheap’ish e/p. I have yet to try it with one of my star diagonals and an e/p in place to see it will achieve focus. I am planning to use the lens for some imaging and basic ‘quick & dirty’ astro-imaging, mainly lunar, planetary and solar [with an appropriate solar-filter] when I have found/located my mislaid T-ring to Nikon DSLR adapter).

Going back a few years when I had two Pentax ME-super [35mm] SLR bodies. I had a Vivatar 80-200mm/f4.5 zoom lens. I managed to purchase a secondhand Vivatar Pentax-K bayonet mount telescope adaptor, (either online or a camera shop). It made a small and compact low-power telescope. As it included a built-in eyepiece (about the equivalent of 8-10mm). It was OK’ish for low-power terrestrial viewing. The only drawbacks were:

1. Its weight. Being a zoom lens means more glass and weight.
2. No provision for a 1/4-20 tripod mounting, so my arms would get a little ‘tired’ after holding and using it after a few minutes, unless it was supported on an inverted brush/broom or wall/fence to rest it on.

Edited September 20, 2022 by Philip R

[DaveL59]

38 minutes ago, DaveL59 said:

You did used to be able to buy an adaptor for M42 lenses, but they're pretty rare to find nowadays

Actually, doing a search it seems you can get new ones still

Astro Essentials M42 to 2" Eyepiece Holder | First Light Optics

RafCamera M42x1 female thread to 1.25" telescope eyepiece adapter...

Can't say these would work with a diagonal but so long as the light path is correct (45mm) then you should find focus. Might need a prism rather than a mirror diagonal tho.

Edited September 19, 2022 by DaveL59

[DaveL59]

Also found this on CN forum

Making a monocular from a m42 lens and an eyepiece - Binoculars - Cloudy Nights

 

[Second Time Around]

On 19/09/2022 at 22:00, Second Time Around said:

To make a telescope from a camera lens I use a Tamron Wide Field Tele-View. This is a 20mm/70 degree eyepiece connected to an Amici prism, so it gives a correct way up, non-reversed image that's much more comfortable to look through.

It attaches to any of Tamron's Adaptall camera lenses, although I haven't tried it with any long focus lenses. Instead I've been using it to make RACI finders.  

The Tele-View is long discontinued now, but does come up fairly often on eBay, as do the Adaptall lenses.

Below is a picture showing my 35-80mm f/2.8-3.8 lens attached to the built-in tripod adapter on the Tele-View. As you can see, I've fitted it with finder rings - a metal screw-in lens hood helps with this. 

With the lens set at 35mm it gives 1.75x magnification with an aperture of 12.5mm and a 40 degree field of view. At 80mm it becomes a 4x21 with a 17.5 deg FOV.

Amongst the other lenses I use are a 35-210mm f/3.5-4.2. This again can be a RACI replacement for a Telrad, giving the same 1.75x magnification with a 40 deg FOV but with an aperture of 10mm. Set at 210mm it becomes a 10.5x50 with a 6.66 deg FOV. It is of course heavier though. 

I've fitted my Tele-Views with crosshairs (the eyepiece screws out with a bit of force).

I've bought 3 Tele-Views, 2 of which have a 49mm internal thread and so with a 42mm step down ring may also take a T thread lens. When I find a suitable one I'll check if it'll reach infinity focus when set up like this. It does of course do so with Tamron's Adaptall lenses.

There's a wide range of these zoom and fixed focal length Adaptall lenses available, including telephotos that would make higher powered scopes.

 

I've just put the Teleview plus the 35-210mm zoom plus finder bracket up onto the For Sale/Swap forum.

[DaveL59]

I came across an adaptor for Minolta AF lenses the other day so decided to hit the button:

 

Surprised how bright the image is in even poor daylight. No idea how it'll be at night but could be an interesting experiment. I've a couple long-ish lenses I can try at some stage, the minolta AF 100-300 & 400, Tamron 18-300 and 150-600mm tho these would be f6.7 at full zoom, also a Hoya M42 75-260 F4 and big Zeiss M42 180mm F2.8. Only the big tamron and the Zeiss have tripod mounts in-built but I do have a Manfrotto carrier that might be adaptable to assist the other zooms if needed.